Sunday, August 30, 2009

Signals from space

The September issue of the RSGB's excellent RadCom was awaiting me on return from holiday. It contained an article about two new atmospheric research micro-satellites, Castor and Pollux, which transmit telemetry using AX.25 packet in the 2m band. This piqued my interest enough to try to have a go at receiving them.

The tiny satellites consist of two 19in. diameter spheres separated by an insulator, which form the two halves of the 2m antenna. There is a super photograph of the two satellites, taken shortly after they were launched at the end of July from the Space Shuttle Endeavour, which can be found on many of the websites that carry information about the launch.

My first problem was to find some way to decode 2m packet. I used to have a copy of MixW, but I had not used it for a couple of years and when I tried, it crashed immediately after start-up. I deleted it and tried installing a new copy but it came up in German! I also realised that I no longer had the registration code for it. So I decided to look for another solution.

I found it at SV2AGW's website. I installed the AGW Packet Engine (AGWPE) and then AGWMonitor to receive the telemetry. Setting up the Packet Engine to receive packet using the sound card is not very intuitive, and in fact I gave up the first time and spent another couple of hours trying to find a backup copy of my MixW installation, without success. Then I found an excellent step-by-step guide to setting up AGWPE with a sound card by KC2RLM that got me going. AGWMonitor requires AGWPE, and the trick is to put it into the Startup Programs option of AGWPE so that the monitor is launched directly after you start the engine.

I used the N2YO Live Real Time Satellite Tracking website to find out when the satellites are visible from my QTH. This shows that they currently pass over very late at night and during the small hours of the morning, when I am asleep, so I left everything on overnight to see what I could receive. The first time, all I got were a number of packets from the International Space Station, RS0ISS.

This morning, I received one packet from Pollux-1 and one from Castor-1 (which confusingly identifies itself as KD4HBO-1 in the packet header.) Just for fun, I decoded the packets using the telemetry decoders written by Mike Rupprecht, DK3WN - though to be honest, the information didn't mean anything to me. Captured telemetry should be sent to ande@juno.nrl.navy.mil and QSL cards will be sent to anyone who submits data.

I also received many more packets from the ISS, which uses the same frequency of 145.825MHz. The result of this is that I have now become interested in trying to make packet radio contacts through the ISS digipeater!

What a great hobby this is! There seems to be no limit to the different things you can try to do with amateur radio!
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