Tracking shows no need for station crew to seek shelter aboard Soyuz (UPDATED)

Editor's note...
  • Posted at 01:53 PM EDT, 04/05/11: Station controllers monitor possible close encounter with space debris
  • Updated at 02:55 PM EDT, 04/05/11: Station crew told radar tracking indicates no need to seek shelter aboard Soyuz
CBS News

Flight controllers monitoring the path of a small piece of debris from the wreckage of a deliberately destroyed Chinese weather satellite decided Tuesday there was no need for the three-person crew aboard the International Space Station to take shelter in their Soyuz TMA-20 ferry craft.

Radar tracking indicated the debris, believed to measure five to six inches across and traveling at some five miles per second, would pass within the pizza box-shaped safety zone NASA monitors around the space station, coming within about 3 miles of the outpost at 4:21 p.m. EDT (GMT-4).

But additional tracking showed the probability of a collision was less than originally believed and Expedition 27 commander Dmitry Kondratyev, flight engineer Paolo Nespoli and NASA flight engineer Catherine "Cady" Coleman were told they would not need to take shelter in the Soyuz TMA-20 spacecraft that carried them into orbit last December.

"The latest update brings us good news," a flight controller radioed. "The probability numbers diminished enough that the status changed from red to green. What that means is that we are going to call off the shelter in place in the Soyuz and our ballistics folks are confident ... the green will not be changing back to red."

"OK, thank you, good news," replied Kondratyev.

"That means we don't get to camp out tonight?" Nespoli joked.

"We're not going to ask you to, no."

The Feng Yun 1C satellite was destroyed in a Chinese anti-satellite test in 2007, creating a huge cloud of debris at an altitude of 530 miles or so. Wreckage from the test has been slowly losing altitude ever since, posing a threat to satellites and, occasionally, the station.

When space debris is spotted early, the station's rocket thrusters can be fired to change its orbit slightly and increase the projected miss distance. A debris avoidance maneuver, or DAM, was carried out Saturday because of wreckage from a 2009 satellite collision. But the Feng Yun 1C debris spotted Tuesday was not seen in time to move the station.

"Initially, we have a screening box, which is .75 kilometers (0.47 miles) radial miss, which would be up or down, by 25 kilometers (15.5 miles) in cross track, which would be left or right, by 25 kilometers down track, which is either in front or behind us," Ron Spencer, a space station flight director, said during an earlier debris encounter.

"Space Command will alert us of any debris objects out there that are going to get that close to us. Then they increase tasking on those objects to try to get a better solution and decrease the uncertainty. And then we calculate a probability of collision on that, based on the data Space Command gives us, on the object and if the probability of collision is greater than 10 to the minus five (1-in-10,000), then we will begin to start looking at taking action."

Kondratyev, Nespoli and Coleman have been on their own aboard the International Space Station since March 16 when three other crew members -- Scott Kelly, Alexander Kaleri and Oleg Skripochka -- returned to Earth aboard the Soyuz TMA-01M spacecraft.

Their replacements -- Alexander Samokutyaev, flight engineer Andrey Borisenko and NASA astronaut Ronald Garan -- were launched from the Baikonur Cosmodrome in Kazakhstan on Monday. They are scheduled to dock at the space station Wednesday evening, boosting the lab's crew back to six.