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RE: AO-40 Longevity




>Hi Guys,
>               Required for a memorial address.  How long is AO-40
>expected to remain in orbit?   Hundreds/thousands of years? Note:
>Not how long will it remain active - a lesser figure I'm sure!!
>    Thanks for any help.
>73
>Fred Kennedy
>Zl1BYP

Following the ARCJET cold out-gassing to raise perigee in June 2001, the 
orbit was modeled and, like AO-10,  it is stable for hundreds  and hundreds 
of years.  I got tired of letting the orbital integrator run!!   I had an 
amsat-bb post regarding this, but can't find it at the moment.  The 
software used is the same software that correctly predicted AO-13's 
re-entry to the DAY, using keps immediately after its second orbital burn, 
just after launch.

In general, low inclination orbits are usually stable if they have 
reasonable perigee heights, because ArgP and RAAN change rather rapidly at 
low inclinations, so bad solar/lunar geometry doesn't last long enough to 
cause serious decrease in perigee, and is soon countered by solar/lunar 
geometry that raises perigee.  With the high inclination of AO-13, the bad 
geometry stayed in place long enough to pull the perigee into the atmosphere.



-- 
  _______________________________________________________________________
  Stacey E. Mills, W4SM    WWW:    http://www.cstone.net/~w4sm/ham1.html
   Charlottesville, VA     PGP key: http://www.cstone.net/~w4sm/key
  _______________________________________________________________________

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