Space is good for amateur radio: the story of SunSat

January 13th, 2017, Published in Articles: EE Publishers, Articles: EngineerIT

 

It has been written and spoken about that amateur radio is a pasttime that contributes to communication, electronic and space activity development and training. In fact it is contained in the ITU definition of amateur radio: “A radio communication service for the purpose of self-training, intercommunication and technical investigations”.

For amateur radio to stay relevant it has to keep up with new developments – and space activities are an important part of this. Radio amateurs were once in the forefront of space exploration when they launched OSCAR 1, a mere four years after the launch of Sputnik in 1967. OSCAR is the acronym for orbiting satellite carrying amateur radio. While the project was the brainchild of US amateurs, many South African radio amateurs turned their antennas skywards to receive its weak signals.

Jacques Roux and Riaan Oliver testing a module in the SunSat lab at Stellenbosch University. Today both have successful careers in industry, testimony to the impact of the SunSat programme. Jacques is still involved in the electronics industry and during his free time works on the AMSAT SA Kletskous CubeSat. Riaan holds a senior managerial position as VP SA at Assaa Bloy SA.

Now 25 years ago, Garth Milne, Arnold Schoonwinkel, Jan du Plessis, and Sias Mostert who were in the computer and control group in the Department of Electrical and Electronic Engineering at Stellenbosch University, decided that a microsatellite project could add a multi-disciplinary engineering research opportunity to the university’s graduate portfolio. Other goals were stimulating significant international interaction through a challenging research initiative and helping stimulate interest of the youth in science and technology.

It is doubtful if they, in their eagerness, could have visualised that it would take them almost nine years to fulfil their dream and launch a satellite. On 23 February 1999, USA Air Force Delta II launched SunSat, South Africa’s first microsatellite, and amateur radio was very much a part of that.

The payload was an imager that would be delivering pictures of Earth similar to the then commercial SPOT 2 satellite. Options were also reviewed for additional functions. Amateur radio’s track record and resources for stimulating interest in communication-based electronics led to a rewarding partnership with the South African Radio League and SA AMSAT (now AMSAT SA). The 64 kg satellite, after starting South African and international amateur radio activities, became known as OSCAR 35 (SO-35).

The SunSat programme achieved its engineering educational goal by involving over 96 graduate students. The programme also produced numerous spin-offs, including components in orbit of satellites from other countries and the formation of SunSpace, later to be incorporated in SpaceTech, a Denel Dynamics company.

But it was not all smooth sailing, as the late Prof. Garth Milne told delegates at the 13th Annual AIAA/USU Conference on Small Satellites in August 1999 in Utah, USA. The initial goal was to launch a satellite in three years, but funding and launch delays stretched SunSat’s development until launch in February 1999.

NASA saved the SunSat programme by offering a launch on the US Air Force P91-1 Argos Delta II mission if SunSat could carry a JPL Turbo-Rogue GPS receiver for geodynamic research. Denmark’s Ørsted magnetic research satellite was already scheduled as a secondary payload, and SunSat could be carried in the opposite sector instead of a balance weight.

A modular design approach had been selected, so an extra tray was easily added to accommodate NASA’s GPS when their launch offer arose. SunSat’s boom design could also be exploited to add wiring and a tip mass magnetometer, star camera, and laser reflectors.

The 857 x 655 km elliptical polar orbit was dictated by science requirements of the Ørsted satellite which was the initial secondary payload. The orbit plane drifted an hour earlier every seventy days, and was aligned with the sun in mid-July 1999. The orbital drift makes long-term repeated imaging impossible, and lowered the expected output of SunSat to demonstrating what the satellite would be able to achieve in a true sun-synchronous orbit.

The team retained the sun-synchronous design for the drifting orbit, and concentrated on communication activities when the sun angle becomes unsuitable for imaging, but provides more average solar power.

For stimulating technical interest in young children the VHF Parrot would be a very attractive additional payload. Significant benefits accrue if the VHF receivers are sensitive enough to receive uplinked signals from 1,5 W hand-held radios. Significant attention was given to receiver spurious and image responses, and maintaining noise figures near 2 dB. The Parrot (receiving a signal, recording the audio for 30 seconds and playing it back) was a success. Ultimately, because of the orbit in which SunSat settled in, the amateur radio transponder became the darling of the amateur radio community worldwide.

SunSpace and Stellenbosch University also built South Africa’s second satellite, SumbandilaSat. Prof. Milne (who became a radio amateur) believed that in this project amateur radio also had to play a role and on his insistence it became what was termed “one of the experiments”. Due to a debilitating illness and untimely death he did not see his vision materialised.

Amateur radio also turned out to be a major part of SumbandilaSat’s operation, particularly when orbiting over Europe, the Americas, Australia, and New Zealand. Unfortunately for South African amateurs, few orbits were available due to operation of its imaging payload while orbiting over South Africa. Radio amateurs hope to have another experimental payload on SANSA’s planned EOS-1 and are also building their own CubeSat, Kletskous.

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