[amsat-bb] Satellite tracking programming ideas
phillor at telstra.com
Thu Jan 17 23:26:18 PST 2008
Thank you for reading this.
I'm currently marooned because of flood water, and likely to be so for at
least another week, so to pass some time I decided to upgrade my satellite
tracking program. Disappointingly, playing with the current satellites in
this country is pointless so the programming exercise is purely academic.
Originally, my tracking program displayed the link frequencies but I decided
that was unnecessary since the radio has a perfectly good display itself. So
to make frequency corrections, due to hardware errors, or to listen to
another part of the downlink I simply used the radio's tuning knob. The
program detected that the receiver's frequency had changed and calculated a
new uplink frequency.
This requires some manual intervention in that I have to stop the automatic
tracking, turn the knob and then restart the tracking. This could take a few
seconds which would mean that the tracking could be a few seconds behind.
The alternative is to click on an up / down tuning arrow which will stop the
tracking and adjust the received frequency. Clicking on a restart button
would restart the tracking. I think that's the way satpc32 works.
I've probably got too much time on my hands and both methods seem to work
equally well. Does one method have an advantage over the other?
The update interval has to be fairly short so that a manual frequency change
can be quickly detected. I'm currently updating the radio based on time. The
alternative is to update based on frequency, say every time the higher
frequency changes by 20Hz. This would lessen the number of radio updates
during periods where the Doppler effect is at a minimum but does it matter
if the radio is undated unnecessary? The rotator bearing is updated every
ten degrees but that's to lessen mechanical fatigue.
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