U.S., Russian orbiting satellites collide over Siberia
http://news.xinhuanet.com/english/2009-02/12/content_10805228.htm
WASHINGTON, Feb. 11 (Xinhua) -- One privately owned U.S.
communications satellite collided with a defunct Russian satellite in
space shooting out a pair of massive debris clouds and posing a slight
risk to the international space station, NASA said Wednesday.
It was the first such collision in space, NASA spokesman Kelly
Humphries said, adding that the magnitude of the accident was still
unknown.
NASA will take weeks to determine the full magnitude of the crash,
which occurred Tuesday nearly 790 km over Siberia, an altitude used by
satellites that monitor weather and carry telephone communications
among other things.
According to an email alert issued by NASA Wednesday, Russia's
Cosmos 2251 satellite slammed into the Iridium 33 satellite at 11:55
a.m. EST (0455 GMT). The incident was observed by the U.S. Defense
Department's Space Surveillance Network, which later was tracking two
large clouds of debris.
"This is the first time we've ever had two intact spacecraft
accidentally run into each other," said Nicholas Johnson, chief
scientist of NASA's Orbital Debris Program Office at the Johnson Space
Center in Houston. "It was a bad day for both of them."
He said outdated spacecraft, rocket stages and other components
break apart in space every year, but there have only been three
relatively minor collisions between such objects in the last 20 years.
Never before have two intact satellites crashed into one another by
accident, he added.
The debris created in Tuesday's collision is being tracked to
assess its risk of damaging other satellites and the International
Space Station, which is currently home to two American astronauts and
one Russian cosmonaut.
The space station flies at an altitude of about 354 km, well below
the impact point between the Russian and U.S. satellites.
NASA believed any risk to the space station and its three
astronauts is low. There also should be no danger to the space shuttle
set to launch with seven astronauts on Feb. 22, officials said, but
that will be re-evaluated in the coming days.
But the risk of damage from Tuesday's collision is greater for the
Hubble Space Telescope and Earth-observing satellites, which are in
higher orbit and nearer the debris field.
At the beginning of this year, there were roughly 17,000 pieces of
manmade debris orbiting Earth, Johnson said. The U.S. Space
Surveillance Network detected the two debris clouds created Tuesday.
Litter in orbit has increased in recent years, in part because of
the deliberate breakups of old satellites. It's gotten so bad that
orbital debris is now the biggest threat to a space shuttle in flight,
surpassing the dangers of lift off and return to Earth.
NASA is in regular touch with the network to keep the space
station a safe distance from any encroaching objects, and
shuttles,too, when they're flying.
Iridium, which operates a constellation of 66 low Earth orbiting
satellites providing mobile voice and data communications globally,
also said Wednesday that the incident could result in limited
disruptions of service.
In a prepared statement, the Bethesda, Maryland-based Iridium
characterized the incident as a "very low probability event" and said
it was taking immediate action to minimize any loss of service.
The company has a system of active satellites that relay calls
from portable phones that are about twice the size of a regular mobile
phone. It has more than 300,000 subscribers. U.S. Defense Department
is one of its largest customers.
Iridium said its system remains healthy and that it would
implement a "network solution" by Friday.
"Within the next 30 days, Iridium expects to move one of its in-
orbit spare satellites into the network constellation to permanently
replace the lost satellite," the statement said.
The 560-kg Iridium 33 satellite involved in the collision was
launched in 1997 while the 900-kg Russian satellite was launched in
1993 and presumed non-operational.
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