Thursday, February 14, 2008

Loose Satellite Now a Target -- Why?

As mentioned in a previous post American reconnaissance satellite USA-193 was to come to Earth soon. Now it has been announced that it will be shot down by a missile fired from a U.S. Navy ship. Ostensibly concerns about the remaining rocket fuel on the 5000 lb. craft is the reason for the unusual move. As the Times On Line reports the actual hazard appears to be small:

" The statistical risk of death or injury is considered small. Even when the space shuttle Columbia broke up over Texas and scattered debris over two states no one on the ground was hurt. Two thirds of the Earth’s surface is covered with water. In the past 50 years about 17,000 man-made objects have re-entered the atmosphere, including the 78-ton Skylab space station that fell into the Indian Ocean and across west Australia in 1979."

Others however question the effects of the announced shoot-down, among them Jeffrey Lewis from ArmsControlWonk, who makes the following observations:

"I am very worried about the debris creation — particularly the debris that the light-weight interceptor will kick into higher orbits when it hits the massive (bus-sized) satellite. Thnk, as Geoff Forden suggested, of a ping pong ball hitting a superball.

Virtually all the debris should come down quickly. Cartwright said 50 percent would come down within two orbits, with the rest coming down in weeks and months. That seems plausible, at first blush.

But those two orbits could be hairy and some of the debris will remain in orbit. Michael Griffin, NASA Administrator, said there are “good times and bad times” to conduct the intercept, based on the position of the ISS but that “bad times are not all that bad” comparing the risk to an order of magnitude lower than flying the shuttle.

Last I checked, the PRAN for the shuttle was 1 in 100. Extrapolating, there would be only a 1 in 1000 chance of wiping out the ISS."

Other purposes for doing this seem to be more belligerent especially after American concerns about a Chinese anti-satellite program. Plus there is the question of whether there is something about this satellite that the U.S. doesn't want others to know about, as noted by The Times On Line:

"USA 193 was launched on December 14, 2006, from the Vandenberg US Air Force Base in California. Once it reached orbit it failed to communicate with its ground controllers, making it uncontrollable. Though its design is top-secret, it is reported to be a high-resolution radar satellite that would take images for the National Reconnaissance Office.

Defence analysts have suggested that the Pentagon may be reluctant to allow a large piece of its most sophisticated technology to fall into the hands of a rival such as Russia or China."

The whole thing seems odd.

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