WASHINGTON — The Bush administration has decided to try to shoot down a failing 5,000-pound spy satellite, fearing its rocket fuel could turn into a deadly toxic gas if the spacecraft crashed in a populated area, officials said Thursday.
The unusual operation, to be carried out in the next several days, would be the first U.S. attempt to shoot down a satellite since Cold War-era military tests ended in the 1980s.
Pentagon officials plan to use the same ships and missiles that are part of the Navy's nascent missile defense system. Ships in the North Pacific plan to fire a tactical missile at the satellite when it reaches a low orbit of about 150 miles over their general location.
Some experts theorized that the administration was influenced by concern that classified components on the intelligence satellite could fall into hostile hands. Denying that, Marine Gen. James E. Cartwright, vice chairman of the Joint Chiefs of Staff, said any sensitive instruments would burn on reentry.
"Once you go through the atmosphere and the heating and the burning, that would not be an issue in this case," Cartwright said at a news conference. "It would not justify using a missile to take it and break it up further."
However, the government has never resorted to shooting down a disabled spacecraft or satellite, despite dozens of crashes and reentries over decades of spaceflight. Administration officials said this instance is different because the satellite failed shortly after its launch in December 2006, leaving almost all of its 1,000 pounds of hydrazine rocket fuel frozen in the uncontrollable spacecraft.
Because of its size -- Cartwright compared it to a bus -- only half of the craft is likely to burn on reentry. That means the fuel tank could survive if it is not destroyed by the missile strike. Normally, aging satellites -- their onboard fuel mostly consumed -- are steered into the ocean at the end of their life. But with the spy satellite's power and communications inoperable, it is tumbling, unguided, to Earth.
Officials compared the effects of hydrazine fuel to those of chlorine or ammonia.
"It affects your tissues and your lungs -- it has the burning sensation," Cartwright said. "If you stay very close to it and inhale a lot of it, it could in fact be deadly."
Experts on military satellites agreed that the dispersal of hydrazine could pose a serious health hazard, although even Cartwright said it likely would be spread only over an area the size of two football fields.
John F. Pike, a military analyst who specializes in space-based weapons and intelligence systems, said that under normal circumstances, dying satellites are guided into the Pacific Ocean, primarily so that foreign rivals do not get their hands on sensitive components.
"I'm not arguing that hydrazine isn't a problem," Pike said. "But they're so concerned in normal circumstances about things falling into the wrong hands that I'm not sure I believe them. I think they want to get ahead of the story here."
Administration officials insisted public safety was the reason President Bush approved of the plan to shoot down the satellite.
The satellite was operated by the National Reconnaissance Office, the intelligence agency responsible for the nation's spy satellites. The officials would not comment on the satellite's mission or its cost and could not estimate the cost of shooting it down.
U.S. officials harshly criticized China after learning last year that its military shot down an aging weather satellite. That incident recharged an international debate over space weapons and prompted a Pentagon review of the safety of U.S. orbiters.
Drawing a contrast with the more secretive Chinese operation, U.S. officials dispatched diplomats around the world Thursday to explain their decision to shoot down the spy satellite.
The officials also said the Chinese destroyed their satellite at a higher orbit than the U.S. has planned for hitting its spy satellite. China's shoot-down left debris orbiting the Earth, while the Pentagon plans call for hitting the craft just as it enters the atmosphere, so debris will burn on reentry.
Under the plan, the Navy will position a mix of three destroyers and cruisers equipped with sophisticated Aegis radar systems in the North Pacific to prepare for the shoot-down. Only one of the ships will be assigned the duty of firing on the satellite, with the other two in the area in case the first ship fails.
Cartwright said it was possible, but unlikely, that a second shot would be taken a couple of days after the first one if it missed.
The Pentagon would not say which ship will be assigned the task. One Aegis cruiser, the Lake Erie, has conducted more extensive testing than other ships of the Standard Missile 3 -- a defensive rocket that will be used to shoot down the satellite. The Lake Erie is stationed at Pearl Harbor, Hawaii.