[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

SUNSAT UPDATE 28FEB1999



SUNSAT UPDATE 28 FEBRUARY 1999

Sunsat  continues to do well. This status report  was compiled by Garth
Milne ZR1AFH after this morning’s 03:00 SAST ( 01:00 UTC) pass over
South Africa.

SUNSAT IS NOT AVAILABLE FOR GENERAL USE. IT IS EXPECTED THAT THE
SATELLITE WILL BE RELEASED FOR GENERAL AMATEUR SERVICE BY END MARCH.
WATCH THIS SPACE!

“It seems that each day we make a major step on Sunsat.

We deployed the boom about 24 hours ago and can see this from
magnetometer telemetry. We did this before detumbling because of our
comms problem (possibly (probably?) caused by Sunsat staying in an
unfavorable attitude due to the Z-spin causing the satellite to cone
rather than tumble.

We have now had 3 passes where we established telecommand at 5 degrees
elevation. The  OBC1 was booted more than 24 hours ago and was still
running when we activated the packet communications on it in the last
pass.

The file system is operating on Sunsat's on board computer. We gathered
1 minute of Whole Orbit Data telemetry data into a file, closed it and
downloaded it under AX25 packet communications protocols at 9600 baud.
The packet communications was faultless, apparently with no retries
needed. (We need to mod our ground software to log the retries, but our
guys say the comms appeared more reliable than over-air tests in the
lab.) We only had 14 minutes on the pass and had to complete a number of
things, so this was a test of the correct operation of the on-board
software rather than a serious WOD data gathering attempt. Before LOS we
started a 24h WOD gathering file at 10 minutes per sample which we will
download later. (The sample rate is slow because we haven’t commissioned
the RAM disk yet and are relying on limited memory on the OBC1.)

The 10 min/sample will be enough for us to establish Sunsat's deployed
tumble motion, and to see solar panel charging currents for the first
time. We still can't make contact with Sunsat in the day, but have good
night passes. - most intriguing!

Our UHF downlink works excellently when the satellite attitude is
favourable. On the 3AM 28 February (SA time) pass, we had
coax-cable-like signals with UHF TX's on both low and high power. On
high power we got +- 106 dBm signals from our ground station yagi
antennas. The UHF ground receiver sensitivity should be  about -120 dBm
so these are really needle-bending signals.

We expect to be able to decode this level of signal with an
omnidirectional ground antenna. (Will try this tomorrow too!)

VISIT the SUNSAT WEbsite for daily updates http://sunsat.ee.sun.ac.za

WHERE IS THE UNIVERSITY OF STELLENBOSCH?

The University of Stellenbosch is situated in Stellenbosch the second
oldest Town in South Africa, not far from the southern tip of the
African continent some 50 km east of Cape Town.

The University has in excess of 14 000 students and is the oldest
University in the country with an excellent academic record.


Hans ZS5AKV

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home