ORLANDO, FLA. — With his ship still docked at the International Space Station, shuttle commander Lee Archambault fired up Discovery's steering jets Sunday to move the linked craft into a new position that will reduce their chances of colliding with a piece of space junk.
According to NASA, Archambault turned the station and the shuttle 180 degrees with the shuttle leading the station as it orbits Earth. That should increase the natural drag of the craft on the edge of the atmosphere enough to slow them down by about a foot per second, and lower their orbit just enough to avoid a piece of debris threatening the station.
"Had we not taken this action, the first time of closest approach would have been about two hours into Monday's spacewalk," NASA said in a news release.
The debris is part of a spent Chinese satellite and is estimated to be 4 inches across. It is in a similar altitude as Discovery and the station but in a slightly different inclination, meaning the debris would have crossed the shuttle-station orbit repeatedly for several days. The maneuver eliminates that risk, NASA said.
This is the third time in the last few weeks that the station has had to worry about space junk speeding around Earth on a possible collision course. Ten days ago, before Discovery launched, the crew of the station had to take shelter in a Russian Soyuz lifeboat capsule as a 5-inch piece of spent rocket motor came within striking distance; it missed. And in February, two satellites collided, creating a field of debris.
"Space debris is becoming an ever-increasing challenge," flight director Kwatsi Alibaruho said Sunday evening. When it comes to dodging junk, "it's a big deal. It's very tiring. Sometimes it's exhausting."
The latest episode occurred as NASA scrambled to put together a spacewalking repair plan for a jammed equipment platform at the space station.
Today, on the third and final spacewalk of Discovery's mission, astronauts plan to return to an equipment storage shelf that jammed and could not be deployed Saturday. The spacewalkers accidentally had inserted a pin upside down. On Sunday, Alibaruho said the catch for the mechanism is considerably stiffer than expected and engineers think the upside-down pin might not be the culprit after all.
Today's spacewalkers -- former teachers Joseph Acaba and Richard Arnold -- will use all their strength to get the shelf properly deployed. If nothing works, the jammed platform will be tied down with sturdier tethers.
A hastily assembled team of experts spent Saturday night and much of Sunday trying to figure out how best to deal with the problem.
The storage platform is meant to secure big spare parts that will be needed once NASA's shuttles stop flying.
Despite the recent incidents, Discovery's astronauts said they didn't worry about space junk when they were outside.
"We have enough other risks and worries to take on as we go outside," said Steven Swanson, who took part in the first two spacewalks.
While Archambault was steering the station away from danger Sunday, other astronauts were trying to figure out what was wrong with the water-recycling unit. The unit, designed to turn astronaut urine and sweat into drinking water, was not working properly despite a new part.
The processor, delivered in November by the shuttle Endeavour, hasn't worked since after Christmas. Recycling urine is crucial to NASA's long-range plans to support a full-time crew of six on the space station, beginning this year.
Discovery will leave the station Wednesday.
The Associated Press contributed to this report.