NASA is tracking a debris fragment from a Soviet military satellite that could speed close to the International Space Station and Atlantis on Tuesday, during the STS-135 flight's only scheduled spacewalk, Mission Management Team chairman LeRoy Cain told a NASA news briefing late Sunday.
If an avoidance maneuver is necessary, it would likely be made using low thrust jets on the shuttle -- and perhaps late Monday, so as not to interrupt preparations for the space walk.
The time of closest approach of the debris from Cosmos 375, a 7,300 pound military reconnaissance spacecraft launched in late 1970, was projected for Tuesday at 12:59 p.m., EDT.
The mass of the object and the projected miss distance were still under assessment, said Cain.
The Atlantis crew docked with the International Space Station on Sunday, uniting 10 U. S., Russian and Japanese astronauts from the two spacecraft for a seven to eight-day cargo exchange.
The space agency received notification of a possible close approach from the U. S. Strategic Command, the Department of Defense agency responsible for tracking space debris, Cain said.
Tuesday's six-and-a-half-hour spacewalk, assigned to U. S. station astronauts Mike Fossum and Ron Garan, is scheduled to get under way at 8:44 a.m., EDT.
During the excursion, the two men will transfer a robotic satellite refueling experiment from the shuttle's cargo bay to the exterior of the space station for future technology demonstrations. The spacewalkers will also move a failed station thermal control system circulation pump from the orbiting laboratory to the cargo bay of Atlantis.