The new Amateur Radio satellite ARISSat-1 has been switching into low duty cycle mode even while in full sun which has suprised observers.
When the satellite is in darkness, in order to conserve battery power, it switches into a low duty cycle mode (also known as low power mode) where it transmits for 40 seconds and then shuts down for 2 minutes. On Thursday, August 11, a number of Radio Amateurs reported that ARISSat-1 was in low duty cycle mode when the satellite appeared to be fully illuminated by the sun.
On the AMSAT bulletin board Tony AA2TX, ARISSat SDX software and hardware developer. provided an explanation:
My analysis indicates that at certain “bad” sun angles, the solar panels may not provide enough power to run the satellite even in full sun.
The power from the panels can actually drop to as low as 2.5 watts at really bad angles but the satellite needs around 8 watts average to run in high power mode. This means that the satellite would have to draw current from the battery to run in high power mode even though it is in the sun.
This discharge would reduce the life of the battery so to minimize the damage and prolong the life of the satellite, it will switch itself to low power mode under these conditions.
I don’t know for sure if this is what is happening but this condition is within the predicted nominal operation of the satellite.
ARISSat-1 Reception Certificates (for voice and Slow Scan TV reports)
http://arissat1.org/v3/index.php?option=com_content&view=category&layout=blog&id=61&Itemid=137
Free Slow Scan TV Software MMSSTV uses your PCs Soundcard http://mmhamsoft.amateur-radio.ca/
The IZ8BLY Vox Recoder software enables you to record ARISSat-1 on 145.950 MHz FM while you’re at work or asleep http://antoninoporcino.xoom.it/VoxRecorder/
Online Satellite Pass Predictions, select ARISSat-1 http://www.amsat.org/amsat-new/tools/predict/
ARISSat-1 Website http://www.arissat.org/
AMSAT Bulletin Board (AMSAT-BB) http://www.amsat.org/amsat-new/tools/maillist/