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Re: seasonal off-pointing of AO40




>Wayne replies:
>
>Is there a layman's explanation of why AO40's seasonal off-pointing
>requirements do NOT coincide with the seasons here on earth?  Alon/alat was
>very poor in January/February 2002, but it looks like it will be good in
>January/February 2003.
>
>I'm very glad to hear that alon/alat will be good from November thru 
>February.
>It's time to book my winter Caribbean vacation/AO40 DXpedition.
>
>Wayne Estes W9AE
>Mundelein, IL, USA

Hello Wayne,
The off-pointing does not occur at precisely the same time each year 
because the orbit, particularly the RAAN, is precessing.  For AO-40, RAAN 
decreases about 0.1632 degs/day (60 degs/yr).  This means that the plane of 
the orbit shifts 60 degs each year, so that the geometry with the sun 
varies accordingly.  If the orbital elements were rock solid, the 
off-pointings would be at exactly the same times each year.




-- 
  ________________________________________________________________________
  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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