[aprssig] Suggestion for APRS over Satellite

Scott Miller scott at opentrac.org
Tue Apr 22 10:10:34 EDT 2008

I used to run orbital prediction software on my Palm III.  Certainly an 
ARM7 class device can do it, even if it might take several seconds to 
calculate.  But all you have to do is run it once, get your next AOS, 
and go to sleep.

That said, I don't want to be the one to have to write embedded orbital 
prediction software!

Maybe there's some easier way of broadcasting pre-computed ground track 
and footprint data?  It wouldn't need to stay valid or accurate for 
long, maybe just a couple of passes at a time.


Stephen H. Smith wrote:
> Hans Johnson wrote:
>> Hi All,
>> I've been toying around with the idea of building some equipment for 
>> extreme remote telemetry stuff to be done over satellite.  (Similar to 
>> Bob's project in Mongolia).
>> Anyhow, one of the things that would be extremely useful is if the 
>> satellite could (occasionally) include its current orbital data in the 
>> beacon packet, something like a condensed version of the Two Line 
>> Element and a CRC.  Using this information, it could then power down 
>> the radio until the next useful satellite pass.  This would 
>> drastically reduce the power requirements for a remote site.  Also, 
>> things like asatlogger and what not could use the information to 
>> update their pass predictions automatically.
> Won't the remote device then need to have fairly hefty computing power 
> to crunch the orbital elements into a useful AOS/LOS prediction for the 
> particular location the device is located at? 
> I would guess that the power consumption of a controller with enough 
> horsepower to do this would exceed the total power consumption of just 
> having a much simpler dumber device power up the radio for a few seconds 
> every 5 or 10 mins if the transmit bursts are really short.
> Not to mention you will also need to power a receiver that won't be 
> needed with a "dumber" device, and a real-time clock to wake up the 
> controller/transmitter at the appropriate times.   
> -- 
> Stephen H. Smith    wa8lmf (at) aol.com
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