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Re: Odyssey Orbit



Ken,

I think you are correct. Twice the average distance of the spacecraft
from Mars should be equal to the sum of the peri-Mars distance (maximum
distance from Mars) and the ap-Mars distance (minimum distance from Mars).




Steven T. Ratliff
Professor of Physics
Northwestern College
3003 Snelling Ave. N.
St. Paul, MN 55113-1598
U. S. A.

Internet: stratliff@nwc.edu





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10/25/01 04:15 PM
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Subject: Odyssey Orbit


Well Odyssey arrived and is in orbit. As fate would have it in one higher
level calss we are wrapping up a discussion of orbits etc. The drawings in
the paper show an elongated orbit that will be made circular by both
"aerobraking" and thrusters. A lot of nice conceptual Physics here for
those of us in high schools. But I have a question.

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.

also: Does anyone know where to get the orbital elements from JPL? I have
not found the route. I am not asking google the right question yet.

Ken Fox
Science Department Coordinator
IB Physics Teacher
Smoky Hill High School
Aurora, CO
kfox@mail.ccsd.k12.co.us