STS-119/ISS-15A MISSION ARCHIVE (COMPLETE)
Updated: 03/28/09

By William Harwood
CBS News/Kennedy Space Center

The following copy originally was posted on the Current Mission space page at http://cbsnews.com/network/news/space/current.html.

Comments, suggestions and corrections welcome!

TABLE OF CONTENTS


11:30 PM, 3/29/09, Update: Shuttle tile experiment pays off

In an experiment that could lead to improved heat shield designs for future spacecraft - along with insights into shuttle aerodynamics - temperature data and infrared imagery confirm a modified tile on the underside of the shuttle Discovery's left wing caused air rushing over the belly of the orbiter to transition from smooth to turbulent flow as expected.

The goal of the research is to gain a better understanding of how smooth, laminar airflow, which provides a thin layer of insulation during peak heating, can change to the disturbed, turbulent flow that can cause downstream temperatures to climb, possibly affecting aerodynamics and causing damage.

That change is known as a boundary layer transition.

The shuttle's transition from laminar to turbulent flow occurs naturally as the spacecraft slows down, typically at velocities around mach 8, or eight times the speed of sound, about 20 minutes after atmospheric entry begins. In some cases, however, the transition can occur earlier than that because of defects in the heat shield.

For example a protruding tile spacer called a "gap filler" can shake loose during launch and extend up into the airflow, triggering an early, asymmetric boundary layer transition during re-entry. When that happens, the shuttle's aerodynamics can be affected and downstream tiles can be subjected to more extreme heating.

During shuttle mission STS-28 in 1989, for example, the boundary layer "tripped" 15 minutes after entry, at around mach 18. During shuttle mission STS-50 in 1992, one side of the shuttle's belly went turbulent more than a minute ahead of the other side, causing a change in aerodynamics that prompted autopilot flight control inputs.

For Discovery's boundary layer transition - BLT - experiment, a single tile on the bottom of the shuttle's left wing, about 10 feet behind the leading edge, featured a 0.25-inch-high ridge that was expected to cause the insulating boundary layer downstream to go turbulent between mach 12 and 14. That, in turn, was expected to raise the temperatures of downstream tiles by 500 to 600 degrees Fahrenheit.

The tiles in that region of the wing normally experience maximum temperatures of 1,500 to 1,600 degrees when the re-entry airflow across the wing is smooth. Preliminary reports indicated the maximum temperature experienced by the "protuberance tile" was around 2,000 degrees, somewhat less than expected. If those measurements are confirmed, engineers may request a slightly higher protuberance for a future flight.

Along with temperature data, a Navy P-3 Orion aircraft flying over the Gulf of Mexico southwest of Tampa captured infrared images of the shuttle's belly when the orbiter had slowed to about 8.5 times the speed of sound.

A wedge of higher heating downstream of the protuberance tile was clearly visible in the unprocessed, raw imagery, along with a broader zone of turbulence.

Wedge of turbulent flow behind modified tile

It was not immediately known if the "turbulence from an unknown origin" seen in the P-3 image reflected a normal or asymmetric transition to turbulent flow, either on-time or earlier than expected. But an engineer familiar with boundary layer issues said the image likely reflected a "typical" shuttle boundary layer transition.

Location of Navy P-3 Cast Glance aircraft during
Discovery's delayed re-entry on orbit 202

Engineers reported the protuberance tile looked normal and undamaged on the runway after Discovery's landing, although superficial markings were seen on several downstream tiles. No such markings were seen on tiles behind a protruding gap filler that was spotted during an on-orbit inspection on one of Discovery's elevons.

For additional details about the BLT experiment, please see the 10 a.m. 3/28 update below, "Tripping the boundary layer: shuttle heat shield experiment promises entry insights."


3:40 PM, 3/28/09, Update: Shuttle Discovery lands in Florida (UPDATED at 7:35 p.m. with post-landing crew conference; managers briefing)

The shuttle Discovery glided to a windy touchdown at the Kennedy Space Center today, wrapping up a challenging three-spacewalk mission that left the international space station with a new set of solar arrays and a repaired water recycling system.

Running one orbit late because of high winds and low clouds, commander Lee Archambault and pilot Dominic "Tony" Antonelli guided the orbiter through a partly cloudy sky to a tire-smoking touchdown on runway 15 at 3:13:17 p.m.

"Houston, Discovery, wheels stopped," Archambault radioed as Discovery rolled to a halt.

"Houston copies, wheels stopped," replied George Zamka from Houston. "Welcome home, Discovery, after a great mission to bring the international space station to full power. ... To the entire crew of STS-119, great job everybody."

"Thank you very much, it's good to be back home," Archambault said.

Mission duration was 12 days 19 hours 29 minutes and 33 seconds, covering 5.3 million miles and 202 complete orbits since blastoff March 15 from nearby pad 39A.

Archambault, Antonelli, flight engineer Steven Swanson, John Phillips, Joseph Acaba and Richard Arnold doffed their pressure suits and gave Discovery a quick runway inspection before heading back to crew quarters.

"We had a very successful mission, I'm very proud we were able to bring up the S6 truss, the final power segment for the international space station, and we're very, very happy we were able to bring Discovery right back here to the Kennedy Space Center in Florida," Archambault said on the runway.

Said Launch Director Mike Leinbach, "the vehicle performed great, it looks good on the runway, very few dings to the tiles, it looked really, really good."

Returning space station flight engineer Sandra Magnus made the trip back to Earth resting on her back in a recumbent seat set up on the shuttle's lower deck to ease her transition back to gravity after four months in weightlessness. She did not join her crewmates on the runway, but Archambault said she came through entry "doing extremely well for someone who's been in space for four months. She was in very good spirits."

Shuttle Discovery rolls down runway 15

Magnus was replaced aboard the station by Japanese astronaut Koichi Wakata, who took off aboard Discovery and who remained behind when the shuttle departed Wednesday.

During re-entry, Discovery's crew participated in a final experiment. A heat-shield tile on the underside of the ship's left wing was modified to affect the flow of air across the belly of the orbiter during its high-speed descent to learn more about the physics of hypersonic flight. The data are expected to pay dividends when it comes to designing heat shields for future spacecraft.

LeRoy Cain, deputy manager of the shuttle program at the Johnson Space Center in Houston, said an aircraft flying below Discovery was able to photograph the ship's plume with an infrared camera as Discovery descended toward Florida. That imagery will be combined with temperature measurements from sensors on the shuttle to help engineers map turbulent air flow and its roll in re-entry heating.

"All indications are we were able to capture some good data," Cain said. "It's the only vehicle that flies like this in a hypersonic regime where we're able to capture this kind of aerodynamic data. So we're real excited to get this test data."

As Discovery's crew prepared for re-entry today, station commander Mike Fincke, Yury Lonchakov and Wakata, orbiting at a slightly higher altitude more than 1,000 miles behind the shuttle, welcomed two more crew members - and one guest - aboard the international outpost.

Expedition 19 commander Gennady Padalka, NASA flight engineer Michael Barratt and space tourist Charles Simonyi, making his second paid trip to the station, docked at the Zvezda command module's aft port at 9:05 a.m. After leak checks, they floated into the station around 12:36 p.m.

Padalka and physician-astronaut Barratt are replacing Expedition 18 commander Fincke and Lonchakov, who were launched to the outpost last October. After a 10-day handover, Fincke, Lonchakov and Simonyi will return to Earth aboard the Soyuz TMA-13 spacecraft on April 7.

If all goes well, three more crew members - cosmonaut Roman Romanenko, European Space Agency astronaut Frank De Winne and Canadian Space Agency astronaut Robert Thirsk - will ride another Soyuz to the lab complex in late May, boosting the full-time crew to six for the first time.

The Discovery astronauts paved the way to the latest space station milestone by installing a fourth and final set of solar arrays and delivering a replacement centrifuge for the lab's urine recycling system.

The new arrays will double the amount of power available for scientific research, from 15 kilowatts to 30 kilowatts, and the water recycling system will provide water for drinking and personal hygiene after the shuttle is retired in 2010.

A team of engineers was standing by in Florida to remove water samples from Discovery that will be analyzed to determine purity. If all goes well, station crews could be cleared to begin using recycled water within a month or so.

Discovery also brought back frozen blood, urine and other biological samples collected over the past few months as part of on-going space medicine research aboard the station.

With Discovery safely back on the ground in Florida, NASA plans to move the shuttle Atlantis to pad 39A Tuesday to prepare the ship for launch May 12 on a long-awaited mission to service the Hubble Space Telescope.

Because Hubble is in a different orbit from the space station, the servicing crew cannot seek safe haven aboard the outpost if any major problems threaten a safe re-entry. From the beginning, NASA managers have planned to have a second shuttle - Endeavour, in this case - ready for launch on a quick-response rescue mission if necessary.

NASA managers looked into the possibility of using the same launch pad for Atlantis and Endeavour, but Gerstenmaier said today Endeavour would be mounted on pad 39B while Atlantis is processed on nearby 39A. Pad 39B had been booked for a test flight of NASA's new Ares rocket, but that launch is being delayed and Endeavour will use the pad instead to improve processing efficiencies.

"We've talked to the teams, we've decided to use two pads for the HST flight," said Bill Gerstenmaier, director of space operations at NASA headquarters.

After Atlantis takes off, assuming a rescue flight is not needed, Endeavour will be moved over to pad 39A for work to prepare the ship for blastoff in June on another space station mission.

"As we look forward a little bit to the future, we've got to start thinking now about how we're going to really utilize space station," Gerstenmaier said. "I would just ask us all to stop for a moment and reflect on what's happening in space. ... This is a very special time in space flight and we need to make sure we get the absolute most out of it."

Antonelli clearly got the most out of his first space mission. Talking to reporters after landing, he summed up his experience saying "this whole living in 1-G thing is for the birds. Zero G, I think, is the way to go. It's a blast!"


12:20 PM, 3/28/09, Update: Shuttle entry delayed

The Discovery astronauts were told to delay re-entry for one orbit in hopes blustery winds and low clouds at the Kennedy Space Center might abate enough to permit a landing around 3:14 p.m., the crew's second and final opportunity to come home today.

Entry Flight Director Richard Jones at the Johnson Space Center in Houston made the decision just after 12:10 p.m. "OK, Discovery, Houston, here's the picture on the weather," radioed astronaut George Zamka radioed from Houston. "Things are still somewhat variable, but a trend we saw that we weren't comfortable with was a layer at 3,000 feet, bottoms at roughly 2,700 up to about 4,000, that were moving east from the west into the area of the field. We just didn't like that.<

"Also, the winds have been variable and exceeding the crosswind limits. We think both those things have a good chance of looking better for our second opportunity today.

"Discovery copies," replied shuttle skipper Lee Archambault Assuming the weather cooperates, here's the timeline for the crew's second and final landing opportunity today:

EDT...........EVENT

02:08:44 PM...Deorbit rocket firing (dT: 3:01; dV: 231 mph)
02:11:45 PM...Deorbit burn complete

02:42:21 PM...Entry interface (range to KSC: 5,023 miles)
02:47:21 PM...1st roll command to right
02:56:36 PM...1st right-to-left roll reversal
03:03:00 PM...C-band radar acquisition
03:07:24 PM...Velocity less than mach 2.5
03:09:37 PM...Velocity less than mach 1
03:10:23 PM...Shuttle banks to line up on runway 15
03:13:59 PM...Landing
Discovery has enough on-board supplies to remain in orbit until Tuesday. As a result, NASA is not staffing any backup landing sites today or Sunday. If the shuttle is still in orbit Monday, Edwards Air Force Base, Calif., will be activated and Archambault will bring the shuttle down on one coast or the other.


10:00 AM, 3/28/09, Update: Tripping the boundary layer: shuttle heat shield experiment promises entry insights

During the shuttle Discovery's high-speed plunge back to Earth, engineers will be collecting data from a unique experiment to understand exactly how airflow over the orbiter's belly transitions from smooth, laminar flow, which provides a thin layer of insulation, to the disturbed turbulent flow that can cause downstream temperatures to climb, possibly damaging a spacecraft's heat shield.

A single tile on the bottom of Discovery's left wing, about 10 feet behind the leading edge, features a quarter-of-an-inch-high ridge that will cause the insulating "boundary layer" downstream to go turbulent between mach 12 and 14. That, in turn, will raise the temperatures of downstream tiles by 500 to 600 degrees Fahrenheit.

The tiles in that region of the wing normally experience maximum temperatures of 1,500 to 1,600 degrees when the re-entry airflow across the wing is smooth. During Discovery's entry, those tiles will experience a deliberate boundary layer transition to turbulent flow that will cause temperatures to climb as high as 2,200 degrees earlier than they normally would.

That will not cause any problems for Discovery or its crew. The aluminum skin of the shuttle under the heat shield in that area will only get 15 to 20 degrees warmer when the heat finally "soaks" into the structure after landing. But the data will help engineers better understand the extreme environment of re-entry, which will pay off in the design of future spacecraft.

"It's an incredible opportunity for us to demonstrate how NASA is working to understand spaceflight better and apply what we learn," said Charles Campbell, the boundary layer transition - BLT - experiment's principal investigator.

Heat shield tile with ridge

Shuttle Program Manager John Shannon said the modified tile was mounted "in an area that has a lot of thermal margin, the tiles are very thick there. This tile is special because it has a bump in it. It's only a quarter-inch bump, but it's molded into the tile itself.

"Downstream of that tile in the airflow wake, we mounted nine thermocouples that can record the temperature. What we expect to have happen is that we will take that boundary layer from laminar to turbulent flow at a higher velocity than we typically would if we didn't have a bump. This adds to our understanding of how flow transitions from laminar to turbulent flow and then what type of heating rate you can have for that. ... Every time Discovery flies we will continue to use this special area that is instrumented."

During re-entry, the shuttle plunges back into the atmosphere at some 5 miles per second with its nose elevated to an angle of attack of around 40 degrees. As the shuttle descends, the thin air in front of the shuttle nose, belly and wing leading edges compresses and forms a boundary layer, a region just a few inches thick that resists further compression and provides a natural zone of insulation.

Just outside the boundary layer protecting the shuttle's wing leading edge panels, for example, temperatures can exceed 10,000 degrees. But the boundary layer keeps the reinforced carbon carbon leading edge panels at around 3,000 degrees - the most extreme temperatures experienced during a normal re-entry.

A smooth, laminar flow is critical for achieving boundary layer insulation during peak heating. The flow naturally goes turbulent at some point during re-entry as the shuttle's velocity decreases. But the longer it is maintained, the better. If the shuttle's surface is marred by a defect, causing the boundary layer to "trip" and go turbulent at higher speeds than normal, the disturbed airflow can bring much higher temperatures closer to the surface.

"Once you understand when you are tripping that flow and getting the higher heat rate, now you can use that, you can put different coatings on tiles, you can put different types of tiles downstream from that and mimic a lunar return or higher heat than a normal shuttle return would be and you can do materials testing on the underside of the vehicle in a real flight environment," Shannon said.

Along with data collected by downstream thermocouples, engineers also hope to collect infrared imagery from a research aircraft flying below the shuttle as it glides toward Florida.

"Our models show that around between mach 12 and 14 we wold expect the trip," Shannon said. "It depends on what ground track you fly. Our typical ground track which has us coming over the Yucatan and the tip of Cuba into Florida, we tend to fly that one a lot, it would be over the Gulf of Mexico. So we will have to carefully stage the viewing aircraft to make sure they have a good view of the underside of the vehicle as it passes overhead.

"This first flight, we're going to see, where it trips," he said. "I certainly don't expect it to trip any higher than mach 15 or 16. If it does, that would be great data. This one is a pretty conservative first step."

Region of increased heating

Extensive testing in an arc jet furnace that can simulate the re-entry environment, along with a detailed engineering analysis, showed the temperature increase for the aluminum airframe below the regions of interest will only change by 15 or 20 degrees by the time Discovery lands.

"Think about how long it takes your kitchen counter top to warm up when you leave the oven on," Campbell said. "It takes time for that heat to soak in to the countertop, just like it takes time for the heating on the orbiter surface to soak into the structure. And as a side note, yes, the aluminum structure stays thousands of degrees cooler than the tile surface - a pretty excellent insulation!"

Shannon described the temperature change as minimal, saying "we have a lot of thermal margin in the tile area."

"Just because of the shape of the wing, the tiles are thicker in this area, they're almost three-inch-thick tiles," he said. "So we're not at all concerned about underside heating. We actually had to make sure the thermocouples would be able to sense the transition. ... So there's no risk to the shuttle for doing this. And it's a great test to understand, in a controlled manner, the flight environment for re-entry."


9:45 AM, 3/28/09, Update: Soyuz TMA-14 docks with space station

Cosmonaut Gennady Padalka took over manual control and guided the Soyuz TMA-14 spacecraft to a smooth docking with the international space station today to cap a two-day orbital chase that began with blastoff Thursday from the Baikonur Cosmodrome in Kazakhstan.

Sailing 220 miles above central Asia, the Soyuz capsule's forward docking mechanism engaged its counterpart on the Zvezda command module's aft port at 9:05 a.m., a few minutes ahead of schedule.

"We have contact... we have capture," someone said. "We have capture."

"Congratulations," Russian flight control radioed.

"Thank you," Padalka replied.

View from Soyuz of Zvezda module's aft docking port
a few moments before capture

Returning to the space station for a second tour of duty as commander, Padalka was joined by NASA flight engineer Michael Barratt, a physician-astronaut making his first flight, and Charles Simonyi, a wealthy software developer making his second paid trip to the station.

The new crew entered the station around 12:30 p.m., gathering in the Zvezda module.

Gennady Padalka, far left,, chats with his daughter in Moscow
while flight engineer Mike Barratt holds the crew's mascot

Today's approach to the station was uneventful until a few minutes before docking when Padalka was told to abort the Soyuz's automated approach and to take over manual control at a distance of a few hundred feet. The veteran cosmonaut had no problems with the final approach, commenting at one point that it was "just like the simulations."

Russian managers said later the automated control system had problems with a specific thruster, prompting the call for manual control.

Padalka and Barratt are replacing outgoing Expedition 18 commander Mike Fincke and flight engineer Yury Lonchakov, who were launched to the outpost last October. Their crewmate, newly arrived Japanese astronaut Koichi Wakata, will join Padalka and Barratt to form the station's 19th full-time crew.

Another Soyuz is scheduled for launch May 27 to carry three more crew members to the station: cosmonaut Roman Romanenko, European Space Agency astronaut Frank De Winne of Belgium and Canadian Space Agency astronaut Robert Thirsk. The transition to a six-person crew marks a major milestone in the evolution of the international space station.

Fincke and Lonchakov will spend the next 10 days or so in a handover period, familiarizing their replacements with the intricacies of station operation. If all goes well, Fincke, Lonchakov and Simonyi will return to Earth on April 7, landing in Kazakhstan aboard the same Soyuz TMA-13 spacecraft that carried the outgoing station crew to orbit last October.

Simonyi, a Hungarian-born software developer, is the first private citizen to make two trips to the international space station. Such flights list for about $35 million each.

"I think it will be an interesting experience," Simonyi said in a telephone interview before launch. "I had a discussion with Sergei Krikalev, who is probably the most experienced cosmonaut in the world, and he told me the big difference between going first and going second, the first time people just learn how to live in space. And the second time, one can actually accomplish work, really work effectively."

During his second visit, Simonyi plans to chat with school kids via ham radio, write about his experiences on his web site and help Russian engineers calibrate space radiation sensors.

While he will spend most of his time in the Russian segment of the station, "with the permission of the commander I can go to other segments as well, and I plan to visit the American segment as well as the two new segments that weren't there before, the Japanense and the European segments.

"There is a lot of room. The way I describe it, it is the size of three city buses. And now, they've added two more RVs on the side with the European and the Japanese segments. So if you have three people up there, it's enormous. With six people, it will still be very, very comfortable and you can hide if you want and get solitude and privacy if you want."

While Simonyi would not discuss how much he actually paid for his second trip, he said "the price is going up. Future seats that NASA has bought are even more expensive. This has to be put into perspective because other means of getting to space are even more expensive, so this one is actually quite cost effective at the current state of technology."


7:45 AM, 3/28/09, Update: Astronauts set for landing; Soyuz closes in on space station

As the Discovery astronauts rigged the shuttle for re-entry and landing, the crew of the Russian Soyuz TMA-14 spacecraft closed in on the international space station today, carrying two fresh crew members and a wealthy space tourist.

Cosmonaut Gennady Padalka, who will take over command of the station from outgoing skipper Mike Fincke, planned to guide the Soyuz capsule to a docking at the station's aft port around 9:14 a.m. to wrap up a two-day orbital chase that began with blastoff from Kazakhstan on Thursday.

After leak checks to make sure the Soyuz is firmly latched in place, hatches will be opened and Fincke, flight engineer Yury Lonchakov and newly arrived Japanese astronaut Koichi Wakata will welcome Padalka, Michael Barratt and Charles Simonyi aboard.

Padalka and Barratt, a NASA physician-astronaut, will replace Fincke and Lonchakov, who plan to return to Earth April 7 along with Simonyi, a software developer making his second paid visit to the station. Padalka, Barratt and Wakata, who hitched a ride to the station aboard Discovery, will form the lab's 19th full-time crew. If all goes well, three more crew members will join them in late May as NASA and its partners transition to six-member crews for the first time.

Hatch opening is expected just after noon, shortly before the Discovery astronauts plan to fire their braking rockets to drop out of orbit.

Commander Lee Archambault and his six crewmates have two landing opportunities today. The first requires a deorbit rocket firing at 12:33:44 p.m. for a touchdown on runway 15 at the Kennedy Space Center at 1:39:42 p.m. The second opportunity calls for a deorbit burn at 2:08:44 p.m. for a landing at 3:13:59 p.m.

The morning forecast from the Spaceflight Meteorology Group at the Johnson Space Center in Houston called for scattered clouds at 4,000 and 20,000 feet, winds out of 170 degrees at 15 knots with gusts to 23. For a landing on runway 15, that works out to peak headwind of nearly 22 knots, just below NASA's 25-knot limit. Maximum crosswind is about 8 knots. There is also a slight chance for a broken deck of clouds at 4,000 feet.

Joining Archambault aboard Discovery are pilot Dominic "Tony" Antonelli, flight enginer Steven Swanson, shuttle and station veteran John Phillips, Richard Arnold, Joseph Acaba and outgoing station flight engineer Sandra Magnus. Launched last November, Magnus was replaced by Wakata. She will make the trip home resting on her back in a reclining chair on Discovery's lower deck to ease her transition back to gravity after four months in space.

Discovery has enough on-board supplies to remain in orbit until Tuesday. As a result, NASA is not staffing any backup landing sites today or Sunday. If the shuttle is still in orbit Monday, Edwards Air Force Base, Calif., will be activated and Archambault will bring the shuttle down on one coast or the other.

Here is an updated timeline of today's activity (in EDT; includes Soyuz activities; best viewed with fixed-width font):

EDT...........EVENT

05:13 AM......Crew wakeup
07:53 AM......Inertial measurement unit alignment
08:33 AM......Deorbit timeline begins
08:48 AM......Radiator stow
08:58 AM......Mission specialists seat installation
09:04 AM......Computers set for deorbit prep
09:08 AM......Hydraulic system configuration

09:14 AM......Soyuz TMA-14 docking with space station

09:33 AM......Flash evaporator checkout
09:39 AM......Final payload deactivation
09:53 AM......Payload bay doors closed
10:03 AM......Mission control 'go' for OPS-3 entry software load
10:13 AM......OPS-3 transition
10:38 AM......Entry switchlist verification
10:48 AM......Deorbit maneuver update
10:53 AM......Crew entry review
11:08 AM......CDR/PLT don entry suits
11:25 AM......Inertial measurement unit alignment
11:33 AM......CDR/PLT strap in; MS suit don
11:50 AM......Shuttle steering check
11:53 AM......Hydraulic system pre start
12:00 PM......Toilet deactivation
12:08 PM......Vent doors closed for entry

12:10 PM......Soyuz TMA-14 hatch opening

12:13 PM......Mission control 'go' for deorbit burn
12:19 PM......Astronaut seat ingress
12:28 PM......Single hydraulic power unit start
	
Rev. 201 deorbit to KSC:

12:33:44 PM...Deorbit ignition (dT: 3:01; dV: 231 mph)
12:36:45 PM...Deorbit burn complete

01:07:58 PM...Entry interface (range to KSC: 4,942 miles)
01:12:57 PM...1st roll command to left
01:27:56 PM...1st left-to-right roll reversal
01:30:00 PM...C-band radar acquisition
01:33:09 PM...Velocity less than mach 2.5
01:35:20 PM...Velocity less than mach 1
01:36:31 PM...Shuttle banks to line up on runway 15
01:39:42 PM...Landing

Rev. 202 Deorbit to KSC:

01:48 PM......MCC 'go' for deorbit burn
01:54 PM......MS seat ingress
02:03 PM......Single APU start

02:08:44 PM...Deorbit ignition (dT: 3:01; dV: 231 mph)
02:11:45 PM...Deorbit burn complete

02:42:21 PM...Entry interface (range to KSC: 5,023 miles)
02:47:21 PM...1st roll command to right
02:56:36 PM...1st right-to-left roll reversal
03:03:00 PM...C-band radar acquisition
03:07:24 PM...Velocity less than mach 2.5
03:09:37 PM...Velocity less than mach 1
03:10:23 PM...Shuttle banks to line up on runway 15
03:13:59 PM...Landing


6:30 PM, 3/27/09, Update: Entry flight director optimistic about Saturday landing

With forecasters predicting generally good, if somewhat windy, weather ahead of an approaching front, the shuttle Discovery's astronauts tested the ship's re-entry systems and packed for landing Saturday back at the Kennedy Space Center.

Commander Lee Archambault, pilot Dominic "Tony" Antonelli, flight engineer Steven Swanson, John Phillips, Joseph Acaba, Richard Arnold and returning space station flight engineer Sandra Magnus planned to get up at 5:13 a.m. Saturday and to begin working through the deorbit timeline around 8:38 a.m.

Flying upside down and backward over the Indian Ocean, Archambault and Antonelli plan to fire Discovery's twin braking rockets for three minutes and one second starting at 12:33:44 p.m., slowing the ship by about 231 mph to drop out of orbit.

After crossing Central America just west of the Panama Canal, Discovery's flight path will carry the ship north above central Cuba and then up Florida's east coast to the Kennedy Space Center. Landing on runway 15 is expected at 1:39:42 p.m. A backup opportunity is available one orbit later, at 3:13:59 p.m.

While the shuttle astronauts are rigging the shuttle for entry, a Russian Soyuz spacecraft is scheduled to dock with the international space station. The Soyuz TMA-14 spacecraft blasted off from the Baikonur Cosmodrome in Kazakhstan on Thursday, carrying incoming space station commander Gennady Padalka, flight engineer Michael Barratt and a wealthy space tourist, Charles Simonyi.

If all goes well, Padalka will guide the Soyuz to a docking at the space station's aft port around 9:14 a.m. Expedition 18 commander Mike Fincke, flight engineer Yuri Lonchakov and Japanese astronaut Koichi Wakata plan to welcome Padalka and his crewmates aboard the station around 12:10 p.m., less than a half-hour before Discovery's deorbit rocket firing.

"The hurricane is coming," Fincke radioed flight controllers late today. "The next crew is on their way."

Fincke, Lonchakov and Simonyi plan to return to Earth on April 7.

To provide a bit of additional clearance, a rocket firing was planned today "to phase the Discovery out in front and beneath the international space station, it'll be well out in front by the time tomorrow rolls around," said entry Flight Director Richard Jones. "As you know, yesterday there was a successful launch of a Soyuz and we have another crew that is heading to international space station. Right now, they should be docking around (9:14 a.m. EDT) tomorrow, just as the 119 crew is getting ready to enter deorbit preparations. So there's a lot of traffic up there on orbit right now."

Jones said Discovery has enough on-board supplies to stay in orbit until Tuesday at the latest and that NASA will not staff its backup landing site at Edwards Air Force Base, Calif., on Saturday or Sunday. If Discovery is still in orbit Monday morning, however, all of NASA's sites will be staffed and the shuttle will be brought down on one coast or the other.

The Spaceflight Meteorology Group at the Johnson Space Center in Houston is predicting generally acceptable weather at Kennedy Saturday with scattered clouds at 5,000 and 20,000 feet, winds from the south at 13 knots with gusts to 21 knots and a slight chance of a broken cloud deck at 5,000 feet.

The forecast worsens Sunday, with low clouds and possible thunderstorms in the area as the front moves through, but conditions are expected to improve by Monday.

"In terms of an entry strategy, we have a lot of consumables," Jones said. "What that means is, we have plenty of capability to go out until end of mission plus three, on Tuesday, if we need to. Hopefully, we won't need all of that. With that capability behind us, we'll be able to look at Kennedy Space Center tomorrow as well as Sunday, exclusively, we won't be calling up any alternative sites until Monday, that's what we call our pick-'em day. We'll be calling up Edwards and Northrup (Strip, N.M.) at that time if we we go past our KSC opportunities between now and then."

There are no technical problems of any significance with the space shuttle and NASA's Mission Management Team today officially cleared the ship's nose cap and wing leading edge panels for entry.

Here is a timeline of major entry-day events for the two Florida landing opportunities Saturday (in EDT; times subject to change; best viewed with a fixed-width font):

EDT...........EVENT

Rev. 201 Deorbit to KSC

08:33 AM......Begin deorbit timeline
08:48 AM......Radiator stow
08:58 AM......Mission specialists seat installation
09:04 AM......Computers set for deorbit prep
09:08 AM......Hydraulic system configuration
09:33 AM......Flash evaporator checkout
09:39 AM......Final payload deactivation
09:53 AM......Payload bay doors closed
10:03 AM......Mission control 'go' for OPS-3 entry software load
10:13 AM......OPS-3 transition
10:38 AM......Entry switchlist verification
10:48 AM......Deorbit maneuver update
10:53 AM......Crew entry review
11:08 AM......CDR/PLT don entry suits
11:25 AM......Inertial measurement unit alignment
11:33 AM......CDR/PLT strap in; MS suit don
11:50 AM......Shuttle steering check
11:53 AM......Hydraulic system pre start
12:00 PM......Toilet deactivation
12:08 PM......Vent doors closed for entry
12:13 PM......Mission control 'go' for deorbit burn
12:19 PM......Astronaut seat ingress
12:28 PM......Single hydraulic power unit start
	
12:33:44 PM...Deorbit ignition (dT: 3:01; dV: 231 mph)
12:36:45 PM...Deorbit burn complete

01:07:58 PM...Entry interface (range to KSC: 4,942 miles)
01:12:57 PM...1st roll command to left
01:27:56 PM...1st left-to-right roll reversal
01:30:00 PM...C-band radar acquisition
01:33:09 PM...Velocity less than mach 2.5
01:35:20 PM...Velocity less than mach 1
01:36:31 PM...Shuttle banks to line up on runway 15
01:39:42 PM...Landing


Rev. 202 Deorbit to KSC

01:48 PM......MCC 'go' for deorbit burn
01:54 PM......MS seat ingress
02:03 PM......Single APU start

02:08:44 PM...Deorbit ignition (dT: 3:01; dV: 231 mph)
02:11:45 PM...Deorbit burn complete

02:42:21 PM...Entry interface (range to KSC: 5,023 miles)
02:47:21 PM...1st roll command to right
02:56:36 PM...1st right-to-left roll reversal
03:03:00 PM...C-band radar acquisition
03:07:24 PM...Velocity less than mach 2.5
03:09:37 PM...Velocity less than mach 1
03:10:23 PM...Shuttle banks to line up on runway 15
03:13:59 PM...Landing


07:30 AM, 3/27/09, Update: Astronauts prep shuttle for Saturday landing (UPDATED at 9:45 a.m. with revised forecast; correcting landing time for second opportunity)

The Discovery astronauts worked through a busy day in orbit today, checking out the shuttle's re-entry systems and packing for the glide back to Earth Saturday to close out a challenging space station assembly mission.

The Spaceflight Meteorology Group at the Johnson Space Center in Houston is predicting generally acceptable weather ahead of an approaching front, with scattered clouds at 5,000 and 20,000 feet and winds out of 170 degrees at 13 knots with gusts to 21. That works out to a crosswind of just 5 knots or so but headwind/tailwinds up to 20 knots. Forecasters also are predicting a slight chance for a broken deck of clouds at 5,000 feet that could cause problems.

The forecast for Sunday calls for out-of-limits crosswinds gusting to 20 knots, a chance of broken clouds at 8,000 feet and possible thunderstorms within 30 nautical miles of the runway. The forecast calls for acceptable conditions in Florida on Monday.

Deorbit ignition on orbit 201 is planned for 12:33:44 p.m. Saturday with landing at the Kennedy Space Center expected around 1:39:42 p.m. A second Florida landing opportunity is available one orbit later, at 3:13:59 p.m. Entry Flight Director Richard Jones will brief reporters on his landing strategy today at 4 p.m. As of this writing, NASA does not plan to staff its backup landing sites Saturday.

Commander Lee Archambault, pilot Dominic "Tony" Antonelli and flight engineer Steven Swanson are scheduled to test Discovery's flight control systems starting at 9:43 a.m., following by test firings of the ship's small steering jets beginning at 10:58 a.m. Their crewmates - John Phillips, Richard Arnold, Joseph Acaba and returning space station flight engineer Sandra Magnus - plan to begin packing for the trip home just after 8 a.m.

A final public affairs event is scheduled for 1:03 p.m. when the astronauts will field questions from school kids in Hawaii. Later this afternoon, the astronauts will check out their pressure suits and set up a reclining seat on Discovery's lower deck for Magnus. Returning to Earth after four months in space, Magnus will make the trip home resting on her back to ease her return to the unfamiliar tug of gravity.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision Q of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/27/09
05:13 AM...11...09...30...Crew wakeup (flight day 13)
08:13 AM...11...12...30...Cabin stow begins
09:43 AM...11...14...00...Flight control system checkout
10:58 AM...11...15...15...Reaction control system hotfire
11:33 AM...11...15...50...Crew meal
12:33 PM...11...16...50...Deorbit review
01:03 PM...11...17...20...PAO event
01:23 PM...11...17...40...Cabin stow resumes
02:28 PM...11...18...45...Landing comm checks
03:43 PM...11...20...00...Ergometer stow
04:00 PM...11...20...17...Mission status briefing
04:13 PM...11...20...30...Recumbent seat setup
04:38 PM...11...20...55...Wing leading edge sensor system deactivation
04:58 PM...11...21...15...PILOT landing simulator practice
05:13 PM...11...21...30...Launch/entry suit checkout
06:18 PM...11...22...35...Computer network stow (part 1)
06:38 PM...11...22...55...KU antenna stow
09:13 PM...12...01...30...Crew sleep begins
10:00 PM...12...02...17...Daily highlights reel

03/28/09
05:13 AM...12...09...30...Crew wakeup (flight day 14)
07:53 AM...12...12...10...Inertial measurement unit alignment
08:38 AM...12...12...55...Deorbit timeline begins
09:14 AM...12...13...31...Soyuz TMA-14 docking with space station
10:00 AM...12...14...17...Payload bay door closing
12:10 PM...12...16...27...Soyuz TMA-14 hatch opening
12:33 PM...12...16...50...Deorbit ignition (rev. 201)
01:30 PM...12...17...47...MILA C-band radar acquisition
01:39 PM...12...17...56...Landing
02:00 PM...12...18...17...Soyuz TMA-14 post-docking video file
The astronauts have two landing opportunities in Florida on Saturday and multiple opportunities at Kennedy, Edwards Air Force Base in California's Mojave Desert and Northrup Strip in New Mexico on Sunday and Monday. Here are the latest deorbit and landing times for all of those opportunities (in EDT throughout):

ORBIT...SITE...TIG.......LANDING.....WEATHER

Saturday, March 28:

201.....KSC....12:33 PM...01:39 PM...SCT050 SCT200, 17013P21
202.....KSC....02:08 PM...03:14 PM...SLGT CHC BKN05

Sunday, March 29:

217.....KSC....01:00 PM...02:02 PM...SCT030 BKN080, 26013P21,
218.....KSC....02:35 PM...03:37 PM...CHC BKN030 CHC TSRA WI 30NM

219.....EDW....04:05 PM...05:07 PM...SCT250, 26020P30
220.....EDW....05:41 PM...06:42 PM

Monday, March 30:

232.....KSC....11:48 AM...12:50 PM...FEW030 SCT250 06006P12
233.....KSC....01:32 PM...02:25 PM

234.....EDW....02:54 PM...03:56 PM...SKC, 06008P13
........NOR....02:55 PM...03:57 PM

235.....EDW....04:29 PM...05:31 PM
........NOR....04:31 PM...05:33 PM


6:15 AM, 3/26/09, Update: Soyuz rocket set for launch; shuttle crew heat shield inspection on tap (UPDATED at 8:45 a.m. with Soyuz launch)

As the shuttle Discovery orbited more than 70 miles in front of the international space station, a Russian Soyuz rocket took off today from the Baikonur Cosmodrome in Kazakhstan carrying the station's next commander, a NASA doctor and a wealthy space tourist.

With Expedition 19 commander Gennady Padalka and flight engineer-physician Michael Barratt at the controls, the Soyuz TMA-14 spacecraft blasted off from site 254 - Yuri Gagarin's launch pad - at 7:49:18 a.m. EDT. Joining them for the two-day trip to the station was Charles Simonyi, a Hungarian-born U.S. software developer making his second multi-million-dollar visit to the lab complex.

Soyuz TMA-14 blasts off from Kazakhstan

Today's launching appeared flawless and nine minutes after liftoff, the Soyuz slipped into its planned preliminary orbit. There were no technical problems of any significance and the crew was in good spirits.

Padalka and Barratt will join Japanese astronaut Koichi Wakata aboard the station and replace Expedition 18 commander Mike Fincke and flight engineer Yury Lonchakov, who are in the final days of a five-and-a-half-month tour of duty. Fincke, Lonchakov and Simonyi will return to Earth April 7 aboard the Soyuz TMA-13 spacecraft that carried the outgoing station fliers into orbit last October.

Wakata, Japan's first long-duration station crew member, hitched a ride to the outpost aboard Discovery. He replaced outgoing flight engineer Sandra Magnus, who is returning to Earth aboard the shuttle after a four-month stay in space.

Today's launching marks a milestone for NASA and the Russian space agency, the first of two flights intended to boost the station's crew size from three to six. In late May, another Soyuz is scheduled for launch to carry three more crew members to the lab: cosmonaut Roman Romanenko, a second-generation cosmonaut, European Space Agency astronaut Frank De Winne of Belgium and Canadian Space Agency astronaut Robert Thirsk, a shuttle veteran.

Discovery's crew helped pave the way to six-person crew operations by delivering and installing a fourth and final set of solar arrays, doubling the amount of power available for science operations, and a replacement centrifuge for the station's water recycling system.

"To put this into perspective, it's not just that we're doubling the crew size, we're actually up manning to adequately staff the space station, if you will," Barratt said. "It's very large and very complex and to get the maximum productivity out of it, we need six pairs of hands aboard.

"So for that reason, we all understand that whatever small difficulties there are in dealing with that many more bodies and competing for resources, we need that many bodies and there's a lot more to pitch in when help is needed and again, to get the maximum productivity out of it."

If all goes well, Padalka, Barratt and Simonyi will dock with the space station urday around 9:14 a.m., just four-and-a-half hours before Discovery's planned landing at the Kennedy Space Center to close out the 125th shuttle mission. Touchdown at the shuttle landing strip is targeted for 1:38 p.m.

The shuttle crew plans to unlimber the ship's robot arm later this morning for a post-undocking inspection of the ship's reinforced carbon carbon nose cap and wing leading edge panels. The inspection is designed to spot any impact damage that might have occurred since an identical survey was carried out the day after launch. The astronauts plan to pack Friday for the trip home.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision P of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/26/09
06:13 AM...10...10...30...Crew wakeup
07:00 AM...10...11...17...HD highlights
07:00 AM...10...11...17...Soyuz TMA-14 launch coverage begins
07:49 AM...10...12...06...Soyuz TMA-14 launch
09:13 AM...10...13...30...Spacesuit install
09:13 AM...10...13...30...Inspection boom (OBSS) unberth
09:43 AM...10...14...00...EVA unpack/stow
10:00 AM...10...14...17...Soyuz TMA-14 post-launch video file
10:13 AM...10...14...30...Post-undocking EVA entry prep
10:28 AM...10...14...45...Starboard wing survey
12:08 PM...10...16...25...Nose cap survey
12:58 PM...10...17...15...Joint crew meal
01:58 PM...10...18...15...Port wing survey
03:30 PM...10...19...47...Mission status briefing
03:43 PM...10...20...00...OBSS berthing
04:43 PM...10...21...00...Robot arm powerdown
05:08 PM...10...21...25...L-1 comm checks
05:28 PM...10...21...45...Crew choice downlink
09:13 PM...11...01...30...Crew sleep begins
10:00 PM...11...02...17...Daily highlights reel


4:30 AM, 3/26/09, Update: Spectacular time-lapse video of space station fly-around

Spaceflightnow.com has posted a dramatic one-minute 10-second version of the shuttle Discovery's fly-around of the international space station Wednesday. The fast-action time-lapse video begins with Discovery directly in front of the lab complex and follows the station through most of a complete loop. This was one of the most visually stunning fly-arounds yet seen and with the station now boasting a complete set of solar arrays, the complex has finally taken on a long-awaited "assembly complete" appearance.

Still image from space station fly-around


07:30 PM, 3/25/09, Update: Dramatic undocking/fly-around photos

The Discovery astronauts downlinked spectacular video late today showing the international space station during a slow 360-degree fly-around, with its newly installed S6 solar arrays giving the lab complex a symmetric appearance that finally matches the engineering drawings that started the program.

Looking at an initial snapshot of the space station taken as Discovery undocked and pulled away earlier today, lead Flight Director Kwatsi Alibaruho called the view "the $100 billion photograph," referring to the lab's presumed price tag.

"The photograph kind of shows it all," said Dan Hartman, chairman of NASA's space station Mission Management Team. "We're just very, very proud to see our integrated truss assembly complete, solar arrays deployed. The S6 element is working perfectly, we're working no anomalies associated with it and we couldn't be happier."

Looking down on the space station; the new S6
solar arrays are visible at far left

Shuttle Discovery above Mexico, as seen from the space station

Against the limb of the Earth; the new S6 solar arrays
are visible at the far left, white radiator panels flank
the central pressurized modules

Shuttle Discovery behind the space station

"We've certainly achieved a very important milestone," Alibaruho said of Discovery's mission. "We had a successful undocking of the space shuttle Discovery from the ISS. The undocking operations were smooth, everything occurred on time, there were no issues and we got all the cargo transferred that we needed to get transferred, including the double cold bags with the science samples.

"Those bags containing some 75-plus vials of urine and blood and other biological samples. We got all that stuff packed on the shuttle and ready to come down. We also transferred water samples from the ISS water recovery system. Those samples are the ones that are needed for the post-flight analysis that will be used to clear the system for use by six-person crew. So that was a tremendous success for us.

"And of course, the final mission objective ... was making sure we enabled the shuttle to get a good picture of the international space station with the newly installed solar arrays."

The international space station


3:55 PM, 3/25/09, Update: Shuttle Discovery undocks from international space station

With pilot Dominic "Tony" Antonelli at the controls, the shuttle Discovery undocked from the international space station today at 3:53 p.m. as the two spacecraft sailed 220 miles above the Indian Ocean to close out a challenging three-spacewalk assembly mission.

"Houston and Alpha, Physical separation," a shuttle astronaut radioed.

Shuttle Discovery separates from space station

As the 105-ton shuttle slowly pulled away directly in front of the 346-ton space station, Expedition 18 flight engineer Koichi Wakata rang the ship's bell, intoning "space shuttle Discovery (departing)."

"Discovery, Alpha, Godspeed," station commander Mike Fincke radioed. "Thanks for making us symmetrical, giving us full power, and all the other wonderful things you did for us. You did great work. Come again."

"Thanks for the great work as well," shuttle commander Lee Archambault replied. "Have a good one, we'll see you on the ground in about a month."

With its nose pointed toward deep space and its open payload bay facing the station, Discovery slowly separated in the direction of travel. Piloting the orbiter from the aft flight deck, Antonelli planned to manually guide the ship through a 360-degree loop around the outpost while his crewmates photographed the lab and its now-complete set of solar arrays with a variety of cameras.

