'Jury-rigged' missile to destroy falling spysat
- 23:22 14 February 2008
- NewScientist.com news service
- Jeff Hecht
The Pentagon is going to shoot down an ailing US spy satellite before it can fall out of control into the atmosphere. And despite its huge arsenal, the US says it has nothing to pull off the shelf to do the job.
The experimental spy satellite failed almost immediately after launch in December 2006. It never deployed the solar arrays that normally power such spacecraft, and remained in an orbit so low that atmospheric drag is causing it to spiral towards Earth. The satellite is totally unresponsive, so there is no way to control where it falls.
A Pentagon analysis indicates that about 1100 kilograms of material from the 2.5-tonne satellite will survive re-entry, including a tank containing some 450 kilograms of toxic hydrazine fuel. Although the remains are unlikely to fall in a populated area, the Pentagon says President Bush decided the risk to human lives is high enough to justify shooting down the satellite.
The US destroyed one of its own satellites with an anti-satellite missile in 1985, and the Bush Administration has been spending billions of dollars a year on missile defense. Yet those systems were not equipped to target a satellite, despite the conventional wisdom that satellites are easy targets because their orbits are easy to track and readily predictable.
Instead the Pentagon is modifying three "Standard Missile 3" interceptors used for the sea-based Aegis element of the missile defense system. Those are now carried on ships stationed in the Sea of Japan for possible interception of short- to intermediate-range North Korean missiles.
The modifications involve changing the software to target a satellite rather than a missile, says David Wright of the Union of Concerned Scientists.
"This interceptor is really intended for missiles travelling at 3 to 4 kilometres per second; the satellite they're going to be shooting at has a speed of 7 to 8 kilometres per second."Three ships will be involved in the mission, which will occur during a "window of opportunity" from late February to early March.
But the modifications don't sound like major ones to Wright, who told New Scientist the Pentagon "has never wanted to explicitly say the [missile defense] system has an anti-satellite capability, so they're dancing to say that we had to modify the system" to target a satellite. He wonders how China and Russia will respond, especially after their recent proposal for a ban on weapons in space.
Wright also worries about space debris. The target satellite is orbiting at an altitude of about 240 kilometres, so most of the debris should drop out of orbit in hours or days. But the satellite is 2.5 times more massive than the Chinese satellite that scattered a tremendous amount of debris into higher orbits when it was hit in 2007 by an anti-satellite missile.
"Do they understand this well enough to quantify theorbiting at 340 kilometres, he asks.
risk to the space station"
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