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Pentagon to shoot down failing satellite

The Pentagon will attempt to shoot down an unresponsive spy satellite before it enters the Earth’s atmosphere due to concerns that the rocket fuel on board could harm people when it crashes, U.S. officials said Thursday.

The Navy has been working on software modifications for three weeks and will deploy three Aegis-equipped ships to intercept the 5,000-pound National Reconissance Office (NRO) imagery satellite somewhere in the northern hemisphere of the Pacific Ocean in the coming weeks, said Marine Corps Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff.

Cartwright refused say which ships will be deployed or where they will go to fire.

Cartwright said a “window of opportunity” for an attempt to shoot down the satellite with a ballistic missile will open in two to three days and is expected to last as long as seven to eight days.

If the first shot misses, the Navy will have two backup missiles and as long as two days to make a decision on a second attempt. The goals are to destroy the hydrazine rocket fuel and to push the satellite on a trajectory to land in the ocean, Cartwright said.

“If we fire at the satellite, the worst is that we miss. If we graze the satellite, we’re still better off because we’ll bring it down sooner and more predictably,” he said. “The regret factor of not acting clearly outweighs the regret factors of acting.”

If it is not intercepted, the satellite is expected to hit the atmosphere sometime in early March. The path it would take as it tumbled through the atmosphere would be “very, very unpredictable and impossible to engage,” Cartwright said.

The White House ordered the take-down because of concerns about the potential toxic effects of the satellite’s hydrazine fuel.

Hours after the December 2006 launch from Vandenberg Air Force Base in California aboard a Delta II rocket, the NRO lost contact with the satellite and has not been able to re-establish the connection. Because they have had no control over the satellite, there has been no way for the NRO to instruct it to burn off or even warm the frozen fuel, Cartwright said.

“We have had no way to communicate to invoke the safety measures that are already on the bird,” he said.

Officials said they expect about 2,800 pounds of debris — slightly more than half of the school-bus-sized craft — to survive re-entry, though the size of the pieces and the path they will take to the surface are impossible to predict.

NASA Administrator Michael Griffin said he expects the hydrazine tank to be the largest piece of debris, and while it will likely hit the earth intact, “it will have been breached because it will have been ripped from the fuel lines,” he said.

Griffin estimated there will still be about 1,000 pounds of fuel in the 40-inch-diameter tank when it hits the Earth’s surface.

Exposure to hydrazine irritates the throat and lungs and eventually affects the central nervous system. Extended exposure can cause liver and kidney damage and is eventually fatal.

Cartwright said a similar, though much larger, hydrazine fuel tank survived when the space shuttle Columbia was destroyed on re-entry in February 2003. The tank came to rest in a wooded area in Texas, with the fuel mostly burned off, Cartwright said.

The satellite’s tank could contaminate an area the size of two football fields, Cartwright said.

DISCUSS: The use of Hydrazine … is it safe?