GoogleTrack map showing undocking location

The fly-around was timed to begin at orbital sunrise, ensuring good lighting for the long-awaited pictures. But flight controllers - and the public - had to wait for a video replay. The shuttle's KU-band television antenna was not expected to have a good link with NASA's relay satellites until after the fly-around was complete.

"Just want to give you an update, we will have KU all the way through undocking time and 10 minutes after undocking," astronaut Greg Johnson radioed from Houston. "At that point, we will lose KU for about an hour and 25 minutes. We will get KU back after sep 1 burn."

"Oh, OK, that's unfortunate," said Archambault. "We were hoping to give you guys a live downlink. But we'll certainly tape it all and play it back some other time."


01:45 PM, 3/25/09, Update: Shuttle crew bids station astros farewell

Closing out a busy assembly mission, the Discovery astronauts, accompanied by outgoing station flight engineer Sandra Magnus, said farewell to the international space station's three-man crew today and floated out of the lab complex for the last time to rig the shuttle for undocking at 3:53 p.m.

Gathered in the Harmony connecting module in front of the port leading to Discovery, station commander Mike Fincke thanked shuttle skipper Lee Archambault and his crewmates for delivering a final set of solar arrays and other critical equipment, along with Magnus' replacement, Japanese astronaut Koichi Wakata.

Lee Archambault bids farewell to station commander Mike Fincke

"I'd like to say thanks to you and your crew for an outstanding mission," Fincke said. "You made the space station much better than it was before, you gave us more power ... you gave us a new crew member, you're giving Sandy a ride back home. You brought up some equipment we really needed for a six-person crew.

"That's what we were really hoping to get done with Expedition 18. And Sandy, the six-person crew, when they get up here (in late May), they're going to be thanking you for all your organization, all your hard work, the things that you built on board. You've done an outstanding job and I'd like to say thank you."

Launched aboard the shuttle Endeavour last November, Magnus is wrapping up a four-month stay aboard the station. Wakata plans to remain aboard the outpost until June when another shuttle will deliver his replacement.

Fincke and flight engineer Yury Lonchakov are scheduled to return to Earth on April 7 aboard the Soyuz TMA-13 spacecraft they rode into orbit last October. Their replacements - Expedition 19 commander Gennady Padalka and flight engineer Michael Barratt - are scheduled for launch Thursday at 7:49 a.m. EDT from the Baikonur Cosmodrome in Kazakhstan.

Padallka, Barratt and Wakata will be joined in late May by cosmonaut Roman Romanenko, European Space Agency astronaut Frank De Winne, a Belgian, and Canadian Space Agency astronaut Robert Thirsk, a shuttle veteran, boosting the station's crew size to six.

At a pre-launch news conference, Barratt, a former NASA flight surgeon, said the busy pace of crew exchanges and assembly missions, along with the planned increase to six full-time crew members, illustrates the growing maturity of the space station program.

"The requirement for a complex air traffic control system on the ground is a symbol of a vibrant and busy air transportation system, and I think it's exactly the same for us," he said. "It will make things a little bit harder, but I for one welcome this complexity. It's a sign of a vibrant space program and it's only going to get better - or worse! - depending on your point of view."

Assuming an on-time liftoff Thursday, the Soyuz TMA-14 craft carrying Padalka, Barratt and space tourist Charles Simonyi will dock with the space station urday morning, a few hours before Discovery's planned landing. Simonyi will return to Earth with Fincke and Lonchakov.

Aboard the station today, Fincke told the Discovery astronauts that saying farewell "is the toughest part of the mission, at least to me. On the one hand, it's a moment of triumph. And yet on the other hand, we're going to really be missing you. It was really great having you up here. All the things we got to talk about and do together, that's what the dreams in our lives are made of. So thank you everybody, thank you very much."

Fincke packs experiment samples in a 'cold pack'
for return aboard Discovery

Archambault, in turn, thanked Fincke and Lonchakov, saying "we are very, very appreciative for the hospitality you all extended to us."

"You were very well prepared for us, you were happy to help us where we needed help and you were key and instrumental in getting three good EVAs (spacewalks) out the door and back in safely," Archambault said. "We're very proud to have left the space station with more power, hopefully power that for many, many years will provide very, very useful research to your future payloads."

Magnus floated across the "top" of the Harmony module above the heads of her shuttle crewmates. Wakata floated just below in the hatch leading to the European Space Agency's Columbus module.

"And Koichi, it's going to be tough to leave you," Archambault said. "You're always going to be a member of STS-119, you've done a lot of great work for us and I wish you the very best. We do look forward to seeing you back in Houston."

Finally, he added to Fincke: "you're an awesome commander. Best of luck. You've got just another couple of weeks here. Have happy travels and let's get together when you get back. Thank you very much."

The shuttle crew then floated through the docking port and out of sight into the space shuttle. Last to leave were Magnus and Archambault. The shuttle hatch was closed a few minutes later.


8:00 AM, 3/25/09, Update: Astronauts prepare for undocking

The Discovery astronauts prepared for undocking today, working through a busy timeline of packing and experiment sample transfers from the space station to the shuttle. After a final joint meal with their space station colleagues, the combined crews will hold a brief farewell ceremony around 1 p.m. before closing hatches for the shuttle's departure at 3:53 p.m.

Joining the shuttle crew for the trip home will be outgoing space station flight engineer Sandra Magnus, who is wrapping up a four-month stay in space. Her replacement, Japanese astronaut Koichi Wakata, will remain behind in her place with Expedition 18 commander Mike Fincke and flight engineer Yury Lonchakov.

"I appreciate everyone's help, everyone's support, everyone's patience and understanding as we've done the work up here and I really look forward to seeing you all on the ground," Magnus radioed today during her final space station planning conference. "So I'll say goodbye from the space station this last time."

"Goodbye, Sandy," mission control replied. "Have a safe trip home."

Fincke and Lonchakov plan to return to Earth April 7 aboard the Soyuz TMA-13 spacecraft that carried them into orbit last October. Their replacements, Expedition 19 commander Gennady Padalka and NASA flight engineer Michael Barratt, are scheduled for launch Thursday at 7:49 a.m. from the Baikonur Cosmodrome in Kazakhstan aboard the Soyuz TMA-14 ferry craft.

Soyuz TMA-13, foreground, and Progress supply craft docked to space station

If all goes well, Padalka, Barratt and U.S. space tourist Charles Simonyi will dock with the station at 9:14 a.m. urday, about four-and-a-half hours before the shuttle Discovery lands back at the Kennedy Space Center in Florida. Simonyi, making his second $35 million trip to the station, will return to Earth with Fincke and Lonchakov.

To make way for the Soyuz mission, Discovery's astronauts had to undock today at the latest. Shuttle crews normally say farewell and close hatches the day before undocking to make departure day a bit more relaxed, but the Soyuz deadline prompted NASA managers to replan the Discovery crew's departure, delaying hatch closure and the transfer of frozen experiment samples until the last minute.

The experiment samples must remain frozen. Some will be packed in a shuttle freezer, but the rest will be packed in double cold bags. The delayed hatch closure and cold pack transfers will give the samples the maximum possible shelf life aboard the shuttle in case of any weather-related landing delays.

Along with the experiment samples, the Discovery astronauts also will be bringing water samples back to Earth from the station's new urine recycling system. The water recovery system has had problems since it was first activated late last year, but a new distillation assembly centrifuge installed during the shuttle mission appears to be working normally and engineers are hopeful the samples will confirm the system can be used by future station crews.

This morning, the astronauts will pack "some of the last items of cargo that are going to be transferred from the space station to the shuttle," said Flight Director Kwatsi Alibaruho. "That includes some of the scientific samples that are going to be coming back in those double cold bags we talked about earlier. The crew will also take the final water samples that we have from the WRS, the water recovery system, so those samples can be returned home and examined to perhaps clear the system for use by a six person crew."

Padalka, Barratt and Wakata will prepare the lab complex for the arrival of three more full-time crew members - Russian cosmonaut Roman Romanenko, European Space Agency astronaut Frank De Winne of Belgium and Canadian Space Agency astronaut Robert Thirsk - in late May.

"The station's in great shape," deputy Program Manager Kirk Shireman said Tuesday in Baikonur. "We're very excited about having the new solar arrays there. The urine processor went through the first wet cycle yesterday and it ran for about four hours, very successfully. Of course, we'll be testing it continuously here over the weeks coming before we launch the six-person crew. So again, the space station couldn't be in better shape, we're very pleased with how things are going."

After the shuttle-station "stack" is maneuvered into the undocking orientation with Discovery's belly facing the direction of travel, the docking system on the forward port will disengage at 3:53 p.m.

With pilot Dominic "Tony" Antonelli at the controls, Discovery will pull straight away from the station's forward docking port and then loop around the lab complex for a photo survey, giving flight controllers and the public their first wide-angle look at the station with its completed solar power system. The primary goal of Discovery's mission was installation of a fourth and final set of arrays on the right end of the station's main power truss.

The newly installed S6 solar arrays (far right)

"I'll be very excited," Antonelli said in a NASA interview. "First, because I'll get to get my first crack at flying the space shuttle, which is kind of what I'm in the business to do. So I'm really looking forward to the undocking and separation and the whole fly around, getting to take pictures of the space station. (We will) get pictures now for the first time looking like how the artists have been drawing it for so many years."

Alibaruho said the fly-around is "partially to get good imagery of the space station, not just for posterity, but also to inspect the vehicle for any damage that we may not have been able to see with the space station's external cameras. We're not looking for anything specifically, just sort of a general photographic survey to inspect the general condition of the space station as well as see the fruits of the astronauts' labor."

Said shuttle commander Lee Archambault: "When we pull out for the undock and fly around, which our pilot Tony Antonelli will be doing, at that point, really for the first time we'll probably look at the station and say, 'there it is.' "It'll be a real sense of mission accomplishment. We've done our job. We've delivered the S6 truss. We've installed it. It's out there working and producing power for the space station.

"It's the first time that we'll really absorb it all and, by the way, that's also the first time we'll actually be able to send pictures to the ground, both stills and video, showing the space station in its newest configuration. When we do all that, the sense of accomplishment will be phenomenal."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision O of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/25/09 06:13 AM...09...10...30...Crew wakeup 07:43 AM...09...12...00...ISS daily planning conference 09:13 AM...09...13...30...Post spacewalk reconfig 09:43 AM...09...14...00...Water samples 10:18 AM...09...14...35...Experiment cold bag pack 10:53 AM...09...15...10...Rendezvous tools checkout 11:38 AM...09...15...55...Experiment cold bag transfer 11:53 AM...09...16...10...Joint crew meal 12:53 PM...09...17...10...Farewell ceremony 01:08 PM...09...17...25...Egress and hatch closure 01:38 PM...09...17...55...Leak checks 02:23 PM...09...18...40...Group B computer powerup

02:37 PM...09...18...54...Maneuver to undocking attitude 02:42 PM...09...18...59...Sunrise 03:06 PM...09...19...23...ISS in undockling orientation 03:10 PM...09...19...27...Noon 03:23 PM...09...19...40...U.S. Ku-band antenna parked 03:33 PM...09...19...50...PMA-2 prepped for undocking 03:34 PM...09...19...51...Russian arrays feathered 03:37 PM...09...19...54...Sunset

03:53 PM...09...20...10...UNDOCKING

03:54 PM...09...20...11...Initial separation 03:54 PM...09...20...11...ISS holds attitude 03:58 PM...09...20...15...Range: 50 feet; reselect -X jets 03:58 PM...09...20...15...PMA-2 depressurization 04:00 PM...09...20...17...Range 75 feet; low Z 04:09 PM...09...20...26...Russian arrays resume sun track 04:13 PM...09...20...30...Sunrise 04:22 PM...09...20...39...Range: 400 feet; start fly around 04:31 PM...09...20...48...Range: 600 feet 04:33 PM...09...20...50...Shuttle directly above ISS 04:41 PM...09...20...58...Noon 04:43 PM...09...21...00...U.S. arrays resume sun track 04:43 PM...09...21...00...ISS in TEA attitude 04:45 PM...09...21...02...Shuttle directly behind ISS 04:56 PM...09...21...13...Shuttle directly below ISS 05:08 PM...09...21...25...Separation burn No. 1 05:09 PM...09...21...26...Sunset 05:36 PM...09...21...53...Separation burn No. 2

05:38 PM...09...21...55...Post undocking computer reconfig 05:53 PM...09...22...10...Group B computer powerdown 05:53 PM...09...22...10...ISS management conference 06:00 PM...09...22...17...Mission status briefing 06:18 PM...09...22...35...Undocking playback ops 06:28 PM...09...22...45...ISS daily planning conference 07:43 PM...10...00...00...Crew choice downlink 08:04 PM...10...00...21...JAXA PAO event 09:00 PM...10...01...17...JAXA PAO event replay 10:13 PM...10...02...30...Crew sleep begins 11:00 PM...10...03...17...Daily highlights reel


5:10 PM, 3/24/09, Update: Astronauts enjoy quiet day before undocking

After taking a phone call from President Barack Obama, the Discovery astronauts and their space station colleagues transferred spacesuits and equipment back to the shuttle and took the afternoon off before a busy day Wednesday completing final transfers and undocking from the international lab complex.

The presidential phone call "was a special treat for the crew," lead Flight Director Kwatsi Alibaruho told reporters. "That downlink event went very well and I know both the president and his guests, as well as the crew, I'm sure they all enjoyed that."

Shuttle Discovery above Florida

On the eve of undocking, the astronauts were about 78 percent complete with work to transfer equipment and experiment samples from the station to the shuttle for return to Earth. The most critical return items - frozen biological samples and 4 to 5 liters of water from the station's new urine recycling system - will be transferred Wednesday.

Visiting shuttle astronauts normally finish transfers and close hatches between the shuttle and the station the day before undocking to make separation day a bit less rushed. But to protect against the possibility of weather delays, NASA managers decided to wait until the last minute to close the hatches this time around to make sure the experiment samples, some stored in a shuttle freezer and the rest in double cold packs, have a sufficient shelf life.

As a result, flight planners gave the astronauts a second half-day of off-duty time today.

"With all the spacewalks we've done and all the assembly activities, they've had a limited amount of time just to kick back and share experiences, both the Discovery crew and the space station crew, share their experiences with each other and just have some time for fellowship," Alibaruho said. "So, that's something they were able to do today that they very much enjoyed.

"Tomorrow will be a busy day of course. We'll start with the packing of some of the last items of cargo that are going to be transferred from the space station to the shuttle. That includes some of the scientific samples that are going to be coming back in those double cold bags we talked about earlier. The crew will also take the final water samples that we have from the WRS, the water recovery system, so those samples can be returned home and examined to perhaps clear the system for use by a six-person crew."

Under the revised flight plan, the two crews will gather for a brief farewell ceremony in the Harmony module around 1 p.m. before closing hatches between the two spacecraft and carrying out leak checks. Undocking is targeted for 3:53 p.m. Shuttle pilot Dominic "Tony" Antonelli plans to guide the shuttle through a complete loop around the station, giving engineers and the public a look at the lab's now-complete set of solar arrays.

"They'll take pictures of the space station so we can see how it looks with all of its solar arrays completely unfurled and in a symmetric configuration," Alibaruho said. "The shuttle will execute separation burns and move to a lower orbit where it will remain for a day or so in preparation for landing on urday at the Kennedy Space Center."


10:45 AM, 3/24/09, Update: President Obama calls shuttle-station crew

President Barack Obama, hosting school kids and members of Congress, called the crews of the shuttle Discovery and the international space station today, quizzing the astronauts about life in space and offering congratulations for a successful station assembly mission.

Calling from the White House as the shuttle-station complex sailed 220 miles above the southern tip of South America, Obama chatted easily, relaying questions from school children and fellow law makers.

"Hello, commander, can you hear us?" Obama called.

"Mr. President, welcome aboard the international space station where we are joined with our international crew from the space shuttle Discovery," commander Mike Fincke replied. "Welcome aboard, glad to hear your voice, we hear you loud and clear, sir."

"Well, thank you so much for taking the time to speak with us," Obama sad. "We've got a crew of wonderful school children here who are all interested in space and we've got some members of Congress who are like big kids when it comes to talking to astronauts. I'm told you're cruising at about 17,000 mph so we're glad you are using the hands-free phone."

"Mr. President, we go around the planet once every 90 minutes. It's quite a thrill and it is very fast. We see 16 sunrises and 16 sunsets every day."

"That is unbelievable," Obama said. "Well, the first thing we want to do is just let you know how proud we are of you."

The astronauts talk to President Obama

The seven-member shuttle crew - commander Lee Archambault, pilot Dominic "Tony" Antonelli, John Phillips, Sandra Magnus and spacewalkers Steven Swanson, Joseph Acaba and Richard Arnold - joined Fincke, flight engineer Yury Lonchakov and Koichi Wakata in the station's Harmony connecting module to take the presidential phone call.

Discovery's crew delivered and installed a fourth and final set of solar arrays for the space station, a new urine processor system centrifuge and Wakata, Japan's first long-duration astronaut. He replaced Magnus, who will return to Earth aboard Discovery after four months in space.

Swanson, Acaba and Arnold carried out three spacewalks and while they accomplished all of the mission's primary objectives, they were unable to deploy an external cargo platform when its mechanism jammed. As a result, deployment of a second storage platform was deferred, along with work to re-wire an electrical patch panel.

If all goes well, the shuttle will undock from the station at 3:53 p.m. Wednesday. After a final heat shield inspection Thursday, the astronauts will pack up and return to the Kennedy Space Center urday, landing around 1:43 p.m.

"We are really excited about the project you are doing," Obama radioed. "This is really exciting because we're investing back here on the ground (in) a whole array of solar and other renewable energy projects. And so, to find out you're doing this up at the space station is particularly exciting."

After asking how the astronauts installed the station's new arrays, the president said "obviously, we're really proud about the extraordinary work our American astronauts are doing. You are representative of the dedication and sense of adventure and discovery that we're so proud of.

"But one of the things that's so wonderful about this is that it is an international space station and I know we have our Japanese and Russian counterparts on board as well. We'd love to say hello to them and hope this is an example of the kind of spirit of cooperation we can apply not just in space but here on the ground as ell."

"It's an honor to have a chance to talk with you, Mr. President," Wakata replied. "We have a Russian crew member, and American crew member and I'm from Japan. We have 16 countries working together in this wonderful project, the international space station. ... It really symbolizes the future of the scientific development of the world. And I'm just happy to be part of this."

Said Lonchakov, a Russian cosmonaut: "Mr. President, we work together to do everything. It's really, really important for us."

Obama quizzed the astronauts on the research being conducted on the station, asking how much time the crew spends on science and simply maintaining the outpost.

"Well sir, we have experiments already up here that we've been doing for many years, we'll be able to double that with the addition of the solar array that our shuttle friends brought up. We do a lot of experiments on combustion, understanding materials. You know, we're guinea pigs, so understanding how people's bodies change in space. All this is in preparation for long-duration missions to moon and Mars.

"And the exciting thing about doing science up here is we really don't know what we don't know. And that gives you the greatest potential for learning. And we've had a lot of cases where people have sent up experiments and we've conducted them here on the space station only to find out we've learned something new, something more about the fundamentals about the processes and the science. So it's a really great place to learn a lot."

Magnus wears her hair long and it floats out in zero gravity. Obama asked, "were you tempted to cut your hair shorter while you were up there?"

"That's a really good question," Magnus replied. "Because there's a little bit of overhead to take care of long hair here. I think ideally, a short haircut's the way to go but quite frankly, on me it wouldn't be so nice. So I kept it long."

"I think it's a real fashion statement," Obama laughed.


7:20 AM, 3/24/09, Update: Crew gets more time off; preps for undocking

The Discovery astronauts were given another half-day off today before undocking Wednesday to begin wrapping up a busy space station assembly mission. A traditional joint crew news conference is planned for 1:05 p.m. Crew off-duty time begins an hour later.

"Good morning from Discovery," astronaut John Phillips radioed at crew wakeup. "It's great to hear from you and it's great to wake up to the sounds of the Houston band Tree Stump, including my daughter on bass guitar. We're looking forward to a day of getting our big motor home ready for the open road and pulling out of the driveway."

NASA TV will carry b-roll footage of the Soyuz TMA-14 rollout to the launch pad at the Baikonur Cosmodrome in Kazakhstan at 11 a.m., showing preparations for launch of a new station crew at 7:49 a.m. Thursday. NTV also will air launch footage shot by cameras mounted in the shuttle Discovery's solid-fuel booster rockets at 3 p.m.

Today "will be largely an off-duty day for both the shuttle and the station crews," said station Flight Director Kwatsi Alibaruho. "They're basically going to enjoy some well-earned, well-deserved, much-needed time off. It's very important for us to rest the orbiter crew particularly, since in just a few days from now they're going to have to successfully execute re-entry and landing, and do that accurately."

A few equipment transfers are planned, along with other preparations for undocking at 3:53 p.m. Wednesday. The combined crews will pose for a traditional joint crew photo and share a meal before off-duty time begins.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision K of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/24/09 Tue 06:13 AM...08...10...30...Crew wakeup Tue 08:13 AM...08...12...30...ISS daily planning conference Tue 09:48 AM...08...14...05...PAO event Tue 10:23 AM...08...14...40...Oxygen system teardown Tue 11:03 AM...08...15...20...Post-EVA reconfig/transfer Tue 12:03 PM...08...16...20...Joint meal Tue 01:03 PM...08...17...20...Crew news conference Tue 01:43 PM...08...18...00...Crew photo Tue 02:03 PM...08...18...20...Shuttle crew off duty Tue 06:38 PM...08...22...55...Rendezvous tools checkout Tue 06:58 PM...08...23...15...ISS evening planning conference Tue 09:43 PM...09...02...00...ISS crew sleep begins Tue 10:13 PM...09...02...30...STS crew sleep begins


9:10 PM, 3/23/09, Update: Urine processor working normally; engineers assess cargo carrier problem for fix by station or future shuttle crew

The failure to fully deploy an external cargo carrier mechanism during the Discovery crew's final spacewalk today will have no immediate impact on space station assembly, the flight director said today. The jammed carrier, intended to support pallets carrying spare parts and other equipment for downstream use, may be repaired by the station crew or astronauts on an upcoming assembly flight.

"All in all, it was a very productive spacewalk," lead Flight Director Kwatsi Alibaruho said. "We did learn several things about what might be ailing that mechanism and we're certainly going to look toward plans for remediating that in the future.

"This, of course, was the third and final spacewalk for the mission. So tomorrow will be largely an off-duty day for the crew. The day after tomorrow, on Wednesday, the crew will be preparing for the final transfers of equipment and logistics supplies as well as hatch closure and subsequently, undocking."

Undocking is targeted for 3:53 p.m. Wednesday. If all goes well, Discovery will land back at the Kennedy Space Center around 1:44 p.m. urday.

"Overall, we're absolutely thrilled and very happy that we were able to accomplish what we did," Alibaruho said. "We certainly accomplished our highest priority objectives and certainly the ones that we were most concerned about were executed flawlessly."

Alibaruho said the station's complex water recycling system, including a repaired urine processing assembly, appears to be working normally after installation of a new distillation centrifuge unit Friday. After initial tests and checkout, the astronauts ran a water sample through the system overnight and no problems were reported.

"We had great success with the operation of the urine processor assembly," Alibaruho said. "We were able to perform the full processing cycle of about 70 pounds of urine that has been washed through the urine processor and has been converted into clean water. So we're very excited about that.

"The new distillation assembly appears to have performed very well, with no anomalies. In fact, we got a report from the crew that all-around performance of that unit was much better from a vibration perspective and an acoustic perspective. So that gives us some indication that that new distillation assembly that we flew up is in good shape and quite healthy. So we're very excited about that activity today."

The water recycling system is designed to convert condensate and urine into potable water for drinking, crew hygiene and oxygen generation. The urine processor was installed during a shuttle flight last November, but the vacuum distillation assembly centrifuge malfunctioned and eventually failed.

Getting the recycling system up and running is critical for NASA's plans to boost station crew size from three to six in late May. While the station has enough fresh water to support six astronauts in the near term, recycling is required for long-term support.

"What's next on the plate for checkout of our advanced life support systems equipment is basically to take end-of-mission water samples from various places in the water recycling loop, from some of the sensor areas that look at water quality, we take a sample from the actual galley water dispenser, the ambient temperature line and the hot temperature line, as well as the rack interface area where we make the connection of the water recycler rack to the main water buss in the U.S. laboratory," Alibaruho.

"So we'll take about four samples, four water samples, for return home," he said. "Those will be analyzed by specialists to determine if the whole system can be cleared for use by the crew. So those water samples were a very important mission objective for us in addition to the installation of the (S6 solar array) truss and deployment of the solar arrays, of course."

He said it likely will take about a month to complete analysis of the returned water samples. Assuming they meet the required standards, the station crew will be cleared to begin using recycled water.


6:15 PM, 3/23/09, Update: Spacewalk No. 3 ends

Astronauts Richard Arnold and Joseph Acaba began repressurizing the space station's Quest airlock at 6:04 p.m., closing out a six-hour 27-minute spacewalk, the third and final excursion planned for the shuttle Discovery's crew.

Arnold and Acaba successfully repositioned an equipment cart, installed a new cart coupler, inspected and lubricated the grapple snares on one end of the station's robot arm and reconfigured clamps on two ammonia coolant jumpers in the lab's thermal control system.

Ricky Arnold's helmet cam view of the station arm's grapple fixture

But they were unable to fully deploy a jammed cargo carrier mechanism on the station's left-side power truss that Acaba and Steven Swanson first attempted to extend urday. Despite repeated efforts to force the mechanism into position, the unpressurized cargo carrier attachment system, or UCCAS, refused to budge. Acaba and Arnold then tied it down with straps to prevent inadvertent movement.

Because of the problem with the UCCAS hardware, flight controllers told the spacewalkers to forego deploying a second cargo attachment system on the right side of the station's power truss that uses a similar mechanism. Engineers will study the problem and another repair attempt likely will be made on an upcoming shuttle flight.

Arnold and Acaba also never got around to reconfiguring an electrical patch panel on the zenith 1, or Z1, truss. Because of an earlier problem, one of the station's four stabilizing gyroscopes is tied into another gyro's control circuitry and astronauts have been unable to free a jammed connector to restore normal redundancy.

This was the 123rd spacewalk devoted to station assembly and maintenance since construction began in 1998, the third and final EVA for Discovery's crew and the second for Arnold and Acaba. EVA time for all three Discovery spacewalks stands at 19 hours and four minutes while total station EVA time stands at 775 hours even.


4:00 PM, 3/23/09, Update: Cargo carrier securely tied down; spacewalkers move to final tasks

Spacewalkers Joseph Acaba and Richard Arnold, unable to deploy a jammed cargo carrier today, strapped the mechanism down to prevent any inadvertent movement and pressed on with work to inspect and lubricate a robot arm grapple fixture and replace a coupler on a crew equipment cart.

"Great work out there, guys," astronaut Steven Swanson radioed the spacewalkers as they finished securing the jammed carrier mechanism. "I know it didn't turn out the way we wanted it to, but you guys did a great job of getting it in a safe config."

Ricky Arnold near the station's robot arm

The only other remaining task is work to reconfigure a wiring patch panel in the zenith 1, or Z1, truss to restore full redundancy to gyro control circuits. The planned deployment of a cargo carrier mechanism on the right side of the station's power truss was called off because of problems with the jammed carrier on the port side.


2:25 PM, 3/23/09, Update: Astronauts free jammed pin but cargo carrier doesn't budge

When elbow grease wasn't enough, spacewalkers Joseph Acaba and Richard Arnold retrieved a hammer from the space station's airlock and whacked a jammed locking pin to get it out of the way and free an external cargo carrier for full deployment. But with the adjustable diameter pin, or ADP, finally out of the way, the carrier mechanism still failed to extend properly.

Arnold made another attempt to muscle the mechanism into place, but he was not successful. Both astronauts then inspected the mechanism again, looking for any sign of what might be causing the problem.

"You know, it's rotating there, you see where it's going, right Ricky?"

"It just looks like a simple hinge there," Arnold said.

"I know. If you look along the line of it, I don't see anything in the way."

Helmet cam view of cargo carrier mechanism

Pushing together, the spacewalkers made two final attempts to force the mechanism into place.

"Three, two, one, go." one said as they began pushing.

"Negative," someone observed.

Acaba, left, working on cargo carrier mechanism

After a second attempt, flight controllers in Houston told Arnold and Acaba to strap the mechanism down and move on to other tasks.

"Basically, we concur with your assessment of it that we're going to need to study this thing some more," Rick Davis radioed from mission control. "So what we would like to do is implement the long-duration tie down at this time."

Because of the problems with the port-side cargo carrier, the spacewalkers were told not to attempt deployment of another cargo carrier on the right side of the station's main truss that employs a similar mechanism.


1:20 PM, 3/23/09, Update: CETA cart repositioned

Astronaut Joseph Acaba, anchored to the end of the space station's robot arm, held an equipment cart in his gloved hands and carried it to the other side of the space crane's mobile transporter today to clear the path to a worksite that will be used by the arm in June to install a new Japanese experiment platform.

Joe Acaba carries an equipment cart while anchored to the
international space station's robot arm

The space station is equipped with two crew equipment and translation aid - CETA - carts coupled to the station arm's mobile transporter. The transporter and the carts move along rails on the front side of the station's main power truss to reach worksites that provide access to various station components.

For the June flight, the arm needs to work on the left side of the station's power truss. To reach that worksite, one of the CETA carts had to be moved from the left side of the transporter to the right.

With Acaba holding onto the cart, Arnold released its wheels from the track and John Phillips, operating the robot arm from inside the Destiny lab module, moved Acaba and his cargo to the right side of the arm's mobile transporter. Arnold then locked it back down to complete the relocation.

The view from Acaba's helmet cam as the CETA cart
was secured. Arnold is visible to the left

Acaba and Arnold next plan an attempt to fully deploy a jammed external cargo carrier on the bottom of the port 3, or P3, truss segment. Acaba and astronaut Steven Swanson were unable to get the mechanism locked in place during a spacewalk urday.

Engineers initially believed a clamp that was mistakenly installed in the wrong orientation was causing physical interference. They now think the detent is simply stiffer than expected and that if the astronauts apply a bit more force, the linkage will fully extend and lock in place.


11:50 AM, 3/23/09, Update: Spacewalk No. 3 begins

Astronauts Richard Arnold and Joseph Acaba, floating in the space station's Quest airlock module, switched their spacesuits to battery power at 11:37 a.m. to officially begin a planned six-and-a-half-hour spacewalk.

The goals of today's excursion, in order, are to reposition an equipment cart; complete the deployment of an external cargo mounting mechanism; to extend another cargo carrier on the far side of the station's solar power truss; to lubricate the grappler on the station's robot arm; and to reconfigure a wiring patch panel.

Airlock hatch open, Acaba and Arnold prepare to exit
(note pulled-up radiator insulation above airlock)

This is the 123rd spacewalk devoted to station assembly and maintenance since construction began in 1998, the third and final EVA for Discovery's crew and the second for both Arnold and Acaba. Going into today's spacewalk, total space station EVA time stood at 768 hours and 33 minutes, or about 32 days.


08:15 AM, 3/23/09, Update: Arnold, Acaba prepare for final spacewalk

Editor's note...
Russian engineers are readying the Soyuz TMA-14 spacecraft for launch at 7:49:15 a.m. EDT Thursday carrying two new space station crew members and a wealthy U.S. space tourist. NASA will air b-roll footage of pre-flight preparations today at 10 a.m. B-roll footage of the Soyuz rollout to the launch pad will air at 11 a.m. Tuesday and replay of the crew's pre-launch news conference will run on NASA TV at 10 a.m. Wednesday.

Astronauts Richard Arnold and Joseph Acaba, both former school teachers, are preparing to venture back outside the international space station today for a planned six-and-a-half-hour spacewalk. The primary objectives are to complete the deployment of an external cargo mounting mechanism; to extend another cargo carrier on the far side of the station's solar power truss; to lubricate the grappler on the station's robot arm; to reconfigure a wiring patch panel; and to reposition an equipment cart.

Floating in the Quest airlock module, Arnold and Acaba plan to switch their spacesuits to battery power at 11:43 a.m to officially kick off the Discovery crew's third and final spacewalk. This will be the 123rd spacewalk devoted to station assembly and maintenance since construction began in 1998 and the second for Arnold and Acaba.

The first item on the agenda is to relocate one of two CETA carts, small rail cars coupled to the mobile transporter on the front side of the station's solar power truss that moves the lab's robot arm to various worksites. The CETA carts currently are on the left side of the transporter. Acaba, anchored to the end of the station arm, will pick up one cart and move it to the starboard side of the transporter so the arm can reach the proper left-side worksite in June to install a Japanese experiment platform.

"The first task right out of the hatch is to get Joe on the robotic arm," Arnold said. "We have these CETA carts, they're crew and equipment transfer vehicles. They're like little train cars that ride up and down the truss and we need to move one from one side of the station to the other so Joe gets a really exciting ride on the robotic arm. He gets to grab this thing and go around. I'll translate along and the arm will put him back on the other side and we'll mount it back on the track on the other side where it needs to be."

Acaba said today's spacewalk "is going to be a special EVA. ... We're classmates so it's pretty neat for us both to go out the door at the same time."

With the CETA cart transfer complete, Arnold and Acaba will make their way to the partially deployed unpressurized cargo carrier attachment system, or UCCAS, on the underside of the port 3, or P3, truss segment. Acaba and Steven Swanson attempted to swing the mechanism out during a spacewalk urday, but they were unable to pull it into place.

Engineers speculated that a variable-diameter locking pin in a clamp that was mistakenly installed in the wrong orientation was causing physical interference. But it now appears that might not be the case. Engineers suspect the mechanism will deploy if a bit more force is applied.

"Our leading theory was the adjustable diameter pin, because of the way it was installed, might have been causing some interference with the mechanism," said Flight Director Kwatsi Alibaruho. "Based on a thorough analysis of schematics, as well as CAD models for that mechanism, we think that is probably unlikely. After some conversation with the EV crew on orbit, we came to the conclusion that it is highly likely the detent for that mechanism is simply very stiff, much stiffer than we expected.

"We train our astronauts not to apply excessive forces on any kind of rotating mechanism. So when the mechanism did not rotate freely with a slight application of force, we investigated the possibility there was some binding or some interference with the mechanism. So the fix for it may be as simple as pulling on it harder to free it from the detent.

"But this is again a theory, we won't really know until we get the spacewalkers at the site. And then we'll have some idea about how to go forward. Of course, our first order will be to try to pull harder to try to get the mechanism to its nominal position. If we're not able to free the mechanism ... we will employ a long-duration tie down, where we simply attach some very sturdy straps and tie that swinging platform into a configuration we can leave it in for an extended period."

After the UCCAS work is complete, Arnold and Acaba will make their way to the starboard 3, or S3, truss segment and deploy another built-in cargo support mechanism that will be used later to hold spare parts and other equipment.

The spacewalkers then will split up. Acaba will lubricate the gripping snares on one end of the station's robot arm while Arnold attempts to re-wire a patch panel on the zenith 1, or Z1, truss segment to restore full redundancy to the station's gyro control circuits.

Four control moment gyroscopes in the Z1 truss are used to maintain the station's orientation. One gyro was tied to another gyro's circuit breaker during an earlier mission and astronauts have not been able to unlatch the connector to plug the gyro back into its own control circuit.

If all goes well, the astronauts will begin repressurizing the Quest airlock around 6:13 p.m., bringing today's spacewalk to a close. A mission status briefing is planned for 7 p.m.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision K of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/23/09 06:43 AM...07...11...00...Crew wakeup 07:18 AM...07...11...35...EVA-3: 14.7 psi repress/hygiene break 08:08 AM...07...12...25...EVA-3: Airlock depress to 10.2 psi 08:28 AM...07...12...45...EVA-3: Campout EVA preps 08:43 AM...07...13...00...ISS daily planning conference 09:58 AM...07...14...15...EVA-3: Spacesuit purge 10:00 AM...07...14...17...ISS-19/Soyuz TMA-14 pre-launch b-roll 10:13 AM...07...14...30...EVA-3: Spacesuit prebreathe 11:13 AM...07...15...30...EVA-3: Crew lock depressurization 11:43 AM...07...16...00...EVA-3: Spacesuits to battery power 11:48 AM...07...16...05...EVA-3: Airlock egress 12:13 PM...07...16...30...EVA-3: Setup 12:33 PM...07...16...50...EVA-3: CETA relocate 01:33 PM...07...17...50...EVA-3: P3 nadir UCCAS deploy attempt 03:58 PM...07...20...15...EVA-3: S3 outboard zenith PAS deploy 04:58 PM...07...21...15...EVA-3/Arnold: Z1 patch panel reconfig 04:58 PM...07...21...15...EVA-3/Acaba: SSRMS LEE-B lube 05:38 PM...07...21...55...EVA-3: Cleanup and ingress 06:13 PM...07...22...30...EVA-3: Airlock repressurization 06:28 PM...07...22...45...Spacesuit servicing 07:00 PM...07...23...17...Mission status briefing 07:48 PM...08...00...05...Evening planning conference 08:13 PM...08...00...30...Crew choice downlink 09:43 PM...08...02...00...ISS crew sleep begins 10:13 PM...08...02...30...STS crew sleep begins 11:00 PM...08...03...17...Daily video highlights reel


9:25 PM, 3/22/09, Update: Shuttle crew not worried about debris; prepared for spacewalk Monday; begin delayed urine processing tests

Discovery commander Lee Archambault maneuvered the shuttle-space station "stack" today to avoid multiple close encounters with a piece of Chinese space junk that could have posed a threat during a third and final spacewalk Monday. Space station commander Mike Fincke, meanwhile, made solid progress with lab's urine recycling system and resumed testing late in the day after resolving a snag earlier in the day.

"We had a little bit of a problem loading up the RFTA, the filter assembly," outgoing station flight engineer Sandra Magnus told CBS News in a space-to-ground interview. "We ended up changing that and now Mike's back in the mode of dumping some of our urine tanks, our full urine tanks, into the processor to fill it up and start the processing. So things are moving ahead and we're hoping for a good outcome here in a few hours or a few days."

Urine processor centrifuge on the big screen in mission control

Late this evening, Fincke positioned a microphone next to the urine processors newly installed distillation assembly centrifuge for a "dry spin" test to collect acoustic data for an engineering analysis. The system's original distillation unit failed shortly after installation last year, presumably due to internal mechanical interference of some sort.

"The dry spin is going very successfully," Fincke reported as the new centrifuge spun up. "I remember the original distillation assembly and I never remember it being this quiet. ... It's looking great so far."

"Concur. We see good data as well, happy day," replied Lucia McCullough in mission control.

Fincke planned to oversee the start of the first "wet" test using stored urine later this evening.

While the Discovery astronauts enjoyed a half-day off earlier today, flight controllers at the Johnson Space Center in Houston began evaluating a predicted close encounter with a piece of Chinese space junk. Tracking data indicated the 4-inch-wide debris would repeatedly cross the space station's path Monday afternoon.

Concerned about having to carry out a debris avoidance maneuver during a spacewalk, lead flight director Kwatsi Alibaruho said mission managers decided to protectively make a subtle change today to preclude any close encounters. Rather than firing rocket thrusters and making a major change in the station's trajectory, flight planners had Archambault maneuver the combined shuttle-station stack into a normal undocking orientation with Discovery's belly pointed in the direction of travel.

In that orientation, atmospheric friction, or drag, would provide most of the energy needed to lower the station's altitude slightly with the same result as a rocket firing that changed the station's velocity by 1 foot per second. Archambault maintained that undocking attitude for about three hours before moving back to the normal orientation with the shuttle behind the station.

"Space debris is becoming an ever increasing challenge," Alibaruho agreed. "On one level, it causes us great concern, it's potentially hazardous to the spacecraft. We've been very fortunate, and also very diligent about monitoring for space debris, we do that in partnership with other government agencies that gives us the capability to try to predict when we may have a problem and adjust.

"The process of adjusting the orbit of the space station is a big deal. It requires a lot of planning, it's very resource intensive. When we do not have a shuttle there, it requires a great deal of coordination and analysis between mission control in Houston and mission control in Russia. ... It's a big deal, it's very tiring. But at the same time, we accept it as a necessary part of our business."

The threat posed by space debris has been in the news in recent weeks following a collision between to satellites in February and a predicted encounter just before Discovery's launch that forced the station crew to briefly take refuge in the lab's Soyuz lifeboat.

For his part, Archambault told CBS News he believed the events of recent weeks "seem like a coincidence. We have had a couple of these in the last couple of weeks, but as far as I know, it is coincidental."

Asked if the spacewalkers viewed space debris as a concern, astronaut Steven Swanson said "I guess I don't think too much about that. We have enough other risks and worries to take on as we go outside and I'm just trying to get the job done right. That's what I'm concentrating on."

During a spacewalk urday, Swanson and Joseph Acaba had problems deploying an external payload storage mechanism on the station's left-side solar power truss. During a briefing later, officials said a clamp appeared to have been installed incorrectly, preventing the mechanism from rotating into the fully deployed position.

Alibaruho said today the clamp did, in fact, appear to be in the wrong orientation, but he and Swanson both said that did not appear to be what was preventing a full deployment.

The detent that must be disengaged to allow smooth movement was "a lot stiffer than we thought it was going to be," Swanson told CBS. "And I didn't actually pull down very hard on it. So once it wouldn't come down with just a little pull, we started looking around (for what might be wrong). That pin might have been a little big out of config, but it shouldn't have actually stopped it.

"So we started looking around and we were worried about that, but now since we came back in and have more data, it looks like if I'd just pulled hard on it, it would have come on down. So tomorrow, when Joe and Ricky (Arnold) go out, that's one of the first things they're going to do ... is to pull down on it with more strength and see if it comes loose."

Partially deployed cargo carrier mechanism

If that doesn't work, however, the spacewalkers likely will simply tie the mechanism down with straps to prevent inadvertent movement and move on to other tasks.

"The idea for plan B is we were probably going to just tie it down for right now until the ground can come up with more ideas on what the real problem is," Swanson said. "Because that's what all the models, all the engineering analysis, shows, it's probably just the detent position. So if it's not that, then they really don't know and we don't know exactly what the problem is and (to make sure) we don't hurt anything else, we're just going to tie it down for long duration so it can stay up here for a while while they work on the problem and come up with a solution."

Alibaruho said part of the problem urday was that "we train our astronauts not to apply excessive forces on any kind of rotating mechanism. So when the mechanism did not rotate freely with a slight application of force, we investigated the possibility there was some binding or some interference with the mechanism. So the fix for it may be as simple as pulling on it harder to free it from the detent.

"But this is, again, a theory, we won't really know until we get the spacewalkers at the site. ... Our first order will be to try to pull harder to try to get the mechanism to its nominal position. If we're not able to free the mechanism ... we will employ a long duration tie down, where we simply attach some very sturdy straps and tie that swinging platform into a configuration we can leave it in for an extended period."


3:00 PM, 3/22/09, Update: Shuttle maneuver ordered to avoid space debris; urine processor work continues (UPDATED at 4:45 p.m. with debris details, urine processor work)

Shuttle commander Lee Archambault used Discovery's steering jets today to re-orient the shuttle-space station "stack" and in so doing, slightly lower their altitude. The maneuver was ordered to reduce the odds of a potential close encounter, or conjunction, with a 4-inch-long piece of Chinese rocket debris.

Station commander MIke Fincke, meanwhile, replaced a filter assembly in the lab's finicky urine processor assembly late today and was cleared to load the processor with stored urine for a delayed processing test. FIncke spent most of the morning troubleshooting a lower-than-expected flow rate that delayed plans to start a test run before noon.

Flight controllers later told Fincke to stand down while engineers on the ground tried to figure out what the problem might be. Later, they suggested swapping out a filter and Fincke was cleared to make another attempt to load urine for the so-called "wet" test. A complete processing cycle takes about five hours to complete.

"Houston, station, on space-to-ground 2 for UPA," Fincke called. "We took it up to 65 percent and we can see it's going through the filter now with the nominal, so far, apparently, decrease rate."

"And Mike, we copy and concur based on what we're seeing," Rick Davis replied from Houston. "So hopefully it'll continue that way, that would be great."

The space station's urine processor assembly

While Fincke was resuming work with the urine processor, Archambault was maneuvering the shuttle-station stack into the same orientation that will be used next week for undocking, one in which the belly of the orbiter is pointed in the direction of travel.

