labels: Space - aero, National Aeronautics and Space Administration
Space crash destroys Iridium-owned satellite news
12 February 2009

United States and Russian satellites collided over Siberia on Wednesday in the first crash between such objects at orbital speed, shooting out two massive debris clouds and posing a slight risk to the international space station, space agencies from both countries said.

The collision occurred 491 miles (790 km) above Siberia at 11:55 am New York time yesterday, destroying a privately-owned Iridium LLC communications satellite and a defunct Russian Cosmos 2251 craft, the National Aeronautics and Space Administration spokesman John Yembrick said, without identifying the cause.

It was the first crash between two intact space craft traveling at orbital speed, about 17,500 miles per hour, NASA spokeswoman Beth Dickey said. While the resulting debris clouds elevated the risk to the International Space Station, which orbits at about 220 miles, it is within acceptable limits, Dickey said. She estimated the debris field contained between 200 and 300 objects.

Roscosmos, Russia's space agency, said the collision was too close to Earth for the debris to be a threat to the space station. The defense ministry is responsible for the craft, a Roscosmos spokesman told Bloomberg in Moscow. The US defense department's Strategic Command is responsible for tracking the debris, according to Dickey.

Iridium, the Bethesda, Maryland-based company which uses its network of 66 satellites to provide wireless telephone and data services worldwide, said customers might experience limited disruptions. It will replace the lost satellite within 30 days with a spare already in orbit, the company said.

NASA's next shuttle mission, scheduled to visit the space station when it launches on or after 22 February, won't be affected by the crash, according to Dickey. "There's nothing that would give us any reason for concern at this point," she said.

The agency's earth observing satellites orbit closer to where the crash occurred, with an altitude of about 439 miles, and are of highest concern, according to Yembrick.

At the beginning of this year, there were roughly 17,000 pieces of manmade debris orbiting earth, said Nicholas Johnson, chief scientist of NASA's Orbital Debris Program Office at the Johnson Space Center in Houston. (See: The great junkyard in outer space).

A Chinese space expert said on Thursday that the massive debris of the satellite collision may pose grave, but controllable danger to other spacecraft in case they hit them. "The debris of the two big satellites may create holes on other spacecraft, or even bigger losses, if they hit," Pang Zhihao, a Chinese expert on space techniques, told Xinhua.

"The degree of the possible danger's graveness depends on the number, size and flying direction of the debris," he said. He predicted that the flying speed of debris may reach 7.8 km per second, or even faster, and may remain in space for decades.

But the leading British astronomer, David Whitehouse, believes most of the wreckage will burn up in the earth's atmosphere. "Hundreds, perhaps thousands of bits of debris have been created from the wreckage of these two satellites and they will stay in the high orbit and will slowly come back to earth," he said.

"However they will disperse, and by the time they get to lower orbits where the space shuttle and the space station is, they shouldn't be a problem."

Prior to this, three major collisions were confirmed between spacecraft and space junk in history. In December 1991, defunct Russian satellite 'Cosmos 1934' hit a big piece of debris from another Russian satellite, 'Cosmos 926', breaking the satellite in half.

In July 1996, French telecommunications satellite 'Helios 1A' was hit by a piece of debris produced during the process of an "Ariane" rocket entering orbit years before, damaging one of its observation device, and pushing the satellite out of its normal orbit.

On 17 January 2005, wreckage of the Chinese 'Long March 4' rocket which was launched six years before, collided with the castoff of an American rocket "Thor" at a speed of 5.73 km per second, lowering the rocket wreckage's perigee orbit by 14 km while breaking the castoff into four pieces.
However, these were all minor incidents compared to Wednesday's crash.

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Space crash destroys Iridium-owned satellite