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AW: Satellite control via Iridium?



Dear Robert,

after the discussion about IRIDIUM and GLOBALSTAR I want
also mention that there is also ORBCOMM as satellite communication
system, using pure data message orientated services.

Some companies still used ORBCOMM to command and control
their satellite payloads in LEO orbits, as the existing satellite
network and its worldwide coverage is dense enough. ORBCOMM needs
no special directive antennas and needs no special actions due to
its satellite beam. (IRIDIUM has splitted its main beam in several
cells and uses roaming services while the target is moving, ORBCOMM
has only one "wide" area without roaming within separate cells).

The problem is to find modems for the use in space regarding to
the environmental conditions. "Normal" commercial modems even in
with "industry" or "automotive" environmental categories will
fail due to used commercail electrical component quality. They
need to be modified.

The doppler effect was no problem due to the communication protocol
and the use of short message service. The low data troughput was
no problem for TM and TC. The latency has to be taken into account.

The benefit was still described by Johann: you can get in touch
with your payload nearly every time from your office via Internet.

I prefer Bob's approach: Our existing and still growing
amateur radio satellite network of the APRS satellite(s) is
able to offer an adequate cost effective and "amateur radio
like" non-commercial alternative to receive transmitted
messages from (nearly) all over the world.

But, one question remains: Can I also use this "open" network
to allow commanding of the satellite only by the service team
and even avoid "sabotage" by destructive third parties... ?

At the moment, this may be a reason to use "external" satellite
services to ensure proper 24/7 access.

73 de Oliver, DG6BCE

Mailto:                DG6BCE@aatis.de
AATiS-Homepage:        http://www.aatis.de
SAFIR-M homepage:      http://amend.gmxhome.de

 



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