Ingenuity and innovation by the SumbandilaSat ground control team has resulted in bringing the satellite back to life with a real possibility
that Amateur Radio communication may resume next month while the satellite is in sunlight.
The ground stations at SANSA Space operations at Hartbeeshoek and the Electronic Systems Laboratory at Stellenbosch University are receiving
telemetry when the satellite’s solar panels are illuminated by the sun.
Johann Lochner, ZR1CBC, said that in early June 2011, for an unknown reason (but probably related to a major radiation event on 7 June), the
primary controller on the power distribution unit (PDU) powering the On-Board Computer (OBC) stopped responding to commands from the ground
It later appeared that the battery had failed and nothing was heard from the satellite for some time. The ground segment software to monitor the
passes over South Africa and to contact the satellite to initiate the recovery procedure was automated. After a month contact was made again.
This was mid November. “We set in place a planned recovery procedure and within 3-4 days we came to the conclusion that the main battery had
failed”, Johann said. With SumbandilaSat responding when it is in full sunlight Johan Lochner is confident that some operations will be restored
even to the point where it may be possible to do some imaging and have the amateur radio transponder back in operation. More on recovery efforts are
on line at www.amsatsa.org.za.
20:05 UTC very strong signals, parrot active (very difficult on a very crowded FM transponder)
20:40 UTC please use SO-67 with a very low modulation index !
overmodulated signals on the transponder
21:23 UTC thanks Alan for this graph
No fading evident on these records.
18:30 UTC scheduled but not active
18:38 UTC good activity, heard: UR5BFX, IT9AUH, OK1DNT, SQ5BUO/p, YO6VEB, ON5NY, TK4LS, SP8CGR and SP5XSD
17:12 UTC pass worked UR5BFX Nikolay at 1 deg elevation :-)
09:30 UTC SO-67 with good signals active over Europe
many stations using too much power, decrease your modulation index !
14:40 UTC – thanks John, K8YSE (truly madly deeply…)
The North American Pass of SO-67 on 27 Dec 2009 at 1443z is now on my webserver. The bird was strong as usual. It is difficult not to respond immediately to a call to your station, but those that wait for the “tail timer” to expire, will have more than 3 seconds to exchange their information.
Watch the S meter and wait for the tail to expire before you transmit. This doesn’t always work if there are others still transmitting after the tail timer expires. Their signal is not repeated but it prevents the repeater from re-transmitting your signal.
Full duplex allows you to hear the bird when you are transmitting and makes successful qso’s much easier.
We have two new satellites to work with but they don’t work exactly like AO-51 etc.
Each bird has their own unique characteristic and it’s up to us to figure out what works and then do it.
The problem is that everyone doesn’t do that and this leads to chaos and not many qso’s. I hope this will be resolved such that these new birds work somewhat like the old ones. With their high power (both SO-67 and HO-68) and the higher orbit on HO-68, they have a lot of potential.
09:45 UTC over Europe – See an interesting note from Alan to the tail after each transmission below. You can see that clearly in the VHF spectrum.
Alan, ZL2BX: Well I have just had a pass over ZL with only one other station on and the performance was quite interesting and repeatable. When the transponder is triggered it stays on and does not drop out. Once the transponder is released it has a few seconds of tail. Every attempt to retrigger the transponder during the tail resulted in a drop-out of two or three seconds.
If you wait until the tail drops out it will retrigger as normal and hold in without a problem.
In other words if I drop my carrier the transponder seems to enter its “tail mode”. If the second station begins transmitting within this tail the transponder ignores that signal and still drops out. If the second station waits for the tail to drop and then starts transmitting the transponder holds in without drop-out.
08:16 UTC strong downlink signals over Europe
… listen to the complete pass (10 minutes)
If I listen to the pass I am left wondering wheter it is what we want, what we need.
And again I remember of some golden rules published many times not only by Ib, OZ1MY:
It is obviously about time to repeate a few good points about operating via the FM repeater satellites.
1. Do not transmit if you can not hea
2. When the satellite is busy – limit the number of QSO’s to ONE
3. Do not call over an ongoing QSO
4. A valid QSO just needs the call and the report
5. Give way to weak stations like /p and /m
6. Allow DX-peditions to make as many QSO’s as there are callers
SumbandilaSat was successfully launched at 16:55:09 UTC.
Uplink 145.880 MHz (FM voice Transponder and Parrot)
Downlink 435.350 MHz (FM voice Transponder and Parrot)
435.300 MHz (Voice Beacon)
The system a parrot repeater, a device that will record 20 seconds of audio and plays it back on 435.350 MHz.
Another feature of the payload is an audio beacon (435.300 MHz) that will carry a 15 second message. The beacon is programmable from the ground and various messages can be uploaded. The beacon message was selected from entries in a country-wide competition and recoded by the winner, at the time a Kimberley Technical High School Student, Anton Coetzee. The message reads: “This is ZS0SUM in space. I am the voice of the South African youth. We are knocking on the door of opportunity, marking our place in the orbit of space research and communication. Hear us! Listen to us!”