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Re: how abt ao-40 beacon on mode-S?



Hi folks,
MA means Mean Anomaly.. this determines the position of the satellite on
the orbit.
If you take the orbit period and divide it by 256, you have the time,
the sat takes for 1 MA unit (right now AO-40 has a period of roughly
11.5 hours, that means one MA unit is 2.7 minutes). MA 0 is defined as
pergee.. that means that MA 128 is the apogee . And MA 20-26 is 54-70
minutes after perigee.. note that the distance AO-40 travels in one MA
unit depends on the MA value itself: at apogee (MA 128) the sat is slow,
so one MA unit is a small amount of distance, at perigee (MA 0) the sat
is fast and one MA is some already distance..

MA 20-26 has been chosen because of the flight attitude of nearly
alon/alat 270/0. that means in perigee (or MA 0) the motor is pointing
opposite flight direction(backwards), so at MA 20-26 the motor (and so
the hi gain antennas, because they are mounted on the same side) are
pointing to earth. Remember, AO-40 is still spin stabilized, so its axis
remains fixed. This is why MA20-26 is a good position for listening to
any hi gain antenna right now.. I wouldn't be surprised if there were
any tests with the 70cm TX..

73s Achim, DH2VA

Jon Ogden wrote:
> 
> on 11/29/00 9:54 AM, Achim Vollhardt at avollhar@physik.unizh.ch wrote:
> 
> > Hi folks,
> > seems, the 'mode-s beacon for testing' - idea wasn't so bad at all..
> > live telemetry(29.11.00, 15:47 UT) announces the Mode-S general beacon
> > to be turned on between MA 20 and MA 26. So anybody with mode-s equip:
> > start listening, but beware of doppler, which will be huge at MA20-26,
> > calculations for my qth say about 25 khz down the announced 2400.200
> > MHz! Happy hunting..
> 
> What does the term "MA" mean?  Right now MA is at 166.  When does it
> change....and what is it?
> 
> 73,
> 
> Jon
> NA9D
>
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