Message posted by Matthew Ruch on February 12, 2009 at 13:25:03 PST:
Two satellites collide in orbit In an unprecedented space collision, a commercial Iridium communications satellite and a presumably defunct Russian Cosmos satellite ran into each other Tuesday above northern Siberia, creating a cloud of wreckage, officials said today. The international space station does not appear to be threatened by the debris, they said, but it's not yet clear whether it poses a risk to any other military or civilian satellites. "They collided at an altitude of 790 kilometers (491 miles) over northern Siberia Tuesday about noon Washington time," said Nicholas Johnson, NASA's chief scientist for orbital debris at the Johnson Space Center in Houston. "The U.S. space surveillance network detected a large number of debris from both objects." One source said nearly 300 fragments were being tracked, but Johnson said it was not yet clear how much debris was generated. "It's going to take a while," he said. "It's very, very difficult to discriminate all those objects when they're really close together. And so, over the next couple of days, we'll have a much better understanding. But it's at a minimum, I think we're talking many, many dozens, if not hundreds." Asked which satellite was at fault, Johnson said "they ran into each other. Nothing has the right of way up there. We don't have an air traffic controller in space. There is no universal way of knowing what's coming in your direction." Iridium Satellite LLC operates a constellation of some 66 satellites, along with orbital spares, to support satellite telephone operations around the world. The spacecraft, which weigh about 1,485 pounds when fully fueled, are in orbits tilted 86.4 degrees to the equator at an altitude of about 485 miles. Ninety-five Iridium satellites were launched between 1997 and 2002 and several have failed over the years. Representatives of Iridium did not immediately return calls for additional details. Johnson said the collision Tuesday was unprecedented. "Nothing to this extent (has happened before)," he said. "We've had three other accidental collisions between what we call catalog objects, but they were all much smaller than this and always a moderate sized objects and a very small object. And these are two relatively big objects. So this is a first, unfortunately." As for the threat posed by the debris, Johnson said NASA carried out an immediate analysis to determine whether the space station faced any increased risk. The station, carrying three crew members, circles the globe at an altitude of about 220 miles in an orbit tilted 51.6 degrees to the equator. "There are two issues: the immediate threat and a longer-term threat," he said. "It turns out, when you have a collision like this the debris is thrown very energetically both to higher orbits and to lower orbits. So there are actually debris from this event which we believe are going through the space station's altitude already. Most of it is not, most of it is still clustered up where the event took place. But a small number are going through station's altitude. "Yesterday, we did an assessment of what the risk might be to station and we found it's going to be very, very small. As time goes on, those debris will (come down) some over months, most over years and decades and as the big ones come down they'll be tracked, we'll see them and the worst-case scenario, we'll just dodge them if we have to. It's the small things you can't see are the ones that can do you harm." Asked if other satellites might be at risk, Johnson said "technically, yes. What we're doing now is trying to quantify that risk. That's a work in progress. It's only been 24 hours. We put first things first, which is station and preparing for the next shuttle mission." Most, if not all, of the debris is expected to eventually burn up in Earth's atmosphere.
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: February 11, 2009
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