US missile strikes stricken satellite

Feb 21, 2008
US missile strikes stricken satellite
http://physicsworld.com/cws/article/news/33003


A missile fired from the American Navy cruiser USS Lake Erie has
successfully disabled a malfunctioning spy satellite that was about
to enter Earth's atmosphere. Marine General James Cartwright said
there was an 80-90% chance that the missiles, fired from the Pacific
Ocean west of Hawaii, had hit the satellite's fuel tank.

Officials had cited the tank's 450 kg of hydrazine as the key reason
for disabling the satellite. Had the fuel tank reached Earth, the
toxic gas could have harmed individuals close by. Cartwright said
that debris from the stricken satellite appeared to be too small,
however, to cause damage on Earth.

The firing represented an early and serendipitous rehearsal of
American anti-missile defense. The SM-3 missile used to hit the
satellite is under development as part of the American Navy's
sea-based missile defense system. It is intended to provide
protection against medium- and long-range ballistic missiles.

Cartwright said that the missile collided with the 2250kg satellite
some 210 km above the Earth's surface, at a combined speed of 35,000
kilometers per hour. "The technical degree of difficulty was
significant here," he said.


However, the difficulty of hitting a satellite in low orbit hardly
compares with that of striking a missile in flight. "This is easier
than the ballistic missile intercept that the system was designed
for," explains Ivan Oelrich, a security specialist at the Federation
of American Scientists. "The satellite is a substantially larger
target -- probably between the size of a minivan and a small school
bus. It's also on a very predictable trajectory. And it's high enough
to predict with high accuracy where it will be." The US Department of
Defense chose to fire from a ship because the ship could be aligned
with the track of the satellite.

Oelrich is among critics who see the event as less a technical test
than a chance for the Bush Administration to showcase its hotly
disputed missile defense system. "I don't think the public safety
argument holds up. The US produces 16 million kilograms of hydrazine
per year, which we ship around in trucks," Oelrich says. "But it's a
brilliant public relations opportunity for the ballistic missile
defense system. We were told that it has saved us from a grave
threat."

Critics have also suggested that the US destroyed the satellite
because it feared that its ultra secret technology could be made
public if large parts of the satellite survived the plunge through
the Earth's atmosphere. That, however, seems unlikely. Analysts
suggest that such technology would automatically be adapted to burn
up before reaching Earth.

More troubling is that the event appears to be a response to China's
use of a ground-based missile to destroy a satellite last year. "We
should be working on a treaty to ban anti satellite weapons," Oelrich
says. "But the Bush Administration opposes it and says it couldn't be
verified."
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