[amsat-bb] Re: Space Debris:

Phil Karn karn at philkarn.net
Thu Apr 29 16:21:16 PDT 2010

Stephen Melachrinos wrote:

> were a major hazard to everyone, themselves included. So they must
> have allocated more resources to the problem, as this is a massive
> undertaking. (Note that some reports say that the US has about 20,000
> objects that are tracked and cataloged. In theory, this means
> propagating the ephemeris of all of these for some number of days and
> comparing all possible combinations across the ti! me period of the
> analysis.)

Computers are cheap, so actually propagating the ephemerides of those 
objects is the easy part.

The hard part is that the published elements are simply not accurate 
enough to reliably predict collisions -- or give sufficient reassurances 
that a collision won't occur.

TS Kelso has written some stuff about this on his website. See


He's been doing his own conflict predicts for some time. He shows many 
close approaches that never result in a collision. Yet he did not rate a 
Iridium 33/Cosmos 2251 collision as especially probable before it 
happened because the TLE numbers simply aren't accurate enough.

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