"Just looking to make our conjunction numbers better during tomorrow's EVA (spacewalk), we want to do a very minor orbit adjust," astronaut Stephen Robinson called from mission control. "So at 20:46 MET (mission elapsed time, or 4:29 p.m. EDT), we'll have you maneuver to the undock attitude using the shuttle, hold that attitude for three hours, then we'll move back to (the normal orientation) and give attitude back to station. We're putting a note together with the details, but that's the big picture."

By maneuvering to the undocking attitude, the shuttle-station vehicle will experience slightly more atmospheric friction, or orbital drag, than usual, causing a very slight change in altitude. The maneuver will have the same result as a rocket firing that changed the station's velocity by about 1 foot per second.

A NASA spokesman said the attitude maneuver will be enough to make sure the debris in question, identified by catalog number 26264 (CZ-4 DEB) and believed to be a 4-inch-long piece of debris from an upper stage, does not get close enough to cause any problems.

"They want to adjust the attitude slightly in order to ensure that they're able to avoid a piece of debris that has been identified in the area," said mission control commentator Nicole Cloutier. "This small maneuver will ensure there is no collision concern."

The threat posed by space debris has been in the news in recent weeks following a collision between to satellites in February and a predicted encounter just before Discovery's launch that forced the station crew to briefly take refuge in the lab's Soyuz lifeboat.


2:00 PM, 3/22/09, Update: Urine flow problem forces station crew to delay processor test

A critical test run using the space station's presumably repaired urine processor system was called off today when the lab crew ran into problems loading the system with stored urine. After several hours of troubleshooting, mission control told station commander Mike Fincke to close the water recovery system rack and call it a day.

Quick-disconnect fittings inside the water recovery system rack

"The troubleshooting steps we just did to try to resolve this problem with the UPA (urine processing assembly) were no joy," Rick Davis called from mission control shortly before 2 p.m. "We are going to stand down from UPA activities for today so that we can get everyone looking at it to come up with some additional ideas."

FIncke passed along the crew's apologies, saying "sorry about that." He indicated the flow problem prevented him from getting enough urine into the system to test the newly installed distillation assembly - DA - centrifuge, the component that broke down shortly after installation last year, delaying UPA tests and checkout. A replacement was carried up aboard the shuttle Discovery and installed Friday.

"I guess we didn't have enough in the (tank) to try out the DA part," Fincke said. "So we'll plan on shutting the doors and reconfiguring all the racks for further use. Thanks for the heads up. Sorry about that, guys. Yeah, I saw that too, once you closed valve 3 it didn't seem to flow. I have no idea why that could be. So good luck with the troubleshooting and we're standing by to answer any questions or be of any use."

Shuttle Discovery above the Strait of Gibralter

Fincke spent most of the morning helping engineers at the Johnson Space Center troubleshoot the flow rate problem. He had hoped to load the system with stored urine and to carry out a five-hour processing run to test the system's performance.

"He had begun configuring the urine processor assembly for a wet run with that distillation assembly this afternoon," said NASA's mission control commentator, Nicole Cloutier. "He had been making those configurations throughout the morning and working with the ground team, noticed that they had a slower-than-expected flow rate in those tanks.

"The ground team has been working with (Fincke) on some different steps to try to identify the cause of the lower-than-expected flow rates and have initiated a couple of commands from the ground, as well as some steps from on board involving the hoses and the quick disconnects."

But so far, the cause of the problem has not been islolated.


12:00 PM, 3/22/09, Update: Sky watchers capture dramatic views of space station

Watching the international space station fly overhead is a popular hobby for many space enthusiasts and with the addition of a fourth and final set of solar arrays, the huge lab complex, already one of the brightest objects in the sky, should be even more impressive. Here are a few particularly dramatic views from a video shot urday by Quintus Oostendorp from his backyard in Vaassen, the Netherlands (used with permission):

Photo by Quintus Oostendorp
300mm f/5 GSO newton; Tele Vue Big Barlow; Canon 350D

Stills and videos from other space station observers also are available at spaceweather.com


8:00 AM, 3/22/09, Update: Crew enjoys off-duty time; urine processor test on tap

The Discovery astronauts are enjoying a half-day off today before gearing up for a replanned third and final spacewalk Monday. The space station astronauts, meanwhile, plan to begin testing the lab's repaired urine processing system later this morning.

The water recycling system, required for long-term support of six full-time crew members, is designed to convert condensate and urine into pure water for drinking, personal hygiene and oxygen generation.

But a key component - a vacuum distillation assembly centrifuge - malfunctioned shortly after it was installed late last year. Based on telemetry and crew reports of vibration and noise levels, engineers suspect some sort of physical interference with rotating components inside the device.

A replacement distillation assembly carried up aboard Discovery was installed Friday and on urday, the crew fired up the new centrifuge for a test run.

"That activation and checkout went very well," station Flight Director Kwatsi Alibaruho said urday. "What we did was, we pointed a high definition camera and microphone at the unit. That unit is like a big centrifuge, kind of similar to a washing machine. So the vibrations and the sounds that it makes tells us quite a bit about its health.

"Basically, that unit functioned normally," he said. "We spun it up for about five or so minutes without any fluid in it, just to make sure that the motor was spinning properly and the rpm and the currents and the voltages on the motor looked normal.

"So tomorrow (Sunday), what's on the plate is to actually fill the urine processor with urine and attempt to do a full process cycle on that and shunt that processed urine to the water recovery system to then allow us to take an end-of-mission sample. So that work is going very well."

But a second dry run test will be carried out this morning before the five-hour urine processing run begins around 12:45 p.m.

"Specialists on the ground are particularly interesting in getting audio, to hear what it sounds like, when the UPA is now engaged," mission control commentator Pat Ryan said early today. "Yesterday's dry spin was recorded on video tape, but the video that was downlinked did not have an audio track. That audio is important so they can perform a narrow-band frequency analysis to isolate the sounds from various components within the DA to determine whether or not anything is damaged or operating improperly.

"The plan calls for a second brief dry spin to be accomplished this morning with sound. That'll be followed by a wet spin, a full processing cycle. Station commander Mike Fincke will be doing the water recovery system. He should kick off the UPA processing cycle at 11:45 Houston time this morning (12:45 p.m EDT).

"The standard run on that cycle is five hours to do a complete treatment of the urine that's been introduced," Ryan said. "Samples from that cycle will be prepared for return to Earth so they can be tested as the international space station team continues to work to certify that the water recovery system is operating properly and the output of the system is indeed potable water that will be safe for the crew members to drink."

At the Johnson Space Center in Houston, divers in NASA's spacewalk training pool are testing procedures for freeing a jammed external cargo stowage rack on the station's port 3 truss segment that could not be fully deployed during a spacewalk urday. The mechanism apparently jammed because one of the spacewalkers installed a clamp backward, causing interference with a variable-diameter locking pin.

An attempt to free the jammed pin likely will be added to the spacewalk tasks planned for Monday's EVA.

CBS News will interview the astronauts late today in a round-robin window that opens at 6:14 p.m.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision J of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/22/09 07:13 AM...06...11...30...Crew wakeup 08:43 AM...06...13...00...ISS daily planning conference 10:18 AM...06...14...35...Crew off-duty time begins 12:53 PM...06...17...10...UPA DA observations 02:03 PM...06...18...20...Crew meals begin 03:03 PM...06...19...20...Spacesuit swap 03:43 PM...06...20...00...Equipment lock preps 03:48 PM...06...20...05...WRS rack closed 05:28 PM...06...21...45...Tools configured 05:43 PM...06...22...00...Tool audit 06:14 PM...06...22...31...CBS News crew interview 06:33 PM...06...22...50...Crew choice downlink 06:43 PM...06...23...00...EVA-3: Procedures review 06:45 PM...06...23...02...Mission status briefing (may be cancelled) 08:28 PM...07...00...45...Evening planning conference 09:08 PM...07...01...25...EVA-3: Mask pre-breathe 09:53 PM...07...02...10...EVA-3: Airlock depress to 10.2 psi 10:13 PM...07...02...30...ISS crew sleep begins 10:43 PM...07...03...00...STS crew sleep begins 11:00 PM...07...03...17...Daily highlights reel


10:50 PM, 3/21/09, Update: Mission managers study options for deploying jammed cargo carrier; urine processor centrifuge tested

Engineers are studying options for freeing a jammed locking pin, part of a clamp that apparently was installed backwards by a spacewalker today in the topsy-turvy world of microgravity. The backward clamp prevented a stowed space station cargo carrier from fully deploying and locking into place.

The spacewalkers also ran into familiar problems re-configuring a wiring panel because of a stuck connector that has defied repeated disconnection attempts.

The patch panel, located near the station's vertical zenith 1, or Z1, truss, routes power to and from the lab's four stabilizing gyroscopes. One gyro was tied into a circuit breaker used by another stabilizer during an earlier mission because of a circuit failure. The circuit breaker was replaced, but attempts to disconnect the cable in question so it could be hooked back up to its own circuit breaker were unsuccessful during an earlier mission and astronaut Steven Swanson was unsuccessful making another attempt today.

Lead flight director Kwatsi Alibaruho said Swanson was trained to simply re-wire the panel from the back, but he ran out of time during today's spacewalk. The work may be added to a third and final spacewalk Monday or deferred to a later assembly mission. The gyros operate normally in the current configuration, but a single worst-case failure in the circuitry could disable two gyros at the same time and NASA managers want to restore normal redundancy as soon as possible.

"We had certainly another exciting day in space today," Alibaruho said. "We didn't accomplish everything we wanted to accomplish on this EVA, but just know we did accomplish all the critical-path items that were scheduled."

Inside the space station, meanwhile, the astronauts carried out a critical test of a new urine processor distillation assembly centrifuge that was carried up by Discovery.

The station's water recycling system is designed to convert sweat, condensate and urine into pure water for drinking, personal hygiene and oxygen generation. But the original distillation assembly malfunctioned shortly after it was installed late last year, victim of some sort of internal vibration or interference issue.

The water recycling system is crucial to NASA's plans for eventually supporting a full-time crew of six aboard the station.

The replacement distillation assembly was installed Friday and today, the crew fired up the new centrifuge for a test run.

"That activation and checkout went very well," Alibaruho said. "What we did was, we pointed a high definition camera and microphone at the unit. That unit is like a big centrifuge, kind of similar to a washing machine. So the vibrations and the sounds that it makes tells us quite a bit about its health.

"Basically, that unit functioned normally. We spun it up for about five or so minutes without any fluid in it, just to make sure that the motor was spinning properly and the rpm and the currents and the voltages on the motor looked normal. All of that looked very normal and in fact, we did get feedback from the ISS crew that that new distillation assembly actually sounded much quieter than the original. So, just based on qualitative feedback from the crew, we know there's certainly a difference in performance of this unit versus the original that was installed on the last mission.

"So tomorrow (Sunday), what's on the plate is to actually fill the urine processor with urine and attempt to do a full process cycle on that and shunt that processed urine to the water recovery system to then allow us to take an end-of-mission sample. So that work is going very well."

As for today's spacewalk, Alibaruho said Swanson and Acaba accomplished the highest-priority objectives: breaking torque on a solar array battery pack that will be replaced in June; installing a GPS antenna on a Japanese module; and photographing radiator panels to help engineers assess an area of damage and any other possible problems.

But the astronauts were unable to unstow and deploy an unpressurized cargo carrier attachment system, or UCCAS, on the lower side of the port 3, or P3, solar array truss segment. The UCCAS was built into the truss segment and has been stowed since launch. During today's deployment, Swanson and Acaba removed clamps and locking pins and attempted to rotate the mechanism outward.

As it turns out, one variable-diameter locking pin, part of a clamp-like device, was reinstalled in the wrong orientation, causing the pin to physically interfere with the deployment. The spacewalkers struggled to free the jammed pin, even using a tool as an impromptu lever. But they were unsuccessful.

"One of the first things they do when they come out to prep the UCCAS for its deploy is to pull the adjustable-diameter pin out of the hinge line where it's holding it from deploying inadvertently, and move it over to the stow location," said lead spacewalk officer Glenda Laws-Brown.

"As you know, when you get to the international space station there is no up and down. And my guess is they thought they had it in the right configuration, but because up is down and down is up, it was actually 180 degrees out from where it should have been."

Spacewalk planners are evaluation options for freeing the jammed pin and an attempt may be added to the crew's third spacewalk Monday. In the meantime, Swanson tied down the UCCAS mechanism with tethers before today's spacewalk ended to make sure the system cannot inadvertently move.

"All in all, it was a successful EVA in that the highest priority tasks were completed and as far as the tasks we had difficulty with, tasks that we had problems with, these are things where there will be no long term programmatic impact," Alibaruho said.

"However, we do want to take a much closer look at that UCCAS mechanism that was not fully deployed today. We had the crew attach some tethers to that, we had the crew essentially put it in a safe configuration to where it can sustain all of the planned structural loading of events from thruster-driven attitude control or gyroscope-driven attitude control. So the station is in a perfectly safe configuration right now. But we will be looking at that in more detail and we probably attempt some remediation on EVA 3."


7:40 PM, 3/21/09, Update: Spacewalk No. 2 ends with mixed results

Astronauts Steven Swanson and Joseph Acaba began repressurizing the Quest airlock module at 7:21 p.m., closing out a grueling six-and-a-half-hour spacewalk after running into problems deploying a balky cargo platform and reconfiguring gyroscope control cables.

The astronauts successfully loosened a solar array battery pack as planned, however, attached a GPS antenna to a Japanese module and carried out a detailed photo-survey of the station's big radiator panels, all high-priority items.

Toward the end of the excursion, Swanson used tethers to tie down the balky unpressurized cargo carrier attachment system, or UCCAS, to prevent any inadvertent movement while engineers devise a way to lock it into place.

"Congratulations, guys. We sure appreciate the hard work you did for our beautiful space station," commander Mike Fincke radioed the spacewalkers from the outer airlock. "You guys provedśthat flexibility is definitely key. And a special congratulations to Joe. This was your first time out there, great job, my friend. So congratulations."

Steve Swanson securing a partially deployed cargo carrier

But time lost trying to fully deploy the UCCAS mechanism forced the spacewalkers to defer the deployment of another cargo platform on the right side of the station's solar power truss. Swanson also had problems disconnecting a cable from a patch panel on the zenith 1, or Z1, truss segment extending up from the Unity connecting module.

This was the 122nd spacewalk devoted to station assembly and maintenance since construction began in 1998 and the second of three planned for Discovery's mission. Total space station EVA assembly time now stands at 768 hours and 33 minutes, or about 32 days.


6:25 PM, 3/21/09, Update: GPS antenna installed; radiator imaging complete (UPDATED at 6:40 p.m. with change in crew assignments)

Using visible light and infrared cameras, spacewalker Joe Acaba carried out a detailed photo survey of the space station's huge radiators today to help engineers assess the health of critical insulation blankets. One blanket on one panel has pulled away and while it has had no apparent affect on the station's cooling system, engineers want to find out what might have caused the breakdown.

Astronaut Steven Swanson, meanwhile, bolted a GPS navigation system antenna to the top of the Japanese logistics module. He then started work to reconfigure wiring in a patch panel on the zenith 1, or Z1, truss segment that controls the station's control moment gyroscopes. Acaba was asked to tie down a partially deployed cargo platform the crew had trouble with earlier.

Joe Acaba, visible between the Kibo module and the space station's solar array truss during work to photograph radiator panels

View from Acaba's helmet cam showing pulled-up insulation on a right-side space station radiator panel

Acaba's view of the Texas-Louisiana coastline 220 miles below

5:00 PM, 3/21/09, Update: Engineers ponder storage platform deploy solution; astronauts told to move on

Spacewalkers Steve Swanson and Joseph Acaba, unable to fully deploy an external storage platform, have been told to move on to other tasks while engineers on the ground try to come up with a solution. Deployment of a second storage platform on the other side of the station has been bumped from the crew's task list because of time lost trying to get the unpressurized cargo carrier attachment system, or UCCAS, unfolded and locked in place on the port side of the station's power truss.

Joe Acaba collecting tools before carrying out a photo survey of the space station's radiator panels

"FIrst of all, unless you guys think you're going to be able to solve this in the next few minutes, what we would really like to do is press on to the next set of tasks, which is radiator imaging and the GPS antenna install since they are higher priority items," Rick Davis radioed from Houston. "That'll allow our guys to think through this some more, maybe come up with some better ideas for you. The starboard PAS deploy is off the table today so we can make sure we have time to one, make sure we get these other tasks and two, if necessary, to tie this UCCAS down. That's where we are right now."

"Do you want them to tie this down before heading on to do the GPS, or after?" asked spacewalk coordinator Richard Arnold from inside the shuttle Discovery.

"Ricky, it'll be after, because we've got to make sure we have a good tie-down plan and so we'll have words for you after those higher priority task (are) done."

"OK, copy, thanks Rick. Swanny, what do you think?" Arnold asked.

"I don't think it's moving right now," Swanson replied. "We need another plan."

While engineers considered options for either getting the UCCAS fully deployed or securing it as is, Swanson focused on installing a GPS navigation system antenna on a Japanese module while Acaba planned to photograph the station's main radiator panels with an infrared camera.

In earlier updates, it was reported that Acaba would handle the GPS installation, but a recent flight plan update listing the crew's tasks was in error.


4:30 PM, 3/21/09, Update: Astronauts have problems deploying storage platform;; urine distillation assembly spun up

After successfully loosening bolts on a solar array battery pack, spacewalkers Steven Swanson and Joseph Acaba ran into problems fully extending an external hardware storage platform on the space station's port 3 power truss segment.

After unbolting clamps and rotating the platform toward its deployed position, interference with a locking pin prevented them from fully extending its support mechanism. Applying elbow grease, the spacewalkers attempted to muscle the hardware into place and discussed tools that might be able to provide additional leverage.

They were running about a half-hour ahead of schedule when they started work to deploy the unpressurized cargo carrier attachment system, or UCCAS, on P3 truss segment but they lost time struggling to get it fully deployed.

The view from Steve Swanson's helmet cam. looking through the P3 truss, over the Atlantic Ocean. Joe Acaba can be seen on the other side of the truss

Inside the station's Destiny lab module, meanwhile, the astronauts began testing a new vacuum distillation assembly centrifuge unit that was brought up aboard Discovery and installed in the station's water recycling system Friday.

The system's original distillation assembly failed shortly after it was installed late last year. Recycling condensate and urine is critical to NASA's long-range plans to support a full-time crew of six on the space station.

Urine distillation assembly during 'dry spin' test

The original unit experienced some sort of internal interference issue. After removing rubber vibration dampers in the DA's mounting system, the astronauts were able to coax it into operation but it eventually halted and could not be restarted.

The replacement DA is identical to the one that failed and engineers say it could suffer the same problem that derailed the original. But during an initial spin test with the new unit, space station commander Mike Fincke reported the centrifuge was running smoothly.

"And Houston, you can see the same good spinning," he said. "We can barely hear any change in noise, which is much different than the last time we did this."

The station crew plans to test the new distillation assembly by processing urine on Sunday.


2:40 PM, 3/21/09, Update: Battery bolts loosened; spacewalk ahead of schedule

Spacewalkers Steven Swanson and Joseph Acaba have completed the first task on their agenda, loosening six bolts holding batteries in place on the port 6, or P6, solar array at the far left end of the space station's power truss. As of 2:30 p.m., the astronauts were running about 20 minutes ahead of schedule as they collected their tools before moving on to the next task: deployment of an equipment storage platform.

Working on the far end of the huge truss, the astronauts apparently imparted enough force on the structure to "saturate" the control moment gyroscopes that are normally used to maintain the orientation of the shuttle-space station "stack." This is not unusual, but it required flight controllers to switch attitude control to the shuttle Discovery's small vernier thrusters.

"Just to let you guys know, with all this work being done out at the end of the truss structure, the CMGs momentum has built up," astronaut George Zamka radioed from mission control. "Nothing to worry about. The bottom line is we may lose attitude control on the CMGs but we'll switch over to shuttle VRCS. Just so you guys are aware of it. Not a problem."

Swanson and Acaba at work on the station's port-side solar power truss


1:10 PM, 3/21/09, Update: Spacewalk No. 2 begins

Astronauts Steven Swanson and Joseph Acaba, floating in the international space station's Quest airlock module, switched their spacesuits to internal battery power at 12:51 p.m. to officially kick off a planned six-and-a-half-hour spacewalk.

This is the 122nd spacewalk devoted to station assembly and maintenance since construction began in 1998, the third so far this year and the second of three planned for DIscovery's mission. Going into today's excursion, total space station EVA time stood at 762 hours and three minutes. This is the fourth spacewalk for Swanson - his second of this mission - and the first for Acaba.

Joe Acaba exits the Quest airlock; Swanson floats to the left

The first item on the agenda today is loosening six bolts holding a set of batteries in place on the far left side of the station's main power truss. The "get-ahead" work will save time when the batteries are replaced in June by the crew of the next shuttle assembly mission.

Swanson and Acaba then plan to deploy an equipment stowage platform, attach a GPS navigation system antenna to a Japanese module, photograph the station's main radiator panels, deploy another payload mounting rack and reconfigure power lines used to control the lab's stabilizing gyroscopes.

8:30 AM, 3/21/09, Update: Astronauts prepare for second spacewalk

Astronauts Joseph Acaba and Steven Swanson are preparing for a revised six-and-a-half-hour spacewalk today. The major goals of the excursion, the second of three planned for the shuttle Discovery's mission, are to prepare a set of solar array batteries for replacement in June; to deploy storage platforms on the international space station's solar power truss; to install a GPS navigation system antenna on a Japanese module; and to photograph two sets of radiator panels with an infrared camera. Insulation on one radiator panel has pulled away and engineers want to assess the health of the system.

Today's spacewalk, the 122nd devoted to station assembly and maintenance since construction began in 1998, is scheduled to begin at 12:43 p.m. when Swanson and Acaba, floating in the station's Quest airlock module, switch their spacesuits to internal battery power. For identification, Swanson will be wearing a suit with red stripes and use the call sign EV-1. Acaba, EV-2, will be wearing a suit with broken red stripes.

Overnight, engineers at the Johnson Space Center in Houston continued checking out the newly deployed S6 solar array wings that were successfully extended Friday. Pat Ryan, the overnight mission control commentator, said checkout was proceeding smoothly. Engineers are charging and conditioning the batteries that store power from the new arrays when the station is in Earth's shadow, but that power is not yet being fed into the station's electrical distribution system.

"The new arrays are gathering solar energy and converting it to electrical power, but at this point that electrical power is being used only to charge the batteries out there," Ryan said. "The plan is that these two new power channels will not be incorporated into the station power grid until after the completion of today's spacewalk. That's a precautionary measure to prevent any disruption of station systems while crew members are outside."

Discovery's mission originally included four spacewalks, but one had to be eliminated when launch was delayed from Feb. 12 to March 15, putting the shuttle mission in conflict with upcoming Russian flights to rotate space station crew members. Facing a March 25 deadline to undock and make way for the Russians, one spacewalk had to be eliminated.

NASA flight planners re-prioritized the tasks planned for Discovery's spacewalkers, moving some work up and deferring other activities.

The first item on the agenda today is work to prepare batteries on the port 6, or P6, solar array truss segment for replacement during assembly mission STS-127 in June.

"What the crew will do is, they'll go out to that worksite and break the torque on those batteries and install some foot restraints and pre-stage some tools that they'll use to save the crew of the next mission some time when they go to do the complex operations to replace those batteries. So we're going to do that get-ahead task," said lead flight director Kwatsi Alibaruho.

"We'll also deploy external cargo carriers, one cargo carrier on the port side, one on the starboard side. They are to prepare for installation of cargo or payload carriers on a future flight. Finally, we'll install a prox ops GPS antenna on the Japanese experiment module. This will be the second of two installations of these antennas. And this is in preparation for the launch and rendezvous of the H2 transfer vehicle from Japan later on this year."

Unlike the shuttle, Russian Soyuz and Progress vehicles and the European Space Agency's Automated Transfer Vehicle, which rendezvous and dock with the station, the unmanned Japanese H-2 Transfer Vehicle is designed to approach the lab complex and then wait for the station's robot arm to grab it and move it to a docking port. The GPS antennas are part of the Japanese proximity navigation system that will be used for those missions.

"We'll also do some additional EVA get-aheads to include some imaging, infrared imaging of the port and starboard radiators, as well as reconfiguration of an electrical patch panel that provides power to the station's control moment gyros," Alibaruho said.

Swanson will carry out the radiator photo documentation while Acaba installs the GPS antenna on the Japanese module.

"We've noticed one of the panels on our radiators, which help us basically release heat out into space, has begun to peel back," spacewalk coordinator Richard Arnold said in a NASA interview. "We don't really yet understand what that means, how it was caused and how it's impacting our ability to get rid of excess heat off the station."

"So (Swanson will) head aft, get in a foot restraint and take some infrared thermal images of both the radiators. That's to see if we can get some data that helps us understand what's going on with the radiators and why this panel is peeling back and how that's affecting us."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision I of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/21/09 07:43 AM...05...12...00...Crew wakeup 08:18 AM...05...12...35...EVA-2: 14.7 psi repress/hygiene break 09:08 AM...05...13...25...EVA-2: Airlock depress to 10.2 psi 09:13 AM...05...13...30...ISS daily planning conference 09:28 AM...05...13...45...EVA-2: Campout EVA preps 10:58 AM...05...15...15...EVA-2: Spacesuit purge 11:13 AM...05...15...30...EVA-2: Spacesuit prebreathe 11:33 AM...05...15...50...Distillation assembly install part 1 12:03 PM...05...16...20...EVA-2: Crew lock depressurization 12:43 PM...05...17...00...EVA-2: Spacesuits to battery power 12:48 PM...05...17...05...EVA-2: Airlock egress 01:03 PM...05...17...20...EVA-2: Setup 01:43 PM...05...18...00...EVA-2: S6 battery R&R preps 02:43 PM...05...19...00...EVA-2: P3 nadir UCCAS deploy 03:58 PM...05...20...15...EVA-2/EV-2: JLP GPS antenna B install 03:58 PM...05...20...15...EVA-2/EV-1: S1/P1 radiator imaging 04:18 PM...05...20...35...Water recycling system rack closed 04:58 PM...05...21...15...EVA-2/EV-2: Z1 patch panel reconfig 05:28 PM...05...21...45...EVA-2: S3 PAS deploys 06:28 PM...05...22...45...EVA-2: Cleanup and airlock ingress 07:13 PM...05...23...30...EVA-2: Airlock repressurization 07:28 PM...05...23...45...Spacesuit servicing 08:00 PM...06...00...17...Mission status briefing 08:48 PM...06...01...05...Crew choice downlink 09:08 PM...06...01...25...Evening planning conference 10:43 PM...06...03...00...ISS crew sleep begins 11:13 PM...06...03...30...STS crew sleep begins


7:20 PM, 3/20/09, Update: Discovery's heat shield in good shape; minor issues remain to be resolved; flight plan revised, sticks with 3/28 landing

NASA managers, thrilled at the successful deployment of a fourth and final set of solar arrays on the international space station today, approved a revised flight plan that will delay hatch closure and the shuttle Discovery's undocking slightly to improve the odds of getting critical experiment samples back to Earth in case of weather wave-offs that might delay the orbiter's return.

LeRoy Cain, chairman of NASA's Mission Management Team, said the revised flight plan will optimize the crew's docked timeline while still ensuring a touchdown on March 28 as originally planned. By delaying hatch closure and undocking slightly, experiment samples that must be shipped home cold can stay in the space station's freezer longer, giving them more shelf life aboard Discovery.

"End of mission remains ... a week from tomorrow," Cain said. "The difference is the option we settled on will allow us a little bit more time during the docked phase for the crew to take advantage of some other work, including transfers and other items. It'll result in the hatch closure and undocking occurring on the same day, on flight day 11. It kind of optimizes the docking timeline and gives us a little bit of margin."

Cain also said Discovery's heat shield is in good shape. A detailed assessment based on launch imagery, an inspection by the crew in orbit and a photo survey carried out by the station's crew during Discovery's final approach revealed only a few relatively minor problems.

"As far as the thermal protection system, we've essentially cleared the vehicle for all intents and purposes," Cain said. "We haven't officially made that determination in the Mission Management Team because there is one item of interest that is outstanding, but it's not going to be an issue for us in terms of being able to execute a safe deorbit and landing of Discovery."

Along with a damaged tile on Discovery's left inboard elevon, or wing flap, close-up photography also revealed a protruding gap filler, a thin spacer used to keep adjacent tiles from rubbing against each other. The damaged tile is not considered a problem and protruding gap fillers have been seen on other shuttle flights. This one, at the back of the shuttle, is not believed to be a problem.

At worse, Cain said, some downstream tiles could suffer enough damage to require replacement. On the other hand, vibrations associated with the elevon's movement - or the re-entry airflow - could work the gap filler loose or simply bend it over. But the issue has not yet been closed out.

"There's a gap filler on one of the elevons, the left inboard elevon, one of the little spacers between the tiles is protruding," Cain said. "We have a lot of flight experience with tile and gap filler and different kinds of issues in this part of the underside of the orbiter and the team's very confident this one's not going to be an issue. But we have a little bit of analysis and we want to give the team an opportunity to peer review all that. But I anticipate we'll officially clear the vehicle sometime over the weekend."

As for Discovery's performance during the climb to space last Sunday, Cain said the shuttle's boosters, main engines and external fuel tank all performed well.

"We just had exceptionally good performance out of the propulsion elements," Cain said. "The booster element reported they have no significant anomalies, but they do have what they characterized as 'squawks.' I look forward to seeing in greater detail, probably on Monday, what some of those more or less minor issues are. ... But the verbal quick-look presentation looked very good today now that the boosters are back in the hangar at the Cape."

Aboard the international space station, the astronauts checked out the tools and equipment they will need for a spacewalk urday while Sandra Magnus worked to install a replacement distillation centrifuge carried up by Discovery for the station's urine recycling system.

The water recycling system is critical to NASA's long-range plans to support six full-time astronauts aboard the outpost. The system is designed to convert condensate and urine into clean water for drinking, personal hygiene and oxygen generation.

But when the system was activated late last year, engineers ran into problems with the vacuum distillation assembly, a critical component that features a high-speed centrifuge. A new DA was flown up aboard Discovery and engineers hope to activate it over the weekend.

In the meantime, NASA managers were thrilled with the crew's successful deployment of the new S6 truss segments two solar wings earlier today. The extension of both panels, the channel 1B array first and then the 3B wing, "went very well. We didn't have any problems with it, we were very pleased with how the plan came together, how it was executed," said lead flight director Kwatsi Alibaruho.

"As we mentioned yesterday, we were going to be paying particularly close attention to the deployment of that (second) 3B solar array," he said. "One of the things that was of particular concern to us during the deployment of that solar array was the fact that that array had been packed away for so long. I mentioned in yesterday's mission status briefing that it had been packed for three years. It was actually packed for eight years."

During deploy today, television views showed a "considerable amount of deformation of the solar panels due to tension and stiction," Alibaruho said. "There was much more stiction in the 3B solar array than there was in the 1B solar array. ... The good news is all of that was in family with our experience. We executed the plan we had developed pre-flight for the thermal conditioning and all of that went very well."

Said Dan Hartman, chairman of the space station mission management team: "It was a truly fantastic day in space. The international space station team and its partnerships are on cloud nine with the completion of the integrated truss assembly as well as the finalization of our electrical power grid on the space station. It took years to get here. We had some struggles along the way, but it's a major accomplishment for NASA and the partnership team."


1:30 PM, 3/20/09, Update: Channel 3B solar array successfully deployed (UPDATED at 2:40 p.m. with Reuters interview)

A second set of solar blankets was successfully deployed today from the newly installed S6 solar array truss on the international space station, accomplishing the primary goal of the shuttle DIscovery's mission. The deployment completed the lab's U.S. power system eight years after assembly of the electrical system began with launch of the first set of solar panels.

The astronauts successfully extended S6 segment's channel 1B solar wing earlier today and despite concerns about past problems with blanket slats sticking together due to a phenomenon known as "stiction," there were no problems of any significance.

Likewise, the channel 3B solar wing, compressed and packed away for years in two storage boxes, pulled out and extended normally as a central self-assembling mast slowly pulled the blankets out. After stopping at the halfway point to allow sunlight to warm the mast and blankets, the extension was restarted and within a few minutes - at 1:17 p.m. - the huge array was fully deployed and locked in place.

The two new S6 solar wings, the fourth and final set of U.S. power panels to be attached to the station, stretch 240 feet from tip to tip. The space station's power truss, which runs at right angles to the axis formed by the station's central pressurized modules, stretches longer than a football field with two sets of dual-wing arrays on each end, giving the lab complex a welcome but unfamiliar symmetry.

Going into Discovery's mission, the station's three previously attached sets of solar arrays generated 198 kilowatts of total power. Of that total, 90 kilowatts was considered usable power. The S6 arrays added up to 30 kilowatts of additional usable power and doubled the power available for science from 15 to 30 kilowatts.

Channel 3B solar array fully deployed

"It all looks good," shuttle commander Lee Archambault reported. "The array blanket looks flat. ... We think we're fully deployed, we think we're done with this procedure."

"You are complete with the procedure," mission control replied. "Great work."

"We're very happy as well and we're pressing on," Archambault replied. "Thank you. Full power!"

Space station commander Mike Fincke later described the deployment in an interview with Reuters.

"The shuttle crew ... they worked very hard and they trained very hard for this day," he said. "So they did all of the work. Sandy (Magnus), Yury (Lonchakov) and I, we monitored to make sure everything was going smoothly aboard our space station.

"It's a very big solar array, it's huge. And that's what the American side brings to this international cooperation, we bring the electrical power because that's something we're very good at. And so today, we brought up our fourth and final solar array and it was absolutely beautiful.

"It slowly unfurls, the box itself is just a few feet thick, but it extends out, it telescopes out to be, oh boy, I don't know, 30, 40, 50 feet out. It's just really amazing. We did it very slowly, this was our fourth and last one. The first couple of ones gave us some troubles, we learned from that and made it very smoothly. And I'm very proud of the ground team that worked for years to make sure that today came to pass and it went without a hitch."

Asked if there was a collective sigh of relief when the second array extended, Fincke said "I don't think it was a sigh of relief as much as it was a shout of triumph."


12:40 PM, 3/20/09, Update: Channel 3B array deployed halfway

With one new solar array successfully deployed, the astronauts aboard the international space station began extending a second set at 12:35 p.m. to complete the lab's U.S. power system.

"Ready, ready, mark," shuttle commander Lee Archambault radioed as the deploy command was sent. Television views from space showed the array slowly extending against the dark of deep space.

Channel 3B array 49 percent extended

As with the first set, the initial extension of the channel 3B arrays went smoothly as a self-assembling mast pulled folded array slats from their storage boxes. Astronaut John Phillips halted the extension at the halfway point, as planned, to let solar heating warm the components. A few of the slats making up the blanket appeared stuck together, due to a phenomenon known as "stiction," but flight controllers said it did not appear to be a problem.

"We believe we are good to go," the ground radioed.

If all goes well, the extension procedure will resume around 1:10 p.m.

12:00 PM, 3/20/09, Update: Channel 1B solar array successfully deployed

After a wait to let the sun heat up the channel 1B solar array blankets, astronaut John Phillips resumed deployment operations today, sending commands to extend the new array from about halfway to fully deployed. The extension went smoothly and the folded blankets pulled out of their storage boxes with little of the "stiction" that marred earlier array deploys.

"Houston, Discovery, it looks like we had a very good deploy," shuttle commander Lee Archambault radioed. "The tension reel came up exactly as predicted at 31 bays and we see no anomalies."

"That's very good news, we copy all," mission control replied.

Computer graphic showing channel 1B array deployed

With the starboard 6 truss segment's channel 1B array now in place, the astronauts will wait for the next daylight pass to deploy its counterpart, the channel 3B array.


11:10 AM, 3/20/09, Update: Solar array deploy begins

With video cameras running, telemetry flowing to Earth and 10 sets of eyes looking for any signs of trouble, astronaut John Phillips issued a computer command at 11:06 a.m. to begin extending the newly installed S6 solar arrays on the international space station.

"Ready, ready, mark," shuttle commander Lee Archambault radioed as the array began extending. "Houston, we see good motion."

The self-assembling mast of the channel 1B array's two blankets began extending as expected, its members snapping into place as they emerged from a storage canister, pulling folded blankets from boxes on either side. As the central mast extended, the blankets rippled and swayed from time to time as stuck-together slats held briefly and then released.

Channel 1B solar array begins extension

There were no problems, and extension was halted as plannecd with the 1B array about halfway deployed to let solar heating help free up the rest of the slats. A similar two-step procedure is planned for the 3B array's blankets starting around 12:30 p.m.


08:00 AM, 3/20/09, Update: Solar array deploy on tap

The Discovery astronauts and their three space station counterparts plan to carefully extend a newly attached set of solar arrays today in a critical operation that will complete the station's U.S. power system after eight years of construction. The starboard 6, or S6, solar array truss segment, the station's fourth and final set of power panels, was attached during a spacewalk Thursday, plugged in, activated and prepped for array extension. Its arrays will stretch 240 feet from tip to tip when fully extended, doubling the power available for science from 15 kilowatts to 30 kilowatts.

"We're looking forward to a wonderful day in space highlighted by the deployment of the S6 solar array wings, which really is going to bring the station to full power," astronaut John Phillips said to mission control after crew wakeup. "It's going to be a full-up effort from the ground and the crew on orbit and we're really looking forward to working with you."

Along with extending the S6 solar arrays, the astronauts also plan to install a new urine distillation assembly centrifuge in the station's water recycling system, replacing a DA that failed shortly after installation late last year. Getting the water recycling system up and running is critical to long-term station operations and plans to support a full-time crew of six. The new unit will be installed late today, starting around 5:30 p.m., with testing and activation on tap this weekend.

Solar array deployment originally was planned for Sunday, but it was moved up two days after mission managers decided a focused inspection of the shuttle Discovery's heat shield, work that would have been carried out today, was not needed. Overnight, flight controllers deployed the arrays one mast bay to make sure there was no interference and to begin thermal conditioning. The actual array deployment procedure will begin around 10:50 a.m.

A fully extended solar array panel

Because of problems with past array deploys - the folded blanket slats can stick together after being packed in their storage boxes for years - the astronauts will attempt deploy in a stepwise fashion, first heating each array in sunlight and then extending them halfway before another "bake out." Only then will each panel be extended the rest of the way.

"We will start by maneuvering the international space station and the shuttle into what's called a solar-inertial attitude," said flight director Kwatsi Alibaruho. "What that really means is that we will maneuver in a manner such that one side of the space station is always pointed at the sun at every point in its orbit. That's particularly important because of what we have to do thermally with the solar arrays."

"In the first phase of solar array deploy, we'll deploy the solar arrays to approximately 45 to 50 percent of full deploy. We'll extend the solar array mast and as the mast extends, the blankets, which are currently folded in these blanket boxes, they will start to unfold like an accordion unfolds when the latches are released.

"As the solar arrays unfold, there's a phenomenon that we call 'stiction' that we're concerned about. Essentially, whenever you have brand new plastics that have been packed for quite a while there are polymers and other chemicals in these plastics that like to stick together. The solar arrays are coated with such substances and what happens is, beyond the 45 percent to 50 percent point, the sticking effect tends to create excessive tension on the mast deployment mechanism. And if the tension exceeds the recommended limits, then you could have problems with the guidewires and the tension reels on the mechanism.

An earlier solar array deploy showing blanket unfolding

"In order to alleviate that sticking, at about the 45 percent, 50 percent point of deploy in that solar-inertial attitude, we'll be maneuvered such that we'll get constant sun on the solar arrays and as the sun lands on the arrays, what we have seen in the past is the panels simply release. As they warm up the polymers and the plastics on the solar array coating, they become less sticky and they release on their own without creating excessive tension on the mechanism.

"As they release, as we thermally condition the arrays, we'll then deploy ... to the full deploy point. At that point, we'll set the mast mechanism in full tension mode. This process is slow and somewhat gradual. We expect it will take us about three full orbits, basically about four-and-a-half hours, to get both solar arrays deployed."

Complicating the procedure, the station's gyroscopes cannot be used to maintain the proper orientation during array deploy. Instead, Russian rocket thrusters at the rear of the station will be used when the arrays facing in the opposite direction are extended and shuttle thrusters will be used when their oppositely aimed counterparts are deployed. The thruster changes are required to avoid "pluming" the panels with exhaust gases.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision G of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/20/09 07:43 AM...04...12...00...Crew wakeup 09:13 AM...04...13...30...ISS daily planning conference 10:13 AM...04...14...30...Maneuver to solar array deploy attitude 10:13 AM...04...14...30...Distillation assembly unpack/transfer 10:48 AM...04...15...05...Solar array deploy operations begin 10:58 AM...04...15...15...Channel 1B array to 49 percent 11:43 AM...04...16...00...Channel 1B array to 100 percent 12:28 PM...04...16...45...Channel 3B array to 49 percent 01:13 PM...04...17...30...Channel 3B array to 100 percent 01:28 PM...04...17...45...Station arm (SSRMS) maneuver 01:58 PM...04...18...15...PAO event 02:18 PM...04...18...35...Crew meals begin 03:28 PM...04...19...45...Spacesuit component swap 04:18 PM...04...20...35...Equipment lock preps 04:58 PM...04...21...15...Tool configuration 05:30 PM...04...21...47...Mission status/MMT briefing 05:33 PM...04...21...50...Distillation assembly R&R (part 1) 05:58 PM...04...22...15...Tool audit 06:43 PM...04...23...00...Distillation assembly R&R (part 2) 07:43 PM...05...00...00...EVA-3: Procedures review 08:13 PM...05...00...30...Distillation assembly pack/transfer 08:43 PM...05...01...00...Evening planning conference 10:08 PM...05...02...25...EVA-3: Mask pre-breathe 10:53 PM...05...03...10...EVA-3: Airlock depress to 10.2 psi 11:13 PM...05...03...30...ISS crew sleep begins 11:43 PM...05...04...00...STS crew sleep begins

03/21/09 12:00 AM...05...04...17...Flight day highlights 07:43 AM...05...12...00...Crew wakeup

Phillips will push the button that starts and stops solar array deployment. His shuttle crewmates and station counterparts will be monitoring a dozen camera views, ready to shout out an abort order if any unusual behavior is detected.

"There are two solar array wings and each of them has two solar blankets, two big long solar panels," Phillips said in a NASA interview. "So there's four solar panels in all and they are in what's called 'blanket boxes,' these complicated metal boxes. The ground preps the whole thing. The ground unlocks the boxes and does a lot of checks and then they turn it over to us.

"We've got the entire shuttle crew working on this. We've got 12 TV monitors looking at different views. We've got a guy on the shuttle, six guys on the station and I. It's a big team effort. When we unfold these arrays, they're coming out of the boxes and they're pleated together. The pleats are flattening as they come out of the boxes. You don't want to put too much tension on them but you have to put enough tension on them to unfold them.

"We've learned some lessons over the years in how to do these," Phillips said. "This is, should be the final such operation in the history of the station, I hope. We've got six people stationed around monitors on the station, one on the shuttle. Two guys are just watching the tensioning devices on the boxes that the arrays are coming out of. Two people are counting the number of bays or the number of panels that have unfolded. I'm the guy who pushes the button that says "deploy."

"We will deploy each solar array wing half way out and then I will abort that deploy. We do this during orbital day time. It takes about five minutes to do half the array and then we've got around 30 minutes to bake it out, where we let the sun get on it. That will keep the panels from sticking together. Then we deploy it the rest of the way.

"And then the next solar day we do the other side. This is the fourth time we've deployed solar panels but what's very interesting is that these have been in the boxes for a long time. Once side has been in the box for five years, the other side about eight years. During that time they haven't been stretched out. Now the folks at Kennedy Space Center have taken some measures to minimize problems that might occur but we're still anticipating that some of these pleated together panels might stick and might not come apart so easily."


7:30 PM, 3/19/09, Update: Spacewalk ends

Astronauts Steven Swanson and Richard Arnold began repressurizing the space station's Quest airlock module at 7:23 p.m., officially ending a successful spacewalk to attach the new S6 solar array truss segment to the lab complex.

"Swanee and Ricky, you guys just did a fantastic job today. Right now, we're looking at about six hours, so it was really good work," astronaut Joseph Acaba radioed from inside the shuttle Discovery. "And Houston, thanks for all your support. Couldn't have done it without you."

"Hey, we just echoed that," Lucia McCullough called from mission control. "That was outstanding. For you and the rest of the combined crew, we're delighted to accept delivery and installation of the S6 truss."

