A camera outside the International Space Station reveals the shuttle Discovery just after its March 17, 2009 docking during the STS-119 mission.
Credit: NASA TV.
This story was updated at 8:27 p.m. EDT.
The International Space Station dodged a small piece of space junk Sunday leftover from a spent Chinese rocket that broke apart in orbit nine years ago.
Mission Control radioed the crew of the space shuttle Discovery, which is docked at the station, to perform a small thruster maneuver that changed the orientation of the space station, slowing it slightly and putting more clearance between the $100 billion orbiting laboratory and approaching space junk, NASA officials said.
NASA officials said the chunk of orbital debris is a small 4-inch (10-cm) piece of a Chinese satellite rocket stage that launched in 1999 and broke apart in March 2000.
Space station flight director Kwatsi Alibaruho said the space trash was going to fly near the space station up to twice each orbit, the first time occurring Monday about two hours into a spacewalk by astronauts. NASA traditionally does not make orbital adjustments while astronauts are outside the station because of the high forces the maneuvers put on the structure.
?Because of our concerns about having to take action during a spacewalk, we preemptively adjusted the orbit of the International Space Station and the space shuttle,? Alibaruho told reporters late Sunday.
Discovery commander Lee Archambault fired the shuttle?s thrusters at about 4:00 p.m. EDT (2000 GMT) in a half-hour maneuver to change the station?s position as it flies through space. The orientation places the shuttle in front of the station and is the same that will be used when Discovery undocks on Wednesday. It should slow the station by about 0.1 feet per second due to atmospheric drag, NASA officials said.
?Over several hours, this will lower the orbit very slightly, enough to avoid a piece of orbital debris whose erratic orbit makes it a potential threat,? NASA officials said.
NASA and its space station partners typically move the 1 million-pound (453,592 kg) orbiting lab when a piece of debris is expected to fly within an imaginary box that extends 15 miles (24 km) to either side of the outpost, which is longer than a football field.
?Space debris is becoming an ever-increasing challenge,? Alibaruho said. ?We?ve been very fortunate, and also very diligent, about monitoring space debris.?
Space debris traffic
The Chinese debris is the third piece of space junk to fly near the space station in two weeks. Mission managers have said that while there seems to be recent uptick in space debris, the events can ebb and flow like freeway traffic on Earth.
?I think these types of things will come and go in seasons,? Alibaruho said. ?Right now, we?re going through a season where we?ve had a number of things that we?ve had to dodge.?
On March 17, the remains of a Soviet-era military navigation satellite prompted flew past the space station just before Discovery docked at the orbiting laboratory. That debris was a small piece of the defunct Cosmos 1275 satellite, but it zoomed past the space station at a far enough distance that no avoidance maneuver was required.
That was not the case for another piece of space trash that buzzed the space station on March 12. That debris, a 5-inches (13-cm) wide piece of spent satellite rocket motor, flew within 2.4 miles (4 km) of the space station at a clip of about 19,800 mph (31,865 kph). The space station orbits the Earth at about 17,500 mph (28,163 kph).
Notice of the March 12 debris event came too late for flight controllers to move the space station. Instead, station commander Michael Fincke and his two crewmates had to take shelter in their Russian-built Soyuz spacecraft, which doubles as a lifeboat and ferry to and from the orbital laboratory.
Space debris has been a growing threat for the International Space Station and other satellites in orbit. On Feb. 10, an outdated Russian satellite collided with a U.S. communications satellite in an unprecedented crash that created two large clouds of debris.
NASA said the collision increased the risk of a debris strike during a space shuttle mission to the station by about 6 percent, or a 1-in-318 chance.
?There?s a lot of debris out there,? Fincke said in a televised interview on Friday, adding that space trash poses a risk to astronauts in space as well as the satellites that aid life on Earth. ?We need to be able to truly have a way to dispose of our satellite when we?re finished with them.?
Discovery?s seven-astronaut crew had a half-day off at the space station Sunday morning as the spaceflyers prepare for their third and last spacewalk on Monday. The shuttle has passed the midpoint of its 13-day mission to replace a station crewmember and deliver the outpost?s final pair of U.S. solar wings, which were unfurled on Friday.
Discovery is due to undock from the space station on Wednesday.
SPACE.com is providing continuous coverage of STS-119 with reporter Clara Moskowitz and senior editor Tariq Malik in New York. Click here for mission updates and SPACE.com's live NASA TV video feed.
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- Video: How the Iridium/Cosmos Satellite Crash Happened