A small chunk of space trash made an uncomfortably close pass by the International Space Station late Friday, but not close enough to force the astronauts aboard to take shelter in their Russian lifeboats.
NASA's Mission Control woke the six astronauts on the station from their sleep late Friday as the space debris approached, but ultimately decided not to send the crew into their Soyuz spacecraft to ride out the orbital trash's near miss. The astronauts were told they could go back to sleep.
"Sorry we had to do it that way, and we had to wake you up in the middle of the night," the station's Russian Mission Control radioed the crew. The debris was projected to fly within 1,640 feet (500 meters) of the orbiting laboratory Friday night at 10:48 p.m. ET.
Sending the astronauts into their Soyuz lifeboats would have been a precaution only. Earlier Friday, NASA officials said the space junk posed no threat to the station or its crew, but news of its close approach came too late to steer the massive orbiting lab clear using its Russian thrusters.
"It's pretty unusual," Kirk Shireman, NASA's deputy station program manager, told Space.com Friday. "I wouldn't be surprised if the need to do it for this [debris event] goes away."
That is exactly what happened. A closer analysis of the object by NASA Friday found it to be a small, 2-inch (5-centimeter) piece of space trash that would not hit the space station.
"Good news," NASA's Mission Control told the station crew. "The tracking data has come through, and shown that the conjunction's no longer a threat to station."
The object was very small, making it difficult to track initially, NASA spokesperson Rob Navias told Space.com. Station astronauts thanked Mission Control for the news and said they were looking forward to grabbing more shut-eye. They headed back to their sleeping quarters at about 4:30 p.m. ET and were due to begin their Saturday in space after the debris passed by.
"I'll get around to all my crew members here, and we can go back to sleep," said station commander Frank De Winne, a Belgian astronaut representing the European Space Agency. "Thanks a lot for working all this tonight, Houston."
The space station is currently home to two Americans, two Russians, a Canadian and De Winne, who commands the team's Expedition 21 mission.
This is not the first time a piece of wayward space junk has come close enough for astronauts to consider taking refuge in their Russian lifeboats.
A close pass by an old rocket engine remnant sent three station astronauts into their Soyuz spacecraft in March. Since then, however, the space station's crew size has doubled to six astronauts, so two Soyuz vehicles are currently docked to the station.
NASA also delayed the departure of a Japanese cargo ship from the space station last week because of a space debris threat.
NASA typically prefers to move the space station when the odds of a space debris impact are within a 1-in-10,000 chance. Astronauts take shelter when debris is expected to fly within a so-called "red zone" and the space station doesn't have time to dodge, Shireman told Space.com.
There is also a "pizza box"-like buffer around the station that mission managers prefer to keep free of any debris. That safety zone extends about 15 miles (25 kilometers) around the space station, as well as about a half-mile (0.75 kilometers) above and below it. The station flies in an orbit about 220 miles (354 kilometers) above Earth at a speed of about 17,500 mph (28,163 kilometers per hour).
But a debris avoidance maneuver – as dodging space junk is known at NASA – can take days to plan. The space station's Mission Control team did not have that opportunity because of the short lead time, Navias said.
Space debris has been a growing threat for manned spacecraft and other satellites in orbit.
The collision between two communications satellites earlier this year brought the issue to the forefront. That smashup, as well as China's intentional destruction of a satellite during a 2007 anti-satellite test, have sparked a renewed push to better track, and possibly reduce, the more than 20,000 pieces of space junk currently watched by various agencies.