[amsat-bb] Re: ALON/ALAT and Squint

["Stacey E. Mills" <w4sm@xxxxxxxxxx>]

>Several of the tracking programs require input of ALON/ALAT value
>together with a date. Our last known date of ALON/ALAT 0/0 is November
>21 taken from the AO-40 Update page on www.amsat-dl.org which reflects
>the data from AO-40 telemetry. So the program will take this a the base
>for calculations.
>
>Actually the command stations are always fighting against the ME and
>are correcting the attitude more or less in every orbit. So the date
>for ALON/ALAN will be updated every day.

[snip]

>Still learning!
>
>73
>  Reinhard, DJ1KM

ALON/ALAT is defined in satellite coordinates and as the satellite orbit 
precesses, mainly in RAAN and ArgP, the value of ALON/ALAT will change even 
though the satellite is still pointing at the same point in inertial 
space.  If your tracking program converts ALON/ALAT on a given day to 
inertial coordinates, then the value of ALON/ALAT in your program will vary 
progressively with time, just as Reinhard indicated.  My program functions 
in just this fashion.  However, we are counteracting both the ME and 
inertial "drift" by holding ALON/ALAT at nominal 0/0 (+/- 1 deg) with 
magnetorquing, so you may need to update your ALON/ALAT date to reflect this.



-- 
  _______________________________________________________________________
  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