Said space station commander MIke Fincke: "I just wanted to say welcome back aboard the space station. It's a lot bigger than when you left it. Great job out there. You guys were outstanding. Thanks for the hard work."

Today's spacewalk began at 1:16 p.m. and ran six hours and seven minutes, ending 23 minutes ahead of schedule. This was the 121st spacewalk devoted to station assembly and maintenance, the second so far this year and the first of three planned by Discovery's crew. Total EVA construction time now stands at 762 hours and three minutes, or nearly 32 days.

A mission status briefing is scheduled for 7:30 p.m.


7:00 PM, 3/19/09, Update: Spacewalkers deploy solar array mast canisters; wrap up successful spacewalk

Spacewalkers Steven Swanson and Richard Arnold attached the S6 solar array truss segment to the international space station today, plugged in power and data cables, unlocked a set of radiator panels and coaxed two mast canisters and blanket boxes into position for array deployment Friday.

They had to apply a bit of elbow grease to get the mast canisters and their beta gimbal assemblies rotated into position and in one case, only three of four support masts could be locked in place. But that was sufficient and mission control told the astronauts to press on.

S6 solar array boxes, mast canisters (visible behind S4 arrays) in position for extension Friday

"We can confirm that we have the other three confirmed locked," astronaut Joseph Acaba radioed from inside Discovery. "So we show ourselves in a good config."

"We did copy all of that discussion," replied Lucia McCullough from Houston. "We are good to proceed."

Swanson and Arnold then rotated solar array blanket boxes into position for deployment, removed thermal covers from electrical components and jettisoned them overboard as planned.

A thermal cover sails away, one of four jettisoned during today's EVA

Before wrapping up the excursion, Swanson asked to double-check the unlatched support bar and to take pictures if he was unable to coax it into its final position.

"I tried to pull that pin out," he reported. "It did not move. I tried to get a little leverage on it and I still could not get it to move. And so it seems to be just kind of stuck in a halfway spot."

Flight controllers re-confirmed the array canister was firmly supported with three locked bars and the astronauts began collecting their tools before heading back to the airlock.

A helmet cam view showing the four support bars at the base of an S6 array mast canister. One of the four could not be locked in place

The final task on today's agenda was deployment of a folded set of radiator panels the spacewalkers unlatched earlier. The radiator appeared to unfold normally.

S6 radiator unfolds as Swanson (center) and Arnold wrap up work


4:00 PM, 3/19/09, Update: S6 attached to space station

The $300 million S6 solar array truss segment has been bolted into place on the far right end of the space station's main power truss.

Astronauts John Phillips and Koichi Wakata, operating the space station's robot arm from a work station inside the Destiny laboratory module, carefully guided the 31,000-pound starboard 6, or S6, truss segment into contact with the S5 spacer segment at 2:17 p.m.

Spacewalker Richard Arnold used a power tool to drive an internal capture claw closed, pulling the two segments together. Four big corner bolts then were driven home to complete the physical attachment at 3:06 p.m.

Ricky Arnold drives an internal capture claw closed, locking the S6 truss segment in place. Four corner bolts finished the job

Arnold and Steven Swanson then connected two electrical cables and a pair of data cables, struggling at times with several clamps. But just before 4 p.m., the cable connections were complete and flight controllers were told they could begin activation procedures.

"Houston, Discovery. It wasn't quite as smooth as we had hoped, but those guys did a great job and I'm very happy to say you have a go for S6 activation," astronaut Joseph Acaba radioed from inside the shuttle Discovery.

"Outstanding news," mission control replied. "Thanks for all the hard work on that. We'll put the activation in work right now."

Remaining work includes stowing a keel pin, removing launch locks, releasing a stowed radiator and deploying the canisters and blanket boxes that hold the folded solar arrays in place. If all goes well, the panels will be extended by remote control Friday.

Mission managers continue to discuss possible flight plan changes to make sure experiment samples get back to Earth in good condition even if the shuttle Discovery's landing is held up by bad weather.

Planners initially considered shortening the mission one day to provide a bit of a cushion, but they now are considering delaying space station hatch closure to undocking day instead of the day before. That would give the experiment samples additional shelf life without having to shorten the flight. But no final decisions have been made.


1:20 PM, 3/19/09, Update: Spacewalk begins

Floating in the Quest airlock module, astronauts Steven Swanson and Richard Arnold switched their spacesuits to internal battery power at 1:16 p.m. to officially begin a planned six-and-a-half-hour spacewalk to attach a 31,000-pound solar array truss segment to the international space station.

After arranging safety tethers, the spacewalkers will make their way to the far right end of the station's main power truss where the 45-foot-long S6, or starboard 6, segment has been positioned by the lab's robot arm.

The S6 solar array truss segment poised for attachment

Swanson and Arnold plan to bolt the new segment in place, hook up electrical and data cables, release a variety of launch locks, deploy four stowed array blanket boxes and two mast canisters and release a set of folding radiator panels that will be used to dissipate heat.

Astronaut Ricky Arnold beginning today's spacewalk

This is the 121st spacewalk devoted to station assembly and maintenance since construction began in 1998, the first of three planned for DIscovery's mission, the third for Swanson and the first for Arnold, a former school teacher making his first flight. Going into today's excursion total station EVA time stood at 755 hours and 56 minutes, or 31.5 days.


09:00 AM, 3/19/09, Update: Astronauts prep for spacewalk

Astronauts Steven Swanson and Richard Arnold are gearing up for a planned six-and-a-half-hour spacewalk today to attach a 31,000-pound solar array truss unit to the international space station. The $300 million starboard 6, or S6, truss segment was pulled from the shuttle Discovery's cargo bay Wednesday and parked overnight near its attachment point on the far right side of the lab's main power truss. The station's robot arm will move it into place for installation starting around 11:08 a.m. and if all goes well, Swanson and Arnold, floating in the Quest airlock module, will switch their suits to battery power at 1:13 p.m. to officially begin their spacewalk.

This will be the 121st spacewalk devoted to station assembly and maintenance since construction began in 1998, the second so far this year and the first of three planned for Discovery's crew. For identification, Swanson will be wearing a suit with red stripes and use the call sign EV-1. Arnold's suit has no strips and he will use the call sign EV-2. Joseph Acaba will serve as the spacewalk director, or IVA, inside the shuttle.

Assuming S6 is successfully attached and connected, the arrays likely will be extended Friday. They originally were scheduled for deployment Sunday, but with the decision Wednesday to forego additional docked heat shield inspections - work that would have been carried out Friday - the astronauts likely will get the green light to extend the arrays Friday, ahead of schedule.

If that scenario plays out, mission managers may look into the possibility of bringing Discovery back to Earth one day earlier than currently planned to ensure that time-critical experiment samples make it down safely even if the shuttle crew runs into multiple weather delays. Discovery currently is scheduled to land March 28, but by re-arranging off-duty time and other activities, sources say it may be possible to shave a day off the mission without impacting any mission objectives or off-duty time, giving the experiment samples additional cushion. But at this point, no such decisions have been made.

The installation of the S6 truss segment is the primary objective of the 125h shuttle mission. Measuring 45.4 feet long and 16.3 feet wide in its stowed configuration, the 31,060-pound S6 is the fourth and final set of solar arrays to be attached to the lab complex and the final heavyweight payload scheduled for launch aboard a shuttle. According to Boeing, the prime contractor, S6 cost $297,918,471.

Originally built as a structural test article and then delayed by the 2003 Columbia disaster, S6 has endured a long wait for launch. It will join the S4 arrays on the right side of the station and match the port 4 and 6 arrays on the left end of the power truss. All four sets of arrays, each set stretching 240 feet from tip to tip, are designed to rotate like giant paddle wheels as the station orbits the Earth to stay face on to the sun.

The S6 arrays will provide an additional 30 kilowatts of power for science experiments above and beyond what they generates for station systems.

"Once the S6 is installed on the space station, the entire space station's power generation capability, at least from the U.S. provided hardware, will be right around 264 kilowatts," said Kwatsi Alibaruho, the station's lead flight director. "So it's very impressive. We're excited about having that much power available to support not only core space station systems operations, but also all of the science that's going to be performed."

Swanson and Arnold spent the night in the station's Quest airlock at a reduced pressure of 10 pounds per square inch to help purge nitrogen from their bloodstreams. This is a standard procedure to ensure the spacewalkers don't get the bends working in NASA's 5-psi spacesuits.

While they are preparing to leave the airlock, John Phillips and Japanese astronaut Koichi Wakata, operating the station arm from a work station inside the Destiny laboratory module, will move S6 into position for installation. The arm is anchored at a work site on the far right side of the power truss. Even so, it will still have to be fully extended across the S4 arrays and the S5 spacer segment to get S6 into position.

"There's quite a bit of choreography going on there because John and Koichi are going to be getting S6 into position," Arnold told reporters before launch. "When they have it in position, Swanee and I will go out the door and make our way to the interface where we're going to mate the S6 truss.

"From there, we have four attachment points to bolt the two pieces of truss together. Basically, it's like backing your car in the garage. We'll be telling John, 'a little bit closer, a little bit to the left, little bit to the right,' and they will fly it into position where we can then drive the bolts."

As S6 is moved toward contact with the S5 spacer truss, Phillips and Wakata will pause at one foot and six inches to make sure the alignment is precise. Initial capture will be accomplished using a central "capture claw" that will engage to hold S6 and S5 together while four attachment bolts at each corner are driven in.

"While Swanee's going around driving the bolts, we're going to attach some grounding straps, we're going to go ahead and make sure the two truss interfaces are mated," Arnold said. "Once that's all done, we then have to make some electrical connections and some data connections and then head on out to get the solar array blanket boxes deployed. The blanket boxes are in a launch configuration now."

Four electrical connections are required between S5 and S6: two for power and two for data. At this point, S6 will be structurally and electrically mated to the station. But the boxes holding the folded array blankets, and the canisters housing the collapsed masts that will be used later to pull them out, must be rotated out of their stowed positions and locked in place. The mast canisters and their associated beta gimbal assemblies - used to move the arrays from side to side once extended - will be deployed first, followed by the blanket boxes. A folding set of radiator panels will be deployed toward the end of the spacewalk.

"Swanee's going to be doing some stuff to get the mast canisters ready and while he's doing that, I'm going to be removing some launch locks that are holding the blanket boxes containing the solar arrays. I have four of those launch locks in total that I have to remove. Once the launch locks are removed, the arrays are able to move away from the truss and ... we're expecting they're going to largely go out on their own, deploy on their own. But we'll probably have to give them a little bit of a shove to get them into position."

Once the mast canisters are deployed and locked in place, "we're going to make our way up onto the mast canisters and then we have to pull the blanket boxes out into the deployed position," Arnold said. "It's a pretty complex EVA, we've got a lot of robotics going on. We have a lot of different kinds of work to do. But we're hoping when we're all done, we'll come back inside and if we don't need a focused inspection the next day, we're going to be able to go ahead and deploy the arrays."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision C of the NASA television schedule):

EDT........DD...HH...MM...EVENT

08:13 AM...03...12...30...Crew wakeup
08:48 AM...03...13...05...EVA-1: 14.7 psi repress/hygiene break
09:38 AM...03...13...55...EVA-1: Airlock depress to 10.2 psi
09:58 AM...03...14...15...ISS daily planning conference
09:58 AM...03...14...15...EVA-1: Campout EVA preps
11:08 AM...03...15...25...Station arm (SSRMS) moves S6 to pre-install
11:28 AM...03...15...45...EVA-1: Spacesuit purge
11:43 AM...03...16...00...EVA-1: Spacesuit prebreathe
12:43 PM...03...17...00...EVA-1: Crew lock depressurization
01:13 PM...03...17...30...EVA-1: Spacesuits to battery power
01:18 PM...03...17...35...EVA-1: Airlock egress
01:48 PM...03...18...05...EVA-1: Setup
02:03 PM...03...18...20...EVA-1: S6 attachment operations
03:08 PM...03...19...25...EVA-1: S6 umbilical connections
03:08 PM...03...19...25...SSRMS releases S6
04:03 PM...03...20...20...EVA-1/EV-2: Blanket box launch lock release
04:03 PM...03...20...20...EVA-1/EV-1: Radiator cinch/winch release
04:28 PM...03...20...45...SSRMS solar array viewing maneuver
04:48 PM...03...21...05...EVA-1/EV-1: Keel pin stow
05:03 PM...03...21...20...EVA-1/EV-1: Beta gimbal joint release
05:18 PM...03...21...35...Ergometer repair
05:33 PM...03...21...50...EVA-1: Unstow blanket boxes
06:33 PM...03...22...50...EVA-1: SSU/ECU cover removal
06:43 PM...03...23...00...EVA-1: Cleanup and ingress
07:43 PM...04...00...00...EVA-1: Airlock pressurization
07:58 PM...04...00...15...Spacesuit servicing
08:30 PM...04...00...47...Mission status briefing
08:58 PM...04...01...15...ISS evening planning conference
09:38 PM...04...01...55...Crew choice downlink
11:13 PM...04...03...30...ISS crew sleep begins
11:43 PM...04...04...00...STS crew sleep begins
				
03/20/09
12:00 AM...04...04...17...Daily highlights reel
07:00 AM...04...11...17...HD highlights
07:43 AM...04...12...00...Crew wakeup


8:00 PM, 3/18/09, Update: S6 truss segment moved to overnight park position; MMT decides heat shield in good shape, no focused inspection

A $300 million, 31,000-pound solar array truss segment was plucked from the shuttle Discovery's cargo bay today, handed off, re-grappled and moved to an overnight park position near the right end of the international space station's main power truss for installation Thursday during a planned six-and-a-half-hour spacewalk.

NASA's Mission Management Team, meanwhile, wrapped up its initial assessment of launch photography, an inspection of the shuttle's nose cap and wing leading edge panels Monday and a photo survey of heat shield tiles on the orbiter's belly that was carried out during final approach to the station Tuesday.

The reinforced carbon carbon nose cap and wing leading edge panels, which experience the most extreme heating during re-entry, were given a clean bill of health and late today, engineers decided a damaged tile on the left inboard elevon, or wing flap, did not warrant any additional inspections.

As a result, time blocked out before launch for a "focused" inspection will be given up and deployment of the new S6 solar panels, originally planned for Sunday, will be moved up two days to Friday if the spacewalk goes well and no other problems develop.

"After fully analyzing the data, we've determined that the focused inspection is not required," astronaut Greg "Box" Johnson called from mission control. "So we're going to modify the timelime via the pre-flight agreement for no focused inspection. Margins are good for the RTV bond for that damaged tile and factor of safety is 1.8 or better. So we are ready to press with the pre-flight agreement."

"Houston, Alpha, got you loud and clear, Box," shuttle commander Lee Archambault replied from the space station. "Thank you very much! That's absolutely great news and we look forward to seeing the re-worked timeline."

Not having to carry out a focused inspection will help the crew stay on schedule in an already complicated mission and provide a bit of a cushion in case other problems develop. But so far, the astronauts have stayed on or ahead of schedule and had no trouble today getting the S6 truss segment from DIscovery's cargo bay to its overnight park position.

Because of interference issues, the shuttle's robot arm could not be used to pull S6 from the payload bay and the station's arm could not carry out the move by itself. Instead, the station's mobile crane, operated by John Phillips and Sandra Magnus, had to first pull S6 from its mounting point in the shuttle's cargo bay and then hand it off to the shuttle arm, operated by pilot Tony Antonelli, about two hours later.

The station arm's mobile base then moved down rails on the front face of the power truss to a work site at the far right end. The shuttle arm then extended S6 out over Discovery's right wing and Phillips re-grappled it with the station arm. The shuttle arm unlatched and S6 was maneuvered to a park position where it will not get too hot or to cold.

S6 truss in overnight park position

"This was a highly successful operation," Alibaruho said. "It required a great deal of choreography between the shuttle and the space station crews as well as the ground. We were very concerned about the controllability of the international space station, maneuvering such a heavy piece of equipment as the S6 truss from the payload bay to the overnight park position.

"But the spacecraft performed very well. The shuttle performed very well, we had no anomalies with either robotic arm. We actually ran slightly ahead of the timeline for most of the day. ... We are very pleased with what we were able to accomplish."

Astronauts Steven Swanson and Richard Arnold will spend the night in the station's Quest airlock at a reduced pressure of 10 pounds per square inch to help purge nitrogen from their bloodstreams. This is a standard pre-spacewalk procedure to ensure spacewalkers don't get the bends after working in NASA's 5-psi spacesuits. The spacewalk, the first of three planned for Discovery's mission, is scheduled to begin around 1:13 p.m. Thursday.

In other work today, Magnus collected water samples from the station's potable water dispenser for shipment back to Earth aboard Discovery. Earlier testing showed the system had a higher-than-allowable bacteria count and an iodine solution carried up aboard Discovery was pumped in Tuesday.

"You may recall we conducted some activities last night to try to remediate some bacterial growth that was in the ambient temperature water line of that potable water dispenser," Alibaruho said. "We applied a biocide to that line yesterday and we let it soak overnight to make sure we reduced the bacterial count to an acceptable level.

"At this point, Sandy Magnus is following through with that procedure, which includes the collection of a water sample for return to the ground as well as an in-flight microbial sample, which will be read in a couple of days that we will use to verify the bacterial count is back to where we expect the system to normally operate."


06:20 PM, 3/18/09, Update: Station arm re-grapples S6 truss segment, completes second hand-off, sets stage for Thursday spacewalk

Astronauts John Phillips and Koichi Wakata, operating the space station's robot arm, re-grappled the 31,000-pound S6 solar array truss late today, taking it back from the space shuttle Discovery's robot arm in a complex sequence of maneuvers required to position it for installation Thursday during a planned six-amnd-a-half-hour spacewalk.

Sailing 224 miles above the South Pacific Ocean, the station arm locked back onto the 45-foot-long S6 truss at 6:15 p.m. After the shuttle arm disengages, Phillips and Wakata will move the truss segment to an overnight park position near its attachment point on the far right end of the station's main power beam.

The space station's robot arm (left) moves in to re-grapple the S6 truss segment, held in place by the shuttle Discovery's arm (right)

Astronauts Steven Swanson and Joseph Acaba plan to spend the night in the space station's Quest airlock module to prepare for the installation spacewalk. If all goes well, the excursion will begin around 1:13 p.m. Thursday.


5:40 PM, 3/18/09, Update: Station arm repositioned; crew prepares to re-grapple S6 solar array truss

The space station's robot arm pulled the new S6 solar array truss from the shuttle Discovery's cargo bay today, handed it off to the orbiter's mechanical arm and then rode a mobile transporter to the far end of the lab's main power truss.

While that was going on, the shuttle arm, operated by pilot Tony Antonelli and Joe Acaba, moved the 45-foot-long truss segment into position for handoff back to the station arm, operated by astronaut John Phillips and Koichi Wakata inside the U.S. Destiny laboratory module.

"The shuttle arm is at the handoff position with the brakes on," a shuttle astronaut called. "You have a go for the S6 grapple."

"Roger, Alpha copies," Phillips replied.

The space station robot arm at the far right end of the lab's power truss

Once locked on, Phillips planned to carefully move the 31,000-pound S6 solar array truss segment to an overnight park position to await installation Thursday during a spacewalk by astronauts Steve Swanson and Ricky Arnold.


1:45 PM, 3/18/09, Update: Shuttle robot arm locks onto S6 truss segment

The space station's robot arm pulled the S6 solar array truss out of the shuttle Discovery's cargo bay today and, after positioning it "above" the orbiter, handed it off to Discovery's robot arm around 1:42 p.m.

"Alpha and Houston, from Discovery, the grapple is complete," an astronaut radioed from inside Discovery. "Brakes are on and you have a go for S6 release."

"Great! Thank you very much," replied Sandra Magnus from inside the U.S. Destiny lab module where the station arm is operated.

The station arm, anchored to a mobile transporter, now will be moved along rails on the front face of the lab's main power truss to the far right end where the new S6 element will be installed during a spacewalk Thursday.

After the station arm is locked back down, it will re-grapple S6 and the shuttle arm will let go. S6 will remain attached to the station arm overnight in a "park" position close to its eventual attachment point.

Discovery's robot arm locks onto S6 from below. The station's arm can be seen still attached to an upper grapple fixture


12:10 PM, 3/18/09, Update: S6 solar array truss lifted from shuttle cargo bay

Astronaut John Phillips, assisted by Sandra Magnus, used the space station's robot arm to carefully lift the 31,000-pound S6 solar array truss segment from the shuttle Discovery's cargo bay. The unberthing procedure began at 12:08 p.m., the first step in a complex series of maneuvers to move the huge 45-foot-long segment to its eventual position on the right end of the station's main power truss.

The P6 solar array truss segment being pulled from shuttle Discovery's cargo bay

View from space station's starboard truss camera, showing S6 unberthing


8:50 AM, 3/18/09, Update: Astronauts gear up for S6 unberthing; spacewalk preps

The Discovery astronauts get down to business today, kicking off a two-day procedure to install a $300 million solar array truss segment on the international space station. The crew was awakened at 8:43 a.m. by a recording of Johnny Cash's "Walk the Line" beamed up from mission control.

Before the astronauts went to bed just after midnight, mission control gave them a brief update on work to assess photos shot during Discovery's approach to the space station Tuesday. Only one area of presumably minor damage was noted on one of the shuttle's wing flaps, or elevons.

"A quick look of the RPM imagery is showing there is a tile on the left-inboard elevon that has some substrate exposed," Greg Johnson radioed from Houston. "That's the only item that the team is scrutinizing at this point. There is no decision regarding any focused inspection, but we will continue to analyze that spot overnight."

"Ah, thank you very much," commander Lee Archambault replied. "We appreciate the good words and we'll anxiously await what you find. But thanks for that heads up."

The space station's U.S. power system currently consists of three sets of solar arrays, the port 4 and 6 - P4 and P6 - arrays on the left end of the lab's integrated power truss and the starboard 4, or S4, array on the right end. The 31,000 pound starboard 6, or S6, truss segment carried aloft by Discovery will be mounted on the far right side of the integrated truss during a spacewalk Thursday by astronauts Steven Swanson and Richard Arnold.

"The real fundamental payload that we're carrying is called the S6 truss and it's the final piece of the American electrical power generating truss assembly and it's been a long time coming," astronaut John Phillips said in a NASA interview. "When you look at pictures of the station now, it looks very asymmetric. Well, we're going to complete the symmetry.

"This is almost 16 tons. It fills up the entire payload bay of the shuttle. We're going to deliver that and install it and deploy it, that is, unfold the solar arrays and complete the power generation part of the U.S. segment of the space station which will enable all these brand new labs, the Japanese lab and the European lab, to have the power they need to do the experiments they're going to do."

According to NASA, the addition of the S6 arrays "will nearly double the amount of power available to perform scientific experiments on the station - from 15 kilowatts to 30 kilowatts."

The international space station before attachment of the S6 truss

With its arrays stowed for launch, the S6 element measures 16.3 feet by 14.7 feet by 45.4 feet long. It weighs 31,060 pounds.

Getting S6 from Discovery's cargo bay to its attachment point on the right end of the station's power truss is a complex, multi-step procedure. Because of interference issues, the shuttle's robot arm cannot pull S6 from the payload bay. Instead, the station's mobile crane will first pull S6 from its mounting point in the shuttle's cargo bay just before noon and then hand it off to the shuttle arm about two hours later.

The station arm's mobile base then will move down rails on the front face of the power truss to a work site at the far right end. After a break for lunch at 3:18 p.m., the shuttle arm will be positioned to hand S6 back to the station arm around 6 p.m. The station arm will hold the new truss segment in an overnight park position near its eventual attachment point. During the spacewalk Thursday, S6 will be bolted in place and electrically tied into the station's power system.

"I'm sort of the lead crane operator for the station, the space station robot arm," Phillips said. "Now, the space shuttle carries a robot arm but that arm by itself cannot pick this truss out of our payload bay and install it. So what we have to do is, Sandy Magnus and I, driving the space station robot arm, will pick the truss up out of the payload bay. Then we will hand it off to the space shuttle robot arm and they will hold it for us while the little railroad car that our robot arm is based on moves out to another position, way out on the starboard side of the station.

"Then we're going to grab it back from them and position this new truss for installation way out on the extreme starboard end of the existing truss structure. And then, the next morning, the EVA team is going to go outside and they're going to be standing by right there at the interface between the old truss and the new one that we're bringing, and we're going to bring them together and then they're going to bolt the truss together and do a bunch of other manipulations to allow it to unfold the solar blankets."

While NASA always has contingency plans and alternate procedures in case something goes wrong, the station arm simply has to work to get the new truss segment installed.

"We cannot install this truss without the space station robot arm," Phillips said. "We just can't do it. Fortunately, the space station robot arm has built in redundancy. It has multiple ways to get power to it. It has ways to operate it in a degraded mode if you've lost one particular joint or one particular black box. So we're pretty confident that will keep working.

"Now the shuttle robot arm also plays a key role because we have to hand the truss back to the shuttle robot arm in order to move the railroad car on which the station's arm is based out to where it needs to be. If we had a shuttle robot arm problem there are ways we can work around it. It's pretty complicated and would involve a lot of real-time analysis by folks on the ground. You could perhaps temporarily park this truss on a part of the station. If that happened, it will be a bad day. It would be a day that would require a lot of work from a lot of people to come up with a new plan. In the end I think we'd still get it installed."

The international space station with S6 installed

While the S6 unberthing and repositioning work is going on, Swanson and Arnold will be checking out the tools and equipment they will use Thursday to connect the arrays. They will spend the night in the station's Quest airlock at a reduced pressure of 10 pounds per square inch to help purge nitrogen from their bloodstreams. This is a standard pre-spacewalk procedure to ensure spacewalkers don't get the bends after working in NASA's 5-psi spacesuits.

The astronauts also will take time later today to troubleshoot the shuttle's exercise bike, or ergometer. When the device was set up earlier, the astronauts reported the pedals were jammed. Alternative bungee cord-type exercises are available, as well as exercise equipment aboard the space station.

The astronauts will participate in a media interview today at 2:58 p.m. and NASA mission managers will hold their daily briefing at 6:30 p.m.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision C of the NASA television schedule):

EDT........DD...HH...MM...EVENT

08:43 AM...02...13...00...STS/ISS crew wakeup
10:18 AM...02...14...35...ISS daily planning conference
11:08 AM...02...15...25...Shuttle arm (SRMS) powerup
11:38 AM...02...15...55...Station arm (SSRMS) S6 grapple/unberth
12:53 PM...02...17...10...SSRMS moves S6 to handoff position
01:13 PM...02...17...30...Equipment lock preps
01:43 PM...02...18...00...SRMS grapples S6
01:58 PM...02...18...15...EVA-1: Tools configured
02:03 PM...02...18...20...SSRMS ungrapples S6
02:18 PM...02...18...35...SSRMS transporter moves to worksite 1
02:43 PM...02...19...00...SOKOL suit leak check/dry
02:58 PM...02...19...15...PAO event with Channel One News
03:18 PM...02...19...35...Crew meals begin
04:18 PM...02...20...35...EVA-1: Tool audit
04:43 PM...02...21...00...SRMS moves S6 to handoff position
05:58 PM...02...22...15...SSRMS grapples S6
05:58 PM...02...22...15...Ergometer maintenance/repair
06:28 PM...02...22...45...SRMS ungrapples S6
06:30 PM...02...22...47...Mission status/MMT briefing
06:43 PM...02...23...00...SSRMS to overnight park position
08:28 PM...03...00...45...ISS evening planning conference
08:43 PM...03...01...00...EVA-1: Procedures review
10:28 PM...03...02...45...Crew choice downlink
10:38 PM...03...02...55...EVA-1: Mask pre-breathe
11:23 PM...03...03...40...EVA-1: Airlock depress to 10.2 psi
11:43 PM...03...04...00...ISS crew sleep begins

03/19/09
12:13 AM...03...04...30...STS crew sleep begins
01:00 AM...03...05...17...Daily highlights reel
08:13 AM...03...12...30...Crew wakeup
Discovery docked with the space station Tuesday and Japanese astronaut Koichi Wakata officially joined the station crew at 9 p.m. when his custom Soyuz seatliner was installed in the station's Russian re-entry craft. Wakata replaced Magnus on the Expedition 18 crew and she will take his place aboard Discovery when the shuttle undocks next week.


08:00 PM, 3/17/09, Update: Station crew welcomes shuttle astronauts aboard

With hugs, smiles and handshakes,the crew of the international space station welcomed shuttle commander Lee Archambault and his six crewmates aboard late today after a picture-perfect docking over western Australia.

Manually flying Discovery from the aft flight deck, Archambault guided the orbiter to a docking at a port on the front of the lab complex at 5:20 p.m. After the docking mechanisms locked the two craft together and leak checks showed tight seals, a final hatch was opened at 7:09 p.m.

Expedition 18 commander Mike Fincke, Russian flight engineer Yury Lonchakov and NASA engineer Sandra Magnus greeted Archambault, pilot Dominic "Tony" Antonelli, station veteran John Phillips, Japanese astronaut Koichi Wakata and spacewalkers Steven Swanson, Joseph Acaba and Richard Arnold aboard the lab complex.

"Space shuttle Discovery, arriving," Magnus said, ringing the ship's bell as the Discovery astronauts floated into the Harmony module. Magnus promptly welcomed her replacement, Wakata, aboard with an enthusiastic embrace. Wakata will remain behind aboard the station when Discovery undocks next week, becoming Japan's first long-duration astronaut. Magnus will return to Earth in his place after four-and-a-half months in orbit.

"All right, to the crew of Discovery, welcome aboard our beautiful international space station," Fincke said. "We've been waiting for you guys for a while. We understand you have a couple of really important things for us. First and foremost, Koichi-san, first long-duration Japanese guy in space ever. Welcome aboard!

"We also understand you have a (solar power) truss out there - more power to us - got some spacewalks lined up, we're excited for that. And also, it's always proper to recognize a former space station crew member. John, welcome back. It's gotten a lot bigger since we both first flew on here."

"It's great to be back," said Phillips, who completed a 179-day stay aboard the station in 2005.

"So welcome, Lee, welcome to your entire crew, we are dang glad to see you!" Fincke concluded.

Replied Archambault: "Mike, it's an honor to be here again, the second time for myself and Swanee and John. We're really delighted to join you, Sandy, Yuri. We've got a lot of work to do, we're looking forward to it. But this is a very special moment. So thanks for having us aboard."

"So let's get to work!" Fincke said.

After a mandatory safety briefing, the first item on the post-docking agenda was to transfer spacesuits from Discovery to the station, along with a custom seatliner that will enable Wakata to use the station's Soyuz lifeboat in an emergency. At that point, Wakata will become an official member of the ISS-18 crew and Magnus will take his place aboard Discovery.

Fincke and Lonchakov will be replaced later this month by Expedition 19 commander Gennady Padalka and Michael Barratt, who plan to launch March 26 aboard the Soyuz TMA-14 spacecraft. Fincke and Lonchakov will return to Earth April 7 aboard the Soyuz TMA-13 craft that carried them into orbit last October.

Lead Flight Director Paul Dye said Archambault flew a textbook rendezvous and docking, adding that no problems of any significance have yet developed. "We had a wonderful rendezvous today, it was extremely smooth," he said. "I can't think of any one that I've had in recent memory that went that smooth. All the major burns we did were spot on, we didn't have to do any trimming, targeting was really nice. The manual phase, in close, flown by the crew was very efficient, it looked really really good to me. Everything was within our normal parameters. I've haven't gotten the prop (fuel usage) numbers yet, but I'm guessing they're pretty good."

During final approach to the station, Archambault paused 600 feet directly below the complex and carried out a graceful 360-degree flip to let the station astronauts photograph the heat-shield tiles that protect the shuttle's belly during re-entry.

"The RPM photos of the belly of the orbiter will be coming down as soon as the crew can get them onto the computer system," Dye said. "I think they're already being downloaded and that'll give our engineering community a chance to look over the belly of the orbiter. I have not gotten any definitive word on the inspection we've done yesterday, but I haven't heard any issues come up so I think that's going very well. I know they've looked at about 70 percent of it already this morning."


5:25 PM, 3/17/09, Update: Shuttle Discovery docks with space station

With commander Lee Archambault at the controls, the space shuttle Discovery gently docked with the international space station today at 5:20 p.m. as the two craft sailed through orbital darkness 220 miles above western Australia.

"Houston and Alpha, capture confirmed," someone radioed.

"Welcome to the space station, Discovery. We're glad you're here," called station commander Mike Fincke.

"Thanks, Mike. We're glad we're here also."

After the docking mechanism firmly locks Discovery to its port on the front end of the Harmony connecting module, the astronauts will stand by for leak checks to make sure the interfaces are secure. If all goes well, Fincke, Sandra Magnus and Yury Lonchakov will welcome the shuttle astronauts aboard around 7 p.m. (exact time TBD).


4:30 PM, 3/17/09, Update: Shuttle crew flips for station

The shuttle Discovery, streaking above South America at 5 miles per second just 600 feet directly below the international space station, carried out a spectacular flip maneuver today, pitching end over end to expose the belly of the orbiter to the station crew for a photo survey to help assess the health of the shuttle's heat-shield tiles.

Television views from the station gave ground controllers and the public a bird's eye view of the graceful rendezvous pitch maneuver, or RPM, as Expedition 18 commander Mike Fincke and flight engineer Sandra Magnus shot hundreds of digital images with 400-mm and 800-mm telephoto lenses.

There were no obvious signs of damage in the television views, but it will take another day or so for engineers to complete their initial assessment of ascent imagery, data from an inspection of the shuttle's nose cap and wing leading edge panels Monday and the RPM shots taken today. But from Fincke's perspective, Discovery appeared to be in good shape.

"We did catch the orbiter when it started to move, we do believe we've given you some really good shots," Fincke radioed Houston. "The orbiter looked clean, very nice, and we'll start downloading the photos now."

Sailing 220 miles above Lima, Peru, on a track across the heart of South America, commander Lee Archambault carried out the rendezvous pitch maneuver from Discovery's aft flight deck. As Discovery returned to its starting orientation, with its payload bay facing the station, the shuttle was crossing the northeast coast of South America. From there, Archambault began a slow climb up to the station velocity vector, aiming for a point roughly 400 feet directly in front of the 662,000-pound lab complex. With Discovery's nose pointed toward deep space and its open payload bay pointed toward the station, Archambault planned to guide the orbiter to a docking around 5:13 p.m. at a pressurized mating adapter on the front of the Harmony connecting module.

The start of the nine-minute RPM was delayed slightly by communications problems between the station and mission control, but it was a minor glitch in an otherwise flawless final rendezvous sequence. If all goes well, Fincke, Magnus and Russian flight engineer Yury Lonchakov will welcome the Discovery astronauts aboard around 7 p.m.


2:45 PM, 3/17/09, Update: Final rendezvous sequence begins

Trailing the international space station by about nine statute miles, shuttle commander Lee Archambault fired Discovery's orbital maneuvering system rockets today shortly after 2:30 p.m. to start the final phase of a two-day rendezvous procedure. If all goes well, 4iscovery will be positioned about 600 feet directly below the lab complex around 4:10 p.m. for a dramatic 360-degree pitch maneuver. As the shuttle slowly flips end over end, the station crew will photograph the ship's heat shield tiles to help engineers assess their condition. From that point, Archambault plans to guide the shuttle up to a point about 310 feet directly in front of the station before pushing in to dock around 5:13 p.m.


07:10 AM, 3/17/09, Update: Shuttle closes in on station

The space shuttle Discovery is closing in on the international space station today, on track for a docking around 5:13 p.m. Commander Lee Archambault and his six crewmates - pilot Dominic "Tony" Antonelli, John Phillips, incoming space station flight engineer Koichi Wakata and spacewalkers Steve Swanson, Richard Arnold and Joseph Acaba - plan to kick off final rendezvous operations shortly after wakeup at 9:43 a.m.

"We get in our rendezvous timeline real quickly after we wake up," Archambault said in a NASA interview. "About 90 minutes after the crew wakes up, the core rendezvous team - myself, Tony Antonelli and John Phillips - will jump into the rendezvous timeline. The rendezvous timeline starts about five-and-a-half hours, approximately, before the actual docking.

"For the first three hours, Tony, myself assisted by John, will conduct a series of burns to position ourselves in close proximity with the (station). At the end of those three hours, we'll conclude that with what's called a TI (terminal initiation) burn. With the successful completion of that TI burn, for all intents and purposes the orbiter will be on sort of a collision course with the space station."

The TI rocket firing, scheduled for 2:34 p.m., will occur with the shuttle trailing the space station by about 9.2 miles. From there, Discovery will approach from behind and below.

"Once we finish the TI burn, we play musical chairs with where we're at in the cockpit," Archambault said. "I will transition from the commander's seat to the aft flight deck where we have the controls and also can look out through the overhead window. Tony will jump over from his seat to mine and that's where we bring Joe Acaba into the pilot seat. Joe will assist Tony executing the checklist procedures.

"For about the next hour and 15 minutes, Tony assisted by Joe will perform a series of very small correction burns to poise ourselves, at the end of that fourth correction burn, to place our orbiter within approximately two thousand feet, coming up the station from slightly behind and slightly below. At that point I'll begin manually flying the orbiter.

"I'll initially fly it to a point directly below the station at about 600 feet and that's when we (perform) the RPM, or the rendezvous pitch maneuver."

In what is a now-standard post-Columbia feature of shuttle-station dockings, the orbiter will perform a slow computer-driven 360-degree back flip directly under the space station to let the lab crew photograph the orbiter's heat shield tiles with 400-mm and 800-mm telephoto lenses. The digital images will be downlinked to mission control in Houston for a detailed assessment to make sure there are no problems that might affect a safe re-entry at the end of the mission.

Shuttle pitch maneuver/heat shield photo documentation

"I think these are some of the most spectacular pictures I've seen in the entire history of the shuttle program, the pictures we get durning the RPM, to see the Earth rotating underneath the orbiter as the orbiter basically does a loop in one spot," said lead flight director Paul Dye.

With the pitch maneuver complete, "I'll again take manual control of the vehicle and I'll fly what's called a TORVA (twice orbital rate V-bar approach), where I transition the vehicle from that point 600 feet below the station to a point about 300 feet out in front of the station (on the velocity vector)," Archambault said. "From there, essentially I'll just back it right on in and rendezvous with the space station."

During final approach, the shuttle will be oriented with its nose facing deep space, it's tail pointed at Earth and its open cargo bay facing the station. Docking is expected to occur as the two spacecraft sail 220 miles above Indonesia.

"Ultimately, when we dock with the station we're moving at a snail's pace of like one to two inches per second," Archambault said. "We have four guys working actively on this part of the process. Once we do dock or make contact with the station, Swannie and Ricky will take over operating the APDS, or the docking system, to perform all the hook closures and make sure we have a good tight seal with the space station.

"And while all that's going on, we've got Koichi running all the photo and TV gear and capturing all the video that you're going to see here down on the ground. So it's a complete team effort. There's no one just sitting around on this one."

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision B of the NASA television schedule and the rendezvous timeline):

EDT........DD...HH...MM...EVENT

03/17/09
01:43 AM...01...06...00...Crew sleep begins
08:53 AM...01...13...10...ISS crew wakeup
09:43 AM...01...14...00...STS crew wakeup (begin flight day 3)
09:58 AM...01...14...15...ISS daily planning conference
11:23 AM...01...15...40...Group B computer powerup
11:38 AM...01...15...55...Rendezvous timeline begins
01:02 PM...01...17...19...NC-4 rendezvous rocket firing
01:48 PM...01...18...05...Spacesuits removed from airlock
02:34 PM...01...18...51...TI burn
03:10 PM...01...19...27...Sunset
03:33 PM...01...19...50...Range: 10,000 feet
03:42 PM...01...19...59...Range: 5,000 feet
03:43 PM...01...20...00...Sunrise
03:47 PM...01...20...04...Range: 3,000 feet
03:50 PM...01...20...07...MC-4 rendezvous burn
03:54 PM...01...20...11...Range: 1,500 feet
03:57 PM...01...20...14...RPM start window open
03:59 PM...01...20...16...Range: 1,000 feet
04:02 PM...01...20...19...KU antenna to low power
04:03 PM...01...20...20...+R bar arrival directly below ISS
04:09 PM...01...20...26...Range: 600 feet
04:10 PM...01...20...27...Start pitch maneuver
04:13 PM...01...20...30...Noon
04:18 PM...01...20...35...End pitch maneuver
04:20 PM...01...20...37...RPM full photo window close
04:21 PM...01...20...38...Initiate pitch up maneuver (575 ft)
04:29 PM...01...20...46...RPM start window close
04:33 PM...01...20...50...+V bar arrival; range: 310 feet
04:33 PM...01...20...50...Range: 300 feet
04:38 PM...01...20...55...Range: 250 feet
04:42 PM...01...20...59...Range: 200 feet
04:52 PM...01...20...69...Sunset
04:44 PM...01...21...01...Range: 170 feet
04:46 PM...01...21...03...Range: 150 feet
04:50 PM...01...21...07...Range: 100 feet
04:53 PM...01...21...10...Range: 75 feet
04:57 PM...01...21...14...Range: 50 feet
05:01 PM...01...21...18...Range: 30 feet; start stationkeeping
05:06 PM...01...21...23...End stationkeeping; push to dock
05:10 PM...01...21...27...Range: 10 feet

05:12 PM...01...21...29...DOCKING

05:15 PM...01...21...32...Sunrise
05:38 PM...01...21...55...Leak checks
06:08 PM...01...22...25...Orbiter docking system prepped for ingress
06:08 PM...01...22...25...Group B computer powerdown
06:23 PM...01...22...40...Post docking laptop reconfig
06:28 PM...01...22...45...Hatch open
06:58 PM...01...23...15...Welcome aboard!
07:03 PM...01...23...20...Safety briefing
07:15 PM...01...23...32...Mission status/post-MMT briefing
07:28 PM...01...23...45...Soyuz seatliner transfer/installation
08:23 PM...02...00...40...Spacesuits transferred to ISS
08:38 PM...02...00...55...Playback ops
08:48 PM...02...01...05...REBA checkout
09:28 PM...02...01...45...Crew HDTV downlink test
09:58 PM...02...02...15...ISS evening planning conference

03/18/09
12:13 AM...02...04...30...ISS crew sleep begins
12:43 AM...02...05...00...STS crew sleep begins
Discovery will dock at the station's forward port, a pressurized mating adapter on the front end of the Harmony connecting module. After verifying tight seals, hatches will be opened and space station commander Mike Fincke, flight engineer Yury Lonchakov and Sandra Magnus will welcome the Discovery astronauts aboard. Fincke will give Archambault and his crewmates a safety briefing before the combined crews get to work.

The main items on the post-docking agenda are to transfer spacesuits from Discovery to the station, along with a custom seatliner that will enable Wakata to use the station's Soyuz lifeboat in an emergency. At that point, Wakata will become an official member of the ISS-18 crew and Magnus will take his place aboard Discovery as she prepares to close out a four-and-a-half month stay in space.

Fincke and Lonchakov will be replaced later this month by Expedition 19 commander Gennady Padalka and Michael Barratt, who plan to launch March 26 aboard the Soyuz TMA-14 spacecraft. Fincke and Lonchakov will return to Earth April 7 aboard the Soyuz TMA-13 craft that carried them into orbit last October.

A briefing is scheduled for 7:15 p.m. to review the day's activities and to provide an update from the Mission Management Team.


6:00 PM, 3/16/09, Update: Discovery in good shape after launch; space debris no threat to station; avoidance maneuver not needed

A quick-look at ascent imagery and other data indicates the shuttle Discovery came through its launch and climb to space Sunday in very good shape with no major issues or anomalies, the chairman of NASA's Mission Management Team said late today. Space station controllers, meanwhile, decided a piece of space junk they had been tracking posed no threat and would not require an avoidance maneuver by the lab crew.

"We also have some good news for you regarding that possible debris avoidance maneuver," mission control radioed. "It will not be required. We've had three good data points, the last two have been very converged in terms of the miss distance, and so we will not need to perform the debris avoidance maneuver."

"OK, the entire crew copies, no debris avoidance maneuver," station commander Mike Fincke replied from orbit.

With no changes to the station's flight path, the Discovery astronauts will carry out their previously planned rendezvous sequence of rocket firings, a carefully choreographed procedure that will result in a docking with the space station around 5:13 p.m. Tuesday.

Mission Management Team Chairman LeRoy Cain told reporters late today Discovery was in excellent condition after a "picture-perfect" launch Sunday.

