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Navy Will Attempt to Down Spy Satellite
The difference, Griffin said, "is, one, we are notifying, which is required by treaties and law, okay?" The Chinese satellite was destroyed at a much higher altitude -- about 600 miles -- creating a field of orbiting space debris that is hazardous for other spacecraft.
The United States and Soviet Union conducted anti-satellite tests in the mid-1980s but stopped once it became clear that the debris from the destroyed spacecraft became a danger to other satellites and even spaceships. Griffin said the low altitude at which the satellite will be targeted -- about 150 miles -- will minimize orbiting debris.
"The lower we can catch this, the quicker the debris reenters," he said. More than half the pieces will burn up or land before making two revolutions around Earth, and the rest will come down in "weeks, maybe a month, but it's a very finite period of time that we can manage."
Jeffrey said that the fuel tank is the only piece of the craft that was not expected to break up on reentry and that it is hoped that the missile can destroy it in space. If it hits the ground, it could leak gas and cause potentially fatal injury over an area of the size of about two football fields, he said, adding that "this is all about trying to reduce the danger to human beings."
Other experts, however, said that they believed the heat of reentry would cause the tank to explode safely high in the air.
Cartwright said that two other Navy cruisers with backup missiles have been dispatched and that they could take additional shots at the satellite, if necessary. He said, however, that the window for shooting down the spacecraft is quite small.
The National Reconnaissance Office satellite lost contact with ground control soon after it was launched in December 2006. Never ordered to burn its maneuvering fuel, it still carries about 1,000 pounds of frozen hydrazine, a substance Cartwright said is "similar to chlorine or to ammonia in that when you inhale it, it affects your tissues in your lungs," adding: "It has the burning sensation. If you stay very close to it and inhale a lot of it, it could in fact be deadly."
The Columbia spacecraft, which broke apart and hit Earth in 2003, also contained a canister of hydrazine gas that landed intact in a Texas woodland. Columbia was at the end of its mission, however, and most of the hydrazine had burned.
Cartwright said that the Aegis missile system aboard the cruiser would fire an SM-3 missile with a heat-seeking nose that destroys its target by hitting it, not blowing it up. The missile, known as Block III, was developed primarily for intermediate missile defense against warheads coming in at low altitude. The Navy has spent the past three weeks modifying missile software normally set for hitting much higher targets, he said.
Asked whether the plan is really an attempt to test the Aegis system as an anti-satellite system -- which would be a very controversial step internationally -- Cartwright said the amount of special modifications being done to the programs used to guide the system would "not be transferable to fleet use."
He also rejected widely disseminated blog allegations that the destruction of the satellite had been planned to keep classified information aboard from landing in non-U.S. hands. Everything other than the gas container, he said, would be destroyed on reentry even without a missile strike.
Members of Congress were briefed on the plan yesterday, as were diplomats from other nations. House Armed Services Committee Chairman Ike Skelton (D-Mo.) said in a statement that "I attended a Congressional briefing this morning by the Department of Defense, and I am satisfied that the destruction of the malfunctioning satellite is the best option available to protect public safety."
"However, it should be understood by all, at home and abroad, that this is an exceptional circumstance and should not be perceived as the standard U.S. policy for dealing with errant satellites," he said. "The House Armed Services Committee will work closely with the Department of Defense and other concerned agencies to oversee the broader policy implications of this action in relation to our space assets."
Staff writers Karen DeYoung in Washington and Colum Lynch at the United Nations contributed to this report.