The US Navy will attempt to shoot down a malfunctioning American spy satellite before it falls to Earth, the Pentagon has confirmed. The plan has been approved by President George Bush, citing concern over toxic hydrazine fuel aboard the spacecraft. However, a top analyst has suggested the US is actually worried about secret technology winding up for sale on the web.
American officials confirming the shootdown plan last night said the Presidential decision was based entirely on the fact that the satellite still carries a full tank of manoeuvring fuel, having never been used. The spacecraft failed to come on line after being launched, and is now slowing down and descending due to friction from the upper atmosphere. At some point over the next few weeks, the gradual descent process will escalate quite suddenly and it will plunge to Earth.
"This is all about trying to reduce the danger to human beings... the likelihood of the satellite falling in a populated area is small, and the extent and duration of toxic hydrazine in the atmosphere would be limited,” said James F Jeffrey, deputy US national security adviser.
"Nevertheless, if the satellite did fall in a populated area, there is the possibility of death or injury to human beings."
Normally, such secret spy sats use the last of their fuel at the end of their useful lives to make a controlled re-entry into the ocean, safeguarding their technology from prying eyes and avoiding any risks to human life.
US Marine general James Cartwright, vice-chairman of the Joint Chiefs of Staff, said three US Navy Aegis warships were being positioned ready to shoot at the satellite. He said the ships are carrying Standard SM-3 ballistic-missile-defence interceptor rockets with specially modified software. According to Cartwright, the window of opportunity to pick off the satellite would open in "three or four" days, and would remain open for "seven or eight" days after that.
"We'll take one shot and assess," he added. "This is the first time we've used a tactical missile to engage a spacecraft."
The general dismissed the idea that the satellite's secret systems were a concern.
"Our assessment is that [the satellite] wouldn't be of high intel value... the hydrazine is the only reason we're taking extraordinary measures," he stated.
The US officials also said there was no comparison with last year's anti-satellite test by the People's Republic of China, in which the Chinese shot at a satellite of theirs just to see if they could hit it. Mr Jeffrey said the debris from a successful US shootdown just above the atmosphere would burn up within a short period; whereas the Chinese test had produced a debris shower which would be a danger to space navigation for centuries.
Nonetheless, it was confirmed that the warships would not fire until the space shuttle Atlantis returns to Earth on 20 Feb. NASA chief Michael Griffin said the risk from the interception to astronauts remaining in orbit aboard the International Space Station would be negligible - actually less than that caused by a routine shuttle mission.
The US administration's repeated insistence that the shootdown is motivated by purely humanitarian concerns seems rather dubious. At least 27 satellites re-entered the atmosphere last year, and more than 100 other items big enough to show on radar.
As for the hydrazine, tanks of nasty rocket fuel come down routinely, often intact or nearly so: a Delta-II second stage tank landed in fairly good condition in Texas in 1997, for example. The Delta-II second stage uses a hydrazine-based fuel, and equally toxic/corrosive dinitrogen tetroxide as oxidiser. The motor is restartable, used to provide multiple controlled burns for precise orbital positioning after the first stage drops away. Such a tank would seldom be entirely empty before it fell back to Earth: and yet nobody considers it normal to worry about Delta-II second stages, scores of which have come down over the years.
Indeed, another Delta-II blew up just seconds above the pad in '97, scattering debris all over Cape Canaveral. Tons of toxic fuel and oxidiser - the entire contents of the second stage - went everywhere. The US government's advice to local residents on that occasion? Stay indoors until the afternoon.
A hydrazine tank is also known to have survived the Columbia space shuttle disaster, as NASA's Griffin admitted last night - again, leading to no ill effects.
Against this sort of background, the idea that the descending satellite's little manoeuvring tank is a serious concern - serious enough to mobilise the US fleet with specially modified missiles - doesn't seem terribly plausible.
So why are the Americans so keen to shoot the satellite down? Well, it might be just to see whether they can; and to show that China isn't alone in being able to knock down spacecraft. That view is being taken by several analysts.
Others suggest the shootdown effort is more in the nature of seizing an opportunity. Normally, testing a missile-defence interceptor requires the use of an extremely expensive target. In this case, the target is effectively free - why not take the chance to improve America missile-defence gear? Not exactly killing two birds with one stone, but you get the idea.
Neither of these motivations really seem sufficient to justify the inevitable diplomatic costs. China and Russia are sure to see the move as provocative, and it could lead to further militarisation of space. The US - far and away the major military/intelligence space user - has a lot more to lose here than its adversaries do.
The most plausible explanation is that the US - no matter what it says officially - is worried about its secret satellite tech falling into the wrong hands. It will be impossible to predict just where the errant sky-spy will fall until shortly before impact, by which point it would be too late to shoot it down - even if there happened to be an Aegis cruiser or destroyer in the right place. So the US will take the sat out while it still can.
John R Pike, a veteran defence/intelligence analyst who runs the authoritative Globalsecurity.org service, told Fox News the US government could still be worried even if the space spyeye came down in America. It seems eBay is part of the espionage threat.
"What they have to be worried about is that a souvenir collector is going to find some piece, put it on e-Bay, and the Chinese buy it," he said, presumably meaning the US government would never find out about the sale and try to outbid the People's Republic.
"The Chinese and the Russians spend an enormous amount of time trying to steal American technology... To have our most sophisticated radar intelligence satellite — have big pieces of it fall into their hands — would not be our preferred outcome."
Pike suspects the satellite is a highly sophisticated ocean-surveillance job, perhaps able to radar-track ships through clouds and storms without using large amounts of power. Previous generations of radar-ocean-recce sats needed expensive, troublesome radioisotope generators - nuclear batteries - or even fully fledged atomic reactors, in the case of some Russian examples.
The US authorities refuse to discuss the secret spacecraft's path, but it is being tracked by amateur sky-watchers. They report that its orbital plane is tilted 60 degrees from that of the equator and it is circling the Earth roughly every 90 minutes: so it could come down anywhere except in the Arctic or Antarctic regions. A handy map webpage for those not up on their orbital mechanics and two-line elements is here.
General Cartwright says the USN will be shooting from positions "in the northern hemisphere and Pacific."
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