"We have no major problems of note from the launch or from the ascent," Cain said. "The space shuttle vehicle performed flawlessly during the ascent phase. ... We only have a very few minor anomalies. But none of them is significant and there isn't anything that's affecting the mission or the vehicle performance in any way whatsoever."

Discovery's launch was delayed more than a month, primarily by concern about suspect hydrogen flow control valves used to pressurize the hydrogen section of the shuttle's external tank. During the previous shuttle launch last November, a small piece of a valve poppet broke off.

Discovery's launch was held up for tests and analyses to better understand what happened and what the potential impact might be. The shuttle was finally cleared for launch using three valves shown to be crack free using a new inspection technique.

Cain said today telemetry from launch Sunday showed "all three valves performed nominally, they were right down the middle of their expected performance. So no indications of any issues there."

The Discovery astronauts spent the day checking out the spacesuits they'll use during upcoming station assembly spacewalks and carrying out a detailed inspection of the shuttle's nose cap and wing leading edge panels. Cain said no obvious problems with the shuttle's heat shield had been seen, but it will take engineers another day or so to complete their analysis. A decision on whether or not an additional, "focused," inspection might be needed after docking is expected late Tuesday or early Wednesday.

Discovery is in a slightly lower orbit and slowly but surely catching up to the station. Shuttle flight planners were prepared to implement minor changes to the rendezvous sequence if the station crew had been told to carry out a debris avoidance maneuver, but that would have been "a very minor impact" on the shuttle crew's timeline.

Last week, the station astronauts briefly entered the station's Soyuz lifeboat to ride out a projected close encounter with another piece of space debris. Cain said two such incidents so close together was probably a coincidence.

But he agreed "space debris is an issue for us. It's real, insomuch that there are objects small and large that we have to contend with. We have to be constantly mindful of the fact there are things being tracked, there are objects too small to be tracked, and that's an issue as well."

Tracking and occasionally dodging space debris "is part of the business, it comes with the territory, and we'll continue to do whatever is necessary to avoid debris when we can and when we know about it."


10:30 AM, 3/16/09, Update: Shuttle heat shield inspection, rendezvous rocket firings on tap

The Discovery astronauts are working through a busy day of heat shield inspections, spacesuit checkouts and work to ready the shuttle for docking Tuesday with the international space station. Flight controllers at the Johnson Space Center in Houston, meanwhile, are continuing to evaluate the orbit of a piece of Russian space junk to determine if a space station debris avoidance maneuver might be necessary later today.

"Tracking data from government resources indicated a piece of a Cosmos spacecraft ... was going to pass within the (safety) threshold," said Pat Ryan in mission control. "Plans at that point were begun for a possible debris avoidance maneuver, an engine burn by the international space station that would move it so that it was well clear of this piece of space junk."

A more recent update indicated "there is now no threshold violation anticipated by this piece of space junk," Ryan said. "But because the target has seemed to be a moving one, the station teams are proceeding with their plans to be ready with a debris avoidance maneuver tonight and they are content to wait until at least the next round of tracking data ... before coming to a final decision."

If a debris avoidance maneuver is required, a rocket firing would be targeted for around 9:50 p.m., Ryan said. The debris, from the Russian Cosmos 1275 military navigation satellite launched in 1981, is expected to make its closest approach to the station around 3:14 a.m. Tuesday. But it was not immediately known how big the debris might be or how close it might come to the station.

Tracking data from U.S. Strategic Command are used to calculate potential debris encounters, or conjunctions, that would result in passage through an imaginary pizza box-shaped zone extending 15 miles to either side of the station and about 2,460 feet above and below.

Shuttle flight planners are preparing to make changes to Discovery's rendezvous rocket firing sequence to accommodate any move by the space station if an avoidance maneuver is, in fact, ordered.

Commander Lee Archambault and his crewmates - pilot Dominic "Tony" Antonelli, shuttle and station veteran John Phillips, incoming space station flight engineer Koichi Wakata, Japan's first long-duration station crew member, and spacewalkers Steve Swanson, Richard Arnold and Joseph Acaba - began their first full day in space around 10:15 a.m. with a recording of Lynyrd Skynyrd's "Free Bird" beamed up from mission control.

"Good morning, Discovery, and especially to Tony," called astronaut Janice Voss from Houston.

"And good morning, Houston," Antonelli replied. "Thanks for that great song. I'd like to say thanks to my family. ... I know we've got a long day, so I guess we should get right to work."

"Indeed you do."

Archambault and Antonelli already planned on two rendezvous rocket firings today, one around 12:42 p.m. and the other just before midnight. The bulk of the crew's day will be devoted to checking out the spacesuits needed for upcoming station assembly spacewalks and inspecting the shuttle's reinforced carbon carbon nose cap and wing leading edge panels.

Using a 50-foot-long boom on the end of the shuttle's robot arm, the astronauts will carry out a now-standard, inch-by-inch inspection with a laser scanner and a high-resolution camera to look for any signs of impact damage that might have occurred during launch Sunday.

The nose cap and wing leading edge panels experience the most extreme heating during re-entry. There were no obvious signs of debris or damage seen in video downlinked from the shuttle during the climb to space, but analysts will need several days to complete a detailed assessment.

NASA's Mission Management Team chairman will brief reporters today at 5 p.m., followed by a mission status briefing at 7 p.m.

Here is an updated timeline of today's activity (in EDT and mission elapsed time; includes revision B of the NASA television schedule):

EDT........DD...HH...MM...EVENT

03/16/09
10:13 AM...00...14...30...Crew wakeup
11:00 AM...00...15...17...Video File on NTV
12:42 PM...00...16...59...NC-2 rendezvous rocket firing
12:58 PM...00...17...15...Shuttle arm (SRMS) unberths inspection boom (OBSS)
01:33 PM...00...17...50...Spacesuit checkout preps
02:03 PM...00...18...20...Spacesuit checkout
02:28 PM...00...18...45...OBSS starboard wing survey
04:18 PM...00...20...35...Ergometer exercise machine setup
04:23 PM...00...20...40...OBSS nose cap survey
05:00 PM...00...21...17...Post-Mission Management Team briefing on NASA TV
05:13 PM...00...21...30...Crew meals begin
06:13 PM...00...22...30...OBSS port wing survey
06:13 PM...00...22...30...Spacesuit prepped for transfer to station
07:00 PM...00...23...17...Mission status briefing on NTV
08:13 PM...01...00...30...SRMS berths OBSS
08:18 PM...01...00...35...OMS rocket pod survey
08:43 PM...01...01...00...Laser scanner data downlink
09:08 PM...01...01...25...Centerline docking camera setup
09:38 PM...01...01...55...Orbiter docking system ring extension
10:08 PM...01...02...25...Rendezvous tools checkout
10:18 PM...01...02...35...Crew choice downlink on NASA TV
11:54 PM...01...04...11...NC-3 rendezvous rocket firing

03/17/09
01:43 AM...01...06...00...Crew sleep begins
03:14 AM...01...07...31...Possible ISS close approach by space debris
08:53 AM...01...13...10...ISS crew wakeup
09:43 AM...01...14...00...STS crew wakeup (flight day 3)
If the space station crew carries out a debris avoidance maneuver later today, the timing of Tuesday's final rendezvous and docking sequence may change slightly. For readers interested in a look ahead, here is the docking timeline as it stands today (in EDT and mission elapsed time):

EDT........DD...HH...MM...EVENT

03/17/09
02:34 PM...01...18...51...Terminal initiation (TI) burn
03:10 PM...01...19...27...Sunset
03:33 PM...01...19...50...Range: 10,000 feet
03:42 PM...01...19...59...Range: 5,000 feet
03:43 PM...01...20...00...Sunrise
03:47 PM...01...20...04...Range: 3,000 feet
03:50 PM...01...20...07...MC-4 rendezvous burn
03:54 PM...01...20...11...Range: 1,500 feet
03:57 PM...01...20...14...Rendezvous pitch maneuver (RPM) start window open
03:59 PM...01...20...16...Range: 1,000 feet
04:02 PM...01...20...19...KU antenna to low power
04:03 PM...01...20...20...+R bar arrival; shuttle directly below ISS
04:09 PM...01...20...26...Range: 600 feet
04:10 PM...01...20...27...Start RPM
04:13 PM...01...20...30...Noon
04:18 PM...01...20...35...End RPM
04:20 PM...01...20...37...RPM full photo window close
04:21 PM...01...20...38...Initiate pitch up maneuver to velocity vector (575 ft)
04:29 PM...01...20...46...RPM start window close
04:33 PM...01...20...50...+V bar arrival; shuttle directly in front of ISS;
04:33 PM...01...20...50...Range: 310 feet
04:33 PM...01...20...50...Range: 300 feet
04:38 PM...01...20...55...Range: 250 feet
04:42 PM...01...20...59...Range: 200 feet
04:52 PM...01...20...69...Sunset
04:44 PM...01...21...01...Range: 170 feet
04:46 PM...01...21...03...Range: 150 feet
04:50 PM...01...21...07...Range: 100 feet
04:53 PM...01...21...10...Range: 75 feet
04:57 PM...01...21...14...Range: 50 feet
05:01 PM...01...21...18...Range: 30 feet; start stationkeeping
05:06 PM...01...21...23...End stationkeeping; push to dock
05:10 PM...01...21...27...Range: 10 feet
05:12 PM...01...21...29...DOCKING
05:15 PM...01...21...32...Sunrise


7:55 PM, 3/15/09, Update: Shuttle Discovery rockets into orbit (UPDATED at 9:30 p.m. with post-launch news conference; no immediate signs of debris; valves, vent line worked normally; flight controllers assess possible station maneuver to avoid space junk)

Running a month behind schedule and facing a Tuesday deadline, the shuttle Discovery finally roared to life and thundered into orbit late today, putting on a spectacular show as it rocketed out of dusk and into sunlight atop a torrent of fire from its twin solid-fuel boosters.

Two minutes after liftoff at 7:43:44 p.m., the spent boosters fell away for a parachute descent to the Atlantic Ocean 29 miles below and Discovery continued its ascent under the power of its three-hydrogen-fueled main engines. Arcing away toward the northeast, the shuttle looked like a brilliant, fast-moving star is it accelerated toward space, visible almost all the way to orbit.

Television views from a camera mounted on the side of the external tank showed the boosters falling away and later, dramatic atmospheric effects that resulted in a brilliant ring of light ballooning, flickering and collapsing around the accelerating spacecraft.

There were no obvious signs of any major pieces of foam insulation or other debris falling away from the tank during the critical first few minutes of flight when the shuttle's fragile heat shield is most susceptible to impact damage. But engineers will need several days to fully evaluate imagery and other data.

"We didn't see anything at all in the first quick look," Bill Gerstenmaier, chief of space operations at NASA, told reporters after launch. "It looked very good."

Eight-and-a-half minutes after liftoff, now streaking through space at 5 miles per second, the main engines shut down as planned and Discovery slipped into its planned preliminary orbit. An orbital maneuvering system rocket firing 37 minutes after launch raised the far side of the orbit, putting the shuttle on track for a docking with the space station around 5:13 p.m. Tuesday.

"I've seen a lot of launches, either as a test director or the launch director, and this was the most visually beautiful launch I've ever seen," said Launch Director Mike Leinbach. "It was just spectacular. ... We could see the orbiter from the firing room seven minutes into flight and at that point in time, the orbiter was somewehere off New Jersey, the New York coast. It was just spectacular."

At the controls aboard Discovery were commander Lee Archambault, rookie pilot Dominic "Tony" Antonelli and flight engineer Steven Swanson. Their crewmates are station-and-shuttle-veteran John Phillips, Koichi Wakata, Japan's first long-duration space station flight engineer, Joseph Acaba and Richard Arnold, both former school teachers.

Arnold and Acaba were selected by NASA as part of a pre-Columbia program to add "educator astronauts" to the agency's roster of shuttle fliers. But with the shuttle program now set for retirement in 2010, the men and women selected as educator astronauts are now viewed as general assignment astronauts with operational roles and responsibilities.

But Acaba and Arnold both said they won't forget their roots.

"When you look at what teachers do every day, it's really an operational background," Acaba said before launch. "I mean, teachers have to think on their feet, they have to adjust all the time and I think that's part of what we do. We train for specific things, but you never really know exactly what's going to happen.

"I think bringing that skill as a teacher is really beneficial," he said. "When we're up on orbit, we may see things that these guys might not notice as an educator that we might want to make note of and when we come back, we'll try to share that with teachers to help them inspire students."

With the shuttle on its way, the station astronauts are gearing up to welcome visitors aboard. They also may be asked to maneuver the station Monday to avoid piece of space debris associated with the Russian Cosmos 1275 spacecraft. If radar tracking indicates a station avoidance maneuver is needed, the "burn" would be carried out Monday evening. The predicted time of closest approach is around 3:14 a.m. Tuesday, about 14 hours before the shuttle docks.

The on-going problem of pace debris has been a major topic of discussion in recent weeks with a satellite collision last month and a close approach last week by a small piece of satellite junk that forced the station fliers to briefly move into their Soyuz re-entry craft as a precaution.

Wakata, a shuttle veteran, will take flight engineer Sandra Magnus's place aboard the station and Magnus will return to Earth aboard Discovery after four months in orbit. Wakata's presence in orbit will highlight Japan's contribution to the space station project, a huge laboratory module known as Kibo.

"It is over 20 years since Japan started this endeavor, participating in the international space station program," he said in a NASA interview. "Early in 2008, two shuttle missions assembled the two components of the Kibo module. Now it is time for us to utilize the wonderful experiment platform."

The other major goals of the 125th shuttle mission are to install a $300 million set of solar arrays on the lab complex, completing its main power generation system. The astronauts also will deliver a new urine processor distillation assembly to help the station crew get its water recycling system up and running after start-up problems late last year.

"We're flying the last power truss to the ISS," said space station Program Manager Mike Suffredini. "In fact, this is the last major U.S. element ... built by the Boeing Corp. and flown by the Boeing-NASA team and I couldn't be more proud of the performance to date."

The new truss segment takes up the entire payload bay and "this is pretty much what our focus will be on the mission, getting the element installed and activated and the wings deployed," Suffredini said.

The day after docking, the 45-foot-long, 31,000-pound solar array truss segment will be pulled from Discovery's cargo bay by the space station's robot arm. It will be handed off to the shuttle arm briefly will the station's crane is moved to the far end of the lab's main solar power truss. Then, the station arm will take the new truss segment and "park" it overnight.P<> On rsday, during the first of four planned spacewalks, Swanson and Arnold will attach the starboard 6, or S6, truss segment and position its solar array blanket boxes for deployment. The folded arrays will be extended later in the mission.

NASA originally planned to launch Discovery Feb. 12. But the flight was repeatedly delayed because of concern about possible cracks in the three hydrogen flow control valves used to pressurize the hydrogen section of the ship's external tank during the climb to space.

After weeks of around-the-clock testing and analysis, engineers using a new inspection technique were able to identify three valves with no hints of any cracks. That, plus impact testing and analysis that indicates the valves can't crack and propagate to failure in a single flight, gave NASA managers confidence it was safe to proceed.

Then, last Wednesday, a launch attempt was scrubbed during fueling when a gaseous hydrogen leak developed at an umbilical plate that connects a 7-inch vent line to the external tank. The line is used to carry away excess hydrogen gas to maintain the proper pre-launch pressure inside the tank

The umbilical plate was disassembled and inspected, but no obvious problems were found. Seals and other components were replaced, the umbilical plate was reassembled and reattached and sensors detected no leakage during today's countdown.

Gerstenmaier said the flow control valves aboard Discovery worked flawlessly and Leinbach said the re-built gaseous hydrogen vent line worked equally well and did not show any signs of leakage today.

But the delay from Wednesday to today, pushed launch to the end of NASA's March launch window. Because of an upcoming Russian mission to swap out space station crew members, Discovery only had until Tuesday to get off the ground of the flight would have been delayed to around April 7.

Discovery must undock from the space station by March 25 to clear the way for the Russian mission. The delay to Sunday means the shuttle astronauts will only be able to carry out three of the four spacewalks they originally planned. But the work being deferred is mostly made up of "get-ahead" tasks needed for downstream assembly missions. The work originally planned for the fourth spacewalk will be carried out later by the station crew of during an upcoming shuttle visit.<

Discovery's flight comes at a crucial moment in the history of the international space station as NASA and its partners in Russia, Europe, Canada and Japan gear up to boost the lab's crew from three to six in late May.

The Soyuz TMA-14 spacecraft is being prepared for launch from the Baikonur Cosmodrome in Kazakhstan on March 26 to deliver the station's next commander and flight engineer, along with Charles Simonyi, a wealthy U.S. space tourist making his second $30 million trip to the station.

Gennady Padalka and Michael Barratt will replace Expedition 18 commander Mike Fincke and flight engineer Yury Lonchakov, who were launched to the outpost last October. Fincke, Lonchakov and Simonyi are scheduled to return to Earth aboard the Soyuz TMA-13 spacecraft April 7.

Padalka, Barratt and Wakata will be joined in late May by cosmonaut Roman Romanenko, Canadian astronaut Robert Thirsk and European Space Agency astronaut Frank De Winne. To ultimately support six full-time crew members, the station's life support system must be able to convert condensate and urine into potable water for drinking, personal hygiene and oxygen generation.

U.S. astronauts installed new water and urine recycling equipment late last year, gear that NASA managers hoped to have fully tested and operational before the additional astronauts and cosmonauts arrive later this Spring.

But the vacuum distillation assembly at the heart of the U.S.-built urine recycling gear has failed to operate properly and a 180-pound backup unit was launched aboard Discovery.

Engineers do not yet know what caused the problem with the unit currently installed and they can't rule out the possibility the new distillation assembly might suffer the same fate. But they need to get the original component back to carry out a detailed failure analysis.

"The bad news is, we try very, very hard to build rigor into the design of every piece of hardware we build such that every single one is built exactly like the other one," Suffredini said urday. "So that's the bad news. The good news is, it could be a tolerance stack-up issue. And if it's a tolerance stack-up issue, it's possible the tolerances just bit us on this one and won't bite us on the next."

He said a similar design processor flown on an earlier shuttle flight worked normally.

"So we have reason to believe the design should be OK," Suffredini said. "But with all that said, we don't know the answer. So after we install it and activate it and make sure it works, we'll turn it back off and wait until we do our failure analysis on the ground to see what the actual cause is to see whether the potential is it will be a problem for the one on orbit. And if yes, is there any way to operate it so we can process urine without failing it?

"That's really forward work for us. What we are doing with all our plans for six-person crew is assuming the DA (distillation assembly) is not working and making sure we have enough water to support that."

The space station can support a six-person crew all summer without using the urine processor assembly at all because of water supplies stockpiled on board and because visiting shuttles typically deliver 1,000 pounds or so of fresh water every visit.


6:05 PM, 3/15/09, Update: Shuttle hatch closed; weather 100 percent 'go'

The shuttle Discovery's crew has strapped in at launch pad 39A and engineers have closed the orbiter's crew cabin hatch in preparation for launch. Leak checks are underway. Based on the latest tracking of the international space station, Discovery's launch time has moved up two seconds to 7:43:44 p.m. There are no technical problems of any significance at the pad and shuttle weather officers have upgraded the forecast to 100 percent "go."

This will be the 125th shuttle mission, the 100th launch since Challenger's final flight, the 12th since the Colubmia accident, the 36th flight for DIscovery in the 25 years since it first flew in 1984 and the 32nd night launch in shuttle history. NASA defines daylight as sunrise plus three minutes through sunset minus three minutes and sunset tonight at the Kennedy Space Center is expected at 7:31 p.m.

This status report will be updated after Discovery takes off, or as conditions warrant. The crew's flight plan, the NASA TV schedule (rev. A) and the ascent abort boundaries timeline are posted on the CBS News STS-119 Quick-Look page.

Here is the remainder of this evening's countdown (best viewed with fixed-width font):

EDT...........EVENT

06:28 PM......Begin 10-minute built-in hold (T-minus 20m)
06:38 PM......NASA test director countdown briefing
06:38 PM......Resume countdown (T-minus 20m)

06:39 PM......Backup flight computer to OPS 1 software
06:43 PM......KSC area clear to launch

06:49 PM......Begin final built-in hold (T-minus 9m)
07:19 PM......NTD launch status verification
07:34:44 PM...Resume countdown (T-minus 9m)

07:36:14 PM...Orbiter access arm retraction
07:38:44 PM...Launch window opens
07:38:44 PM...Hydraulic power system (APU) start
07:38:49 PM...Terminate LO2 replenish
07:39:44 PM...Purge sequence 4 hydraulic test
07:39:44 PM...IMUs to inertial
07:39:49 PM...Aerosurface profile
07:40:14 PM...Main engine steering test
07:40:49 PM...LO2 tank pressurization
07:41:09 PM...Fuel cells to internal reactants
07:41:14 PM...Clear caution-and-warning memory
07:41:44 PM...Crew closes visors
07:41:47 PM...LH2 tank pressurization
07:42:54 PM...SRB joint heater deactivation
07:43:13 PM...Shuttle GPCs take control of countdown
07:43:23 PM...SRB steering test
07:43:37 PM...Main engine start (T-6.6 seconds)
07:43:44 PM...SRB ignition (LAUNCH)
 


4:25 PM, 3/15/09, Update: Astronauts strap in for launch

The shuttle DIscovery's seven-man crew, wearing bright orange pressure suits, began boarding the orbiter in at 4:20 p.m. to await launch on a delayed space station assembly mission. There are no technical problems of any significance at pad 39A - a fruit bat perched on the side of Discovery's external tank is not considered a threat - the weather appears to be cooperating and launch remains on track for 7:43:46 p.m.


2:50 PM, 3/15/09, Update: Engineers troubleshoot minor helium purge issue (UPDATED at 3:20 p.m. with explanation from NASA test director)

Engineers are troubleshooting a slight drop in pressure in a helium purge system used to prevent ice formation on hardware near an umbilical that feeds liquid hydrogen and oxygen rocket fuel into the shuttle Discovery's external tank. A "red crew" was sent to the pad to manually adjust the pressure in the system, but NASA Test Director Steve Payne said the work will not impact today's planning launching at 7:43:46 p.m.

"This will not interfere," Payne said. "We do this every now and then as necessary, it's a procedure we've done many times in the past when we've had to go into the pad to retrieve something or adjust something last minute."

Forecasters say the weather remains favorable for launch, with scattered clouds expected at 4,000 feet and 20,000 feet and winds out of 160 degrees and 9 knots, gusting to 13 knots, well within NASA's safety limits.

Discovery's crew, meanwhile, plans to suit up and head to the pad at 3:53 p.m. to strap in for launch.


2:00 PM, 3/15/09, Update: Fueling complete; no leaks seen

The shuttle Discovery's external tank is fully loaded with liquid oxygen and hydrogen rocket fuel and there are no signs of any leakage from a 7-inch gaseous hydrogen vent line that triggered a launch delay Wednsday. Officials say there are no technical problems of any significance at pad 39A and the weather remains favorable for launch at 7:43:46 p.m.


12:30 PM, 3/15/09, Update: Fueling proceeding smoothly; no leak seen at vent line umbilical

The shuttle Discovery's external tank is nearly filled with liquid oxygen and liquid hydrogen rocket fuel and engineers report no signs of a gaseous hydrogen leak at a 7-inch vent line that grounded the mission Wednesday.

The hydrogen section of the tank is more than 98 percent full and an internal valve is cycling normally to vent excess hydrogen gas overboard through the vent line to help maintain pre-launch internal pressure at 21.7 psi or less (flight pressure is 32 to 34 psi). The umbilical plate that attaches the line to the tank was rebuilt after the leak Wednesday and while no obvious problems were seen in the disassembled hardware, engineers were optimistic replacement of internal seals and other components would eliminate the leak.

As of this writing, readings from sensors around the umbilical plate show no signs of free hydrogen in the area and views from an infrared camera indicate normal operation.

Infrared camera view of gaseous hydrogen vent line

"Right now, there's nothing observable coming from the location of that quick disconnect," NASA spokesman George Diller said from the shuttle firing room. "So at this point, our topping operation, as well as our liquid oxygen filling operation, has been going smoothly. ... There is a lot of confidence this is not going to be a recurring problem for this launch."

There are no other technical problems of any significance, although engineers are keeping tabs on a bat perched on the back side of the external tank.


10:25 AM, 3/15/09, Update: Shuttle fueling begins

Working by remote control, engineers at the Kennedy Space Center began flowing liquid oxygen and hydrogen to the space shuttle Discovery today at 10:20 a.m., beginning a three-hour procedure to load the ship's huge external tank with a half-million gallons of rocket propellant.

The hydrogen section of the tank should be nearly full around 1 p.m., the point at which a gaseous hydrogen leak developed around a vent-line umbilical plate Wednesday, forcing NASA managers to scrub the launch. The vent line umbilical has been rebuilt with new seals and internal components and engineers are hopeful the system will be leak free today.

If all goes well, fueling should be complete by around 1:20 p.m. when the countdown will enter a planned two-hour 30-minute hold. After a final crew weather briefing and suit up, Discovery's crew will head to pad 39A at 3:53 p.m. to strap in for launch.

LIftoff remains targeted for 7:43:46 p.m. Forecasters are predicting an 80 percent chance of acceptable weather and there are no known technical problems of any significance.


8:30 AM, 3/15/09, Update: Shuttle Discovery prepared for fueling

Engineers at the Kennedy Space Center are gearing up to refuel the shuttle Discovery for launch this evening on a delayed space station assembly mission. Work to reconnect and test a gaseous hydrogen vent line is complete and NASA's Mission Management Team plans to meet around 9:45 a.m. to assess the weather and any open items before giving engineers a "go" to begin fueling.

The vent line "is no longer an issue," said a NASA spokesman early today and forecasters are continuing to predict an 80 percent chance of acceptable weather for a launch attempt at 7:43:46 PM. Assuming the MMT gives formal permission to proceed, the three-hour fueling procedure will begin around 10:18 a.m. with transfer line chill down.

A launch attempt Wednesday was scrubbed after sensors detected a significant gaseous hydrogen leak at a vent line umbilical fitting on the side of Discovery's external fuel tank. The leak only showed up when the tank was nearly full and excess hydrogen gas inside the tank was being vented overboard to maintain the proper internal pressure.

The umbilical was disassembled, internal seals and fittings were replaced and the system was reconfigured for another launch attempt. But no "smoking gun" was found to explain the leak and engineers will not know whether the repair work succeeded until the external tank's hydrogen section is loaded with super-cold rocket fuel.

Liquid hydrogen "fast fill" begins around 11:18 a.m. and "topping" will start around 1:13 p.m. It was around the time of topping off Wednesday that the leak occurred, when the tank was 98 percent full.

Here is the remainder of today's countdown, a timeline showing the crew's abort options and a flight plan for the first day in space (includes NASA TV sked (rev. A); best viewed with fixed-width font):

EDT...........EVENT

09:18 AM......External tank ready for loading
09:41 AM......Mission management team tanking meeting
10:18 AM......Resume countdown (T-minus 6 hours)

10:18 AM......LO2, LH2 transfer line chilldown
10:28 AM......Main propulsion system chill down
10:28 AM......LH2 slow fill
10:58 AM......LO2 slow fill
11:03 AM......Hydrogen ECO sensors go wet
11:08 AM......LO2 fast fill
11:18 AM......LH2 fast fill
01:13 PM......LH2 topping
01:18 PM......LH2 replenish
01:18 PM......LO2 replenish

01:18 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
01:18 PM......Closeout crew to white room
01:18 PM......External tank in stable replenish mode
01:33 PM......Astronaut support personnel comm checks
02:03 PM......Pre-ingress switch reconfig
03:18 PM......Final crew weather briefing
03:23 PM......Crew suit up begins
03:48 PM......Resume countdown (T-minus 3 hours)

03:53 PM......Crew departs O&C building
04:23 PM......Crew ingress
05:13 PM......Astronaut comm checks
05:38 PM......Hatch closure
06:08 PM......White room closeout

06:28 PM......Begin 10-minute built-in hold (T-minus 20m)
06:38 PM......NASA test director countdown briefing
06:38 PM......Resume countdown (T-minus 20m)

06:39 PM......Backup flight computer to OPS 1
06:43 PM......KSC area clear to launch

06:49 PM......Begin final built-in hold (T-minus 9m)
07:19 PM......NTD launch status verification
07:34:46 PM...Resume countdown (T-minus 9m)

07:36:16 PM...Orbiter access arm retraction
07:38:46 PM...Launch window opens
07:38:46 PM...Hydraulic power system (APU) start
07:38:51 PM...Terminate LO2 replenish
07:39:46 PM...Purge sequence 4 hydraulic test
07:39:46 PM...IMUs to inertial
07:39:51 PM...Aerosurface steering test
07:40:16 PM...Main engine steering test
07:40:51 PM...LO2 tank pressurization
07:41:11 PM...Fuel cells to internal reactants
07:41:16 PM...Clear caution-and-warning memory
07:41:46 PM...Crew closes visors
07:41:49 PM...LH2 tank pressurization
07:42:56 PM...SRB joint heater deactivation
07:43:15 PM...Shuttle GPCs take control of countdown
07:43:25 PM...SRB steering test
07:43:39 PM...Main engine start (T-6.6 seconds)
07:43:46 PM...SRB ignition (LAUNCH)

..............T+........EVENT......................VELOCITY (mph; inertial)

Abort option: Return to Launch Site (RTLS)

07:43:56 PM...T+00:10...Start roll maneuver.............................921
07:44:04 PM...T+00:18...End roll maneuver.............................1,016
07:44:22 PM...T+00:36...Start throttle down (72%).....................1,261
07:44:34 PM...T+00:48...Start throttle up (104.5%)....................1,432
07:44:45 PM...T+00:59...Max aerodynamic pressure (722 psf)............1,602
07:45:50 PM...T+02:04...SRB staging...................................3,641
07:46:00 PM...T+02:14...Start OMS assist (1:28 duration)..............3,757

Abort option: Trans-Atlantic Landing (TAL)

07:46:21 PM...T+02:35...2E TAL Moron (104.5%, 2S).....................4,023
07:46:26 PM...T+02:40...2E TAL Zaragoza (104.5%, 2S)..................4,091
07:46:37 PM...T+02:51...2E TAL Istres (104.5%, 2S)....................4,296
07:47:40 PM...T+03:54...Negative return (KSC) (104.5%, 3S)............5,523

Abort option: Abort to Oorbit (ATO)

07:49:00 PM...T+05:14...Press to ATO (104.5%, 2S, 160 u/s)............7,773
07:49:11 PM...T+05:25...Droop Zaragoza (109%,0s)......................8,183
07:49:11 PM...T+05:25...1E OPS-3 Zaragoza (109%,0s,2eo simo)..........8,251
07:49:33 PM...T+05:47...Roll to headsup...............................9,001
07:49:46 PM...T+06:00...1E TAL Zaragoza (104.5%,2S,2eo simo)..........9,614

Press to main engine cutoff (planned orbit)

07:50:00 PM...T+06:14...Press to MECO (104.5%, 2S, 180 u/s)..........10,024
07:50:00 PM...T+06:14...1E TAL Moron (109%,0s,2eo seq,1st eo @ vi)...11,183
07:50:00 PM...T+06:14...1E TAL Istres (109%,0s,2eo seq,1st eo @ vi)..11,524
07:50:42 PM...T+06:56...1E press-to-MECO (104.5%, 2S, 600 u/s).......12,069
07:51:07 PM...T+07:21...Negative Moron (2@67%).......................13,638
07:51:07 PM...T+07:21...3G limiting..................................13,638
07:51:27 PM...T+07:41...Last 2E pre-MECO TAL Zaragoza (67%)..........14,865
07:51:27 PM...T+07:41...Negative Istres (2@67%)......................14,865
07:51:34 PM...T+07:48...Last 1E pre-MECO TAL Zaragoza (104.5%).......15,342
07:51:38 PM...T+07:52...Last 3E pre-MECO TAL Zaragoza (67%)..........15,683
07:51:38 PM...T+07:52...23K..........................................15,683
07:52:04 PM...T+08:18...Last TAL Diego Garcia........................17,252
07:52:09 PM...T+08:23...MECO commanded...............................17,592
07:52:20 PM...T+08:34...Zero thrust..................................17,605

..............DD...HH...MM...EVENT

07:56:00 PM...00...00...13...Launch replays on NASA TV
08:20:00 PM...00...00...37...OMS-2 rocket firing
08:28:00 PM...00...00...45...Additional launch replays on NTV
08:33:00 PM...00...00...50...Post insertion timeline begins
08:45:00 PM...00...01...02...Post-launch news conference on NTV
09:08:00 PM...00...01...25...Payload bay door opening
10:13:00 PM...00...02...30...Laptop computer setup (part 1)
10:23:00 PM...00...02...40...Robot arm powerup
11:16:00 PM...00...03...33...NC-1 rendezvous rocket firing
11:23:00 PM...00...03...40...Robot arm checkout
11:38:00 PM...00...03...55...Group B computer powerdown
11:53:00 PM...00...04...10...Wing leading edge sensors activated
11:53:00 PM...00...04...10...External tank photo downlink

03/16/09
12:03 AM...00...04...20...External tank video downlink
02:13 AM...00...06...30...Crew sleep begins
03:00 AM...00...07...17...Engineering launch replays on NTV


4:10 PM, 3/14/09, Update: No 'smoking gun' found for hydrogen vent line leak; new components insTALled for Sunday launch try

Engineers fell several hours behind schedule today fixing an alignment issue and re-connecting a gaseous hydrogen vent line to the shuttle Discovery's external tank, but NASA managers say they should be able to make up the lost time and stay on track for a launch attempt Sunday at 7:43:46 p.m. While no "smoking gun" was found to explain a vent line leak that grounded Discovery Wednesday, Launch Director Mike Leinbach said he was hopeful the repair work resolved the problem.

"We're going to put this back together and go tank and if it doesn't leak we're going to be perfectly safe to go fly," he said. "While we like to have a smoking gun, good root cause, right now we don't have that."

Engineers work to reattach vent line to shuttle external tank

If all goes well, Discovery's countdown will resume at the T-minus 11-hour mark at 3:18 a.m. Sunday. Fueling will begin around 10:18 a.m. and the crew will strap in for launch just before 4:30 p.m.

Shuttle forecasters are predicting an 80 percent chance of good weather Sunday, with just a slight chance of low clouds that could cause problems. The outlook drops to 70 percent "go" on Monday and just 40 percent go Tuesday, the last day this month Discovery can take off. If the shuttle isn't off the ground by then, the flight will slip to around April 7, after a Russian mission to rotate space station crew members.

The primary goals of Discovery's mission are to attach a fourth and final set of solar arrays to the space station; to replace outgoing flight engineer Sandra Magnus with Japanese astronaut Koichi Wakata; to deliver a replacement urine processor sub-assembly needed by the station's water recycling system; and to bring water samples down to assess the purity of the processed water.

NASA originally hoped to launch Discovery Feb. 12, but the flight has been repeatedly delayed, first by problems with suspect hydrogen flow control valves used to pressurize the external tank during ascent and again last Wednesday, by a leak in a gaseous hydrogen vent line.

The 7-inch vent line hooks up to the external tank with a quick-disconnect fitting that is part of a ground umbilical carrier plate. During fueling, pressure in the tank is maintained by venting gaseous hydrogen overboard through the vent line. At launch, the vent line disconnects and drops away from the tank.

Ground umbilical capture plate attached to external tank

During fueling Wednesday, sensors detected a significant gaseous hydrogen leak in or near the umbilical plate. Fueling was halted, launch was scrubbed and the tank was drained.<

Engineers have now disassembled the umbilical plate, replaced the quick-disconnect fitting and the seal on the tank side. While that seal was found to have "rolled" edges, Leinbach described it as more a case of use than anything wrong. Engineers also noted discoloration on an internal surface that apparently indicates the general area of the leak.

But the hardware showed no obvious defects that might explain the leak.

"Smoking gun? No," Leinbach said. "There was some evidence of the flight seal on the external tank side of the disconnect with a slight roll to it. I'm not sure that was the cause. There was a little bit of discoloration on one of the surfaces inside the quick disconnect. I'm not sure that is particularly related. It's probably the result of hydrogen leaking through that area. So no obvious smoking gun."

While he said he was "a little surprised that we didn't find something more obvious, because it was a healthy leak." But he said he was comfortable proceeding with another launch attempt Sunday because the trouble involves a ground system and poses no threat to the crew and because replacing all the hardware likely eliminated whatever was causing the problem.

7-inch gaseous hydrogen vent line umbilical

The only trouble today occurred when engineers ran into "a little bit of an alignment issue with that connection," Leinbach said. "We've performed a standard routine where we insTALled some guide pins to verify the external part of the QD and the internal part on the external tank itself are exactly aligned. Those pins went in perfectly fine, so we know we have a good connection there. So technically, we're in great shape. To do that little bit of extra work costs us probably three or four hours. So we're three or four hours down on the timeline, but we think we can make that up tonight and support the launch tomorrow.

"We'll finish all the closeouts and get into that leak check tonight," Leinbach said. "That final re-torque that was an issue for us, that'll come up at about 6 o'clock tonight. The testing we did on the bench with that new technique for re-torquing actually proved out better than we had anticipated. So I feel real good about positive results.

"We'll get into the ordnance reconnect right after midnight and pick up the count at T-minus 11 hours at 3:18 tomorrow morning," Leinbach said. "Again, we're a little bit down on our timelines, but technically we're exactly where we want to be. So we feel really good and really, really outstanding for a launch attempt tomorrow."

Here is a revised countdown for Sunday's launch attempt (in EDT):

EDT...........EVENT

03:18 AM......ASP cockpit config
03:38 AM......Pad clear of non-essential personnel
03:38 AM......APU bite test
04:28 AM......Fuel cell activation
05:18 AM......Booster joint heater activation
05:48 AM......MEC pre-flight bite test
06:03 AM......Tanking weather update
06:48 AM......Final fueling preps; launch area clear
07:18 AM......Red crew assembled
08:03 AM......Fuel cell integrity checks complete

08:28 AM......Safe-and-arm PIC test
09:18 AM......External tank ready for loading
09:41 AM......Mission management team tanking meeting
10:18 AM......Resume countdown (T-minus 6 hours)

10:18 AM......LO2, LH2 transfer line chilldown
10:28 AM......Main propulsion system chill down
10:28 AM......LH2 slow fill
10:58 AM......LO2 slow fill
11:03 AM......Hydrogen ECO sensors go wet
11:08 AM......LO2 fast fill
11:11 AM......Crew medical checks
11:18 AM......LH2 fast fill
01:13 PM......LH2 topping
01:18 PM......LH2 replenish
01:18 PM......LO2 replenish

01:18 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
01:18 PM......Closeout crew to white room
01:18 PM......External tank in stable replenish mode
01:33 PM......Astronaut support personnel comm checks
02:03 PM......Pre-ingress switch reconfig
03:18 PM......Final crew weather briefing
03:23 PM......Crew suit up begins
03:48 PM......Resume countdown (T-minus 3 hours)

03:53 PM......Crew departs O&C building
04:23 PM......Crew ingress
05:13 PM......Astronaut comm checks
05:38 PM......Hatch closure
06:08 PM......White room closeout

06:28 PM......Begin 10-minute built-in hold (T-minus 20m)
06:38 PM......NASA test director countdown briefing
06:38 PM......Resume countdown (T-minus 20m)

06:39 PM......Backup flight computer to OPS 1
06:43 PM......KSC area clear to launch

06:49 PM......Begin final built-in hold (T-minus 9m)
07:19 PM......NTD launch status verification
07:34:46 PM...Resume countdown (T-minus 9m)

07:36:16 PM...Orbiter access arm retraction
07:38:46 PM...Launch window opens
07:38:46 PM...Hydraulic power system (APU) start
07:38:51 PM...Terminate LO2 replenish
07:39:46 PM...Purge sequence 4 hydraulic test
07:39:46 PM...IMUs to inertial
07:39:51 PM...Aerosurface profile
07:40:16 PM...Main engine steering test
07:40:51 PM...LO2 tank pressurization
07:41:11 PM...Fuel cells to internal reactants
07:41:16 PM...Clear caution-and-warning memory
07:41:46 PM...Crew closes visors
07:41:49 PM...LH2 tank pressurization
07:42:56 PM...SRB joint heater deactivation
07:43:15 PM...Shuttle GPCs take control of countdown
07:43:25 PM...SRB steering test
07:43:39 PM...Main engine start (T-6.6 seconds)
07:43:46 PM...SRB ignition (LAUNCH)
 


10:20 AM, 3/14/09, Update: Vent line seal re-torque in work; forecast remains 'go'

Engineers at launch complex 39A completed replacement of suspect seals and components in a gaseous hydrogen vent line umbilical and started a 15-hour re-torque sequence at 3 a.m. to ensure a leak-free connection to the shuttle Discovery's external tank. The sequence should be complete by around 6 p.m.

Discovery's launch on a delayed space station assembly mission remains on track for 7:43:44 p.m. Sunday and forecasters are continuing to predict generally good weather.

The Spaceflight Meteorology Group at the Johnson Space Center in Houston is calling for scattered clouds and winds out of the southeast at 9 knots with gusts to 13 knots. There is a slight chance of low clouds that could cause problems, but shuttle forecasters at the Kennedy Space Center are predicting an 80 percent chance of acceptable conditions.

Discovery was grounded Wednesday by a gaseous hydrogen leak in the ground umbilical carrier plate, or GUCP, that connects a 7-inch-wide vent line to the side of the shuttle's external tank. The line is used to help maintain the proper pressure in the tank, carrying excess hydrogen gas away as required during and after fueling.

Engineers suspected trouble with a seal in the umbilical and an inspection revealed four areas where the seal had rolled outward, something that apparently can happen if a "slug" of liquid hydrogen cases a bellows to flex near the umbilical plate. Whether that explains the leak seen Wednesday is not yet clear, but the components were replaced and the new seal was locked down early today for a 15-hour period to ensure proper alignment.

NASA's Mission Management Team meets today at 1 p.m. and a news conference is planned for 3 p.m. to update reporters on the status of repairs and work to ready Discovery for another launch attempt.

In the meantime, flight planners at the Johnson Space Center have generated a revised flight plan for Discovery's crew that will allow the astronauts to complete most of their objectives despite delays that have forced them to eliminate one of four planned spacewalks.

The revised flight plan is posted on the CBS News STS-119 Quick-Look page, along with updated launch windows, a revised countdown timeline and an updated ascent abort boundaries chart.


8:58 AM, 3/13/09, Update: No leak detected in hydrogen vent line at ambient temperature (UPDATED at 12 PM with news conference; quotes and details)

As expected, engineers troubleshooting the hydrogen vent line leak that grounded the shuttle Discovery Wednesday were unable to detect any problems using helium at ambient temperatures, officials said today. While no obvious "smoking guns" have been found, engineers are hopeful that replacing the seals and internal components in the shuttle-vent line interface will resolve the problem and clear the way for launch.

"We're going to replace these components and get into a launch attempt Sunday," said Launch Director Mike Leinbach. "If it doesn't leak, we're going to fly. If it does leak again, then we'll stand down and go look at it again."

If an obvious problem is not found during inspection of the vent line umbilical plate hardware, engineers may not know whether their repair work succeeded until Discovery's external tank is re-filled with rocket fuel.

Fueling is scheduled to begin at 10:18 a.m. Sunday for a launch attempt at 7:43:44 p.m. Shuttle weather officer Kathy Winters predicts an 80 percent chance of good weather Sunday, with a chance of low ceilings that could cause problems. The outlook drops to 70 percent "go" Monday and only 40 percent go Tuesday in the wake of an expected fronTAL system.

Flight planners at the Johnson Space Center in Houston, meanwhile, are continuing to evaluate a variety of options to maximize mission content if Discovery encounters any additional delays and launch slips to Monday or Tuesday. If Discovery isn't off the ground by Tuesday, the flight will be delayed to around April 7, after an upcoming Russian mission to rotate space station crew members using Soyuz ferry craft.

Already running more than a month behind schedule because of suspect hydrogen flow control valves, Discovery must undock from the station by March 25 to make way for the Soyuz mission. For a launch Sunday, the crew will have to eliminate one of four planned spacewalks to undock on time.

For a launch Monday, flight plans that include a day set aside for heat shield inspections at the station would feature additional reductions: two spacewalks if a "focused" inspection is required and the crew docks on the third flight day; one EVA if they dock on flight day four. For a Tuesday launch, only one spacewalk would be possible if a focused inspection is required.

