[amsat-bb] Re: Planet Pseudo-Keps

Bob Bruninga bruninga at usna.edu
Sat Feb 27 05:31:00 PST 2010

>> Since the planets revolve around the Sun,
>> and not the Earth, there can't be any Keps.  
>> Keps are based on the Earth being the 
>> center of an orbiting object.

> You're saying that if I lived on another planet 
> or in another star system then my satellites 
> wouldn't have keps and I couldn't use my 
> software to track them?... That sounds rediculous.

Yep. "keps" (as we use the term here regularly) either in AMSAT format or in NASA two-line format are just inputs to an "Earth orbit" propogator that predicts where a satellite is around Earth based on the laws of physics.

If you lived on Mars, and had a "Mars Orbit Propogator" then you could download "Martian Keps" from the Martians and track Martian satellites.  But the Martian tracking program would not be able to track earth satellies, just as ours Earth based programs cannot track theirs.  Because the size and mass of Mars is different from Earth, so the propogators have to be different... or something like that.  I'm on the limit of my meager knowledge here...

Bob, Wb4APR

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