London, Feb 21: The missile fired from a US warship in waters west of Hawaii has successfully struck a disabled American spy satellite.
Military operatives had only a 10-second window to hit the satellite, USA 193, which lost control shortly after it was launched in December 2006. The BBC quoted military officials as saying that they were worried about the fuel on board, which could pose a threat to humans. But Russia suspects that the operation was a cover to test anti-satellite technology under the US missile defence programme.
The US, however, denied that the operation was a response to the anti-satellite test carried out by China last year, which prompted fears of a space arms race. The satellite was believed by some commentators to be radar imaging reconnaissance satellite, which was passing about 130 miles (210km) over the Pacific.
Earlier, the US said that it would use a SM-3 missile fired from the cruiser USS Lake Erie, which is posted on the western side of Hawaii along with the destroyers USS Decatur and USS Russell.
But it is not yet known how successful the operation was - the missile needs to pierce the bus-sized satellite's fuel tank, containing more than 450kg (1,000lbs) of toxic hydrazine, which would otherwise be expected to survive re-entry.
US officials said without an attempt to destroy the fuel tank, and with the satellite's thermal control system gone, the fuel would now be frozen solid, allowing the tank to resist the heat of re-entry.
If the tank was to land intact, it could leak toxic gas over a wide area - harming or kill humans if inhaled, officials had warned.
Officials expect that over 50 per cent of the debris will fall to Earth within the first 15 hours after the strike - or within its first two revolutions of Earth.
USA 193 lost control a few hours after launch on a Delta II rocket.
Left to its own devices, about half of the spacecraft would have been expected to survive the blazing descent through the atmosphere, scattering debris in a defined "corridor" which runs across the Earth's surface.
Professor Richard Crowther, a space debris expert with the Science and Technology Facilities Council (STFC), said that if struck with the missile, about 25 per cent of USA 193 is likely to survive the fall to Earth.
"The smaller the debris is the more likely you are to get burn-through. So if you fragment something before re-entry, less mass will survive to hit the Earth," he told BBC News.