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Re: Odyssey Orbit



At 15:15 -0600 10/25/01, SSHS KPHOX wrote:

I wanted to get a handle on how elongated the orbit is. I found in one
location a period of between 15 and 25 hours, but that it would be brought
to under 20 hrs if it were over. The "peri-martian" altitude is about 250
mi and speed is about 10,250 mph at that point. If the period is 20 hrs I
can use Kepler's Third Law to find the average radius of orbit ( I hope).
Here is the question: Can I take twice this radius to be the sum of
"peri-martian" distance and the "ap-martian" distance? I measure these
from the center of Mars. If so I get an eccentricity of about 0.8.

I'm not sure what all these numbers mean, but KTL doesn't refer to
the "average" orbital radius but the semi-major axis of the orbit, so
If you know the period, what you get right away is the semi-major
axis, and, since I can't remember whether "peri-" refers to the
highest point or the lowest point, I don't know if you then will have
enough information to find the eccentricity of the orbit and hence
the energy. If it means the low point, then you do have enough
information to get most all of the orbital parameters, I think.
Assuming you have the mass and radius of Mars.

But remember what happened the last time that NASA got mixed up with
"American" units, instead of SI.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

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