Space Station Safe From Space Junk
Floating debris won't come close enough to station to be a threat, NASA says.
HOUSTON, March 16, 2009— -- Commander Mike Fincke and his colleagues on the International Space Station got good news from Mission Control this evening: There is no need to dash into the Soyuz or move the space station.
The floating junk that threatened the orbiting outpost won't come near enough to cause a problem.
NASA won't have to change the orbit of the space station, which means the Space Shuttle Discovery won't have to alter its course to dock with the space base Tuesday.
NASA draws an imaginary box around the space station that sets the boundary of how close it will let debris come to the outpost before taking evasive action.
Analysts in Mission Control at the Johnson Space Center started tracking this piece of junk over the weekend -- just days after the crew was forced to close all the airlocks between the modules in the space station and take shelter in the Russian Soyuz.
Last week's alarm was noteworthy, because usually Mission Control gets more notice -- it can take 30 hours to plan to change the orbit of the space station.
Flight Director Paul Dye said he found out about the most recent threat Saturday, that the space junk, dubbed Kosmos 1275, could be targeting the space station, and it gave his team a couple of days to figure out what to do.
But knowing something is up there doesn't mean it's easy to predict where it will go.
"It is difficult to get an accurate track of where it is going, so you put [it] in the computers and it showed up as green, then yellow, then red, which is when we get worried, and then the rest of the tracks were green," Dye said.
If it seems like there is more debris threatening the space station recently, that's because there is.
It's kind of like freeway traffic, according to Dye.
"We seem to have more right now, and you wonder where it comes from, and then it is gone," he said. "It is cyclical."
Leroy Cain, chairman of the Mission Management Team, said this won't be the last time space junk threatens the space station or the space shuttle.
"Space debris is an issue for us," he said. "There are objects we have to contend with, we have to be constantly mindful. It is a random occurrence that we have had to deal with them in such a short succession."
NASA is still waiting to find out if the Hubble Space Telescope is in any trouble from the satellite collision over Siberia last month that sent hundreds of pieces of junk into orbit. Hubble orbits just below the collision site.
Not only is Hubble at risk: If the debris lingers, NASA must decide if it is too risky to send Space Shuttle Atlantis and its crew of seven into a known debris field to repair the aging and failing telescope.
The space station has power, with enough notice, to move out of danger. Not so with Hubble, said Nicholas Johnson, of the Johnson Space Centers orbital debris office.
"It turns out a lot of satellites have no propulsion system at all, so all we could do is re-orient Hubble so it represents [the] smallest risk possible," he said.
The debris from that collision last month has increased the risk of debris impact to the Space Shuttle Discovery from 2 percent to 8 percent during its current mission.
The Air Force Space Surveillance Network tracks approximately 8,500 pieces of cataloged debris and 6,300 unknown objects. NASA's Orbital Debris Program office estimates tens of millions of very small objects (less than one centimeter) are in orbits that cannot be tracked, given the sensing network's limitations.
What's up there now? Current numbers as of March 12, 2009, according to NASA:
Active Payloads -- 1,300
Dead Payloads -- 1,700
Rocket Bodies -- 1,600
Debris -- 8,500
Unknown -- 6,300
Total = 19,400
All of this orbital debris is a threat to any operational spacecraft. Johnson says it wouldn't take much to damage a spacecraft. "An object as small as an inch can disrupt spacecraft."
Space junk and micrometeorites are a threat to every spacecraft. The Space Shuttle Atlantis came back to Earth in 2006 with a hole in the solar arrays on its payload bay doors.
It wasn't a big hole -- about one-tenth of an inch at entry and three-hundredths of an inch at exit -- but it was big enough to be seen without a flashlight, and it was larger than most dings on a space shuttle.
The previous record was held by a small hole in the thermal blanket on the Space Shuttle Columbia, following STS 73 in 1995.