Whole Orbit Data (WOD) collected

We have made a further improvement to our ground station setup by replacing the existing UHF yagi antenna with one which has 4dB more gain.  It is now mounted on the dish which eliminates some obstruction we experienced previously.  During last night's passes we had a marked improvement in communications.

We have now downloaded almost 500kB of WOD, including fluxgate magnetometer readings which will enable us to calibrate the magnetometer.  The ADCS system is continuing to perform well, as are the thermal and power subsystems.

There seems to be a high incidence of Single Event Effects (SEE) due to radiation, especially on the On-Board Computer (OBC).  We have however designed all the electronics with latch-up protection, so none of the SEE occurrences to date have caused any permanent damage.  Sometimes an SEE causes the OBC to reset and we have recently noticed that an auto restart of the processor then does not fully complete.  With the WOD now available to us it seems that the lengthening of a timing constraint in software will be able to alleviate this problem.  Note that we could not test for SEE on the ground so were not able to observe this timing effect prior to launch.

Sumbandila Two-Line-Element (TLE) set

Peterson AFB in America informed us that they have incorrectly labeled Sumbandila as Fregat-IRIS. They are part of the radar tracking network responsible for uniquely identifying over 20,000 objects in Earth orbit! We have therefore up to now tracked the Fregat-Iris (35867) in stead of Sumbandila (35870). 

After correcting the TLE information, our communication with the satellite is more consistent and reliable. 

We intend to affect the improvements that we made to our ground station equipment, to the SAC ground station in the coming week.

Sumbandilasat Technical Status Report No. 1

Sumbandilasat has completed more than 50 Earth orbits in space and we are now in full swing with the various commissioning activities.

The two autonomous Attitude Determination and Control System (ADCS) controllers (Bdot and Y-Thompson; Bdot-Sun) running on a small micro processor on the magnetic subsystem (no floating point processing) are perfectly pitching the satellite at 2°/sec with the main body-mount solar panel facing the sun. The power system is therefore running optimally. We are satisfied with the thermal state of the satellite in the current basic attitude control mode.

As expected, the 500km orbit of the satellite causes incidences of short contact opportunities with the satellite due to the fact that our ground station is located at the Engineering Faculty (in Stellenbosch) where it is surrounded by various high mountains. We have identified certain aspects in our communication setup on the ground which can be improved to make the communications with the satellite more robust and reliable.

In addition, we are re-evaluating the possibility to extend the contact time with the satellite by also employing the Sumbandilasat TT&C ground station at SAC (Hartebeeshoek), by remotely controlling passes from Stellenbosch. 

At the moment we are focusing on the commissioning of the main On-Board Computer that will allow us to collect whole-orbit telemetry data, calibrate the magnetometer and proceed to the more advanced ADCS control modes on the main Attitude Computer.

17/09/2009 20:48 Our first pass

We are extremely pleased with our baby in space!! Our first pass last night at 20:48 local time was a very low elevation Eastern pass with some mountains obscuring the “view” as well, but the satellite responded beautifully almost immediately after sending the first command from the Stellenbosch ground station!

We received real-time telemetry which suggested that the satellite was already executing an autonomous attitude stabilization maneuver. This was confirmed during the second pass where we also had good communications. This morning the satellite was stable in a sun-Thompson mode.

Celebration on our first Contact with Sumbandila