Orbiting debris poses impact risk to astronauts aboard space station.
NASA is preparing contingency plans in case a large piece of orbital debris is deemed a threat to the International Space Station.
The chunk of space junk measures about 19 square meters, large enough to do significant harm to the ISS in the event of a collision. As a precaution, NASA mission controllers are preparing a plan that would see the ISS fire its booster rockets in order to escape the path of the debris, which is circling the earth in an elliptical orbit.
NASA currently estimates that the space junk will come within 3 kilometers of the ISS on Friday morning. "It is a fairly big piece, which makes it easy to track," NASA said. The agency did not state the origin of the debris, but the Earth is encircled by countless particles of refuse from spent satellites, industrial waste, dust, and other sources.
The ISS is equipped with shielding that offers some protection from space junk.
Meanwhile, a pair of astronauts from the space shuttle Discovery changed out a 1,300 pound holding tank from the ISS during a six and a half hour spacewalk that began Tuesday night and ended Wednesday morning.
Astronauts Danny Olivas and Nicole Stott removed the bulky ammonia tank from the ISS and will replace it with a new module during a follow-up spacewalk later in the week.
While Olivas and Stott worked out in space, station crewmembers were busy transferring 7.5 tons of cargo, including an exercise device named after comedian Stephen Colbert, from Discovery to the ISS.
Discovery launched in the pre-dawn hours Saturday morning from the Kennedy Space Center in Florida. NASA aborted several previous attempts due to weather and mechanical issues.
STS-128, as the mission is called, is under the command of shuttle veteran Sturckow. Joining him are six other space goers, including pilot Kevin Ford and mission specialists Patrick Forester, Jose Hernandez, and John Olivas. Christer Fuglesang will represent his native Sweden on the mission.
Discovery crew members are slated to perform three space walks during the mission. The shuttle is expected to land back at Kennedy on September 10.