The Pentagon says it will ask the Navy to shoot down a broken spy satellite that was expected to re-enter the Earth's atmosphere in late February or early March.
In a briefing at the Pentagon, Defense Department officials said they believe about 2,800 pounds of the two-and-a-half-ton satellite could survive and crash, in pieces, on Earth. The satellite, launched in December 2006, broke down soon after reaching orbit. Officials say it was a "test bird," launched by the National Reconnaissance Office, but did not want to give more details.
Globalsecurity.org, a Web site that follows defense issues, has said the satellite is called NROL-21 and was testing new radar systems. Other sources called it USA-193. It was launched from Vandenberg Air Force Base in California by a Delta II rocket.
The chances of the debris actually hitting anyone are quite small, they say; 70 percent of the planet is water, and most of the rest is mountain, desert, tundra, or open farmland.
But the satellite does carry hydrazine fuel in a well-insulated tank, and the officials said they would like to destroy that tank to protect against the chance of its landing near people.
Hydrazine is highly toxic, and the tank would almost certainly leak. Modeling suggests that the tank, 40 inches in diameter, is the largest component likely to survive re-entry.
"That's our objective. Get rid of the hydrazine and have this fall in the ocean," said Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, briefing reporters this afternoon.
"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," said Gen. Cartwright. "The regret factor of not acting clearly outweighs the regret factors of acting."
Some defense analysts said the U.S. has another, unmentioned motive: it doesn't want pieces of the secret satellite falling into the wrong hands.
"I think they are maybe afraid that pieces of it are going to end up in Russian or Chinese hands; souvenir hunters find this thing selling on eBay, and the Russians and Chinese will get into a bidding war to see who can get these pieces," said John Pike, director of GlobalSecurity.org.
Cartwright disagreed. He said the charred wreckage that reaches Earth — if it is ever found — is unlikely to be of much use to an unfriendly country.
The Pentagon said it would deploy three Aegis cruisers, one of which would fire a small missile at the satellite. The other two would act as backups. The Defense Department says it has high confidence that the missile would launch — but actually hitting a satellite in an unstable orbit at 17,000 miles an hour is an iffy proposition.
"This is the first time we've used a tactical missile to engage a spacecraft," said Cartwright.
Officials didn't provide an exact date for the shoot-down, but said late February or early March was likely.
Other sources, who declined to be identified, said the Pentagon may be thinking of this effort as target practice. U.S. forces may someday want to destroy an enemy satellite in wartime.
The case is also potentially embarrassing to the United States in its relationships with other countries, said officials. The U.S. informed other countries when it realized the satellite was likely to re-enter, and has now told them of its plans to intercept it.