Space shuttle Endeavour - the baby of NASA's orbiter fleet - is poised to roll out to its Florida launch pad today to prepare for its last mission, a move that will come just hours after the shuttle Discovery returns home from a last flight of its own.Endeavour is due to head out to the seaside shuttle launch pad at NASA's Kennedy Space Center in Cape Canaveral tonight at 8 p.m. EST (0100 March 10), about eight hours after Discovery's scheduled landing at a nearby runway.
The only potential threat is the weather. An overnight storm expected at the space center could slow or postpone Endeavour's launch pad trip, space center officials said.
NASA will televise and webcast Discovery's landing at 11:57 a.m. EST (1457 GMT) and Endeavor's last launch pad move live on its NASA TV channel.
It should be a rare sight: There's Discovery, NASA's oldest flying shuttle returning to Earth after 13 days flying one final voyage before being retired, setting the stage for Endeavour, the fleet's youngest shuttle gearing up to launch its own final mission on April 19.
Double shuttle sightings
The crews of both space shuttles are expected to discuss their respective missions with reporters today. Discovery's STS-133 crew will recap their historic flight on Discovery's last mission. Endeavour's STS-134 crew will host a preview of what their April flight holds in store.
"Clearly it's a demonstrable changing of the guard," NASA spokesman Allard Beutel told SPACE.com. "Literally, we're at a point where the STS-133 astronauts will be talking with reporters, and then can almost high-five the next group (Endeavour's astronauts) as they come in to talk."
NASA's 30-year-old space shuttle program has turned a corner with Discovery's last mission, which marks the beginning of the end for all three of the agency's flying reusable space planes.
Discovery's next stop will be a museum and the same fate awaits Endeavour and the shuttle Atlantis, which is slated to fly its last mission in late June.
Endeavour's STS-134 mission is a planned 14-day mission and includes four spacewalks. The primary goal is to deliver a $1.5 billion astrophysics experiment called the Alpha Magnetic Spectrometer to the International Space Station. The spectrometer is a powerful tool for studying cosmic rays and searching for antimatter, NASA officials have said.
The mission is commanded by veteran NASA astronaut Mark Kelly, the husband of Arizona congresswoman Gabrielle Giffords, who is recovering from a gunshot wound to the head received during a January shooting spree by a gunman in Tucson. Giffords is making progress and Kelly has said he hopes she will be able to attend Endeavour's launch.
Endeavour shuttle fans welcome
NASA expects thousands of spectators (mostly shuttle program employees and their families) to turn out for Endeavour's slow launch pad trek.
The 100-ton shuttle, now standing vertical and attached to its rocket boosters and fuel tank, will be hauled to Launch Pad 39A atop a massive crawler carrier that was originally built for the Apollo moon missions of the 1960s and 1970s. It should take about six hours for Endeavour to cross the 3.4 miles (5.4 kilometers) to the launch pad.
More than 3,000 people watched Discovery roll out to the launch pad overnight on Jan. 31 for its current flight. Discovery launched on Feb. 24 and spent more than a week linked to the International Space Station while its crew delivered a new storage room and robot.
For Endeavour's last trip to the launch pad, NASA has issued more than 900 family passes to shuttle program employees. The move is part of an ongoing project to give employees a chance to soak in major milestones before the shuttle program ends for good.
Beutel said everything now depends on good weather for tonight's rollout.
NASA space shuttles are particularly vulnerable during the short trip between the cavernous Vehicle Assembly Building - a 52-story building where shuttles are attached to their rocket boosters and fuel tanks - and the launch pad, which has a shell-like service structure to shield orbiters from foul weather.
Beutel said strong winds, lightning and rain are the major concerns for Endeavour.
"Basically we don't want to be moving the shuttle at those times," Beutel said. "It can be safely in the Vehicle Assembly Building or on the launch pad. It's that 3.4-mile distance in between we need to be concerned about."