It would appear that prior reports on the demise of South Africa’s
SumbandilaSat were ‘greatly exagerated’ (with apologies to author Mark
Twain).
A report on the Southern African AMSAT website says partial recov- ery
is possible for Amateur Radio Operation to possibly resume in March
2012.
“We have not given up on our efforts to get SumbandilaSat working again
even if it is only partially”, said Johan Lochner ZR1CBC who is spending
much time on the recovery process and many nights burn- ing the midnight
oil working on new and more intelligent algorithms.
He and his colleagues are making every effort to get the satellite
working again.
SumbandilaSat experienced a corruption in the programme memory of one of
the power switches. This is the interface unit which con- trols a robust
orientation control implementation system which is using output from the
magnetic sensors to point the solar panels to- wards the sun in a safe
mode scenario when for example communica- tions with the ground segment
was not possible for a few days.
The corruption of the program memory prevented the magnetic inter- face
unit from automatically switching on after power-up and thus
preventing access to measurements taken by the magnetometer.
Johann said, “As a result of the malfunction of the magnetic control
unit the satellite started to slowly point away from the sun with
intermittent sun eclipses. When there was no power flowing from the
solar cells the batteries drained and we could not in a safe way
communicate with the satellite, so we backed off. Once we determined
this pattern we stopped communicating with the satellite when we did
not see sufficient charge on the batteries. At other times we had good
communication when could diagnose what was going on. Dur- ing good
communication windows that could last 2 or 3 days we tried to diagnose
the exact nature of the problem in the same way as we had done before
and we started to implement a fix. The particular power switch that
failed was already the redundant one so we were in a worse state than
before.”
SumbandilaSat controllers implemented automated ground segment soft-
ware to make contact with the satellite from both SANSA Space Opera-
tions and the Electronic Systems labs at SU. The objective was to
contact the satellite automatically and to try to implement the recovery
procedure and also notify the team if any contact was made.
Johann continued, “By mid-November 2011 we again made contact with
SumbandilaSat and set in place a planned recovery procedure. Within
3-4 days we came to the conclusion that the main battery had failed.
Earlier the intermittent contact was because the battery could not be
fully charged and that satellite power bus was too low for the
processors and transmitter to function. We surmised that during the
month that we had no contact that the battery must have gone open
circuit. With the battery no longer on the power bus, the voltage on the
bus would rise to 28.5 volts and supply enough current to support
operations when SumbandilaSat was in full sunlight.”
The SumbandilaSat concludes, “We are determined to get this working and
to maintain the scientific value of the satellite as much as possible.
Johann’s focus is now on getting the amateur radio trans- ponder
working, which with the loss of AO-51 will be a great asset to amateur
radio satellite activity. By the end of February we hope to achieve
this!”
Uplink: 145.875 MHz (no tone required)
Downlink: 435.345 MHz
See: http://www.amsatsa.org.za/SumbandilaSat.htm for full coverage of
this news.