WASHINGTON — The U.S. military likely will make its first effort to shoot down a crippled spy satellite that's approaching Earth's atmosphere sometime Wednesday night in what will be a major, if unplanned, test of America's anti-ballistic missile program.
The first hurdle blocking the attempt was cleared at 9:07 a.m. Eastern time when the space shuttle Atlantis, carrying seven astronauts, landed at Camp Canaveral, Florida. Minutes later, the Pentagon announced that the window of opportunity to shoot down the satellite had opened.
The next hurdle will be rough weather in the Pacific, which could still delay the shot, now scheduled for sometime after 10:30 p.m., the Pentagon said.
Planners now say that the USS Lake Erie, an Aegis class missile cruiser, will be about 600 miles west of Hawaii when it launches an SM-3 tactical missile toward the satellite. If that missile misses, the Navy has two other missiles on standby to launch, most likely on Thursday or Friday, the Pentagon said.
A Federal Aviation Administration advisory on Tuesday warned airlines that the launch could happen between 9:30 p.m. and midnight Eastern time.
U.S. officials announced last week that the Navy would try to down the satellite out of concern that a tank carrying 1,000 pounds of hydrazine, an ammonia-like chemical used in rocket fuel, would survive re-entry into the Earth's atmosphere and land in a populated area. Hydrazine can be toxic if swallowed or inhaled.
The plan, however, is controversial. Some experts have suggested that the attempt is really an effort to expand the capabilities of the anti-ballistic missile system to include satellites and to counter China's destruction of an aged weather satellite last year. The United States denounced that Chinese test.
The missile and the roughly 5,000-pound satellite, which failed shortly after it was launched in December 2006, will close in on each other at roughly 20,250 mph, officials said.
The shoot-down isn't a sure thing. The missiles that will be used to strike the satellite were designed to bring down ballistic missiles, and their software had to be rewritten so they could target the satellite, which moves faster than a ballistic missile.
The missiles also will find tracking the satellite difficult because, without power, it will be cooler than a ballistic missile. A senior Navy official, who couldn't be quoted by name under Pentagon press rules, said that the timing of the shoot-down was chosen partly so that the afternoon sun over the Pacific could warm the satellite, making it more likely that the missile would be able to find it 150 miles above the Earth's surface.
If the missile misses the satellite, it will keep traveling into outer space, the Navy said. The satellite will continue approaching Earth.
A successful hit by the missile may not, however, destroy the satellite's hydrazine tank, Pentagon officials said. If another missile strike is needed, that launch most likely would take place on Thursday.
The Pentagon said that any debris from a successful strike is likely to fall into the Earth's atmosphere and burn up within days.
Firing the first missile will cost roughly $40 million, the Pentagon said, including the $10 million cost of the missile.
If the first launch is successful, the other two missiles will be reprogrammed for their original mission, the senior Navy official said.
"We have no requirement to shoot down satellites," the official said.