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US Navy to shoot down falling spy satellite |
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Written by Derek Kessler on
Tuesday, 19 February 2008
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 In an attempt to limit the possibility of large pieces of contaminated debris from landing on your head, the United States government has elected to shoot down the dead spy satellite USA 193. Launched in December 2006, the it died soon after launch, meaning the bus-sized satellite's fuel tank is still filled with 1000 pounds of toxic hydrazine fuel. Russia and China have condemned the move, claiming it is a thinly-veiled real-world test of the USA's fledgling missile defense system.
Shortly after its launch on December 16, 2006, USA 193's main computer died. The satellite was unable to obtain its desired higher orbit and its fuel tank is filled to the brim with hydrazine for the ascent and maneuvering. USA 193 fell into a slowly decaying orbit at an altitude of 160 miles and the Pentagon declared the spy satellite a loss a few months later. And the satellite continued to orbit the Earth, slowly sinking closer, and completely ignored. Until the US government said it was going to fall out of the sky and was carrying a tank full of toxic fuel.
USA 193 is of concern for the US government, not because of the money lost, but because of the potential for loss when it comes down. The satellite is about the size of a commercial bus and weighs 5015 pounds, and carries a sophisticated and secret imaging system, as one would expect from a spy satellite. If left to reenter untouched, more than 2500 pounds of the satellite would survive to the surface, possibly including that tank full of hydrazine. The US government is concerned that the unpredictable reentry point of USA 193 might bring the imaging equipment into enemy hands. The rest of us are just hoping that we aren't hit in the head by a flaming ton of satellite.
And so prevent both from happening, the US Navy is going to shoot it down, to the tune of $60 million. A restricted airspace notice has been issued for Wednesday and Thursday for an area east of the Hawaiian Islands. The Navy has sent the U.S.S. Lake Erie to the region, equipped with a special Aegis rocket. Aegis was designed as a missile defense system and a single rocket has been specially modified to intercept USA 193. Among the modifications needed were adjustments to the rocket's heat sensors; it is designed to intercept hot-tipped warhead-carrying missiles, not satellites cruising along in the frigid reaches of space. The Lake Erie has been equipped with advanced tracking equipment to keep a lock on USA 193, as the satellite is currently orbiting at close to 23,000 mph and the ballistic missiles the Aegis system was designed to track typically don't reach half that speed.
Both China and Russia have come out in condemnation of the shootdown. They say that the rocket firing is a cover for a real-world test of the United States' glitch-plagued missile defense system. The Russian Defense Ministry went on the record, saying, "Such testing essentially means the creation of a new type of strategic weapons." China itself blew up one of its own defunct weather satellites last year, though the satellite was in no danger of reentry. The explosion created an orbiting debris field of small twisted bits of metal that are now frustrating space mission controllers worldwide as they dodge their own orbital equipment around the potentially-debilitating fragments. China's test was entirely unannounced and did not draw criticism from Russia.
No attempt will be made on USA 193 until after the space shuttle Atlantis has safely landed, which it is expected to do so on Wednesday. The Aegis rocket will intercept the satellite at an altitude of approximately 150 miles, detonating an the rocket's warhead. Ground-based radar, telescopes, and sea-based radars aboard the Lake Erie and accompanying ships will monitor the satellite for indications if the interception was successful. The US Air Force will also have a plane flying above the Pacific monitoring for the release of hydrazine.
Computer models predict that the explosion will rupture the hydrazine tank and break the rest of the satellite into pieces small enough that they will not survive reentry. The impact would also dramatically slow the speed of any remaining debris, making it reenter the atmosphere faster and at a higher, more fritional angle. Any hydrazine that is not destroyed in the explosion will disperse over the atmosphere in trace amounts that will be harmless to us on the ground. If first launch is not successful, the Navy has another modified-Aegis rocket on standby to try again two days later.
In the meantime, USA 193 continues to orbit around out blue planet. Because of its relatively low altitude it will be easily visible to the naked eye, assuming that the Navy doesn't blow it up before you get your eyes on it. It will pass over numerous cities world-wide, though the lower altitude will make it appear to move much faster than the higher-orbiting International Space Station or space shuttles. Heavens-Above.com has tracking info for USA 193 and hundreds of other orbiting objects; you can enter in your own location and see if/when USA 193, the ISS, Iridium satellites, or a host of other objects may pass overhead. Though the satellite will not be as bright as the much larger ISS, its magnitude will approached a rating of 1: as bright as any other star in the night sky.
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