The unidentified object came within 1,100 feet of the space station — closer than any piece of space junk ever, said NASA's space operations chief, Bill Gerstenmaier.
Mission Control ordered the astronauts into the two Russian Soyuz capsules parked at the space station Tuesday morning. NASA got just 14 hours' notice of the close approach, not nearly enough time to move the space station out of harm's way.
The call to seek shelter came around 7:30 a.m. EDT. The time of closest approach was a little after 8 a.m. Mission Control gave the all-clear a few minutes later. The two Americans, three Russians and one Japanese floated back into the space station and resumed normal work.
Even a small piece of debris can do big damage. The astronauts could have undocked in their two Soyuz capsules and returned to Earth, in case of a serious collision.
Gerstenmaier said NASA managers are working with their Russian counterparts to reduce the amount of time needed to move the space station away from space junk. Right now, a couple of days are needed. Changes in computer software should improve that.
NASA does not know how big the object was or where it came from. It could well be a chunk of an old satellite or spent rocket.
Space shuttle Atlantis, meanwhile, is on track to blast off to the space station on July 8. It will be the last shuttle flight in NASA history. Atlantis will be filled with a year's worth of food and other station supplies.