Laura Halliday M.A.Sc.

I recently finished my M.A.Sc. at the University of Toronto Institute for Aerospace Studies. My thesis title was Communications Infrastructure for the MOST Microsatellite Project.

An important part of my work was setting up a station at UTIAS to communicate with present-day digital amateur radio satellites. The MOST project will generate vast quantities of data, and I spent a great deal of time studying file transfer from satellites. This resulted in vast quantities of data from the current 9600 baud satellites, UO-22, KO-23, KO-25 and TO-31. I created custom applications to read off the telemetry and also to analyze the protocols they use: throughput, overhead, and so on.

I spent a lot of time poring over AX.25 and things you can do with it. Additionally, I wrote some prototype software for a simulated satellite, both the ground control and spacecraft software. As much as possible I stuck with established formats for things. My telemetry program, for example, decodes UoSAT-3 format whole-orbit data files, and uses the same input data format as the standard AMSAT DTLM program.

My thesis is on file with the National Library of Canada, as all graduate theses are. It would be counterproductive to post the entire thing here, but some excerpts could be handy. Here are some:

From Chapter 2: a discussion of AX.25, HDLC, KISS, and so on (ax25.pdf, 38k).
From Chapter 3: the protocols used by the digital amateur satellites to download files (pbftl0.pdf, 40k).
From Chapter 4: a discussion of whole-orbit data files and formats (wod.pdf, 26k).
From Chapter 7: a presentation of some downloaded telemetry with arm-waving over what some of it means (ground.pdf, lots of graphics, so 990k).

I was particularly pleased with the telemetry decoder program I wrote. Here's a shot of it in operation, interactively displaying whole-orbit data from TO-31:

Telemetry decoder program screen shot

I think the "number of samples" figure is wrong. Who says you can't write real programs in Visual Basic? Complete with bugs. :-)

After trying a fancy ODBC database export facility (sloooooow...) I opted for a simple text format to export telemetry for analysis by other programs. Here's a chart of some TO-31 telemetry from Microsoft Excel:

TO-31 temperature data, 28 November 1999.

The solar panels are on the outside of the spacecraft and show large temperature variations. The battery and transmitter, inside the spacecraft, do not. The temperatures are in degrees Celsius, and the data are from 1200 to 2359 UTC on 28 November 1999.

I asked TO-31's builders about the telemetry format used by TO-31. After getting lots of excuses I decided to reverse-engineer the format. It wasn't hard.

You'll have to talk to UTIAS if you want my telemetry program. They have it. I don't.

Back to Laura's web page.