ARISsAT-1

[Iain McFadyen]

Yes, ARISSat-1 is partially functional. (Almost fully)


When in sunlight, it sends continuous information on 145.950MHz. Spoken greetings, then spoken telemetry (package temp, battery voltage, battery current), then a single slow scan image, then repeats. Audible with a HT, but signal has fading characteristics.

When not in sunlight, it transmits each of the three elements above, with 120 seconds between them, to reduce duty cycle/battery load.

There is also a telemetry beacon on 145.920 BPSK. A decoder is available at the ARISSAT website.

Two CW beacons on 145.919 and 145.939 alternate, based on what mode the BPSK telemetry transmitter is in (BPSK-400 or -1000).

Checkout the bandplan here: 
http://farm6.static.flickr.com/5293/5406273951_f09d07ed7e_o.jpg       or go to arissat-1.org and scroll down on the right.


KO4MA has reported that he received good returned signals when transmitting just 1watt with a 19+19 ele circularly polarized antenna array on UHF, being able to 'hear himself clearly' on the downlink. If that's the case, I would imagine that the tape antenna is broken off at the end of the black shroud, rather than the whole antenna assembly all the way down to the N-type connector being missing. I guess we will never know, unless one of the astronauts confirms, or someone manages to freeze-frame the few seconds of video showing the underside of the satellite, just before their first aborted launch. While I watched the NASA TV live feed at the time of the launch, I was talking to the TV set saying "Where's the UHF antenna? Check the UHF antenna!" I felt the device was being badly handled by the astronauts on the spacewalk. Maybe the abuse existed inside ISS away from the cameras too.

I've heard about 4 passes now, and note that there is deep fading in the signal. There is no stabilization capability on the satellite. (Gradient boom or the like), so it is tumbling with a period of around 7 seconds. One notable pass, I realise that the fading precisely coincided with the timing of the important telem info: I heard:...

" Secret word is )^%^%$,  the M.E.T. is &&&)(&&^^  minutes, the IHU temp is (*^(^)*(.... the board temp is $##@$%, the battery voltage is *&%^@ volts, battery current is minus $^@#^$@ milliamps." 

Perfect sync between fading and information. Perfect...   and that was on a 45degree pass. Maybe lower passes will allow me to get less fading, (but lower signal strength too).

One person responded to another message of mine (about the fading) saying that no stabilization was designed in to the satellite, so that it would freely tumble, and cause even distribution of heating/cooling. I can't believe that was a deliberate design feature...

Keps don't appear to be published yet, but N7YO has a tracker which seems to indicate that he does, (or he guessed). When they are published, it may be called RADIOSCAF-B. The NATO ID is definitely 37772U.

Iain 8P6UK

>________________________________
>From: "bbruhns at erols.com" <bbruhns at erols.com>
>To: tacos at amrad.org
>Sent: Friday, August 5, 2011 6:56 PM
>Subject: Re: ARISsAT-1
>
>Tragic.
>
>I hope it can still do -something-.  Evidently it was able to send some pictures.  This shows the need for auxiliary input link options in the event of some failure or omission.  
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://amrad.org/pipermail/tacos/attachments/20110805/b5c4d6a0/attachment.html>