[amsat-bb] Re: Spanish cubesat

Mark Vandewettering kf6kyi at gmail.com
Mon Jun 16 10:35:22 PDT 2008

On Jun 15, 2008, at 10:07 AM, rct at uvigo.es wrote:

> Dear colleagues,
> The Telecommunication School at Vigo University, Spain, is developing
> a cubesat that will be launched by ESA. It will transmit in amateur
> bands, and the University radioclub (EA1RCT) is collaborating in the
> project. The design is not yet closed and we can send proposals to the
> development team. The radioclub is willing to hear ideas from the
> amateur radio comunity: we would like to have a short list ready by
> next Thursday, June 26, so any proposal we receive before then will be
> carefully read.
> The satellite will be small and lightweight as you know, and it will
> run on a short electrical budget. Moreover, the time schedule is very
> tight. One of the main objectives is to test SDR systems in space (not
> necessarily in amateur bands).
> Neither the bands, power o full-duplex capability have been
> established. It could eventually end up with just a telemetry beacon.
> We would like to hear your opinions about what the amateur radio
> community would prefer to carry on board, in these three scenarios:

First of all, I'd like to thank you for asking.  It is great that you  
are seeking the input of the broader amateur satellite community in  
your satellite project, and it is appreciated.

> · full-duplex communication capability (linear transponder, fm rep,  
> etc)
> · half-duplex systems (digipeater?)
> · beacon modes (afsk, psk, cw)

You will undoubtably get a bunch of requests for a full-duplex linear  
transponder.  It seems to me rather unlikely that a single unit  
cubesat will have sufficient power budget to make such a thing  
possible (DELFI-C3 is 3 units).   You'll get lots of people  
complaining if you put an FM repeater on board (some people hate the  
FM birds with the burning passion of 1000 suns) but I think FM  
repeaters are, well, pretty neat, and doing on in a cubesat would be  
pretty cool, but the power budget is probably just as hard.  I think a  
half duplex satellite would be pretty interesting.  Even a little APRS  
digipeater in the sky would be a nice demonstration, and enable hams  
to do actual QSOs.

Most cubesats in orbit now seem to downlink cw telemetry.  It's a nice  
choice because it is dead easy to decode, but not a very glamorous  
one.  It requires little power, but has little available bandwidth.  I  
think AFSK over FM is nice because it is easy for hams to decode, but  
it kind of squanders your power budget needlessly.   DELFI-C3 uses  
BPSK, which is probably a good choice for higher bandwidth telemetry.

I'm personally interested in imaging, so I am intrigued by satellites  
like CUTE (which carries essentially a cell phone camera), COMPASS-1  
(which carries an as-yet untried camera down link) and SEEDS (which  
has an SSTV downlink).  While many ham radio purists might grumble, I  
like this kind of stuff, and if you are experimenting with SDR, it  
might not be difficult to add additional modes such as these.

Just some ideas...
	Mark KF6KYI

> Best regards,
> EA1RCT RadioClub Telecomunicaciones Vigo
> http://lostrego.uvigo.es
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