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Re: CubeSat launch 27Mar07 6:46:35UT




On Fri, March 23, 2007 12:32 pm, Bruce Robertson wrote:

> There seem to be many AMSAT operators who use large Az/El systems for
> LEOs;
> perhaps, then, an even weaker transmitter on 2m might be acceptable. My
> vote would be for an S-band downlink. It would be possible to put a patch
> antenna on one face, but some of this gain is eaten up in increased 'path
> loss'. Such a bird could be called a 'HardSat' in contrast to the
> so-called
> FM 'EasySats' :-)

Bruce,

I think there is more and more talk about an S-band downlink.  Some of the
guys on CAPE-2 have mentioned using S-band for high speed telemetry with a
FEC scheme based on the Voyager and AO-40 methods (Viterbi and
Reed-Solomon combo).  The biggest problem with a patch antenna is the lack
of attitude control on these small sats.  Many developers are still
playing with ideas on how to achieve this well and some interesting
concepts have come up (for instance, one of Cal-Poly's sats CP3 or CP4 has
magnetotorquers made by passing current through a PCB trace in the inner
signal layers of a 4-layer PCB which also serves as a solar panel).

Also, having spent the last few years working on CAPE-1, a very simple
satellite in many ways, I don't think it's fair to call any sat an
'EasySat,' they're all 'HardSats' and 'HarderSats.'


-- 
Jonathan Wagner, KE5FSG

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