Spy satellite shootdown hinges on tricky factors

The officer briefed reporters at the Pentagon on technical and logistical matters related to the effort. Under ground rules set by the Pentagon, the officer could not be identified by name.

The attempted shootdown, already approved by President George W. Bush, is seen by some as blurring the lines between defending against a hostile long-range missile and targeting satellites in orbit.

Much of the equipment used in the satellite shootdown is part of the Pentagon's missile defense system, a far-flung network of interceptors, radars and communications systems designed primarily to hit an incoming hostile ballistic missile fired at the United States by North Korea. The equipment, including the Navy missile, has never been used against a satellite or other such target.

The three-stage Navy missile, the SM-3, has chalked up a high rate of success in tests since 2002 — in each case targeting a short- or medium-range missile. A hurry-up program to adapt the missile for this anti-satellite mission was completed in a matter of weeks; Navy officials say the changes will be reversed once this satellite is down.

Some people are skeptical.

"The potential political cost of shooting down this satellite is high," said Laura Grego, an astrophysicist with the Union of Concerned Scientists. "Whatever the motivation for it, demonstrating an anti-satellite weapon is counterproductive to U.S. long-term interests, given that the United States has the most to gain from an international space weapons ban. Instead, it should be taking the lead in negotiating a treaty."

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Defense Secretary Gates is being advised directly by Air Force Gen. Kevin Chilton, commander of U.S. Strategic Command. Gates was traveling to Hawaii on Wednesday to kick off a nine-day trip. Officials said his stop at U.S. Pacific Command was scheduled before it was known that the satellite shootdown could happen while he was there.

The military has hours each day to monitor a long checklist of technical factors and conditions before deciding whether to proceed with the missile launch. But there is a very narrow window — described by the senior military officers as "tens of seconds" — in which the missile must be launched in order to have the best chance of having the satellite debris land mainly in the Pacific.

Officials will know within minutes whether the missile has hit the satellite, but it will take a day or two to know whether the fuel tank has been destroyed, officials said.

Left alone, the satellite would be expected to hit Earth during the first week of March. About half of the 5,000-pound spacecraft would be expected to survive its blazing descent through the atmosphere and would scatter debris over several hundred miles.

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