A chunk of a destroyed Chinese weather satellite that veered close to the international space station did not end up forcing a newly arrived crew of astronauts to “shelter in place” early Wednesday.
Around 4 a.m. Eastern time, NASA announced that it had given the all-clear sign to the three astronauts, who arrived at the space station less than a week ago.
On Tuesday afternoon, NASA’s mission control in Houston informed astronaut Dan Burbank that the four-inch piece of space debris might pass close enough to the station early Wednesday morning to trigger the safety measure.
“On our most recent track, it was going to come within a half-mile” of the station, said Kelly Humphries, a NASA spokesman.
The Department of Defense’s Strategic Command, which monitors about 21,000 objects in orbit — including active satellites and space junk — notified NASA of the close call, Humphries said.
But the warning came too late for the usual precaution: firing the station’s thrusters to move the football field-size orbiting outpost out of the way. It takes 30 hours to plan and execute a burn of the station’s Russian-built thrusters, NASA said.
If further tracking had shown the debris heading into the “red zone” around the station, NASA would have ordered Burbank and his two Russian companions to close hatches between station modules and head to their Soyuz escape capsule.
Such a precaution isolates the station’s segments in the unlikely event that debris pierces the station and air begins to escape.
But the astronauts would not have closed the hatch on their escape vehicle. “You don’t close the hatch on Soyuz,” Humphries said. “You don’t want to paint yourself into a corner in case the Soyuz is hit.”
In a statement, NASA said the debris is a piece of a defunct Chinese weather satellite that country destroyed in a 2007 test of an anti-satellite weapon. China targeted the satellite with a ground-based missile, which blew the satellite into at least 3,000 pieces, each a potential threat to the space station. At the time, the test triggered complaints by U.S. national security officials.
About 21,000 pieces of debris larger than a softball orbit the Earth, according to NASA. Strategic Command tracks all of it, but NASA estimates that hundreds of thousands — perhaps millions — of untrackable, small debris litters low Earth orbit.
In September, the National Research Council warned that the space junk problem had passed a “tipping point.” The report called on NASA to research methods for cleaning up the junk that threatens active satellites and the space station.