CAPE CANAVERAL, Fla.- A small piece of space junk drifted dangerously close to the International Space Station on Tuesday, prompting NASA to order the three astronauts to seek shelter in their attached capsule.
Mission Control gave the order after determining there was not enough time to steer the orbiting outpost away from the space junk.
The debris - estimated to be about 6 inches square - is from a Chinese satellite that was deliberately destroyed in 2007 as part of a weapons test. It was projected to pass within three miles of the space station, warranting a red threat level, NASA's highest.
Just last Friday, the space station had to move out of the way of an orbiting remnant from a two-satellite collision in 2009.
Debris is an increasingly serious problem in orbit, because of colliding and destroyed spacecraft. At 5 miles a second, damage can be severe, even from something several inches big. Decompression, in fact, is at the top of any spacefarers' danger list.
More than 12,500 pieces of debris are orbiting Earth - and those are the ones big enough to track.
Mission Control notified the crew of the latest threat Tuesday morning, a few hours after the risk was identified. The three crew members are Dmitry Kondratyev, the station's Russian commander, American Catherine Coleman and Italian Paolo Nespoli.
The orbit of the space junk is extremely erratic, and there's quite a bit of atmospheric drag on it, said NASA spokesman Josh Byerly. Experts monitored the debris into the early afternoon, to determine its exact path.
It's possible the risk of a collision might diminish. If that happened, the three station residents would not have to close themselves off in the Soyuz spacecraft. They arrived at the station in the Soyuz last December. The spacecraft serves as a lifeboat in case of an emergency. It will be used at the end of their six-month mission to deliver the crew back to Earth in May.
But if the risk level remains red, the astronauts would have to remove ventilation lines running from the space station's major modules, seal the hatches to the rooms, and switch the radio channels so they can remain in contact with flight control teams in Houston and Moscow.
They would need to float into the Soyuz capsule about 10 minutes in advance of the time of closest approach - currently projected to be 4:21 p.m. Eastern Time - and remain inside for at least 15 minutes afterward.
The last time a station crew took refuge in a Soyuz was in 2009. That time, the crew had less than an hour's advance warning. This time, the astronauts had nine hours' notice.
A fresh three-person crew is en route to the 220-mile-high outpost after rocketing away from Kazakhstan. That Soyuz is due to arrive Wednesday evening.
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