俄美两国卫星相撞事件

Russian, U.S. satellites collide in space

MOSCOW, Russia (CNN) -- Two satellites, one Russian and one American, have collided some 800 kilometers (500 miles) above Siberia, the Russian and U.S. space agencies, said Thursday.

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Debris from the collision poses no threat to the International Space Station.

The collision on Tuesday produced two large debris clouds, NASA said. The satellites collided at 10 kilometers (6 miles) per second, producing 500-600 new pieces of space debris, the U.S. Strategic Command said.

That debris is not believed to pose a threat to the International Space Station as long as the clouds continue moving in a lower orbit, according to NASA and the Russian federal space agency, Roscosmos.

"There is some elevated risk, but it is considered to be very small to the ISS and to the other satellites that NASA has in orbit," NASA spokeswoman Beth Dickey told CNN. She said experts were still assessing the effects of the debris.

Mikhail Martirosov, from Russian mission control center, told Interfax news agency that the real threat from the debris will become obvious next week, once experts can calculate the trajectory of the fragments' descent.

"We have not received a warning of the possible danger to the ISS. The fragments may descend to the ISS orbit in several years, although I do not rule out that some fragments may go down within several days," Martirosov said.

The Russian satellite was launched in 1993 and had been out of service at the time of the collision, Roscosmos said.

The U.S. satellite was part of the Iridium global mobile communications system and is owned by a consortium headed by Motorola, the space agency said. It was launched in 1997.

A representative of Iridium could not immediately be reached for comment.

NASA's Dickey said a collision like this one is very rare.

"This is the first impact between two intact satellites traveling at hypervelocity," she said. "There have been some other occasions when things have accidentally collided in space, but they have been parts of rockets or parts of satellites and (produced) a very small cloud."

Major Regina Winchester, of the U.S. Strategic Command, said: "Space is getting pretty crowded. The fact that this hasn't happened before -- maybe we were getting a little bit lucky."

Winchester said Strategic Command tracks more than 18,000 pieces of manmade objects in space every day.

"Any time there's an event that creates more debris, it's a concern," she said. "All countries who have assets in space are going to be concerned simply because when there's more debris, there's a higher chance it's going to hit something."


 

Debris Spews Into Space After Satellites Collide

By WILLIAM J. BROAD
Published: February 11, 2009, New York Times 

For decades, space experts have warned of orbits around the planet growing so crowded that two satellites might one day slam into one another, producing swarms of treacherous debris.

It happened Tuesday. And the whirling fragments could pose a threat to the International Space Station, orbiting 215 miles up with three astronauts on board, though officials said the risk was now small.

“This is a first, unfortunately,” Nicholas L. Johnson, chief scientist for orbital debris at the National Aeronautics and Space Administration, said of the collision.

It happened some 490 miles above northern Siberia, at around noon Eastern time. Two communications satellites — one Russian, one American — cracked up in silent destruction. In the aftermath, military radars on the ground tracked large amounts of debris going into higher and lower orbits.

“Nothing to this extent” has ever happened before, Mr. Johnson said. “We’ve had three other accidental collisions between what we call catalog objects, but they were all much smaller than this,” the objects always very small and moderate in size.

The communication satellites, he added, “are two relatively big objects.”

The American satellite was an Iridium, one of a constellation of 66 spacecraft. Liz DeCastro, corporate communications director of Iridium Satellite, based in Bethesda, Md., said that the satellite weighed about 1,200 pounds and that its body was more than 12 feet long, not including large solar arrays.

In a statement, the company said that it had “lost an operational satellite” on Tuesday, apparently after it collided with “a nonoperational” Russian satellite.

“Although this event has minimal impact on Iridium’s service,” the statement added, “the company is taking immediate action to address the loss.” The company’s hand-held phones can be used anywhere around the globe to give users voice and data communications.

Mr. Johnson said the Russian satellite was presumably nonfunctional. Officials at the Russian Embassy in Washington could not be reached for comment.

Mr. Johnson said the United States military’s tracking radars had yet to determine the number of detectable fragments. “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.”

At a minimum, Mr. Johnson added, “I think we’re talking many, many dozens, if not hundreds.”

The debris could threaten the space station and its astronaut crew, he said.

“There are actually debris from this event which we believe are going through space station altitude already,” he said. The risk to the station, Mr. Johnson added, “is going to be very, very small.” In the worst case, he said, “We’ll just dodge them if we have to. It’s the small things you can’t see that are the ones that can do you harm.”

In Houston, International Space Station controllers have often adjusted its orbit to get out of the way of speeding space debris, which can move so incredibly fast that even small pieces pack a destructive wallop.

John Yembrick, a NASA spokesman in Washington, said the agency now judged the risk of collision with the speeding fragments to be “very small.” The threat, he added, is defined and acceptable.

Mr. Johnson, who works at the Johnson Space Center in Houston, said the new swarms of whirling debris might also eventually pose a threat to other satellites in an orbital chain reaction.

“What we’re doing now is trying to quantify that risk,” he said. “That’s a work in progress. It’s only been 24 hours. We put first things first,” meaning the station and preparing for the next shuttle mission.

William Harwood contributed reporting.

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