Mar 03 2009

Satellite Collisions

Published by at under space,sustainability

A new article from sheds some revealing light on the recent collision of an Iridium satellite with a defunct Soviet military satellite.

I think there was a common impression that Norad would pick up the phone and call operators if they saw an impending collision so that they could maneuver to avoid it. It seems though, that the actual state of affairs is much different.

The US Air Force publishes orbital elements, which are apparently not that accurate. In the linked article it states that the French space agency uses additional ground based radars to refine estimates if a probability looks too high. In the case of the Iridium satellite, the collision probability was 1 in 10,000 which gives an idea of the accuracy.

The Air Force does detailed analysis for human spaceflight, but for random commercial satellites, it’s up to the operator to use the orbital elements to determine a course of action.

Instead of the idea that operators are always maneuvering to avoid collisions, my new picture of the state of affairs is that a lot of satellites are pretty much flying blind and could collide at any time. The Iridium orbit, for instance is now polluted with a lot of debris that makes additional collisions more likely. The idea of a runaway chain reaction of increasing debris doesn’t seem very far fetched.

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