But if the heat shield inspection is not needed - and the astronauts won't know that until the fifth or sixth day of the mission - flight planners likely would be able to add one of the lost spacewalks back into the crew's flight plan while still preserving an undocking on March 25.

For a Sunday launch, only three spacewalks are possible under any scenario and that assumes the gaseous hydrogen leak that grounded the shuttle Wednesday can be fixed.

The problem cropped up when sensors detected hydrogen leaking from a vent line attached to the side of the shuttle's external tank. A valve in the tank cycles periodically to reduce pressure when hydrogen gas builds up during the fueling process. The gas is vented overboard and routed to a "flare stack" where the excess hydrogen is burned away.

During fueling Wednesday, when the liquid hydrogen section of the tank was nearly full and the vent line was chilled to low temperatures, a leak developed at the vent line/shuttle interface. That interface, known as a ground umbilical carrier plate, or GUCP, passed leak checks at ambient temperatures and appeared to be leak free during the early stages of fueling. The problem only showed up when the tank was 98 percent full and the line was extremely cold.

"We had to wait until yesterday, about mid afternoon, before we could even get into the launch pad because of the external tank venting off and being inerted," Leinbach said. "Once we did get in, we did a very detailed measurement of the ground umbilical carrier plate where we had the leak. All those measurements turned out fine. We then went into a leak check, a standard leak check we always perform when we mate that guy up and that leak check, at ambient conditions, we saw no leaks, which is what we expected."

The ground umbilical plate is on the end of a swing arm that drops away when the shuttle takes off. After disconnecting ordnance, engineers began a detailed tear down and inspection of the suspect hardware. "We don't have any smoking guns yet," Leinbach said. "We did see one seal that may have a slight nick on it. Not sure if that's the real cause of the issue yet. That's a first report, you've got to give us another six or eight hours before we can really declare whether that's the culprit or not.

"We are going to change out all the components in that system as we had planned to do. Whether we found any issues or not, the plan was to change out the soft goods, the seals, etc., and then get back into the re-mating of that line to the external tank and get into the launch configuration. So we are prepared, if we find nothing, to go ahead and reassemble, reconnect and get back into a launch configuration."

But engineers cannot test the vent line components under cryogenic conditions. Leak tests are carried out using helium at ambient temperatures.

"The proof of the pudding will be when we get into external tank loading," Leinbach said. "It's going to be that thermal effect on the seal, if the seal's the problem, the thermal effect at that location is what we'll be looking for.

"We're going to go through a normal loading, we're not going to change our loading sequence at all," he said. "There will be a lot of eyes on some (data) plots when we get into that topping scenario. We'll know Sunday afternoon."

Here is a countdown timeline for Sunday, starting with a two-hour "hold" prior to the start of fueling (in EDT)

TIME..........EVENT

08:18 AM......Begin 2-hour built-in hold (T-minus 6 hours)
08:28 AM......Safe-and-arm PIC test
09:18 AM......External tank ready for loading
09:41 AM......Mission management team tanking meeting
10:18 AM......Resume countdown (T-minus 6 hours)

10:18 AM......Liquid oxygen/hydrogen transfer line chilldown
10:28 AM......Main propulsion system chill down
10:28 AM......LH2 slow fill
10:58 AM......LO2 slow fill
11:03 AM......Hydrogen ECO sensors go wet
11:08 AM......LO2 fast fill
11:11 AM......Crew medical checks
11:18 AM......LH2 fast fill
01:13 PM......LH2 topping
01:18 PM......LH2 replenish
01:18 PM......LO2 replenish

01:18 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
01:18 PM......Closeout crew to white room
01:18 PM......External tank in stable replenish mode
01:33 PM......Astronaut support personnel comm checks
02:03 PM......Pre-ingress switch reconfig
02:30 PM......NASA TV coverage begins
03:18 PM......Final crew weather briefing
03:23 PM......Crew suit up begins
03:48 PM......Resume countdown (T-minus 3 hours)

03:53 PM......Crew departs O&C building
04:23 PM......Crew ingress
05:13 PM......Astronaut comm checks
05:38 PM......Hatch closure
06:08 PM......White room closeout

06:28 PM......Begin 10-minute built-in hold (T-minus 20m)
06:38 PM......NASA test director countdown briefing
06:38 PM......Resume countdown (T-minus 20m)

06:39 PM......Backup flight computer to OPS 1
06:43 PM......KSC area clear to launch

06:49 PM......Begin final built-in hold (T-minus 9m)
07:19 PM......NTD launch status verification
07:34:44 PM...Resume countdown (T-minus 9m)

07:36:14 PM...Orbiter access arm retraction
07:38:44 PM...Launch window opens
07:38:44 PM...Hydraulic power system (APU) start
07:38:49 PM...Terminate LO2 replenish
07:39:44 PM...Purge sequence 4 hydraulic test
07:39:44 PM...IMUs to inertial
07:39:49 PM...Aerosurface profile
07:40:14 PM...Main engine steering test
07:40:49 PM...Oxygen tank pressurization
07:41:09 PM...Fuel cells to internal reactants
07:41:14 PM...Clear caution-and-warning memory
07:41:44 PM...Crew closes visors
07:41:47 PM...Hydrogen tank pressurization
07:42:54 PM...Booster joint heater deactivation
07:43:13 PM...Shuttle GPCs take control of countdown
07:43:23 PM...Booster steering test
07:43:37 PM...Main engine start (T-6.6 seconds)
07:43:44 PM...Booster ignition (LAUNCH)


4:20 PM, 3/12/09, Update: NASA managers opt for expedited repair, Sunday launch try for Discovery

NASA managers today reviewed plans to fix a leaking hydrogen vent line and decided to implement an expedited repair procedure that, if all goes well, will permit a launch attempt at 7:43:44 p.m. Sunday to kick off a delayed space station assembly mission.

The flight plan calls for Discovery to dock with the space station on Tuesday and for the astronauts to carry out three of four originally planned spacewalks to attach a final set of solar arrays and to perform a variety of get-ahead tasks for upcoming assembly missions.

Discovery's crew also will deliver long-duration crew member Koichi Wakata, Japan's first station flier, bring flight engineer Sandra Magnus back to Earth after four months in space and deliver a replacement urine processor assembly for the lab's water recycling system

The original flight plan called for a four-spacewalk mission two-week mission with two light-duty days. But to avoid conflict with an upcoming Russian mission to fly up two fresh crew members and bring two other crew members back to Earth, the docked phase of Discovery's mission must be completed by March 25.

Originally scheduled for launch Feb. 12, Discovery has been repeatedly delayed, first by problems with suspect flow control valves in the system used to pressurize the shuttle's external tank and again on Wednesday by a leak in a gaseous hydrogen vent line.

Based on past repair experience, a seal in the vent line system must be tightened down after reassembly and allowed to sit for an extended period to correct for possible misalignments during insTALlation. That would have delayed launch to Monday. But engineers decided today they could complete repairs faster than that, and mission managers opted to press ahead for a Sunday launch.

While the astronauts will have to eliminate one of their planned spacewalks in order to complete the docked phase of the mission by March 25, NASA managers decided to add a day of off-duty time after undocking to give the crew a bit of a break before landing back at the Kennedy Space Center on March 28. Here's the revised flight plan timeline:

Fl Day..DATE....EVENT

March 15 Launch (Flight Day 3 docking):

FD-01...03/15...Launch at 7:43:44 PM
FD-02...03/16...Heat shield inspection
FD-03...03/17...Docking
FD-04...03/18...S6 solar array truss unberthing
FD-05...03/19...EVA-1 (S6 solar array truss insTALlation)
FD-06...03/20...Focused inspection (if necessary)
FD-07...03/21...EVA-2
FD-08...03/22...S6 solar array extension
FD-09...03/23...EVA-3
FD-10...03/24...Logistics transfers
FD-11...03/25...Undocking/late inspection
FD-12...03/26...Off-duty time
FD-13...03/27...Entry preps
FD-14...03/28...Landing
Discovery must be off the ground by Tuesday or the flight will be delayed to around April 7. But a launch Monday would force the crew to eliminate two spacewalks while a Wednesday takeoff would require the elimination of three EVAs in order to ensure an undocking on March 25.

An updated flight plan, countdown timeline and other mission information will be posted as soon as possible.


01:50 PM, 3/12/09, Update: NASA managers mull launch options

Kennedy Space Center engineers are assessing two repair scenarios to fix a leaking gaseous hydrogen vent line system that grounded the shuttle Discovery Wednesday. One option, which requires engineers to use an expedited repair timeline, leads to a launch try Sunday while the other, which follows an established timeline based on past experience, would result in a Monday liftoff.

An engineering review was scheduled today, followed by a meeting of NASA's Mission Management Team at 4 p.m. to review repair options and consider how to proceed.

Discovery was grounded Wednesday after sensors detected gaseous hydrogen leaking from a vent line attached to the side of the shuttle's external tank. A valve in the tank cycles periodically to reduce pressure when hydrogen gas builds up during the fueling process. The gas is vented overboard and routed to a "flare stack" where the excess hydrogen is burned away.

During fueling Wednesday, when the liquid hydrogen section of the tank was nearly full and the vent line was chilled to ultra-low temperatures, a leak developed at the vent line/shuttle interface.

Based on past repair experience, a seal in the system must be tightened down after reassembly and allowed to sit for more than a day to correct for possible misalignments during insTALlation. If that repair timeline is followed, Discovery's launch likely would slip to Monday. If engineers can shorten the repair procedure, a Sunday launch try might be possible.

For most shuttle launches, a one day slip would not have major consequences. But for Discovery's already delayed mission, the difference between launching Sunday and Monday is the difference between a three-spacewalk mission and one that could be reduced to a single spacewalk.

The goals of the shuttle Discovery's mission are to insTALl a new set of solar arrays on the international space station; to ferry a new crew member - Japanese astronaut Koichi Wakata - to the lab complex; to bring astronaut Sandra Magnus back to Earth after four months in orbit; and to deliver a replacement urine processor assembly for the station's water recycling system.

Four spacewalks were originally planned, one to attach the new solar arrays and three more to carry out a variety of "get-ahead" tasks for upcoming assembly missions.

But because of a conflict with an upcoming Russian mission to rotate space station crew members using Soyuz ferry craft, the docked phase of Discovery's mission must be completed by March 25. That means Discovery must take off by Tuesday, or the flight will slip to the end of the first week in April, after the Soyuz crew rotation mission is complete.

For a launch try Sunday, docking would occur on flight day three and the astronauts would have to cancel one spacewalk, along with off-duty time, to ensure an undocking on March 25. For a launch Monday, docking would occur on flight day 4. That would force the crew to give up three spacewalks in order to undock by March 25. The same would be true for a launching Tuesday, which features a flight-day-three docking.

All of the mission scenarios assume an undocking on March 25 and landing back at the Kennedy Space Center on March 27. They also all include a non-spacewalk day for a "focused" heat shield inspection and time for urine processor insTALlation and testing

NASA flight controllers at the Johnson Space Center may be able to give the crew a flight-day-three docking opportunity for a Monday launch if they reduce the launch window from five minutes to just one or two minutes. In that case, the crew could dock on flight day three and still carry out two spacewalks before undocking on March 25.

To help clarify the various scenarios, here's a table, based on options developed when Discovery's launch slipped from February to March, showing mission highlights for launch attempts Sunday, Monday and Tuesday:

Fl Day..DATE....EVENT

March 15 Launch (Flight Day 3 docking):

FD-01...03/15...Launch at 7:43:44 PM
FD-02...03/16...Heat shield inspection
FD-03...03/17...Docking
FD-04...03/18...S6 solar array truss unberthing
FD-05...03/19...EVA-1 (S6 solar array truss insTALlation)
FD-06...03/20...Focused inspection (if necessary)
FD-07...03/21...EVA-2
FD-08...03/22...S6 solar array extension
FD-09...03/23...EVA-3
FD-10...03/24...Logistics transfers
FD-11...03/25...Undocking/late inspection
FD-12...03/26...Entry preps
FD-13...03/27...Landing

March 16 Launch (Flight Day 4 docking):

FD-01...03/16...Launch at 7:21:14 PM
FD-02...03/17...Heat shield inspection
FD-03...03/18...TBD
FD-04...03/19...Docking
FD-05...03/20...S6 solar array truss unberthing
FD-06...03/21...EVA-1 (S6 solar array truss insTALlation)
FD-07...03/22...Focused inspection (if necessary)
FD-08...03/23...S6 solar array extension
FD-09...03/24...Logistics transfers
FD-10...03/25...Undocking/late inspection
FD-11...03/26...Entry preps
FD-12...03/27...Landing

March 16 Launch (Flight Day 3 docking):

FD-01...03/16...Launch at around 7:17 PM
FD-02...03/17...Heat shield inspection
FD-03...03/18...Docking
FD-04...03/19...S6 solar array truss unberthing
FD-05...03/20...EVA-1 (S6 solar array truss insTALlation)
FD-06...03/21...Focused inspection (if necessary)
FD-07...03/22...EVA-2
FD-08...03/23...S6 solar array extension
FD-09...03/24...Logistics transfers
FD-10...03/25...Undocking/late inspection
FD-11...03/26...Entry preps
FD-12...03/27...Landing

March 17 Launch (Flight Day 3 docking)

FD-01...03/17...Launch at 6:55:29 PM
FD-02...03/18...Heat shield inspection
FD-03...03/19...Docking
FD-04...03/20...S6 solar array truss unberthing
FD-05...03/21...EVA-1 (S6 solar array truss insTALlation)
FD-06...03/22...Focused inspection (if necessary)
FD-07...03/23...S6 solar array extension
FD-08...03/24...Logistics transfers
FD-09...03/25...Undocking/late inspection
FD-10...03/26...Entry preps
FD-11...03/27...Landing
For reference, here is the mission the Discovery astronauts would have flown if the shuttle had taken off Wednesday, March 11:
March 11 Launch (Flight Day 3 docking):

FD-01...03/11...Launch at 9:20:14 PM
FD-02...03/12...Heat shield inspection
FD-03...03/13...Docking
FD-04...03/14...S6 solar array truss unberthing
FD-05...03/15...EVA-1 (S6 solar array truss insTALlation)
FD-06...03/16...Focused inspection (if necessary)
FD-07...03/17...EVA-2
FD-08...03/18...S6 solar array extension
FD-09...03/19...EVA-3
FD-10...03/20...Crew off-duty time
FD-11...03/21...EVA-4
FD-12...03/22...Off-duty time; hatches closed
FD-13...03/23...Undocking/late inspection
FD-14...03/24...Entry preps
FD-15...03/25...Landing
An updated flight plan, countdown, etc., will be posted as soon as NASA managers pick a launch target and flight planners generate updated timelines.


7:50 PM, 3/11/09, Update: Launch delayed to Sunday at the earliest

Already running a month behind schedule because of subtle hydrogen valve problems, launch of the shuttle Discovery was called off during fueling today when an unrelated hydrogen vent line sprang a potentially dangerous leak. NASA will not be able to make another attempt to launch Discovery until Sunday at the earliest, giving the astronauts just three days or so to get off the ground before the end of the March launch window.

"It's better to be flying than sitting on the ground," said Launch Director Mike Leinbach. "But our business requires perfection, and our vehicle was not perfect today. And so we're going to stand down, we're going to fix the vehicle and we're going to fly when it IS perfect. And on that day, (shuttle weather officer) Kathy Winters will have acceptable weather!"

Winters said she did, in fact, expect fairly good weather throughout the weekend. But engineers will not get access to the suspect vent valve until Friday and completing repairs in time for a Sunday launch try may prove challenging. Another Mission Management Team meeting is planned for Thursday.

If the shuttle is not off the ground by March 17 at the latest, NASA will be forced to delay the 125th shuttle mission to the end of the first week in April, after a Russian mission to rotate crews on the international space station.

Even if commander Lee Archambault and his crewmates get off Sunday, they will have to give up one of their four planned spacewalks and shorten the flight by two days to make sure the docked phase of their mission is completed ahead of the Russian Soyuz TMA-14 spacecraft's planned March 26 launch from the Baikonur Cosmodrome in Kazakhstan.

If the shuttle launch slips to Monday, the crew could be forced to give up three spacewalks, in part because a Monday launch would require a docking on the fourth day of the mission instead of flight day three as currently planned. LIkewise, a launch on Tuesday would be a one-spacewalk mission.

The primary goals of Discovery's flight are to deliver a fourth and final set of solar arrays to the international space station; to deliver a replacement urine processing assembly for the lab's water recycling system; and to ferry a fresh station crew member - Japanese astronaut Koichi Wakata - to replace outgoing flight engineer Sandra Magnus, who plans to return to Earth aboard Discovery.

Going into Discovery's launch campaign, space station managers agreed that three spacewalks, devoted primarily to "get-ahead" work for upcoming assembly missions, could be deferred to the space station crew. The three primary objectives of Discovery's flight can be accomplished with a shortened, one-spacewalk mission in a worst-case scenario.

A launch Sunday would be targeted for around 7:43:38 p.m. Assuming an on-time liftoff, Discovery would dock with the space station around 4:50 p.m. on March 17. The new starboard 6, or S6, solar array nestled in Discovery's cargo bay would be insTALled during a spacewalk by Steven Swanson and Richard Arnold starting around 1:13 p.m. on Thursday, March 19.

Two more spacewalks would be carried out March 21 and 23 before the shuttle undocked on March 25. Landing back at the Kennedy Space Center would be expected the afternoon of March 27, the day after the Soyuz TMA-13 launch and the day before the new crew's docking.

With Discovery already running a month behind schedule because of problems with gaseous hydrogen flow control valves - an issue unrelated to the vent line trouble - today's delay was a frustrating disappointment. There were no other technical problems of any significance and forecasters were predicting near-perfect weather.

But during the automated procedure to pump a half-million gallons of liquid oxygen and hydrogen rocket fuel into Discovery's huge external tank, sensors detected a significant gaseous hydrogen leak at an umbilical where a vent line hooks up to the side of the tank.

The vent system is used to regulate pressure inside the hydrogen section of the tank as it is being filled for launch. As some of the supercold liquid boils off inside the tank, pressure builds up, the vent valve is opened and gas is routed to a "flare stack" near the pad where it burns harmlessly away.

Similar problems have occurred in the past and Leinbach said it was usually possible to clear the system by cycling the valve a few times. Today, the valve was repeatedly cycled by the leak did not go away. Because of the threat of fire from free hydrogen near the shuttle, Leinbach ordered engineers to drain the tank, easing the internal pressure that required venting.

"It is the system that maintains pressure inside the hydrogen tank as we're filling up," Leinbach said. "As we put hydrogen in the tank, it does start to boil off and therefore it increases the pressure inside the external tank. We open this valve briefly to let some of that pressure out, it's a very standard thing that happens several times during fueling.

"When we were going through that phase with the hydrogen low in the tank, the temperature at the disconnect was relatively high and when we opened the vent valve early in tanking, we didn't see any leakages at all. It's when we got virtually completely full, 98 percent full, so now the temperature is lower and we went into the topping routine and opened that vent valve again, now with the colder temperatures we saw the leak.

"Again, it's external to the flight element," Leinbach said. "There's nothing leaking internal. It's when we open that vent valve to control pressure in the tank that we see the leakage overboard at that vent valve. ... All the instrumentation picked it up. It was very easy thing to diagnose from the 'we have a problem perspective.' We won't know what the problem is until we get our hands on it.

"We were never in any danger of over pressurizing, we were never in any danger of under pressurizing," he said. "It's just that every time we opened that valve to keep that pressure steady, we saw the leak."

Despite the disappointment, Mission Management Team Chairman Mike Moses said the launch team would take the latest delay in stride and not make another attempt to launch Discovery until it is safe to do so.

"That's life in the space business," he said. "Sometimes things happen."


3:55 PM, 3/11/09, Update: Mission Management Meeting planned to discuss repair/turnaround options

NASA's Mission Management Team plans to meet at 5 p.m. to discuss the potential impact of a gaseous hydrogen leak that interrupted the shuttle Discovery's fueling today and forced mission managers to order a scrub. Engineers are preserving the option of a possible launch try Thursday, at 8:54:31 p.m., if the MMT concludes the problem can be resolved in time.

"NASA officials scrubbed Wednesday’s attempt at 2:37 EDT to launch space shuttle Discovery after a slight leak was detected in a gaseous hydrogen (GH2) vent line," NASA said in a statement. "The vent line is at the intertank region of the external tank and is the overboard vent to the pad and the flare stack where the vented hydrogen is burned off. The launch team is resetting to preserve the option of attempting a Thursday night liftoff at 8:54 p.m. EDT depending on what repairs are needed and what managers decide. The Mission Management Team is meeting at 5 p.m. today to discuss the issue."

The intertank is the ribbed region of the external tank that separates the hydrogen and oxygen sections. As the hydrogen tank is filled, some of the supercold liquid boils off and the gas must be vented overboard to maintain the proper pressure levels.

Details about the nature of today's problem remain sketchy. Engineers began loading the external tank with liquid oxygen and hydrogen rocket fuel at 11:56 a.m. The trouble with the hydrogen vent valve was noted shortly before 2:30 p.m. when the hydrogen section of the tank was nearly full.

A gaseous hydrogen leak was noticed, apparently related to a specific valve. But as of this writing, it's not clear if the problem is on the ground side of the vent line interface or the shuttle side.

With Discovery already running a month behind schedule because of problems with gaseous hydrogen flow control valves - an issue unrelated to the vent line trouble - today's delay was a frustrating disappointment. There were no other technical problems of any significance and forecasters were predicting near-perfect weather.

Now, thanks to the valve-related delays, NASA is facing a looming deadline. The Russians plan to launch a Soyuz spacecraft carrying the next space station commander and flight engineer on March 26. The docked phase of the shuttle mission must be done by then to avoid a conflict. To get in a full-duration four-spacewalk mission, Discovery must take off by March 13.

By giving up one or two of the mission's planned spacewalks, along with off-duty time, Discovery could launch as late as March 16 or 17 in a worst-case scenario. After that, the flight would slip to April 7, the day outgoing station commander Mike Fincke and flight engineer Yury Lonchakov return to Earth aboard the station's current Soyuz ferry craft. But NASA managers are hopeful it won't come to that.

If engineers are cleared to proceed with a 24-hour turnaround, launch would be targeted for 8:54:31 p.m. Thursday. Fueling would begin at 11:29 a.m. and the astronauts would head for the pad to strap in at 5:04 p.m.

Assuming an on-time liftoff, Discovery would dock with the international space station at 6:01 p.m. Saturday and the first of four spacewalks would get underway at 2:24 p.m. on March 16. Undocking would be targeted for 9:57 a.m. on March 24, with landing back at the Kennedy Space Center expected around 3:01 p.m. on March 26.


2:40 PM, 3/11/09, Update: Fueling interrupted by hydrogen leak; launch delayed

An apparent gaseous hydrogen leak at an interface between the shuttle Discovery's external tank and a vent line forced NASA managers to call off today's launch attempt. The problem cropped up just before 2:30 p.m. when a decision was made to drain the huge tank for additional troubleshooting. A few minutes later, Launch Director Mike Leinbach officially called off today's launch attempt.

With no other technical problems and near-perfect weather expected, the delay was a frustrating disappointment for a mission already running a month behind schedule because of problems with gaseous hydrogen flow control valves used to pressurize the tank during flight.

The problem today cropped up as the hydrogen section of the external tank was nearly filled with supercold liquid hydrogen. Some of the hydrogen boils off in the tank and the system must be able to safely vent to maintain the proper pre-flight pressure.

It's not clear what caused today's problem or what might be required to fix it, although engineers believed the leak was related to the cycling of a specific valve. Additional details will be posted as information becomes available.


2:20 PM, 3/11/09, Update: Engineers troubleshoot hydrogen leak

Engineers are troubleshooting an apparent gaseous hydrogen leak at an external tank umbilical fitting. The problem cropped up as the hydrogen section of the external tank was nearly full. Hydrogen loading was suspended for troubleshooting, while oxygen loading continued. It's not yet clear what the potential im pact of this leak might be. This status report will be updated as more information becomes available.


12:10 PM, 3/11/09, Update: Shuttle fueling under way

With forecasters now predicting a 95 percent chance of good weather, engineers began pumping a half-million gallons of liquid oxygen and hydrogen rocket fuel into the shuttle DIscovery's external tank at 11:56 a.m. The three-hour procedure should be complete by around 3 p.m. There are no technical problems of any significance at pad 39A and launch remains on track for 9:20:14 p.m.


10:00 AM, 3/11/09, Update: Shuttle poised for launch

Engineers are gearing up to load the shuttle Discovery's external tank with a half-million gallons of liquid oxygen and hydrogen rocket fuel this morning for a launch attempt at 9:20:14 p.m. NASA officials say there are no technical problems of any significance at launch complex 39A and forecasters are continuing to predict a 90 percent chance of acceptable weather.

NASA's Mission Management Team plans to meet shortly to assess the weather and any other issues. Assuming no problems crop up, engineers will be cleared to begin the three-hour fueling procedure around 11:55 a.m.

NASA television coverage is scheduled to begin at 4 p.m. and if all goes well, Discovery's crew - commander Lee Archambault, pilot Dominic "Tony" Antonelli, John Phillips, Japanese astronaut Koichi Wakata and spacewalkers Steve Swanson, Richard Arnold and Joseph Acaba - will suit up and head for the pad at 5:30 p.m. to strap in for launch.

Here is a summary of today's countdown milestones (in EDT):

EDT........EVENT

09:55 AM......Begin 2-hour built-in hold (T-minus 6 hours)
10:05 AM......Safe-and-arm PIC test
10:55 AM......External tank ready for loading
11:55 AM......Resume countdown (T-minus 6 hours)

11:55 AM......Liquid oxygen/hydrogen transfer line chilldown
12:05 PM......Main propulsion system chill down
12:05 PM......LH2 slow fill
12:30 PM......Crew medical checks
12:35 PM......LO2 slow fill
12:40 PM......Hydrogen engine cutoff sensors are submerged
12:45 PM......LO2 fast fill
12:55 PM......LH2 fast fill
02:50 PM......LH2 topping
02:55 PM......LH2 replenish
02:55 PM......LO2 replenish

02:55 PM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
02:55 PM......Closeout crew to white room
02:55 PM......External tank in stable replenish mode
03:10 PM......Astronaut support personnel comm checks
03:20 PM......Crew photo/TV opportunity (recorded)
03:40 PM......Pre-ingress switch reconfig
04:00 PM......NASA TV live launch coverage begins
04:55 PM......Final crew weather briefing
05:00 PM......Crew suit up begins
05:25 PM......Resume countdown (T-minus 3 hours)

05:30 PM......Crew departs O&C building
06:00 PM......Crew ingress
06:50 PM......Astronaut comm checks
07:15 PM......Hatch closure
07:45 PM......White room closeout

08:05 PM......Begin 10-minute built-in hold (T-minus 20m)
08:15 PM......NASA test director countdown briefing
08:15 PM......Resume countdown (T-minus 20m)

08:16 PM......Backup flight computer loads OPS 1 software
08:20 PM......KSC area clear to launch

08:26 PM......Begin final built-in hold (T-minus 9m)
08:56 PM......NASA test director launch status verification
09:11:14 PM...Resume countdown (T-minus 9m)

09:12:44 PM...Orbiter access arm retraction
09:15:14 PM...Launch window opens
09:15:14 PM...Hydraulic power system (APU) start
09:15:19 PM...Terminate liquid oxygen replenish
09:16:14 PM...Purge sequence 4 hydraulic test
09:16:14 PM...Inertial measurement units to inertial
09:16:19 PM...Aerosurface test profile
09:16:44 PM...Main engine steering test
09:17:19 PM...Oxygen tank pressurization
09:17:39 PM...Fuel cells to internal reactants
09:17:44 PM...Clear caution-and-warning memory
09:18:14 PM...Crew closes visors
09:18:17 PM...Hydrogen tank pressurization
09:19:24 PM...Booster joint heater deactivation
09:19:43 PM...Shuttle flight computers take control of countdown
09:19:53 PM...Booster steering test
09:20:07 PM...Main engine start (T-6.6 seconds)
09:20:14 PM...Booster ignition (LAUNCH)
Discovery's liftoff is timed for the middle of a 10-minute window at roughly the moment Earth's rotation carries the launch pad into the plane of the international space station's orbit. Late Tuesday, flight controllers at the Johnson Space Center in Houston updated this evening's launch window by a few seconds. An additional update is possible later today, but here are the latest times for Wednesday and Thursday:

DATE.......WINDOW OPEN...LAUNCH........WINDOW CLOSE..STATION DOCKING

03/11/09...09:15:13 PM...09:20:14 PM...09:25:14 PM...Flight Day 3

03/12/09...08:49:31 PM...08:54:31 PM...08:59:31 PM...FD-3
.......................................09:02:41 PM...FD-4
As with all shuttle launchings, Discovery's ascent includes a wide variety of abort options in case one or more of its three hydrogen-fueled main engines shuts down prematurely for any reason.

For the first two minutes and 34 seconds, the only option for a single engine failure would be a return-to-launch-site abort and landing back at the Kennedy Space Center. Between T-plus 2:35 and 5:13, an engine failure could trigger a trans-Atlantic abort and landing in Spain or France. After T-plus 5:14, the crew could abort to orbit in the event of a single engine failure. After T-plus 6:14, the shuttle could reach its normal orbit with a single engine failure ("press to MECO," or main engine cutoff).

For readers interested in the timing of various abort options, here is an updated timeline of major ascent events (velocity includes Earth's rotation):

EDT..........T+........EVENT...................VELOCITY (inertial): MPH

ABORT OPTION: RETURN TO LAUNCH SITE (RTLS)

9:20:14 PM...T+00:00...LAUNCH
9:20:24 PM...T+00:10...START ROLL MANEUVER..........................921
9:20:32 PM...T+00:18...END ROLL MANEUVER..........................1,016
9:20:50 PM...T+00:36...START THROTTLE DOWN (72%)..................1,261
9:21:02 PM...T+00:48...START THROTTLE UP (104.5%).................1,432
9:21:13 PM...T+00:59...MAXIMUM AERODYNAMIC PRESSURE (722 psf).....1,602
9:22:18 PM...T+02:04...BOOSTER SEPARATION.........................3,641
9:22:28 PM...T+02:14...START OMS ASSIST (1:28 duration)...........3,757

ABORT OPTION: TRANS-ATLANTIC LANDING (TAL)

9:22:49 PM...T+02:35...2 ENGINE TAL MORON, SPAIN (104.5%, 2s).....4,023
9:22:54 PM...T+02:40...2E TAL ZARAGOZA, SPAIN (104.5%, 2s)........4,091
9:23:05 PM...T+02:51...2E TAL ISTRES, FRANCE (104.5%, 2s).........4,296
9:24:08 PM...T+03:54...NEGATIVE RETURN TO KSC (104.5%, 3s)........5,523

ABORT OPTION: ABORT TO ORBIT (ATO)

9:25:28 PM...T+05:14...PRESS TO ATO (104.5%, 2s, 160 u/s).........7,773
9:25:39 PM...T+05:25...DROOP ZARAGOZA (109%,0s)...................8,183
9:25:39 PM...T+05:25...1E OPS-3 ZARAGOZA (109%,0s,2EO SIMO).......8,251
9:26:01 PM...T+05:47...ROLL TO HEADSUP............................9,001
9:26:14 PM...T+06:00...1E TAL ZARAGOZA (104.5%,2s,2EO SIMO).......9,614

9:26:28 PM...T+06:14...PRESS TO MECO (104.5%, 2s, 180 u/s).......10,024
9:26:28 PM...T+06:14...1E TAL MORON (109%,0s,2EO SEQ)............11,183
9:26:28 PM...T+06:14...1E TAL ISTRES (109%,0s,2EO SEQ)...........11,524
9:27:10 PM...T+06:56...1E PRESS-TO-MECO (104.5%, 2s, 600 u/s)....12,069
9:27:35 PM...T+07:21...NEGATIVE MORON (2@67%)....................13,638
9:27:35 PM...T+07:21...3G LIMITING...............................13,638
9:27:55 PM...T+07:41...LAST 2E PRE-MECO TAL ZARAGOZA (67%).......14,865
9:27:55 PM...T+07:41...NEGATIVE ISTRES (2@67%)...................14,865
9:28:02 PM...T+07:48...LAST 1E PRE-MECO TAL ZARAGOZA (104.5%)....15,342
9:28:06 PM...T+07:52...LAST 3E PRE-MECO TAL ZARAGOZA (67%).......15,683
9:28:06 PM...T+07:52...23,000 FEET PER SECOND....................15,683
9:28:32 PM...T+08:18...LAST TAL DIEGO GARCIA.....................17,252
9:28:37 PM...T+08:23...ENGINE SHUTDOWN COMMANDED.................17,592
9:28:48 PM...T+08:34...ZERO THRUST...............................17,605
The goal of Discovery's mission is to deliver and insTALl a $300 million set of solar panels on the international space station, the fourth and final set of arrays and the last major U.S.-built station component scheduled for launch on a shuttle.

Four spacewalks are planned to connect the new solar panels, to deploy external storage platforms and to perform a variety of "get-aheads" for upcoming assembly missions. In addition, Wakata, Japan's first long-duration station flier, will replace station flight engineer Sandra Magnus, who will return to Earth aboard Discovery.

Assuming an on-time liftoff, Archambault will guide Discovery to a docking with the space station around 6:30 p.m. on March 13. The shuttle astronauts will be welcomed aboard the station by Magnus, commander Mike Fincke and flight engineer Yury Lonchakov.

Swanson and Arnold plan to stage a spacewalk two days later to attach the new solar array truss segment. Three more spacewalks by Swanson, Arnold and Acaba, working in two-man teams, are planned for March 17, 19 and 21. Undocking is targeted for March 23 with landing back at the Kennedy Space Center expected around 3:27 p.m. on March 25.

Here is the flight plan for the crew's first day in orbit (in EDT/GMT and mission elapsed time):

REV.EVENT.................................MET DD/HH:MM...EDT........GMT

WEDNESDAY, MARCH 11 Flight Day 1/Flight Day 2
....LAUNCH....................................00/00:00...09:20 PM...01:20
....MECO......................................00/00:08...09:28 PM...01:28
1...LAUNCH REPLAYS............................00/00:13...09:33 PM...01:33
1...ADDITIONAL LAUNCH REPLAYS FROM KSC........00/00:45...10:05 PM...02:05
1...POST LAUNCH NEWS CONFERENCE...............00/01:10...10:30 PM...02:30
1...PAYLOAD BAY DOOR OPENING..................00/01:25...10:45 PM...02:45

THURSDAY, MARCH 12 FD-2/FD-3
3...ROBOT ARM CHECKOUT........................00/03:40...01:00 AM...05:00
3...ASCENT FLIGHT CONTROL TEAM VIDEO REPLAY...00/03:40...01:00 AM...05:00
4...LAUNCH ENGINEERING REPLAYS FROM KSC.......00/04:40...02:00 AM...06:00
5...DISCOVERY CREW SLEEP BEGINS...............00/06:30...03:50 AM...07:50
5...FLIGHT DAY 1 HIGHLIGHTS...................00/06:40...04:00 AM...08:00
10...DISCOVERY CREW WAKE UP (FD-2)............00/14:30...11:50 AM...15:50
A complete flight plan is available on the CBS News STS-119 Quick-Look page.

Archambault and his crewmates originally hoped to begin their mission Feb. 12. But the flight was repeatedly delayed because of concern about possible cracks in the three hydrogen flow control valves used to pressurize the hydrogen section of the ship's external tank during the climb to space. The valves insTALled aboard Discovery are believed to be crack free.


5:25 PM, 3/10/09, Update: Spacewalk ends; all objectives accomplished

Space station commander Mike Fincke and flight engineer Yury Lonchakov completed a relatively straight-forward spacewalk today, insTALling a European experiment on the hull of the lab complex, performing minor maintenance and carrying out a detailed photo survey of the Zvezda command module.

The EVA began at 12:22 p.m. EDT and ended at 5:11 p.m. when the spacewalkers closed the outer hatch of the Pirs airlock module, wrapping up a four-hour 49-minutes spacewalk nearly an hour ahead of schedule.

"I want to thank you very much for the work you completed," Russian mission control radioed just before the hatch was closed. "Everything went well, everybody is happy, we're all pleased with the success of the EVA."

"Thank you, Sergei, thank you for the opportunity to do another EVA and complete all the outstanding tasks," one of the astronauts replied.

This was the 120th spacewalk devoted to station assembly and maintenance since construction began in 1998, the sixth for Fincke and the second for Lonchakov. ToTAL space station EVA assembly time now stands at 755 hours and 56 minutes.

The spacewalkers had no problems and ran ahead of schedule almost from the start, cutting off a half-dozen loose straps near the Pirs docking port that represented a potential interference hazard; insTALling the European EXPOSE-R experiment package; repositioning another experiment that was bumped out of place earlier; and conducting a photo survey to document the current condition of the Zvezda command module after nearly nine years in space.

"You know what? I am hungry. This is dinner time, isn't it?" one of the spacewalks said in Russian at one point.

"Pretty much so."

"OK. But at least we have something to think about." "Yes, you're right. I mean, job is job but still, nobody's supposed to go hungry," a translator relayed.

"Right."

"Oh, you know, we're both soldiers, we're military people so we'll have to wait."

A few moments later, as the space station sailed high above north Africa and the Mediterranean Sea during a night pass, the spacewalkers took a break to enjoy the view from 220 miles up.

"We can see the cities and then we see lots of clouds," one said. "I believe we can add the shoreline..."

"You just flew over Egypt and now you're flying over the (Mediterranean)," a Russian flight controller radioed.

"You're TALking about the Red Sea? ... Yes, we can see it."

"It's so incredibly beautiful. You know, there are no words in any language to describe what we see right now. ... It's one thing to look through the window (but) when you're in the suit outside, especially during the eclipse with the lights off, it's just absolutely unbelievable."

"You see, our hard work has some positive moments to it."

"You bet."

Fincke also took a moment to thank crewmate Sandy Magnus, who helped the spacewalkers get ready and who monitored their progress from inside the space station.

"We want to thank Sandy our third crew member, thank you so much for all your help," Fincke called.

"I'm very happy you can enjoy that view, that you had a break from your work for a moment," Magnus replied.

All three station crew members are in the final stages of their stays in orbit. Magnus, launched to the outpost last November aboard the shuttle Endeavour, is scheduled to return to Earth aboard the shuttle Discovery later this month to wrap up a four-month tour of duty.

Discovery, scheduled for launch from the Kennedy Space Center Wednesday, will carry Magnus' replacement - Japanese astronaut Koichi Wakata - to the station.

Fincke and Lonchakov were launched last October aboard a Soyuz spacecraft. Their replacements - commander Gennady Padalka and flight engineer Michael Barratt - are scheduled for launch March 26 from the Baikonur Cosmodrome in Kazakhstan, accompanied by space tourist Charles Simonyi.

Fincke, Lonchakov and Simonyi, making his second $30 million trip to the station, are scheduled to return to Earth April 7 aboard the Soyuz TMA-13 spacecraft that carried the station crew aloft last year.


2:55 PM, 3/10/09, Update: Spacewalkers running well ahead of schedule

Space station commander Mike Fincke and flight engineer Yury Lonchakov are running about 90 minutes ahead of schedule in a spacewalk to insTALl a European experiment on the hull of the lab complex and to carry out a variety of other relatively minor tasks.

The EXPOSE-R experiment package was successfully insTALled and activated and a half-dozen floating straps near the docking port of the Pirs module were shortened as planned to eliminate a potential interference hazard. The astronauts also repositioned another external matrials science experiment that was bumped out of position during an earlier spacewalk.<

The rest of today's excursion will be devoted to a detailed photo-survey to document the condition of the Zvezda command module after nearly nine years in orbit. Targets include handrails, navigation antennas, docking targets, cooling vents, thrusters and radiator panels.


12:40 PM, 3/10/09, Update: Spacewalk begins

Space station commander Mike Fincke and flight engineer Yury Lonchakov opened the hatch of the Russian Pirs module at 12:22 p.m. EDT to officially begin a planned five-hour and 40-minute spacewalk. The two men currently are working to trim loose straps near the Pirs docking interface where a Progress supply ship is currently berthed. Once that work is complete, FIncke and Lonchakov will insTALl a European experiment on the hull of the space station before turning to a variety of other relatively minor tasks.


11:30 AM, 3/10/09, Update: Shuttle countdown on track; weather still 90 percent 'go;' station spacewalk on tap

The shuttle Discovery's countdown continues to tick smoothly toward launch Wednesday on a space station assembly mission, NASA officials said today. Liquid hydrogen and oxygen were loaded aboard the orbiter Monday evening to power the ship's electricity-producing fuel cells and engineers are on schedule prepping the shuttle for fueling and blastoff Wednesday at 9:20:10 p.m.

Aboard the space station, meanwhile, commander MIke Fincke and flight engineer Yury Lonchakov are gearing up for a planned five-hour 40-minute spacewalk this afternoon to mount a European experiment packaged on the hull of the Zvezda command module and to complete a variety of other tasks. Fincke and Lonchakov were unable to complete the experiment insTALlation during their most recent previous spacewalk Dec. 22.

Today's excursion is scheduled to begin around 12:20 p.m. when the spacewalkers, wearing Russian suits, open the hatch of the Pirs docking and airlock module. Crewmate Sandra Magnus will monitor the spacewalk from inside the station.

For identification, Fincke, making his sixth spacewalk, will be wearing a suit with red stripes and use the call sign EV-2. Lonchakov, making his second EVA, will be wearing a suit with blue markings and use the call sign EV-1. No NASA helmet cameras will be used during today's work.

The goals of today's spacewalk include:

  1. Shortening six tie-down straps near the docking interface at the base of the Pirs module.

  2. InsTALling and activating the European materials exposure experiment package.

  3. Repositioning another space exposure package that was bumped out of position during an earlier spacewalk.

  4. Closing an insulation flap on a connector patch panel.

  5. Carrying out a detailed photo survey of the Zvezda command module. The more than two dozen targets include handrails, antennas, docking targets, cooling vents, thrusters and radiator panels.

This will be the 120th spacewalk devoted to station construction and maintenance since assembly began in 1998 and the first so far this year. Going into today's outing, more than 80 spacewalkers representing the United States, Russia, Japan, Canada, Germany, France and Sweden had logged 751 hours and seven minutes of EVA time.

To avoid conflict with an upcoming Russian mission to ferry a new crew to the station and return Fincke and Lonchakov to Earth, the docked phase of Discovery's mission must be finished by around March 26, the day the next crew is set for launch aboard a Soyuz spacecraft.

To carry out a full-duration four-spacewalk mission, the shuttle must get off the ground by March 13 at the latest. A launch as late as March 16 or 17 is possible, but mission managers would have to eliminate one or two planned spacewalks, along with crew off-duty time.

Complicating the picture, the Air Force plans to launch a sophisticated military communications satellite aboard an Atlas 5 rocket on March 14, with March 15 as a backup. While that flight presumably could slip a few days if NASA needed more time for Discovery, shuttle managers are hopeful it won't come to that.

NASA Test DIrector Steve Payne said launch preparations are on track with no technical problems of any significance at launch pad 39A.

"At this point, we have no real concerns," Payne said. "Our systems are in good shape, the countdown is proceeding on schedule like it should be and we are ready for the exciting mission that lies ahead of us Wednesday night."

Shuttle weather officer Kathy Winters said the forecast continues to call for a 90 percent chance of acceptable conditions Wednesday and Thursday, decreasing slightly to 80 percent "go" on Friday the 13th.

"The weather is looking very good for launch," Winters said. "And of course, there's going to be a full moon out so that's going to be a really nice view. Right now, it is looking like very favorable weather conditions for launch."


12:55 PM, 3/9/09, Update: Shuttle countdown on track; weather improves to 90 percent 'go' Wednesday and Thursday

The shuttle Discovery's countdown to launch Wednesday is proceeding smoothly, officials said today, with no technical problems of any significance at the launch pad and excellent weather expected throughout the week. Forecasters are calling for a 90 percent chance of acceptable weather Wednesday and Thursday, decreasing slightly to 80 percent "go" on Friday.

"The weather looks very good for launch, I'm very happy to say. Right now we're just looking at a really nice upper-level ridge that's been holding off the weather, the fronts that tend to come into the U.S. right now," said Kathy Winters, the shuttle weather officer at the spaceport. "There's one in the central U.S., it'll stay there, it will be blocked by this high pressure ridge. So for Florida, the weather looks really good. Nice mild conditions, warm temperatures.

