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RE: Satellite-to-Satellite communications



Hi Drew

> I'm not involved in any significant way with the
> Eagle project, but I can say that if you go to
> the new functional requirements on the webpage
> at http://www.amsat.org/amsat-new/eagle/FuncReqRev1.php
> you'll see the plan is for 100 khz on S band and up to
> 50khz on V band. We all fit fine on AO-40 in about
> 80 khz 98% of the time, and that was with 1 HEO up,
> not 2. I think the team will give us everything they
> can with what they have to work with. Frankly I'll
> take whatever we can get with P3E, Eagle I and II,
> and whatever else comes up. Not going to niggle over
> the details, as I'm worried that if we don't get help
> from OUTSIDE the AMSAT membership we can forget raising
> enough money anyways. I'm considering giving up QST
> and sending the extra money to AMSAT.
>
> My comment on linking the satellites with 10-20 khz
> was just a gut-based guess on what type of uplink
> power would be required to crosslink 2 sats from
> the ground.

One of the points of the SDX is just as the acronym says: it's software
defined. Now the following may be pie in the sky (sic), but it is still my
wish to implement one of the original design criteria of the STELLA software
presented at AMSAT-UK last July. I wanted the opportunity for Joe Ham to be
able to develop and submit his/her own code to be used in space, something
that I'll call a UNA, or User Nominated Adaptor for now.

For this criteria to work, the following stipulations need to be made:

o The UNA development platform must be readily available and affordable for
Joe Ham;
o Published API available to hook into the SDX's STELLA RTOS kernel;
o UNAs must work co-operatively and simultaneously with other modes, not
exclusively;
o What I call _real_ experimenter's days when the UNAs get to be run in
space;
o UNAs are integration and system tested on the ground by peers;
o UNAs are only uploaded and co-ordinated by the ground command team.

For info, the current STELLA software, including a beacon and a 100kHz
transponder takes about 15% of the currently proposed embedded SDX CPU, so
there's certainly room for more applications.

Whether UNAs become reality also depends largely on demand. The development
platform I've been using costs ~$400 including hardware and software, plus
about $30 for the parts for a quadrature sampling detector and exciter. I'm
afraid that to write a UNA you'll have to learn a bit about DSP too, however
I've found the hard way that doing it for real sure beats the heck out of
struggling through a stack of academic books filled with math.

73, Howard G6LVB
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