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*Subject*: [amsat-bb] AO-40 Orbital Stability*From*: "Stacey E. Mills, M.D." <w4sm@xxxxxxxxxx>*Date*: Sun, 24 Dec 2000 19:17:40 -0500*In-Reply-To*: <B66BD509.B8D7%na9d@mindspring.com>

At 04:30 PM 2000-12-24 -0600, you wrote: >One other question to be considered: Is the current orbit stable? I know >next to nothing about orbital mechanics. But AO-13 died a firey death >because of an orbital instability. We wouldn't want the same thing to >happen to P3D. But then again, it might be fine. > >73, > >Jon >NA9D I'll take a shot at this one. The orbit is incredibly stable. It's not the eccentricity per se that creates instability. It's the combination of eccentricity and high inclination, along with RAAN and ArgP that has the potential for instability due to solar/lunar forces. The current low inclination orbit is highly stable. I've integrated the orbital elements, accounting for drag, and the pull of the sun and moon for decades and the orbit is quite stable. Perigee height varies by several hundred km and there is some very minor drag loss when the perigee is at its lowest point, but there is also gravitational "pumping" of energy into the orbit. In fact, after 40 years, mean motion is 1.266, lower (ie. a higher energy orbit) than it is today. For a graph of the orbital elements over the next approx. 10 years, 20 years and 40 years download: www.cstone.net/~w4sm2/software2/AO40-10.gif www.cstone.net/~w4sm2/software2/AO40-20.gif www.cstone.net/~w4sm2/software2/AO40-40.gif NOTE: these graphs, particularly the 40 year graph are very "busy" and difficult to read. However, note that mean motion (in green) barely changes and height at perigee (in black) shows a cyclic variation from a low of about 270 km to a high of about 700 km. If you look carefully, you will also see the cyclic effects of the sun and the moon on the orbital elements. -- _______________________________________________________________________ Stacey E. Mills, W4SM WWW: http://www.cstone.net/~w4sm/ham1.html Charlottesville, VA PGP key: http://www.cstone.net/~w4sm/key _______________________________________________________________________ ---- Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**Follow-Ups**:**Re: AO-40 Orbital Stability***From:*Jon Ogden

**References**:**Re: Further analysis of the last telemetry from AO-40***From:*John P. Toscano

**Re: Further analysis of the last telemetry from AO-40***From:*Jon Ogden

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