"The day of launch we'll probably be getting up to the mid to upper 70s here at Kennedy Space Center and about mid 70s at the pad. And then as we get into that evening, we'll stay nice and moderate with the southeast flow, the flow off the water keeping temperatures moderate. The only slight concern we have is that a ceiling can sometimes come in ... but really, the chances of that are low and with that, we're going with a 10 percent chance of KSC weather prohibiting launch."

With clear skies expected, a rising, nearly-full moon above the launch pad should provide a dramatic backdrop.

"One nice little touch on the launch this time is that the moon is going to be rising about one hour before launch," said Winters. "So it'll be in the east and it's a full moon, it's a 99-percent moon-illumination night. So it should be a really nice night for a launch and hopefully, you'll get some good snapshots of that."

Discovery's countdown began Sunday evening at 7 p.m. and Launch Director MIke Leinbach said today preparations were proceeding smoothly, with engineers gearing up to pump liquid hydrogen and oxygen aboard the shuttle to power its three electricity producing fuel cells.

"Right now, we're not tracking any issues in the firing room that would prevent any major milestones," he said. "A couple of IPRs (interim problem reports) over the weekend, but no big deal. So the team is anxious to go, we're fully trained, ready to execute this mission."

Mike Moses, the new chairman of NASA's Mission Management Team at the Kennedy Space Center, said managers had little to discuss at today's launch-minus-two-day meeting.

"We had a very short meeting today, which is a record for us with STS-119 from what we've become used to," he said, referring to recent discussions of flow control valve issues. "We TALked today about our upcoming operations, we got a weather briefing from Kathy, the launch director, Mike Leinbach, gave us a good status of the team and where they're at. As a management team, we really didn't have that many issues to discuss. We checked with every agency, every center, every project. No one had any issues."

The MMT did review the status of an electronic component in a system used to move the shuttle's orbiTAL maneuvering system, or OMS, rockets. A loose circuit card was found in a secondary controller after a recent shuttle flight, but Moses said the system has enough redundancy to handle any such issues should they occur again.

"Basically, when they took the lid off the electronics box, there's a piece of foam that helps keep those cards seated in their slots," he said. "And they saw that foam had some compression memory in it and one of the cards was loose. They've looked at some other boxes, pulled those apart, found that same compression in the foam but none of those cards were loose. Looking at the history of it, it looks like this card might have been loose from the very beginning."

The shuttle is equipped with two OMS engines for major orbiTAL maneuvers and to provide the braking needed to drop out of orbit. Each engine is equipped with redundant steering control and only one engine is required for deorbit. On top of that, smaller maneuvering jets could be used to drop a shuttle out of orbit if both OMS engines somehow failed.

"Redundancy wise, we're in really great shape there," Moses said. "We TALked it pretty detailed just to make sure we had a handle on it. Nobody had any issues or concerns and I'm perfectly fine with that and we're ready to fly."


11:45 AM, 3/9/09, Update: Mission preview; weather 90 percent 'go' Wednesday and Thursday

After around-the-clock work to resolve concern about suspect hydrogen valves, the shuttle Discovery is set for launch Wednesday on a four-spacewalk mission to attach a final set of solar arrays to the international space station. The huge solar panels, stretching 240 feet tip to tip, are the last major U.S.-built station components scheduled for launch on a space shuttle.

The first of five missions planned for 2009, STS-119 also will ferry Japan's first long-duration station flier - shuttle veteran Koichi Wakata - to the lab complex and bring flight engineer Sandra Magnus back to Earth after four months in space.

Launch is targeted for 9:20 p.m. EDT Wednesday, roughly the moment Earth's rotation carries launch pad 39A into the plane of the space station's orbit. Forecasters are predicting a 90 percent chance of good weather Wednesday and Thursday, decreasing slightly to 80 percent on Friday.

"The vehicle's looking real good, the weather's looking real good," Mike Moses, chairman of NASA's Mission Management Team at the Kennedy Space Center, told reporters today . "I need a piece of wood to knock on, but I think we've got a really good shot Wednesday."

Joining Wakata aboard Discovery will be commander Lee Archambault, rookie pilot Dominic "Tony" Antonelli, shuttle and station veteran John Phillips, and spacewalkers Steven Swanson, Richard Arnold and Joseph Acaba.

Arnold and Acaba are former school teachers, selected as "educator-astronauts" and following in the footsteps of Barbara Morgan, Christa McAuliffe's backup in NASA's original Teacher in Space program.

But unlike McAuliffe and even Morgan, Arnold and Acaba will have no time for teaching.

"When Steve Lindsey, the chief of the (astronaut) office, assigned both me and Ricky to this flight, he wasn't looking at hey, we're going to fly two teachers," Acaba said. "He was looking for astronauts to fill the slots with a certain skill set and I think we fill those. These guys treat us like anybody else and everybody else in the office has been very supportive of the program. So it's been great."

Archambault is making his second flight and his first as commander. Swanson also is making his second flight while Phillips, veteran of a long-duration station tour of duty in 2005, will be logging his third space mission.

Assuming an on-time liftoff, Archambault will guide Discovery to a docking with the space station around 6:30 p.m. on March 13. The shuttle astronauts will be welcomed aboard the station by Magnus, commander Mike Fincke and flight engineer Yury Lonchakov.

Swanson and Arnold plan to stage a spacewalk two days later to attach the new solar array truss segment. Three more spacewalks by Swanson, Arnold and Acaba, working in two-man teams, are planned for March 17, 19 and 21. Undocking is targeted for March 23 with landing back at the Kennedy Space Center expected around 3:27 p.m. on March 25.

Archambault and his crewmates originally hoped to begin their mission Feb. 12. But the flight was repeatedly delayed because of concern about possible cracks in the three hydrogen flow control valves used to pressurize the hydrogen section of the ship's external tank during the climb to space.

During the most recent shuttle flight last November, a small piece of one valve poppet broke free. It was the first such incident in shuttle history and while it caused no problems, NASA managers ordered tests to assess the safety of the system.

As it turned out, the valve cracked and liberated debris because of high-cycle fatigue, the result of harmonics in the flow environment inside the pressurization line that engineers had not suspected. While analysis continued, three valves that passed an electron microscope inspection were insTALled aboard Discovery.

But testing continued and engineers discovered that surface roughness could mask small cracks, raising questions about the valves aboard Discovery. Those valves had flown about a dozen times each and they eventually were removed. Engineers planned to replace them with valves that had four, four and five flights respectively.

While all of that was going on, engineers carried out computer analysis to model the flow inside the hydrogen pressurization line and conducted impact testing to determine whether a piece of debris could cause damage if a fragment broke off in flight. Of special concern was a 90-degree bend in the line just five inches from each valve.

Against this backdrop, engineers came up with a new way to inspect the valves for cracks, adopting so-called eddy current analysis to look tellTALe defects indicative of cracks.

"It's a commercial way that they inspect bolt heads," said shuttle Program Manager John Shannon. "Basically, you put a magnetic field around the circumference of the bolt and then you measure the (induced) voltage you get through that magnetic field. Some of the really smart guys that we have ... adapted that to this problem and we ran several blind trials with (valve) poppets we knew had cracks. It performed so well that it found some cracks that we did not know we had, that we had not seen with the scanning electron microscope. So we had a lot of confidence in this inspection capability.

"So we took apart the valves that we had initially said we were going to put in with lower flight times and checked those out. Two of them were clean and one of them showed two cracks in it. That was a little bit of a surprise to us. So we screened the three valves that we had taken off of DIscovery that had 12 flights apiece and the first one we looked at had a crack in it. Then the next two did not have cracks in them. So we were able to put together, with a very high confidence level, a set of three valves and a flight spare that we could put in Discovery and have a lot of confidence that they did not have initiating cracks.”

Computer modeling and detailed meTALlurgical analysis now show cracks are unlikely to develop and propagate to failure in a single flight and that even if a failure occurred, large pieces are unlikely to break away. In addition, impact testing showed the plumbing can withstand hits from the sort of debris that would be released in a valve failure. Finally, a detailed study of the consequences of an impact puncture in the pressurization line showed much larger debris would be required to cause pressurization or flammability issues.

"So we really attacked this problem from all the different areas, we made sure we had good valves going in without cracks, we showed even if one or two start a crack and liberate, they would be small," Shannon said. "We showed that if it got in the plumbing it's very unlikely to cause damage and then we showed that even if it does cause damage, that damage is not something that we needed to worry about."

For downstream flights, NASA managers are assessing possible redesigns or the feasibility of simply launching with new, verified crack-free valves, each flight.

In the near term, thanks to the valve-related delays, NASA is facing a deadline of sorts with DIscovery. The Russians plan to launch a Soyuz spacecraft carrying the next space station commander and flight engineer on March 26. The docked phase of the shuttle mission must be done by then to avoid a conflict. To get in a full-duration four-spacewalk mission, Discovery must take off by March 13.

By giving up one or two of the mission's planned spacewalks, along with off-duty time, Discovery could launch as late as March 16 or 17 in a worst-case scenario. After that, the flight would slip to April 7, the day Fincke and Lonchakov return to Earth aboard the station's current Soyuz ferry craft. But NASA managers are optimistic it won't come to that.

Discovery's flight comes at a crucial moment in the history of the international space station as NASA and its partners in Russia, Europe, Canada and Japan gear up to boost the lab's crew from three to six in late May. U.S. astronauts insTALled new water and urine recycling equipment late last year, gear NASA managers hoped to have fully tested and operational before the additional astronauts and cosmonauts arrive later this Spring.

But the vacuum distillation assembly at the heart of the U.S.-built urine recycling gear has failed to operate properly and a 180-pound backup unit will be launched aboard Discovery. Engineers do not yet know what caused the problem with the unit currently insTALled and they can't rule out the possibility the new unit might suffer the same fate.

At the same time, telemetry indicates a subtle pressure problem with the U.S. carbon dioxide removal system on board the station and a higher-than-expected bacteria count in the lab's potable water system. Chemicals to reduce the bacteria count will be launched aboard Discovery and new procedures are being implemented to reduce stress on the carbon dioxide scrubber.

Station Program Manager Mike Suffredini says the long-planned move to a six-person crew can continue even if the complex life support systems are not fully operational in May because the lab complex has a good supply of fresh water on board and there are multiple ways to scrub carbon dioxide out of the atmosphere.

In addition, visiting shuttles typically transfer around 1,000 pounds of water to the station each time they visit, a by-product of the reverse hydrolysis process that generates electricity in the ship's three fuel cells.

Other objectives of the 125th shuttle mission include work to ready the station for attachment of a Japanese experiment platform this summer and deployment of spare parts storage shelves on the station's hull that will be used to mount critical backup components before the shuttle fleet is retired in 2010.

The space station's mass will increase to 669,291 pounds - 335 tons - by the end of Discovery's mission and, with eight shuttle flights remaining before the fleet is retired in 2010, the complex will be 81 percent complete.

"We're flying the last power truss to the ISS," Suffredini said. "In fact, this is the last major U.S. element built ... by the Boeing Corp. and flown by the Boeing-NASA team and I couldn't be more proud of the performance to date."

The solar array truss segment, known as starboard 6 or S6 for short, will be attached to the far right end of the station's main power and cooling truss, which extends at right angles to the lab's pressurized modules.

S6 weighs 31,060 pounds and measures 16.3 feet wide, 45.4 feet long and 14.7 feet thick in the shuttle's cargo bay. According to Boeing, the price tag was $297,918,471, which includes costs from a lengthy Columbia-triggered launch delay.

Once attached to the station, its two wings will be deployed, giving the station four panels on each end of its power truss. ToTAL surface area of all the arrays will be roughly one acre, generating 84 to 120 kilowatts of useable power, depending on the time of year and angle to the sun.

The S6 truss segment "takes up the entire payload bay, so unlike the last flight (in November), this is pretty much what our focus will be on the mission, getting the element insTALled and activated and the wings deployed," Suffredini said. "And after doing six wings we feel like we kind of understand them, so I'm hoping this one will be just a normal part of our everyday activation as an element. Of course, it won't turn out that way, but I can always hope."

In addition, he said, "this year is our year to go to six-person crew and important to that is not only this truss we're about to fly, but it's also getting all the (life support system) hardware active that we flew up on previous flights.

"On orbit today, we've activated two of (four planned) crew quarters. ... The potable water dispenser is activated and operating. We have a slightly high bacterial count the last time we measured the water out of the ambient port. That's not unexpected when we don't use it very often and since we're not allowed to drink the water yet, the crew is not using the PWD as much as we will in the future and normal operation will keep the bacteria count down. So we'll flush that with some iodinated water and clear that up.

"The waste and hygiene compartment is working, it's been activated and is working fine. We haven't had any issues with that. The water processing assembly equally has been operating without any issue and we've figured out how to use the oxygen generation assembly (and) it's worked fine as well."

Another bit of good news for NASA is the improved performance of the station's right side solar alpha rotary joint, or SARJ. The lab is equipped with two such units, one on either side of the main power truss. Using massive 10-foot-wide drive gears, the SARJ units are designed to rotate the outboard solar arrays like giant paddle wheels to keep them face on to the sun as the station circles the planet.

The port-side SARJ has worked normally since its activation, but the right-side joint suffered extensive damage to one of its three bearing races due to an apparent lubrication failure after reaching orbit. Each SARJ features redundant drive gears, but NASA managers did not want to take the drastic step of switching to the backup and losing all redundancy in a critical system.

Instead, they began working on a plan to launch and insTALl a replacement, a complex job that would have required multiple spacewalks. At the same time, movement of the starboard SARJ was sharply restricted to minimize vibrations and stress.

Late last year, spacewalking astronauts cleaned and lubricated the damaged gear's bearing races and Suffredini said telemetry indicates it now operates almost as smoothly as its port-side counterpart.

The starboard SARJ is still considered damaged. But given its surprisingly good performance in the wake of its cleaning and lubrication, Suffredini said engineers have been cleared to operate the drive system in sun-pointing "auto-track" mode when necessary.

"Given this data, we're going to release some of the constraints to our ops team," he said. "Today, daily, they go to heroic efforts to manage systems so we can make sure we have enough power to operate the utilization hardware we need to operate. That is, they go in and turn off heaters and other systems every so often when we get to the beta angles that give us power challenges. ... That's an enormous amount of work for the team to do.

"So we're going to try to get ourselves out of that position or relieve some of the work the ops team has to do to provide power for all the systems. So what you'll see us do is give them release, such that when we get to those beta angles where we're challenged, you'll probably see the ops team auto-track for a little while in order to get past that hump as opposed to doing all the analysis to figure out what to turn off and how long to turn it off.

"In addition to that, we've begun a life test where we'll try to determine how much life we'll have on a degraded joint that's been lubricated," he said. "We're going to try to recreate the system as it is in orbit today and then we're going to put it to an accelerated life test and we're going to try to see if it degrades any further and if it does, can we determine life from that? In addition to that, we're going to try to figure out how often we need to re-lubricate that joint in order to keep the currents and vibration levels down to a level that's acceptable."

Testing should be complete later this summer. Engineers now plan to switch to the undamaged starboard drive gear in 2010 and use the current gear as a backup. Playing it safe, however, Suffredini said the replacement ring will be launched and stored on the station for future use if needed.

"Because we feel so good about the results so far, we believe we can keep this joint on orbit as the backup joint and perhaps now return to the concept of switching to outboard ops, make some modifications to the system so we can get the necessary redundancy when we go to outboard ops, and have this joint as a good backup," he said.

Despite the delay getting Discovery off the ground, NASA still hopes to launch five missions this year.

Next up is shuttle Atlantis, scheduled for launch May 12 on a mission to service and upgrade the Hubble Space Telescope. The shuttle Endeavour returns to space around June 13 for a mission to attach an external experiment platform on the space station's Japanese Kibo lab module.

Atlantis is scheduled to fly again in late August, following by Discovery in November or December.


4:00 PM, 3/8/09, Update: Astronauts arrive; start of countdown on tap; weather 90 percent 'go' for Wednesday launch (UPDATED at 7:05 p.m. with start of countdown)

With forecasters predicting a 90 percent chance of good weather, the shuttle Discovery's seven-man crew flew to the Kennedy Space Center today for the start of the countdown to blastoff Wednesday on a delayed space station assembly mission. The countdown began on time at 7 p.m., setting the stage for launch of the 125th shuttle mission at 9:20 p.m. Wednesday.

Commander Lee Archambault, pilot Dominic "Tony" Antonelli, Japanese astronaut Koichi Wakata, station veteran John Phillips and spacewalkers Steven Swanson, Richard Arnold and Joseph Acaba landed at the shuttle runway in two waves, at 2:37 p.m. and around 3 p.m., after flights from Houston aboard T-38 jet trainers.

"I wanted to welcome you here to the Kennedy Space Center and tell you how thankful we are for this launch coming up on Wednesday," Archambault told reporters at the landing strip. "We're very excited to be bringing the S6 truss up to the space station to give its final complement of power. We're ready to get it going Wednesday afternoon."

There are no technical problems of any significance at launch pad 39A and forecasters are predicting good weather all week: 90 percent "go" on Wednesday, dropping slightly to 80 percent Thursday and Friday because of a slight chance of showers in the area. Conditions at emergency runways in California, Spain and France also are expected to be acceptable for launch.

The goal of Discovery's mission is to deliver and attach a $300 million set of solar arrays on the right side of the station's main power truss. The starboard 6, or S6, truss segment is the fourth and final set of power panels to be attached to the lab complex and the final major U.S.-built station component scheduled for launch aboard a shuttle.

Discovery originally was scheduled for launch Feb. 12, but the flight was repeatedly delayed by concern about suspect hydrogen flow control valves used to pressurize the hydrogen section of the shuttle's external tank.

Archambault took a moment today to thank the engineers and technicians who carried out around-the-clock work "over this last month or so to take care of the flow control valve problem."

"We're very happy it's been resolved successfully," he said. "We're ready to get going."


12:25 PM, 3/6/09, Update: Discovery cleared for launch March 11 (UPDATED at 4:15 p.m. with news conference; details)

Senior NASA managers met today at the Kennedy Space Center and officially cleared the shuttle DIscovery for launch March 11 on a delayed space station assembly mission. The decision to proceed was based on a review of extensive testing and analysis, along with results from a new inspection technique, that gave engineers high confidence three hydrogen flow control valves insTALled aboard Discovery are crack free and can be safely launched as is.

"The mood is very, very upbeat compared to a couple or three weeks ago when we didn't know exactly where we were going to get with the launch date," Mike Leinbach, NASA's launch director, told reporters today after a flight readiness review. "Now we have one, and everybody feels really good. Team Discovery's ready to execute and I feel really good about the attempt next Wednesday night."

Shuttle commander Lee Archambault and his crewmates - pilot Dominic "Tony" Antonelli, John Phillips, Japanese astronaut Koichi Wakata and spacewalkers Steve Swanson, Richard Arnold and Joseph Acaba - plan to fly to the Florida spaceport Sunday for the 7 p.m. start of their countdown to launch.

If all goes well, Discovery will rocket away on the 125th shuttle mission at 9:20:10 p.m. Wednesday. Docking with the space station is targeted for 6:27 p.m. on Friday, March 13. Four spacewalks are planned for March 15, 17, 19 and 21 to connect a fourth and final set of solar arrays and to perform a variety of other tasks. Undocking is planned for 10:23 a.m. on March 23, with landing back at the Kennedy Space Center expected around 3:27 p.m. on March 25.

NASA is facing a deadline of sorts with DIscovery. The Russians plan to launch a Soyuz spacecraft carrying the next space station commander and flight engineer on March 26. The docked phase of the shuttle mission must be done by then to avoid a conflict. To get in a full-duration four-spacewalk mission, Discovery must take off by March 13.

By giving up one or two of the mission's planned spacewalks, along with off-duty time, Discovery could launch as late as March 16 or 17 in a worst-case scenario. After that, the flight would slip to April 7. But NASA managers are optimistic it won't come to that.

Archambault and his crewmates originally hoped to begin their mission Feb. 12. But the flight was repeatedly delayed because of concern about possible cracks in the three hydrogen flow control valves used to pressurize the hydrogen section of the ship's external tank during the climb to space.

During the most recent shuttle flight last November, a small piece of one valve poppet broke free. It was the first such incident in shuttle history and while it caused no problems, NASA managers ordered tests to assess the safety of the system.

As it turned out, the valve cracked and liberated debris because of high-cycle fatigue, the result of harmonics in the flow environment inside the pressurization line that engineers had not suspected. While analysis continued, three valves that passed an electron microscope inspection were insTALled aboard Discovery.

But testing continued and engineers discovered that surface roughness could mask small cracks, raising questions about the valves aboard Discovery. Those valves had flown about a dozen times each and they eventually were removed. Engineers planned to replace them with valves that had four, four and five flights respectively.

While all of that was going on, engineers carried out computer analysis to model the flow inside the hydrogen pressurization line and conducted impact testing to determine whether a piece of debris could cause damage if a fragment broke off in flight. Of special concern was a 90-degree bend in the line just five inches from each valve.

Against this backdrop, engineers came up with a new way to inspect the valves for cracks, adopting so-called eddy current analysis to look tellTALe defects indicative of cracks.

"It's a commercial way that they inspect bolt heads," said shuttle Program Manager John Shannon. "Basically, you put a magnetic field around the circumference of the bolt and then you measure the (induced) voltage you get through that magnetic field. Some of the really smart guys that we have ... adapted that to this problem and we ran several blind trials with (valve) poppets we knew had cracks. It performed so well that it found some cracks that we did not know we had, that we had not seen with the scanning electron microscope. So we had a lot  of confidence in this inspection capability.

"So we took apart the valves that we had initially said we were going to put in with lower flight times and checked those out. Two of them were clean and one of them showed two cracks in it. That was a little bit of a surprise to us. So we screened the three valves that we had taken off of DIscovery that had 12 flights apiece and the first one we looked at had a crack in it. Then the next two did not have cracks in them. So we were able to put together, with a very high confidence level, a set of three valves and a flight spare that we could put in Discovery and have a lot of confidence that they did not have initiating cracks.

"Additionally, the teams did a lot of physics work assessing how this valve poppet fractures and they were able to significantly reduce (predictions of) the size of a potential fracture," Shannon said. "And that paired with the point that we were flying valves that didn't have initial cracks to give us a lot of comfort that if we did initiate a crack and it did liberate in one flight, which we've never seen and we don't expect, that the particle would be very small.

"We didn't stop there," he continued. "That was very strong rationale to just go fly but we worked on the consequence side as well with the impact testing and computer analysis that we did. And we showed that the likelihood if you did release a particle of it damaging anything in the orbiter or the external tank plumbing was extremely remote.

"And we didn't stop there. ... We went the extra step and said if we did damage the plumbing, what would that mean? We didn't take it on face value that if you punctured a line that that was an automatic bad day. We looked at all of the different consequences and we found out that the size hole we would need to cause an over-pressure in the aft or a significant flammable problem or not support the external tank structure with pressure, the holes required to do that were orders of magnitude bigger than what we could possibly do with this piece of poppet.

"So we really attacked this problem from all the different areas, we made sure we had good valves going in without cracks, we showed even if one or two start a crack and liberate, they would be small. We showed that if it got in the plumbing it's very unlikely to cause damage and then we showed that even if it does cause damage, that damage is not something that we needed to worry about."

The decision to proceed with launch was unanimous.

"The vehicle's in great shape and we're ready to pick up with our normal countdown," Shannon concluded.

For downstream flights, NASA managers are assessing possible redesigns or the feasibility of simply launching with new, verified crack-free valves, each flight.


5:50 PM, 3/4/09, Update: NASA managers agree to hold readiness review Friday; set NET 3/11 launch target for Discovery

Shuttle managers met today to review tests and inspections of suspect hydrogen flow control valves and agreed enough progress had been made to justify another flight readiness review Friday and a March 11 target launch date for the shuttle Discovery's delayed space station assembly mission.

"The space shuttle program moved the targeted launch a day earlier following extensive review of flow control valve inspection data and assessment of ongoing and planned work," NASA said in a brief statement. "A formal presentation of the flow control work and a thorough review of all aspects of flight will be made at Friday’s readiness review."

The unanimous decision to press ahead with a third FRR Friday came after a full day of discussions aimed at developing an acceptable rationale for launching Discovery with flow control valves that are susceptible to fatigue-induced cracks.

The valves are used to keep the hydrogen section of the shuttle's external tank pressurized during the climb to space. During the most recent shuttle flight last November, a piece of one valve poppet broke free. It was the first such incident in shuttle history and while it caused no problems during the November ascent, NASA managers ordered tests to assess the safety of the system.

Thanks to the successful use of an alternative eddy current inspection technique, engineers are confident valves insTALled aboard Discovery this week are crack free. They also are confident, based on extensive testing and analysis, that a crack cannot develop and propagate to failure in a single flight.

Other factors in today's decision included analyses showing multiple valve failures with debris releases larger than the one previous in-flight incident would be required to produce tank over-pressurization and dangerous hydrogen venting during the first two minutes of flight. Conversely, to underpressurize the tank, a larger leak would be required than impact testing showed was reasonable.

Finally, a leak that would release enough hydrogen into the shuttle's aft engine compartment to cause a problem would require a "significant" rupture in the pressurization line, which orbiter engineers concluded was unlikely.

Even so, engineers developed a plan earlier to insTALl braces, or doublers, on 90-degree bends in the pressurization lines just 5 inches from the valves to protect against the possibility of an unexpected valve failure that could shoot high-velocity debris down the line.

But during today's meeting, engineers concluded the doubler would not be ready in time and that given the inspections and analysis of the valves aboard Discovery, the shuttle could be safely launched as is. But shuttle managers did not rule out using the doublers for downstream flights.

Going into today's meeting, NASA sources said a decision to proceed to an FRR Friday would mean strong support for a formal decision to proceed with launch. After two previous readiness reviews, managers were reluctant to fly to Florida again if there was serious doubt about the outcome.

On the assumption a March 11 launch will, in fact, be approved Friday, Discovery's seven-member crew - commander Lee Archambault, pilot Dominic "Tony" Antonelli, John Phillips, Japanese astronaut Koichi Wakata and spacewalkers Steve Swanson, Richard Arnold and Joseph Acaba - planned to begin a standard week-long medical quarantine this evening.

For a launch on March 11, the astronauts would fly to the Kennedy Space Center Sunday afternoon and the countdown would begin at 7 p.m. that evening. Launch of the 125th shuttle mission would be targeted for 9:20 p.m. next Wednesday.

Assuming an on-time liftoff, Discovery would dock with the international space station at 6:27 p.m. Friday, March 13. Four spacewalks are planned, on March 15, 17, 19 and 21, starting between 2:50 p.m. and 12:50 p.m. Undocking would be targeted for around 10:23 a.m. on March 23, with landing back at the Kennedy Space Center expected around 3:27 p.m. on March 25.

See the March 3 update below for additional details on the flow control valve issue. An updated flight plan, countdown and ascent timeline will be posted on the CBS News STS-119 Quick-Look page as soon as possible.


10:00 PM, 3/3/09, Update: NASA managers to assess valve analysis; possible launch dates

NASA managers will meet Wednesday to assess ongoing tests and inspections of suspect hydrogen flow control valves and to discuss whether to press ahead with a flight readiness review Friday that would set the stage for launch of the shuttle Discovery on March 11 or 12. Valve testing has not turned up any major show stoppers, sources say, and a different inspection technique adds confidence three valves being insTALled aboard Discovery this week are, in fact, free of any cracks that could worsen in flight and release debris inside a critical external tank pressurization line.

Engineers are still debating whether braces should be insTALled on three 90-degree bends in the pressurization lines just five inches away from the valves in question. Debris released from a cracked valve could hit an elbow joint at high speeds, possibly causing a rupture in a worst-case scenario.

Some engineers believe the braces are not needed because the new inspection technique clears the valves being insTALled aboard Discovery and there is no evidence a crack could develop and propagate to failure in a single flight. They also argue any change to the pressurization line could alter the acoustics that contribute to valve stress. Others believe the shuttle should not be launched until brand new valves can be built and insTALled. The valves currently slated for use aboard Discovery have logged four, five and 12 flights each.

If shuttle managers decide Wednesday that test data supports pressing ahead, an executive-level flight readiness review will be held at the Kennedy Space Center on Friday to set an official launch date. As of this writing, the unofficial target is March 12, but sources say managers are optimistic about moving the target up one day, to March 11, if engineers don't encounter any additional problems.

If so, commander Lee Archambault and his six crewmates would return to the Kennedy Space Center on Sunday for the start of the countdown to launch. In that case, liftoff would be targeted for 9:20:10 p.m. next Wednesday. If March 12 eventually is selected, the countdown would begin Monday evening for a liftoff at 8:54:27 p.m. next Thursday.

Either way, it will be a busy week. Space station commander Mike Fincke and flight engineer Yury Lonchakov plan to stage a six-hour spacewalk Tuesday, starting around 12:20 p.m., to insTALl a European experiment on the station's hull and to carry out a variety of other tasks.

On the shuttle front, getting an additional day would give NASA a better chance of getting Discovery off the ground before running into a conflict with the upcoming March 26 launch of a Russian Soyuz spacecraft carrying the international space station's next commander and flight engineer.

The shuttle must be off the ground by March 13 for the crew to conduct a full-duration two-week-long mission. A launch on March 14 or later is still possible, but the crew would have to give up one or more of the mission's four planned spacewalks. If Discovery misses the March window, launch will slip to around April 7.

The valve issue cropped up after the most recent shuttle launch last November when engineers discovered one of three gaseous hydrogen flow control valves used to pressurize the hydrogen section of the external tank suffered a crack and lost a small piece of its poppet assembly.

Subsequent analysis showed the valves were subjected to more stress than engineers originally believed and managers ordered a battery of tests to determine how cracks develop and propagate and to get a better understanding of the consequences of an in-flight failure.

Discovery originally was scheduled for launch Feb. 12. But the flight was delayed because of the valve issue, first to no earlier than Feb. 19, then to Feb. 22, Feb. 27 and eventually to March 12.

Three presumably crack-free flow control valves were insTALled aboard Discovery that had logged about 12 flights each. Engineers then discovered it was possible for cracks to elude detection using electron microscopy and dye penetration tests because of surface roughness.

Because valve cracks may be related to repeated exposure to stress, engineers were asked to replace Discovery's valves with three valves that had flown four, four and five times respectively.

Over the past week or so, engineers subjected the valves to eddy current inspections, a non-destructive testing technique that uses subtle changes in currents set up by electromagnetic induction to find signs of cracks.

Eddy current testing can detect cracks that surface roughness might mask. Engineers earlier contemplated having to polish valves to remove any such roughness, a procedure that would physically alter a valve and possibly change the way it responds to stress.

Using eddy current testing, one of the two four-flight valves slated for use aboard Discovery showed two "indicators" of cracks. The other two valves were pristine and the results for all three were confirmed by electron microscopy. The valves that had been removed earlier also were tested. Again, one showed a single indicator while the other two were clean.

As a result, engineers were cleared to insTALl crack-free valves with four, five and 12 flights respectively.

"So we have three going in that we know are clean and there's a group that believes the worst you could come out with after a flight is a crack," said one NASA official. "But there are some people who still might feel the best thing to do is not to fly until you have a brand new poppet every flight."

This week's discussions are focused on developing rationale for launching Discovery with valves of the current generation. For downstream flights, NASA managers may order a redesign or simply fly with brand new valves each time. Only eight missions are currently planned beyond Discovery's flight.


7:10 PM, 2/25/09, Update: NASA sets March 12 target launch date for Discovery

NASA managers decided today enough progress had been made testing and evaluating suspect hydrogen flow control valves to tentatively set a March 12 target launch date for the shuttle Discovery's delayed launch on a mission to attach a final set of solar arrays to the international space station.

Another program-level review is scheduled for March 4 and if no major problems develop, senior managers will hold an executive-level flight readiness review - Discovery's third - on March 6 to make an official decision on whether to proceed with launch.

"NASA's space shuttle program has established a plan that could support shuttle Discovery's launch to the international space station, tentatively targeted for March 12," NASA said in a statement late today. "An exact target launch date will be determined as work progresses with the shuttle's three gaseous hydrogen flow control valves."

If the proposed schedule holds up, Discovery's countdown would begin around 7:30 p.m. EDT on March 9, setting up a launch attempt at 8:54:25 p.m. on March 12. Docking with the international space station would follow on March 14 with four spacewalks planned for March 16, 18, 20 and 22. Undocking would be expected on March 24 with landing back at the Kennedy Space Center on March 26.

The Russian space agency plans to launch a Soyuz spacecraft on Discovery's landing day - March 26 - to ferry the space station's next commander and flight engineer to the lab complex along with a wealthy space tourist. Discovery must be gone by then to avoid a conflict and as a result, the shuttle must take off by March 13 to get a full-duration four-spacewalk mission. A launch on March 14 or even 15 is possible, but the crew would have to give up one or two spacewalks.

If the shuttle does not get off before the Soyuz cutout, the flight will be delayed to April 7, the same day the outgoing station crew - commander Mike Fincke, flight engineer Yuri Lonchakov and the space tourist - returns to Earth.

A shuttle liftoff in March would permit NASA to proceed as planned with the May 12 launch of shuttle Atlantis on a mission to service and upgrade the Hubble Space Telescope. If Discovery is delayed to April, the Hubble flight would slip to around June 2.

Discovery originally was scheduled for launch Feb. 12. But the flight was delayed, first to no earlier than Feb. 19, then to Feb. 22 and eventually to no earlier than Feb. 27 because of concern about the integrity of the shuttle's three hydrogen flow control valves. Last Friday, Feb. 27 was ruled out to permit more time for troubleshooting and analysis.

When launch was targeted for Feb. 12, NASA built a flight plan that called for a so-called ascending node landing, one that resulted in a southwest-to-northeast approach to Florida. That's a standard post-Columbia approach because it minimizes overflight of populated areas during the shuttle's descent from orbit.

But as Discovery encountered repeated delays, flight planners switched to a descending node entry trajectory, changing the timing of major mission events. This was done to avoid forcing the station crew to endure severe sleep shifting after the shuttle's undocking to put them in synch with the arriving Soyuz crew.

Now that the flight has slipped to no earlier than March 12, NASA is going back to the original ascending node approach trajectory. A new flight plan reflecting changes required by the new launch target has not yet been generated and the current timeline posted on the CBS News STS-119 Quick-Look page is out of date. An update will be posted as soon as possible.

Concern about the hydrogen flow control valves, used to keep the hydrogen section of the shuttle's external tank pressurized during ascent, cropped up after the most recent shuttle launch last November.

NASA flow control valve background:
http://www.cbsnews.com/network/news/space/119/119graphics/fcv.pdf

During the climb to space, one of the three flow control valves aboard the shuttle Endeavour began allowing more hydrogen to pass through than expected. The other two valves reduced flow to maintain the proper pressure in the external tank and the shuttle's climb to space was uneventful.

After landing, engineers discovered a small crack and missing material on the lip of the valve in question. NASA managers ordered all the valves in Endeavour, Discovery and Atlantis removed for detailed inspections. At least one other valve was found to have a crack.

Based on electron microscope inspections, engineers concluded the defect was the result of high-cycle fatigue. A fresh set of vales that flew previously on Discovery were inspected and insTALled for launch.

But engineers were surprised that fatigue played a role. Using computational fluid dynamics, they found that the environment inside the system can allow a harmonic resonance to set up that could cause the sort of fatigue seen in Endeavour's valve. Additional tests also found that surface roughness on the valve poppets could mask cracks.

While NASA plans to modify the valves for downstream flights, shuttle managers put Discovery's flight on hold for an exhaustive series of tests to determine if the shuttle could be safely launched as is, focusing on the effects of debris impacts inside the pressurization line.

A decision was made Tuesday to replace Discovery's flow control valves with a set that has flown fewer missions, presumably making them less susceptible to cracking if repeated exposure to stress plays a role. Impact testing using a mockup of the pressurization line shows it can handle impacts from debris that's larger than the piece liberated during Endeavour's flight.

"Technicians have started removing Discovery's three valves, two of which will undergo detailed inspection," NASA said in a statement. "Approximately 4,000 images of each valve will be reviewed for evidence of cracks. Valves that have flown fewer times will be insTALled in Discovery.

"Engineering teams also will complete analysis and testing to better define consequences if a valve piece were to break off and strike pressurization lines between the shuttle and external fuel tank. Hardware modifications may be made to the pressurization lines to add extra protection in the unlikely event debris is released."

Engineers still do not fully understand what causes cracks to develop, how fast they might propagate and how big liberated pieces might be in worst-case scenarios. As such, the March 12 launch date is a tentative target as of this writing.


4:30 PM, 2/23/09, Update: NASA managers hopeful, but not certain, about March launch for Discovery (UPDATED at 8 p.m. with decision to swap out valves; additional details)

NASA managers today ordered engineers to replace suspect hydrogen flow control valves aboard the shuttle Discovery with valves that have less flight time in a bid to reduce the chances of in-flight cracks that could lead to debris in a pressurization line. If ongoing tests and higher fidelity computer models continue to show positive results, Discovery could be cleared for a delayed launch attempt by around March 12, sources said today. That would give NASA just two or three launch opportunities before standing down until April 7 to avoid conflict with a Russian Soyuz mission to the international space station.

A decision to set a new target launch date could come as early as Wednesday, but sources said it was not a done deal because engineers are still debating the root cause of the valve problem that has grounded Discovery. The results of ongoing test results, however, along with the predictions of more realistic computer modeling, may convince skeptics the shuttle's internal plumbing can withstand impacts from valve debris should cracks develop in flight.

While that remains to be seen, a brief update on NASA's web site late today indicated a plan for moving forward could be in place Wednesday.

"Though the plan has not yet been completed, technicians will insTALl flow control valves that have flown fewer times than the ones currently in Discovery's main propulsion system," NASA said in a statement.

"The plan should be finalized by Wednesday and once senior managers are in agreement, a Flight Readiness Review will be rescheduled to assess the readiness for launch and to set a formal launch target date."

The Discovery astronauts were allowed to break quarantine Friday after mission managers put the flight on hold and ruled out a Feb. 27 launch date. At the time, Launch Director Mike Leinbach said Discovery could be launched five days or so after a decision was made to proceed, assuming the shuttle was cleared for flight as is.

But the valves are being replaced and the crew still must put in a full week of quarantine time. Several sources said today it was unlikely Discovery could be ready for launch before March 12, and that assumes engineers and managers can get comfortable enough with the test data to press ahead without any design changes for the valves in question.

To avoid conflict with the upcoming launch of a Russian Soyuz spacecraft carrying two fresh space station crew members and a tourist, Discovery cannot take off after around March 13 unless the Russians agree to delay their own launch. As of this writing, a shuttle launch on March 14 is possible, but it would require the crew to eliminate one of their four planned spacewalks and shorten the flight by a day.

The next available launch date after that would be April 7, the day the station's current commander, flight engineer and the tourist depart in an older Soyuz.

If Discovery launches in March, before the Soyuz "cutout," officials say the shuttle Atlantis will stay on schedule for launch May 12 on a long-awaited mission to service and upgrade the Hubble Space Telescope. If Discovery's flight slips to April, the Hubble mission likely would slip to around June 2.

Complicating the picture in the near term, United Launch Alliance plans to launch NASA's Kepler science mission aboard a Delta 2 rocket on March 5 and an Atlas 5 rocket carrying a military communications satellite on March 9. It does not appear the Kepler mission will be a factor in shuttle planning, but the Atlas flight is in direct conflict.

The Air Force Eastern Range, which provides radar tracking and other services for all rockets launched from Florida, supports one flight at a time and each mission gets at least two launch opportunities on successive days. As of this writing, there are indications the Atlas flight may slip a few days, but no such delay has yet been announced.

Even if the Eastern Range is clear for Discovery, a launch in March assumes no major repairs or redesign work are required to resolve concerns about the suspect hydrogen flow control valves. Originally scheduled for launch Feb. 12, the flight has been repeatedly delayed because of concern a valve could break in flight, sending meTALlic debris into a pressurization line.

The shuttle is equipped with three hydrogen flow control valves that work like pop-up sprinklers to route hydrogen gas to the external tank to keep the hydrogen section properly pressurized at 32 to 34 pounds per square inch during the climb to space.

During the most recent flight last November, a small piece of one valve poppet broke off in flight. It was the first such incident in the 124 shuttle flights to date, but testing and computer analysis indicates cracks in the valves have been a long-standing, but unknown, threat with at least one valve design.

Engineers are carrying out tests to determine what caused the valve to break; how cracks propagate and how large resulting debris might be; and to make sure the pressurization line is tough enough to withstand debris impacts from any future failures.

It's not yet clear whether cracks in the valves are the result of accumulated stress over multiple flights or the result of single-flight events related to unexpected harmonic and structural interactions between the pressurization lines in question and the orbiter.

Managers decided today to replace the current valves, which have flown 11 to 12 times each, with similar 1301-design units that have logged fewer flights. That will protect against multi-flight stress-related cracks and poppet failures. At the same time, older 1301 valves likely will be inspected to make sure there are no signs of cracks that could be age related. None are expected.

Engineers are hopeful more realistic computer models, based on actual impact tests, will show the odds of a catastrophic failure are remote, even in a worst-case scenario.

Testing to date seems to indicate a 90-degree bend in the external tank pressurization lines just five inches from the valves can withstand the sort of impacts one could expect in an actual failure. Earlier less positive assessments were based on knife-edge impacts from debris with worst-case velocities and unrealistically stable paths down the pipe. Using those assumptions, the pressurization line elbow bend could sustain impact velocities of around 560 feet per second.

It now appears the elbow bend may be able to withstand impact velocities higher than 900 feet per second - more than 600 mph - if the debris is relatively small and following a more realistic trajectory. But engineers do not yet know enough about how the valves can break to predict the maximum allowable size of any released debris.

Given the complexities involved, it is perhaps not surprising the issue is not yet clear cut and that additional time may be needed to resolve the matter one way or the other.


12:45 AM, 2/21/09, Update: Managers fail to reach consensus in readiness review; Discovery launch on hold pending additional analysis of suspect flow control valves

After a marathon 13-hour flight readiness review, NASA managers late Friday were unable to reach a consensus on launching the shuttle Discovery Feb. 27 with suspect hydrogen flow control valves. As a result, senior management decided not to set an official launch date and Discovery's mission to deliver a final set of solar arrays to the international space station was put on hold pending additional analysis and discussions next Wednesday.

To avoid conflict with a Russian Soyuz spacecraft set for launch in late March to ferry a fresh crew to the space station, Discovery cannot take off between March 13 and April 6. If NASA managers can develop an acceptable flight rationale to launch Discovery as is following next Wednesday's assessment, the agency has a shot at getting in at least a few launch attempts for the shuttle before the Soyuz cutout. Otherwise, the flight will slip into April.

"We were really, really close to having the entire team at a point where we could accept (the valve risk) and go fly," shuttle Program Manager John Shannon told reporters late Friday. "But as we TALked through all the data, a lot of it came in fairly late this week, a lot of the impact data, a lot of the analysis data. We found a couple of small errors in things as we were going through the data."

When Bill Gerstenmaier, chief of space operations for NASA, "went around and polled the team to get input, there was just a sense of unease that we did not quite have the rigor that we typically expect for a question like this," Shannon said. "It's a very complicated problem."

The decision to defer a launch date decision came as a surprise to many observers who believed extensive test data and computer analyses indicated the valves could be safely flown as is and that the likelihood of in-flight problems was sufficiently remote to press ahead with launch.

But others, including Johnson Space Center Director Mike Coats and the engineering directorates at Johnson and the Marshall Space Flight Center, were opposed, arguing engineers do not have a sufficient understanding of the mechanism that leads to cracks and potentially catastrophic failures. Shannon and Gerstenmaier were in favor of pressing ahead with launch, but they were in the minority and the flight was put on hold.

Gerstenmaier said the long-term goal is to develop a valve redesign that will eliminate concern about cracks and debris shedding once and for all. In the near term, the goal is to develop a better understanding of the valve failure mechanism, to identify pristine valves that should be able to withstand the rigors of launch and to make sure any unexpected valve failures that occur in flight do not lead to catastrophic damage.

"The overall philosophy is, while we're working this redesign we'll have a strategy that allows us to continue to fly with the valves we've got and we'll do that in parallel," Gerstenmaier said.

Discovery originally was scheduled for launch Feb. 12. But the flight was delayed, first to no earlier than Feb. 19, then to Feb. 22 and eventually to no earlier than Feb. 27 because of concern about the integrity of the shuttle's three hydrogen flow control valves.

