Hello John,
You are correct that heating is our main concern during no eclipse. We discussed different strageties last fall like TX off to not generate heat, and TX on as high as possible to use the sunlight that is converted to electricity. What isn't used is converted to heat.
We decided that the best approach was to use as much energy as possible. When the satellite software crashed Sunday we were able to see the effect of no TX. Battery 1 temperature got 41/42 degreees C, not a good situation. Battery 1 is the only battery we have a temperature sensor on.
We kept high TX power (2.28W) on TXA as soon as we recovered command and by the end of one orbit the temperature of Batt 1 had come down to 36 deg C. It is now running 33-34 deg C. Over the last year it has oscillated between 18 - 24 deg most of the time (there were exceptions). We had a number of people doing thermal modeling (like Dick Jansson) and his 30 degree C predictions are on the mark. I did a paper for the 2007 Symposium on the AO-51 power system and talked about these issues. The main chassis is hanging around 30 deg C when we have the TX running enough to keep the low battery voltage above 1.2V. The batteries don't work as well at 30 deg C, so we want to keep their low voltage above a minimum.
Everything is looking well so far and we are getting consistent data, for a fixed total transmitter current setting. I will be uploading the 2008 telemetry data to an ftp site later tonight. There will be raw data, csv (comma separated variable) format after the conversion equations and some Excel data with graphs. http://www.amsat.org/amsat/ftp/telemetry/ao51/
Hope this helps.
73, Gould, WA4SXM ----- Original Message ----- From: John Henderson To: gouldsmi@bellsouth.net Sent: Tuesday, January 15, 2008 7:11 PM Subject: More Eclipse Questions
Gould,
I have been following the threads on the AO-51 issues and I still do not quite understand the problem of " no eclipse". It seems to me the other side of the coin would be the problem from a power stand point. The " No eclipse" would be an overheating problem and I assume the systems are in place to avoid overcharging the batteries. I am confused on this issue.
If you have the time, maybe you could clear this up for me.
Best regards,
John
John Henderson N4NAB
AMSAT Area Coordinator NC
212 Bayside Drive
Cape Carteret, NC 28584
252-725-2744
n4nab@amsat.org