U.S. To Attempt To Shoot Down Faulty Satellite

WASHINGTON — The military will try to shoot down a crippled spy satellite in the next two weeks, senior officials said Thursday. The officials laid out a high-tech plan to intercept the satellite over the Pacific just before it tumbles uncontrollably to Earth carrying toxic fuel.

Gen. James E. Cartwright at the Pentagon on Thursday.

President Bush ordered the action to prevent any possible contamination from the hazardous rocket fuel on board, and not out of any concern that parts of the spacecraft might survive and reveal its secrets, the officials said.

The challenging mission to demolish the satellite on the fringes of space will rely on an unforeseen use of ship-based weapons developed to defend against ballistic missile attacks.

The effort will be a real-world test of the nation’s antiballistic missile systems and its antisatellite abilities, even though the Pentagon said it was not using the effort to test its most exotic weapons or send a message to any adversaries.

The ramifications of the operation are diplomatic, as well as military and scientific, in part because the United States criticized China last year when Beijing tested an antisatellite system with an old weather satellite as a target.

The three-ship convoy assigned to the new task will stalk the satellite’s orbital path across the northern Pacific, tracking the satellite as it circles the globe 16 times a day. The sensors and weapons in the operation, modified from antiaircraft defenses for use as a shield against incoming missiles and installed on Navy cruisers, have been used just in carefully controlled tests.

This time, the target is not an incoming warhead or a dummy test target, but a doomed experimental satellite the size of a school bus and weighing 5,000 pounds. It died shortly after being launched in December 2006 and contains a half-ton of hydrazine, a fuel that officials said could burn the lungs and even be deadly in extended doses.

The tank is believed to be sturdy enough to survive re-entry, based on studies of the tank that fell to Earth after the Columbia shuttle disaster in 2003.

The military and the National Aeronautics and Space Administration have calculated that the best opportunity to shoot down the satellite with an interceptor missile is just before it re-enters the atmosphere and starts to tumble and break apart on a random path toward the surface, an opportunity that begins in three to four days and continues for eight days. At that point, the debris would be quickly dragged out of orbit.

In many ways, the task resembles shooting down an intercontinental nuclear missile, although this target is larger, its path is better known and, if a first shot misses, it will continue to circle the Earth for long enough to allow a second or even a third try.

The weapon of choice, after modifications that are under way, is the Standard Missile 3 on Aegis cruisers. The defensive missiles and supporting radar were being modified and tested to shoot down enemy warheads. So the software is being reprogrammed to home in on the radar and other signatures of a large satellite instead of a ballistic missile, officials said.

Although White House, military and NASA officials described the president’s decision as motivated solely by wanting to avoid a spread of toxic fuel in an inhabited area, the effort has implications for missile defense and antisatellite weapons.

“This is all about trying to reduce the danger to human beings,” said James F. Jeffrey, deputy national security adviser.

The United States has opposed calls for a treaty limiting antisatellite or other weapons in space. On Thursday, officials promised that the United States would remain wholly compliant with treaties requiring the notification to other nations before launching a missile at the disabled satellite.

The American military shot down a satellite in September 1985 in a test of an antisatellite system under development. In that experiment, an F-15 Eagle fighter fired a missile.

Gen. James E. Cartwright of the Marines, vice chairman of the Joint Chiefs of Staff, said that if the first missile failed to strike the satellite, an assessment would be made within days and that two more missiles were ready. General Cartwright described little downside in trying to destroy the satellite.

“If we fire at the satellite,” he said, “the worst is that we miss. And then we have a known situation, which is where we are today. If we graze the satellite, we’re still better off, because likely we’ll still bring it down sooner, and therefore more predictably. If we hit the hydrazine tank, then we’ve improved our potential to mitigate that threat. So the regret factor of not acting clearly outweighed the regret factors of acting.”

Michael R. Gordon and David Stout contributed reporting.

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