The shuttle is equipped with three flow control valves that work like pop-up sprinklers to route hydrogen gas to the external tank to keep the hydrogen section properly pressurized at 32 to 34 pounds per square inch during the climb to space.

The valves are critical to flight safety. An over-pressurized tank could lead to hydrogen being dumped overboard through a relief valve, creating a potentially catastrophic environment depending on when such an incident occurred. Under-pressurization could lead to premature main engine shutdowns. And if debris from a broken valve punctured the pressurization line, hydrogen could be released into the aft engine compartment with potentially catastrophic results.

During the most recent flight last November, part of a flow control valve poppet broke off inside the pressurization line. While the valve that cracked allowed more hydrogen to flow through than normal, the Endeavour's flight computers compensated by reducing flow through the other valves. But engineers were surprised by the incident and tests were ordered to find out what caused the failure.

They quickly discovered small cracks in other valves across the fleet and heretofore unknown harmonic conditions in the pressurization line that can lead to high-cycle fatigue. While the valves aboard Discovery were replaced by presumably crack-free units, additional testing of other valves showed that surface roughness left over from the manufacturing process could mask small cracks.

The issue then was whether whether fresh cracks could form in the flight environment, how fresh or pre-existing cracks might propagate and how far a crack might extend before causing part of the valve poppet to break away.

NASA and its contractors built full-scale mockups of the pressurization line and fired small bits of debris into it under simulated flight conditions to find out what would happen if additional in-flight failures occurred. Borescope examination of the test line showed scuffing where the debris had ricocheted along, but no punctures.

Based on examination of test results and the broken valve from Endeavour, engineers believed a crack could not grow beyond an arc of 90 degrees without that part of the poppet breaking away. This week, fragments representing the results of a 180-degree crack were used for impact testing in a mockup of the pressurization line mounted on the external tank and again, no internal damage to the pressurization line occurred.

But engineers remain concerned about the consequences of debris impacts in a 90-degree bend in the line just five inches from each flow control valve. The hydrogen gas passing through a flow control valve could result in debris impact velocities at that first bend ranging from around 205 mph to more than 600 mph. Additional testing is needed to confirm the pressurization line can stand up to such impacts from debris potentially twice as large as the fragment released during Endeavour's mission.

"We were working towards getting flight rationale to go fly," Gerstenmaier said. "Some of that work is not done and we still need to do a little bit more work to get that completed and get it understood. So we spent a long time today discussing what we know and don't know about the failure, what we know about the consequences if a piece comes off and what it means to us."

In the 124 flights to date, only one flow control valve has ever suffered an in-flight failure like the one observed during Endeavour's mission. While engineers now know cracks may have been present all along, the flight record and the test results over the past two weeks indicate a relatively low probability of any significant problems with Discovery. But additional work is needed to make sure.

"The piece that was kind of missing today was on the orbiter side, if a piece of this valve comes off like it did on (Endeavour's launch), first of all, do we know how big a piece can be, can we bound that?" Shannon asked. "And then, once we understand how big that piece is, can the orbiter plumbing take that piece coming off and hitting it? ... It looks like it can, if the size is about the size of (Endeavour's) or slightly larger. But we didn't have the bow tied around it that we could say that with the definitization that we (normally) do."

The decision comes at a critical time for NASA, with five shuttle flights planned this year and only nine left before the fleet is retired in 2010. But Gerstenmaier said based on what engineers know about the valve issue to date, NASA will stick with the current launch sequence and send up Discovery first, in March or April, followed by a Hubble Space Telescope servicing mission aboard Atlantis and then another space station assembly mission with Endeavour.

"I fully believe we'll be able to put a plan together," Shannon said. "We're not that far away."


4:00 PM, 2/19/09, Update: NASA managers fly to Kennedy for readiness review; updated launch windows; flight plan revision in work, descending node landing planned

Senior NASA managers and engineers headed to the Kennedy Space Center today for a second flight readiness review Friday to assess testing of suspect hydrogen flow control valves and to make a decision on whether or not to press ahead with launch of the shuttle Discovery Feb. 27 on a space station assembly mission.

Some managers are opposed to launch at present, sources say, arguing the valves should be redesigned to eliminate the possibility of cracks that could lead to potentially catastrophic in-flight failures. Others believe exhaustive testing shows Discovery can be safely launched as is while a redesign is implemented for downstream flights. Still others believe a redesign is not necessary, arguing if it's safe to launch Discovery as is, it's safe to launch any mission using carefully inspected valves of the current design.

The stakes are high. With the shuttle fleet facing retirement in 2010 after nine more flights, any significant delays now, for a redesign or any other reason, could result in one or more lost missions.

But the Obama administration has not yet named a new NASA administrator and Friday's flight readiness review will be run by acting administrator Chris Scolese, NASA's former chief engineer, and Bill Gerstenmaier, associate administrator of space operations. As of this writing, a unanimous decision to proceed with launch Feb. 27 appears unlikely, but it's not yet clear how the discussion might play out.

Scolese and other senior managers could decide to press ahead with launch Feb. 27 despite objections; they could opt to put the mission on hold pending a redesign; or they could opt to simply delay the decision another few days, and push launch back accordingly, pending additional analysis.

Discovery originally was scheduled for launch Feb. 12 on a mission to deliver a final set of solar arrays to the international space station. But the flight was delayed, first to no earlier than Feb. 19, then to Feb. 22 and eventually to no earlier than Feb. 27 because of concerns about the integrity of the shuttle's three hydrogen flow control valves.

There are three such valves on every shuttle and they work like pop-up sprinklers, extending as required during ascent to route hydrogen gas to the shuttle's external tank to keep the tank properly pressurized at 32 to 34 pounds per square inch.

During the most recent shuttle launch last November, a valve cracked and a piece of debris was liberated that presumably made its way into the tank. While more hydrogen passed through the damaged valve than normal, the other two valves compensated to maintain a normal pressure and Endeavour's climb to space was uneventful.

Inspection of the damaged valve indicated high-cycle fatigue was the culprit. Engineers were surprised, because they believed the environment inside the pressurization line was relatively benign. Using computational fluid dynamics and extensive testing and inspections, they now understand harmonics can set up inside the line that can subject the valves to the sort of stress that could lead to fatigue. If a crack is present in a valve, under some circumstances it can propagate to the point small sections can break away.

While this scenario has played out only once in 124 missions, tank pressurization is critical and any debris-related punctures to a pressurization line could be catastrophic, depending on when an incident occurred.

Over the past two weeks, engineers using full-scale mockups of pressurization lines flowing air and hydrogen gas have run a variety of tests to find out whether valve debris can puncture the pressurization line or cause any other serious problems should a failure similar to Endeavour's happen again.

Engineers also are trying to find out whether valves can be confirmed to be crack free, how cracks develop in the first place and how fast any such cracks might propagate in flight. In the wake of Endeavour's flight, Discovery's valves were replaced with flight-tested valves that were inspected and believed to be crack free. But other valves presumed to be pristine were deliberately tested to failure and engineers discovered pre-existing cracks that had eluded detection.

Testing to date seems to indicate the valves do not pose a catastrophic threat even if an unseen crack propagated and led to a small piece breaking off. The testing shows such debris, ricocheting down the pressurization line with the same speeds and trajectories one might expect during flight, does not cause punctures or other critical problems.

But the issue is not clear cut and several assumptions are built into the analysis, including how fast cracks can propagate and what size debris can be expected to break off in worst-case scenarios.

The situation is reminiscent of an analysis that took place in late 2002 when NASA managers decided to keep launching shuttle missions while engineers worked on a fix to prevent foam insulation from breaking away from so-called bi-pod ramps on the external tank. The shuttle Columbia was destroyed during re-entry Feb. 1, 2003, because of a bi-pod foam impact during launch.

With the memory of Columbia still fresh even after six years, sources say at least some managers want to ground the fleet until the hydrogen flow control valves can be redesigned.

But others argue the two cases are not so similar. In the case of foam, engineers were misled by a long history of foam shedding and a resulting false sense of security. Foam shedding had evolved into an accepted risk that engineers thought they understood.

In this case, there is no such history. The first indication of any significant trouble with flow control valves in 124 flights occurred during the November shuttle launch.

In any case, the thrust of the recent testing has been to assess the safety of launching Discovery as is. NASA managers have not yet addressed whether a redesign might be needed or what impact such a decision might have.

If Discovery ultimately is cleared for launch on or near Feb. 27, the crew would fly to the Kennedy Space Center this Sunday to begin final preparations. The countdown would begin at midnight Monday, setting up a launch attempt at 1:32:06 a.m. Friday, Feb. 27.

Mission planners are revising the crew's flight plan to help the space station astronauts avoid major sleep cycle changes after the shuttle departs.

When launch was scheduled for Feb. 12, Discovery's mission was designed to end with what is known as an ascending node approach for landing, i.e., along a trajectory from the southwest to the northeast. That's become a standard approach in post-Columbia planning because it minimizes the time a shuttle spends flying over populated areas.

But to avoid having the station astronauts radically change their sleep cycles between the shuttle's departure and arrival of a Russian Soyuz spacecraft in late March, flight planners are now designing a descending node approach that would carry Discovery across the heartland of America from northwest to southeast.

Orbits that permit Florida landings occur roughly 12 hours apart in alternating ascending and descending trajectories. A switch to a descending node approach will move major mission events six to eight hours later each day than originally planned.

Updated launch windows have been posted on the CBS News STS-119 Quick-Look page. But NASA has not yet developed a revised flight plan reflecting landing change and the timeline on the Quick-Look page has been taken down pending an update.


8:30 PM, 2/13/09, Update: Shuttle launch delayed to no earlier than Feb. 27 (UPDATED at 9:10 p.m. with quotes and details)

Launch of the shuttle Discovery on a space station assembly mission, already delayed twice because of concern about suspect hydrogen valves, was pushed back again late today, to no earlier than Feb. 27, to give engineers more time to assess the safety of the shuttle's external tank pressurization system.

NASA managers made the decision at the end of a marathon meeting to discuss test results to date and how those results might fit into a rationale to launch Discovery as is. The alternative - a possible valve redesign or modification - likely would trigger a lengthy delay with potentially significant downstream impacts to space station assembly.

While testing to date has gone well, sources said engineers have not yet been able to reach any major conclusions or even decide on exactly what triggered a failure observed in the most recent shuttle flight. It now seems clear that tiny cracks in the valves in question are a common phenomenon, not rare as previously believed, but only one valve has ever cracked to the point that a piece actually broke away.

In any case, shuttle Program Manager John Shannon decided late today to delay a second flight readiness review from next Wednesday to next Friday, pushing launch to no earlier than Feb. 27.

"The team just needed more time to bring in all of the data, basically," said NASA spokesman Kyle Herring at the Johnson Space Center in Houston. "They've done quite a bit in terms of the progress they've made, significant progress, but there's still some open issues associated with filling in some of the test data. They've still got some data coming in even as the meeting was going on. Shannon just basically decided the best thing to do was give everybody the weekend to put their thoughts together and put the rest of the data together and that just wasn't going to fit a Wednesday flight readiness review."

A NASA statement said the new target date "is not expected to affect the launch dates for missions that will follow Discovery's flight, STS-125 to NASA’s Hubble Space Telescope and STS-127 to the International Space Station."

Herring said the engineering community expressed confidence "they could get all the test data in, build the computer models and bring all of that to the flight readiness review next Friday."

What happens after that is anyone's guess.

Discovery originally was scheduled for launch this week - Feb. 12 - on a mission to deliver a final set of solar arrays to the international space station. But the flight was delayed, first to no earlier than Feb. 19 and then to Feb. 22 because of concerns about the integrity of three critical hydrogen flow control valves.

The valves work like pop-up sprinklers, extending as required during launch to provide hydrogen gas to the shuttle's external tank to keep the tank properly pressurized. If a tank is over pressurized, hydrogen would be dumped overboard through a relief valve, putting the shuttle in a potentially catastrophic environment. An under-pressurized tank could lead to premature engine shutdowns.

The valve issue cropped up after the shuttle Endeavour's flight last November. During launch, telemetry indicated one of the ship's three hydrogen flow control valves allowed more hydrogen gas to pass through than expected. The shuttle's flight computers compensated by having the other two valves deliver less to maintain the proper tank pressurization.

After Endeavour returned to Earth, the suspect valve was removed and inspected. Engineers quickly discovered that a small part of the pop-up valve's lip had broken away, providing a pathway for the additional hydrogen gas. This was the first such incident in 124 shuttle flights.

In the wake of the discovery, all the FCVs on Endeavour, Discovery and Atlantis were removed and inspected, using dye penetration tests to look for signs of cracks. The valves also were subjected to scanning electron microscope inspections.

A few other small cracks were found, and a decision was made to replace the valves aboard Discovery with three that flew a dozen times previously on the same orbiter. They were even insTALled in the same positions.

In the meantime, additional tests were carried out to help engineers figure out what might have led to the crack and debris during Endeavour's launching. The damaged valve showed clear signs of high-cycle fatigue, which was a surprise to everyone. The environment in the pressurization line was thought to be relatively benign, without the sort of acoustics or vibrations that could lead to such stress.

Using computational fluid dynamics, however, engineers were able to identify heretofore unknown harmonic modes that could, in fact, produce the sort of forces that could buffet an extended valve and lead to the sort of fatigue seen in the cracked Endeavour valve.

At the same time, additional testing revealed small, undetected cracks in many valves that apparently were masked earlier by surface roughness in the valve material that were part of the manufacturing process. That meant the supposedly crack-free valves aboard Discovery were suspect.

That kicked off a major effort across multiple NASA field centers to find out what might happen if another crack led to another piece of debris being shot down the hydrogen pressurization line during launch. Mockups of the 79-foot-long pressurization line were built and small fragments similar to what came from the Endeavour valve were shot down the pipes at the same sort of speeds one might expect during a launch.

A possible long-term fix would be to polish off the surface roughness that can mask cracks, assuming additional analysis shows those changes would not significantly change the environment in the lines.

But the goal of the work this week was to show whether Discovery could be safely launched as is, even if one assumed a valve broke during flight. A punctured line would be potentially catastrophic. Initial test runs showed no outright punctures, but several areas of the line have "negative margins," sources said, and multiple variables are in play that make modeling - and impact predictions - difficult.

At the Stennis Space Center in Mississippi, engineers have conducted more than 60 test runs using a full-scale pressurization line flowing hydrogen gas to model the flow pattern, to determine how that affects the movement of debris in the line and whether that debris could cause a puncture.

Those tests are continuing, along with work to accurately model the pressurization line environment so computers can run detailed "what-if" scenarios to help characterize potential risk.

"The testing has been proving velocities and what the particle does as it travels down the line," Herring said. "Does it rotate, does it kind of fall into a set kind of movement? All of that is going very well, but there is just a tremendous amount of information that's being collected."

Some could view a decision to proceed with flight while working to fix a known problem as similar to what happened in late 2002 when NASA managers opted to keep flying while working to fix a problem with external tank foam insulation. The shuttle Columbia was destroyed during re-entry Feb. 1, 2003, because of a hole in the ship's left wing that was caused by impact with foam insulation from the external tank.

But others say the issue with Discovery is very different. NASA had a long history of foam impacts while the valve problem with Endeavour was the first in 124 missions. Even though the acoustic environment in the pressurization line is not what engineers expected, the valves currently aboard Discovery have no obvious flaws and a solid flight history.

If the testing this week and next shows debris impacts pose no significant additional risk, NASA managers may be able to clear the ship for flight. But there are major uncertainties at this point.

"Teams from multiple NASA centers and contractor sites have made significant progress in understanding what caused the damage to a flow control valve in shuttle Endeavour during its mission in November," NASA said in its statement. "The engineering teams have performed a tremendous amount of work, including computer modeling and actual tests to determine the consequences if a piece of a valve were to break off and strike shuttle and external fuel tank components. More time was needed to complete analyses and testing necessary to fly safely."


6:45 PM, 2/11/09, Update: Shuttle valve tests continue; no show stoppers yet, but testing not complete; engineering assessment planned Friday

Testing to determine the threat posed by suspect hydrogen flow control valves - work that has delayed the shuttle Discovery's planned launch from this week to no earlier than Feb. 22 - is proceeding at multiple NASA field centers and so far, engineers say, no show stoppers have been identified. But testing is far from complete and it's not yet known whether NASA can develop an acceptable near-term flight rationale.

NASA is running high-fidelity tests with mockups using air and hydrogen gas in an attempt to accurately model the flow environment inside the 79-foot-long, 0.6-inch-wide line used to pressurize the hydrogen section of the shuttle's external tank during the climb to space. Engineers are trying to make sure a valve fragment, should a piece break off in flight, could not puncture the line with potentially catastrophic results.

So far, no major signs of damage have been seen, although "witness marks" on the inside of the line show where test fragments have impacted as they were blown along. But the testing is not yet complete.

Even so, NASA managers plan to meet Friday to assess the progress of the testing and to decide whether to proceed with another flight readiness review next Wednesday. For a launch on Feb. 22, Discovery's crew would have to go into medical quarantine Sunday and fly to the Kennedy Space Center on Tuesday, before the FRR could set an official launch date.

"They're going to press on for the (meeting) Friday and present what data they have, recognizing that testing is still going on, obviously," said NASA spokesman Kyle Herring. "They haven't seen anything so far that I'd characterize as a show stopper, but there definitely is going to be some open testing, analysis, whatever, that will not be ready by Friday. But they felt comfortable enough that they would have enough information to meet Friday."

The issue came to light after the most recent shuttle flight last November. During launch, one of the three flow control valves aboard the shuttle Endeavour began allowing more hydrogen to pass through than expected. The other two valves reduced flow to maintain the proper pressure and the shuttle's climb to space was uneventful.

After landing, engineers discovered a small part of the valve in question had broken off. NASA managers ordered all the valves in Endeavour, Discovery and Atlantis removed for detailed inspections. One other valve was found to have a crack. Based on electron microscope inspections, engineers concluded the defect was the result of high-cycle fatigue. A fresh set of vales that flew previously on Discovery and were known to be in pristine condition was insTALled for launch.

But engineers were surprised that fatigue played a role. As it turns out, engineers using computational fluid dynamics found that the environment inside the system can allow a harmonic resonance to set up.

"That vibration, if it lined up just with the right structural mode, could end up stressing that piece and causing high cycle fatigue," shuttle Program Manager John Shannon said last week, when the initial launch delay was announced.

The valves currently insTALled aboard Discovery have flown about a dozen times in the same positions they're currently in. They were subjected to dye penetration tests to look for cracks, as well as inspections by a scanning electron microscope. All three valves were thought to be pristine and crack free.

But in subsequent tests, a valve was forced to fail and engineers were surprised to find signs of small cracks even though pre-test inspections indicated the article was crack free. Engineers suspect grooves in the valve material from its original machining may have masked the cracks. If so, Discovery's valves could be suspect as well.

The hydrogen pressurization line features three major bends: a 60-degree bend near the valves, a 90-degree bend down stream and a 102-degree turn inside the external tank. The ongoing impact testing is designed to make sure any fragment of a valve that does break off doesn't puncture the line at a bend or anywhere else.

If the impact testing definitively shows no significant additional risk due to possible valve fragment "liberation," NASA managers may be able to develop a rationale for proceeding with Discovery's launch. Only one such incident has been recorded over the history of the shuttle program - Endeavour's flight last November - and the valves currently insTALled have flown multiple times without any signs of damage.

One possible long-range fix is to polish off the grooves on other flow control valves that might mask small underlying cracks. Assuming those valves passed subsequent inspections, engineers would have confidence the valves were crack free. But such work would require additional testing to make sure the removal of the grooves does not change the flow pattern in the pressurization line and and along with it, the acoustic conditions that can lead to fatigue.

Polishing is not currently an option for Discovery. The current emphasis is on finding out if Discovery can be launched as is.

The issue is complicated and engineers do not want to repeat the errors in judgement that led to a decision in late 2002 to keep flying space shuttles while a fix was implemented to resolve ongoing concerns about foam insulation falling off the external tank. The shuttle Columbia was destroyed during re-entry Feb. 1, 2003, because of damage from the impact of foam debris during launch.


3:45 PM, 2/6/09, Update: Launch date uncertain; test results critical; additional valve cracks assessed (UPDATED at 5:30 p.m. with NASA statement on launch slip to at least 2/22)

Launch of shuttle Discovery on a space station assembly mission, delayed earlier this week from Feb. 12 to no earlier than Feb. 19 because of concern about critical hydrogen flow control valves, now is slipping to at least Feb. 22 to give engineers more time to complete testing, NASA officials said today.

NASA managers initially hoped to assess initial test results next Tuesday and then hold another readiness review Thursday. But officials said today the Tuesday meeting had been called off. A management review now is planned for next Friday and, if test results provide enough data, a "delta" flight readiness review will be held the following week, setting the stage for a possible launch around Feb. 22.

"The Space Shuttle Program will hold a meeting Feb. 13 to review data and determine whether to move forward with a flight readiness review on Feb. 18," NASA said in a statement. "The official launch date will be set at the readiness review, but for planning purposes launch now is no earlier than Feb. 22."

If that schedule holds up, Discovery would take off at 3:31:01 a.m. on Feb. 22 and dock with the international space station around 11:56 p.m. on Feb. 23. Four spacewalks, beginning between 7 p.m. and 9 p.m., would be on tap Feb. 25, 27, March 1 and March 3. Undocking would be scheduled for around 5:29 p.m. on March 5, following by landing back at the Kennedy Space Center around 9:47 p.m. on March 7.

But is not yet clear whether ongoing tests will support a rationale for launching Discovery with its current set of hydrogen flow control valves.

Each shuttle features three such valves, one associated with each main engine, that operate like lawn sprinklers, popping up as required to route hydrogen gas into pipes leading to the external tank to maintain the internal pressure needed to feed propellant to the main engines.

During the most recent launch last November, one of the three flow control valves aboard the shuttle Endeavour began allowing more hydrogen to pass through than expected. The other two valves reduced flow to maintain the proper pressure and the shuttle's climb to space was uneventful.

After landing, engineers discovered a small crack and missing material on the lip of the valve in question. NASA managers ordered all the valves in Endeavour, Discovery and Atlantis removed for detailed inspections. One other valve was found to have a crack. Based on electron microscope inspections, engineers concluded the defect was the result of high-cycle fatigue. A fresh set of vales that flew previously on Discovery and were known to be in pristine condition was insTALled for launch.

But engineers were surprised that fatigue played a role. As it turns out, engineers using computational fluid dynamics found that the environment inside the system can allow a harmonic resonance to set up.

"That vibration, if it lined up just with the right structural mode, could end up stressing that piece and causing high cycle fatigue," shuttle Program Manager John Shannon said Tuesday, when the initial launch delay was announced.

While Discovery's valves were thought to be pristine, additional testing was ordered to assess the potential threat posed by meTALlic debris breaking off during flight and striking the walls of the downstream pressurization line.

"They're just not going to have enough data in from that testing to go to a formal agency FRR next Thursday ... for a launch a week later," a NASA official said, discussing the current Feb. 19 launch target. "And that's just not going to happen. They can't get there."

Complicating the picture, engineers over the past two days have discovered that small grooves in the valves left over from their original machining apparently can mask small cracks. After a valve was subjected to "destructive testing," a source said, engineers discovered evidence that tiny, undetected cracks may have played a role in the failure. That would imply that the supposedly pristine valves aboard Discovery may not, in fact, be crack free.

"If the impact testing comes back and says we can tolerate some conservative bounding cases ... we'll go roll it into a (review) on the 13th, discuss the technical puts and takes and launch the next week," said a shuttle manager. "But it could go the opposite way."

The renewed concern about undetected cracks "kind of puts us back to square one," he said.

Depending on impact test results, NASA managers could opt to launch Discovery as is or stand down long enough to possibly replace the valves with versions that have been polished to remove the grooves and retested to make sure no cracks are present.

Over the next several days, engineers hope to refine the computational fluid dynamics analysis of the acoustic environment inside the pressurization lines to more tightly characterize the sort of stress the valves experience and what sort of velocities debris might achieve. Impact testing will determine what threat any such debris actually poses.

Until test data are assessed, it's not possible to predict how the issue might play out. But sources said Shannon was determined to understand the technical ramifications before making any launch decisions, reflecting a post-Columbia focus on making sure potentially significant problems get the attention they deserve.


8:45 PM, 2/3/09, Update: Shuttle launch delayed at least one week for flow control valve tests

Launch of shuttle Discovery on a mission to deliver a final set of solar arrays to the international space station has been delayed at least one week, to no earlier than Feb. 19, to give engineers additional time to assess the health of critical hydrogen flow control valves that keep the ship's external tank pressurized during the climb to space.

Launch had been targeted for 7:32:11 a.m. on Feb. 12, but senior managers at an executive-level flight readiness review held at the Kennedy Space Center today decided not to set an official launch date and to meet again next Tuesday, on Feb. 10, to assess the results of ongoing engineering analyses.

If the valve issue is resolved, a launch on Feb. 19 would occur at 4:41:47 a.m. Docking with the space station would be targeted for around 1:06 a.m. on Feb. 21 with the first of four spacewalks starting around 10:11 p.m. on Feb. 22. Additional spacewalks would be planned for Feb. 24, 26 and 28, beginning between 9:41 p.m. and 8:11 p.m. Undocking would be expected around 6:39 p.m. on March 2, with landing back at the Kennedy Space Center a few minutes before 11 p.m. on March 4.

Going into today's FRR, shuttle and space station managers faced a variety of issues. On the shuttle front, engineers were still discussing recent problems with flow control valves used to pressurize the ship's hydrogen fuel tank during the climb to space.

Each shuttle features three such valves, one associated with each main engine, that operate like lawn sprinklers, popping up as required to route hydrogen gas to the external tank to maintain the internal pressure needed to feed propellant to the main engines.

During the most recent launch last November, one of the three flow control valves aboard the shuttle Endeavour began allowing more hydrogen to pass through than expected. The other two valves reduced flow to maintain the proper pressure and the shuttle's climb to space was uneventful.

After landing, engineers discovered a small crack and missing material on the lip of the valve in question. NASA managers ordered all the valves in Endeavour, Discovery and Atlantis removed for detailed inspections. One other valve was found to have a crack. Based on electron microscope inspections, engineers concluded the defect was the result of high-cycle fatigue. A fresh set of vales that flew previously on Discovery and were known to be in pristine condition was insTALled for launch.

But engineers were surprised that fatigue played a role.

"It's just like a pop-up lawn sprinkler," said shuttle Program Manager John Shannon. "When you want to flow gaseous hydrogen from the main engines to the external tank to pressurize that tank, it pops up a little bit and allows that flow. What happened on STS-126 (in November) is that a small little piece of it, about the size of the tip end of your thumbnail, liberated, it broke off.

"That was a big surprise to us, because it's really not in an environment where we would expect to have that kind of fatigue. It only cycles about 15 times during the flight. It slowly goes up and down. So it was a surprise that it broke off."

Engineers at NASA's Marshall Space Flight Center in Huntsville, Ala., used computational fluid dynamics to model the hydrogen flow environment in the system. What they found explained what happened.

"The way the flow goes across the top of that valve, just like the harmonic resonance you get when you blow over the top of a Coke bottle, was making it vibrate," Shannon said. "That vibration, if it lined up just with the right structural mode, could end up stressing that piece and causing high cycle fatigue. That was a great bit of investigative work by both the Marshall team and the Johnson Space Center engineering team."

So far so good. Engineers thought they understood the problem and given the pristine valves now aboard Discovery, mission managers had a good rationale for pressing ahead with launch.

But Shannon said today past experience showed "we had a failure of imagination in past design issues. We didn't take it a step further. The guys took it a step further and said OK, the piece is small and it was fine on STS-126 but what if that piece came off at maybe a different time or maybe had a different angle going down the pipe? Could it rupture the tube or could it cause any damage to the tube so we would lose some of the pressurization in the external tank?"

The valves are critical to safe shuttle operation. Even though the tanks are equipped with pressure relief valves to prevent over-pressurization, such venting could expose the shuttle to hydrogen in its immediate environment. At the other extreme, a loss of pressure could lead to premature engine shutdown. And even if the tank maintained the proper pressure, meTALlic debris possibly could rupture a pressurization line with catastrophic results.

Launch was delayed to give engineers time to finish a series of tests, firing small bits of meTALlic debris into targets similar to the pressurization lines to find out what might happen in a truly worst-case scenario.

"We don't expect there to be an issue," Shannon said. "We looked at the witness marks of where the little poppet hit on 126 and there were no issues at all. We could see little gouges or scratches where we think that poppet came off and hit. We don't expect there to be a problem, but we don't have the proof in hand. And we want to go have that proof in hand before we commit to go fly."

Said Bill Gerstenmaier, director of space operations at NASA Headquarters: "We want to make sure we've got this right. This has important consequence to us, so we think standing down a little bit of time and letting the folks do a little more work is a good thing."

On the station front, U.S. and Russian managers agreed earlier today not to carry out a planned reboost of the lab complex Wednesday.

During a reboost maneuver Jan. 14 using two rocket engines in the Russian Zvezda command module, the station crew and engineers monitoring telemetry noted unexpected vibrations and oscillations in the station structure as the thruster firing progressed. The issue later was attributed to human error on the ground, and Russian engineers believe there are no technical issues that would prevent a normal reboost using thrusters in the Russian command module or in a docked Progress supply ship.

But station managers today agreed to defer additional reboost maneuvers pending additional analysis to make sure the vibrations posed no structural threat to the station and that future firings go smoothly.

"There were a number of areas of concern, where initial indications were we had violated design limits for mechanical loads," said Mike Suffredini, space station program manager at the Johnson Space Center.

Areas susceptible to damage from such loads include the aft command module, the connection between the station's huge solar power truss and the top of the U .S. lab module, the docking port where the lab connects to the Unity module and the rotary joint on the left side of the station that repositions two outboard solar arrays.

From a purely structural standpoint, the station's design loads were exceeded by 150 percent during the January reboost maneuver. But when factored in with thermal stresses the station experiences in orbit, engineers concluded no critical safety margins were exceeded.

"The teams worked over the last week and a half or so and at the end of this last weekend cleared the structure both for strength and for the 15-year life," Suffredini said. "So we have found that even though we did excite the stack and created a wonderful video for everyone to watch, we didn't, in fact, shorten the design life of ISS. We did, of course, put more cycles on it than we had planned. So we did shorten its life whatever it is, but it certainly didn't affect our design life and we don't think it really affected significantly the overall life we might otherwise get out of the structure."

The Russians do not need any additional reboost for launch of a new Progress supply ship Feb. 10. Additional rocket firings likely will be carried out in March before launch of a Soyuz ferry craft carrying the next station crew. As of this writing, that launch is expected to slip one day, from March 25 to March 26.

Other issues facing NASA managers today included ongoing problems with the space station's life support system that need to be ironed out to support the planned expansion of the lab's crew from three to six in May.

Urine recycling gear insTALled late last year, part of a complex system to recycle water aboard the station, ran into problems right off the bat with a distillation assembly centrifuge. The station astronauts eventually coaxed it into operation, but it suffered additional problems later and currently is out of action. A replacement is being launched aboard Discovery.

Other nagging problems facing the station include a high bacteria count in the new potable water system and trouble with U.S. carbon dioxide removal hardware, which is experiencing elevated internal pressure. Discovery will carry up chemicals to flush the potable water system and Suffredini said spare CO2 removal system components are scheduled for launch in June.

He said the planned crew increase from three to six can take place as planned in May despite those problems, given the amount of fresh water already on board and the planned delivery of fresh water from visiting space shuttles.

But getting the life support system up and running smoothly is critical to the station's long-term health and to prevent shortages in the event of any extended shuttle delays down the road. Suffredini said engineers hope to have the system fully operational within the next several months.

"As long as the shuttle is flying pretty much on the schedule we've planned, we will be able to support six-person crew," he said. "We'll have to get more water from the shuttle than we might otherwise require, but at least we can support six-person crew. So we do have a little time to sort through those anomalies. Ultimately, we'd like to get the distillation assembly working and process all the water we can."


3:30 PM, 2/3/09, Update: Flight readiness review under way; station reboost maneuver deferred

Senior NASA managers met today at the Kennedy Space Center to assess the readiness of the space shuttle Discovery and the international space station to support a Feb. 12 launch on a mission to deliver and insTALl a final set of solar arrays. A news briefing is expected late today to discuss the flight readiness review and a variety of issues affecting both programs.

On the station front, U.S. and Russian managers agreed earlier today not to carry out a planned reboost of the lab complex Wednesday. Eliminating the altitude-raising maneuver will shorten the shuttle's Feb. 12 "in-plane" launch window - one that will permit a docking on flight day 3 as planned - from around five minutes to just 22 seconds or so, assuming mission managers choose to stick with that date. Full-duration windows are available the next day - Friday the 13th - and for subsequent launch opportunities.

During a reboost maneuver last month using rocket engines in the Russian Zvezda command module, engineers noted unexpected vibrations and oscillations in the station structure as the thruster firing progressed. The issue later was attributed to human error on the ground, sources said, and Russian engineers believe there are no technical issues that would prevent a normal reboost using thrusters in the Russian command module or in a docked Progress supply ship.

But station managers today agreed to defer additional reboost maneuvers pending additional analysis. Engineers want to make sure the vibrations posed no structural threat to the station and that future firings go smoothly.

In the meantime, the Russians plan to press ahead with launch of a new Progress supply ship Feb. 10, but assuming no additional reboosts are carried out in the near term, launch of a Soyuz ferry craft carrying the next station crew would slip one day, from March 25 to March 26.

On the shuttle front, Discovery is in good shape, officials say, but going into today's executive-level FRR engineers were still discussing recent problems with flow control valves used to pressurize the ship's hydrogen fuel tank during the climb to space.

During the most recent launch last November, one of the three flow control valves that route gaseous hydrogen from the main engines of the shuttle Endeavour to the external tank began flowing at a higher rate than normal. The other two valves reduced flow to maintain the proper pressure and the shuttle's climb to space was uneventful.

After landing, engineers discovered a small crack and missing material on the lip of the valve in question that caused more hydrogen to flow than normal. The valve was removed for troubleshooting and engineers blamed the defect on high-cycle fatigue. The valves aboard Discovery were removed and replaced with clean, inspected valves as a precaution.

But because that work was done at the launch pad, engineers were not able to carry out a full-up end-to-end interface test like the one normally carried out inside the Vehicle Assembly Building before rollout. Some engineers believe additional analysis is required, others argue it's not needed.

Other issues facing NASA managers today include ongoing problems with the space station's life support system that need to be ironed out to support the planned expansion of the lab's crew from three to six in May.

Urine recycling gear insTALled late last year, part of a complex system to recycle water aboard the station, ran into problems right off the bat with a distillation assembly centrifuge. The station astronauts eventually coaxed it into operation, but it suffered additional problems later and currently is out of action. A replacement is being launched aboard Discovery.

Another problem facing the station is trouble with the U.S. carbon dioxide removal system, which is not operating at full capacity. Station managers say the planned crew increase from three to six can take place as planned despite those problems given the amount of fresh water already on board and the planned delivery of fresh water from visiting space shuttles.

But getting the life support system up and running smoothly is critical to the station's long-term health and to prevent shortages in the event of any extended shuttle delays down the road.

This status report will be updated after today flight readiness review briefing at the Kennedy Space Center.


8:45 PM, 1/22/09, Update: NASA on course for May 12 launch of Hubble repair mission; managers defer decision on whether second rescue pad needed

With preparations for the Feb. 12 launch of shuttle Discovery on a space station assembly mission in high gear, NASA managers met today and agreed to press ahead with plans to launch the shuttle Atlantis as early as May 12 on a final mission to service and upgrade the Hubble Space Telescope.

But Bill Gerstenmaier, director of space operations at NASA headquarters, deferred a decision on whether to require use of launch pad 39B for a potential emergency rescue mission. A final decision will be made in mid March, after safety analysts fully assess the pros and cons of the single-pad vs dual-pad rescue scenarios and after engineers with NASA's Constellation program report back on the feasibility of making a critical test flight from 39B in July as currently planned.

NASA plans to retire the space shuttle fleet in 2010, after nine more flights and completion of the international space station. The agency plans to replace the shuttle with a towering new rocket known as Ares 1, made up of a five-segment shuttle-derived solid-fuel booster and new upper stage powered by an advanced Apollo-heritage hydrogen-fueled engine. The Ares 1 will boost new Orion crew capsules to the international space station.

To gather engineering data to help validate computer modeling, NASA plans to launch a test rocket, known as Ares 1-X, from pad 39B in July. The test rocket will feature a standard four-segment shuttle booster, a dummy upper stage and an Orion mockup.

As of this writing, the Ares 1-X is about a month behind schedule and observers are not optimistic that time can be made up. If not, the flight likely will slip into the Fall timeframe because of conflicts with other shuttle flights. But during today's meeting, NASA managers decided to preserve the option of a July launch until the processing schedule is more definitive.

Originally scheduled for launch last October, Hubble Servicing Mission 4 was delayed when a data processing system aboard the space telescope malfunctioned in late September. Hubble program managers reported today that replacement hardware is undergoing tests and should be ready in time to support a May 12 launch.

The space telescope operates in a different orbit than the space station and the Hubble crew cannot seek "safe haven" aboard the lab in the event of a Columbia-class problem. Former NASA Administrator Mike Griffin decided early on that a rescue shuttle would be processed on pad 39B and primed for launch within a few days of an emergency being declared.

If NASA sticks with the dual-pad scenario for Hubble, the rescue shuttle - Endeavour - would be processed on pad 39B and, if there are no major problems with Atlantis, moved to pad 39A for launch around June 13 on another space station assembly mission. Using both pads for the Hubble mission would preclude launching Ares 1-X in July.

But if the Ares program can make up lost time, the agency could opt to use a single pad, 39A, for the Hubble mission. Under that scenario, engineers would have to move the rescue shuttle - Endeavour - to pad 39A first to carry out initial processing, then roll it back to the Vehicle Assembly Building. Atlantis then would be hauled to 39A for its launch campaign. In the event of an emergency in orbit, Endeavour then would be moved back out to pad 39A for launch as soon as possible.

Because of the required trips to and from a single launch pad, processing Atlantis and Endeavour using only pad 39A would delay the servicing mission to around May 29 and push the subsequent station assembly mission to around July 13.

Debating the various options today, Gerstenmaier decided to wait until mid March to make a final decision. If the Ares 1-X project can make up enough time to have a realistic shot at a mid July launch, NASA might go with single-pad operations for the Hubble mission. By moving Atlantis to the pad ahead of schedule in March, engineers could free up high bay 3 in the Vehicle Assembly Building for Ares 1-X assembly.

But that assumes a detailed safety assessment shows a rescue mission could, in fact, be launched from the same pad with a reasonable chance of success. Unlike station-bound shuttle crews that can spend weeks aboard the lab complex awaiting rescue, the Hubble astronauts would need to be back on the ground in about a month at the outside.


3:30 PM, 1/19/09, Update: Shuttle astronauts fly to Florida for practice countdown

The Discovery astronauts flew to the Kennedy Space Center today to review emergency procedures and participate in a practice countdown Wednesday, a major milestone on the road to launch Feb. 12 on a space station assembly mission.

Talking to reporters at the Shuttle Landing Facility, commander Lee Archambault said the astronauts will be too busy with training Tuesday to watch the inauguration of President-elect Barack Obama. Asked what he might say to the new president if he had the opportunity, Archambault said "I would like to at least encourage him to keep the course that we're going on."

"We're on a pretty nice course right now, we know we're going to develop a new vehicle, we've got the Constellation program well underway and we're anxious to fly in 2014 or 2015," he said, referring to the new Ares 1 rocket and the Orion crew capsule NASA plans to build as a replacement for the space shuttle.

"Hopefully, we can stay on track with that," Archambault said. "But the long-term goal of getting back to the moon and ultimately beyond and to Mars, I think, is really the future of the program. So we'd love very much for him to stay the course and press on with the Constellation program."

In the five-year gap between the planned retirement of the shuttle in 2010 and the debut of Ares/Orion in late 2014 or 2015, NASA astronauts will be forced to hitch rides to and from the international space station aboard Russian Soyuz spacecraft.

NASA's long-range plan - the Constellation program - calls for launching astronauts to the space station aboard Ares 1/Orion starting around 2015 and eventually on to the moon using the Orion capsule and a new heavy-lift rocket called the Ares 5.

During the presidential campaign, Obama expressed support for adding at least one additional shuttle flight and accelerating development of the Ares 1/Orion to help shorten the gap between the end of shuttle operations and the debut of the new system. But it is not yet clear what actual changes might be on tap for NASA.

The incoming administration did not ask NASA Administrator Mike Griffin, the architect of the Bush administration's Constellation program, to stay on the job and a replacement has not yet been named. Whether Obama will accelerate the Constellation program or perhaps order a change of course for NASA is not yet known.

Archambault and his crewmates - pilot Dominic "Tony" Antonelli, John Phillips, Steven Swanson, Richard Arnold, Joseph Acaba and Koichi Wakata, a Japanese astronaut who will replace Sandra Magnus aboard the space station - are scheduled for launch on the 125th shuttle mission at 7:32 a.m. on Feb. 12.

The primary goals of the mission are to deliver and insTALl a final set of solar arrays on the right side of the station's main power truss; to deliver Wakata and bring Magnus back to Earth after three months in space; and to complete a variety of "get-ahead" tasks needed for future assembly missions.

The astronauts also plan to deliver a new component for the station's urine recycling system, a critical element in NASA's plan to boost station crew size from three to six in May. The recycling system was insTALled during a shuttle flight in November, but the crew has had problems with a distillation assembly. NASA plans to begin six-person operations in May regardless, but the recycling gear must be activated and thoroughly tested as soon as possible to avoid potential problems downstream.

As for Discovery, launch Director Mike Leinbach said today there were no major technical issues at the pad and that the shuttle was in good shape for launch.


4:20 PM, 1/14/09, Update: Shuttle Discovery moved to launch pad (UPDATED at 7:20 p.m.: correcting dates for program-level flight readiness review; Jan. sted Feb.)

The Space shuttle Discovery was hauled from the Vehicle Assembly Building to pad 39A today, setting the stage for launch Feb. 12 on a space station assembly mission, the 125th in shuttle history and the first of five planned for 2009.

The primary goals of the four-spacewalk mission are to insTALl a final set of solar arrays on the right side of the lab's main power truss; to perform get-ahead tasks for upcoming assembly flights; to deliver Japan's first long-duration station crew member; and to bring flight engineer Sandra Magnus back to Earth after three months in space.

Bolted to a mobile launch platform carried by a powerful Apollo-era crawler-transporter, Discovery began the 3.2-mile trip to the pad at 5:17 a.m. and was "hard down" atop the oceanside firing stand at 12:16 p.m.

Discovery's crew - commander Lee Archambault, pilot Dominic "Tony" Antonelli, John Phillips, Japanese astronaut Koichi Wakata and spacewalkers Steven Swanson, Joseph Acaba and Richard Arnold - plans to fly to the Kennedy Space Center on Monday for emergency training and to strap in for a dress-rehearsal countdown Thursday.

The astronauts will field questions from reporters on arrival Monday in their final pre-launch news conference. The media session at the shuttle landing strip normally is held at the launch pad, but it was moved to Monday because of a tight schedule and the presidential inauguration Tuesday.

Shuttle program managers plan to review Discovery's flight readiness Jan. 21 and 22 and senior managers will hold an executive-level review Feb. 3 to set an official launch date.

As of this writing, Discovery is on track for launch at 7:32:10 a.m. Feb. 12. Landing is targeted for 1:48 a.m. on Feb. 26. The flight plan posted on the CBS News STS-119 Quick-Look page has not yet been updated with the latest launch and landing times. An update will be posted as soon as possible.


10:18 PM, 12/4/08, Update: Setting up initial STS-119 page

With the shuttle Endeavour safely back on Earth after a successful space station assembly mission, NASA is pressing ahead with plans to launch the shuttle Discovery on Feb. 12 on a four-spacewalk flight to insTALl a final set of solar arrays on the international lab complex.

Discovery is scheduled to be hauled from its processing hangar to the nearby Vehicle Assembly Building on Jan. 7, followed by roll out to pad 39A on Jan. 14. Launch on Feb. 12 is targeted for 7:28:37 a.m.

An initial flight plan is posted on the CBS News STS-119 Quick-Look page, along with a launch windows chart, personnel, astronaut designations and personnel where known.

These pages will be updated as mission-specific data and timelines become available.