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Re: Lunar Orbits

Hello Trevor!
To my best knowledge, there are two factors contributing to the unstable
lunar orbits. First, the gravitational field of the moon is not as
perfectly spherical, as one would expect it. NASA used data from the
early moon probes to roughly chart these MASCONS (mass concentrations)
before sending Apollo there. Second, the influence of earth is still
rather large which means the actual influence depends on the geometry of
the lunar orbit with respect to the earth.

Both effects suggest, that a low lunar orbit suffers more from the
mascons and a high lunar orbit from the earth's pull. Unfortunately, I
have no idea on which timescale these effects start killing an orbit..
maybe there is no unique answer.

73s Achim, DH2VA

> I read with interest the item on the proposed SSETI Moon Orbiter at
> http://www.southgatearc.org/news/june2006/sseti_moon_orbiter.htm
> Now I understood that all Lunar orbits were unstable and any sat would 
> rapidly crash on the Lunar surface, is that right ? If so does anyone know 
> the expected lifetime of a satellite in low altitude polar Lunar orbit - 
> would in be a matter of months or years ?
> 73 Trevor M5AKA
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