Sumbandila failures are 'normal'
Failures experienced by SA's SumbandilaSat are the norm for all high-risk space programmes, says the SA National Space Agency (Sansa).
“Recent comments that reflected disappointment in the functionality of SumbandilaSat, SA's 'pathfinder' satellite, after solar radiation damaged its on-board computer, wrongly inferred that the country's satellite technology demonstrator programme is not delivering as it should,” it notes.
Democratic Alliance (DA) science and technology shadow minister Marian Shinn said on 23 August that the latest problem with the satellite in early June is disappointing.
She said this time the failure was of the on-board computer to respond to commands from the ground station. It happened in early June and is thought to have been caused by a major radiation event in space.
”While I understand that skilled software engineering has restored operations to the satellite, work is continuing to recover the primary controller of the on-board computer's power distribution unit. SumbandilaSat has so far cost the public purse R100 million.”
Sansa says since the launch of SumbandilaSat almost two years ago, the locally developed prototype satellite programme has shown that failures, which are the norm for all high-risk space programmes, can be dealt with effectively. It thereby achieved its goal of identifying possible problems and ways to mitigate these in future operational satellite programmes.
"SumbandilaSat has also delivered 1 128 very usable, cloud-free images that have been processed and disseminated to end-users by Sansa Space Operations," says Sansa CEO Sandile Malinga.
He adds that the success of the programme as assessed by the international space science community has put SA on the map for its ability to develop and operate small and medium-sized satellite programmes.
According to Malinga, the radiation damage to the primary on-board computer command control power distribution unit occurred on 29 July, when contact with the satellite was lost.
“The last image data from the satellite was downloaded on 27 July. The SunSpace engineers rapidly implemented highly-skilled software engineering, which restored contact with the satellite on 2 August and again demonstrated their ability to deal with the challenges caused by a harsh and often unpredictable space environment.”
He also says the telemetry downloaded from the satellite on 16 August indicated the initial repair work had been successful.
“The satellite is currently in 'safe mode' with all non-essential subsystems switched off to safeguard it and conserve battery power. This includes the damaged magnetic attitude control system (MIUB) that stabilises the satellite, without which the satellite automatically went into a random spin.
“As a result, the solar panel does not get sufficient sun illumination to keep the batteries charged continuously. Intermittent connection with the satellite has indicated that the battery power level is too low for extended contact.”
Malinga explains that with insufficient battery power, the satellite switches off and the SunSpace engineers cannot restore the two damaged MIUB power distribution units to control the satellite's attitude.
“Imaging is also not possible. Work is ongoing by the engineering team to recover the functionality of the switches and execute the powering-on procedure. Once they regain control of either one of the two switches, they can activate the MIUB and the satellite can resume normal operations.”
The CEO says these anomalies are normal occurrences in all satellite programmes, even with the most expensive systems.
"Apart from the anomaly with the power distribution units and stress on the batteries due to the deep discharge cycles, the satellite is in good health and all subsystems are working."
Shortly after its launch in September 2009, SumbandilaSat experienced serious and permanent failures, according to Shinn.
She says these failures were attributed to cost compromises made in the choice of components when constructing the prototype.
”Cabinet decided in March this year to buy the majority shareholding of SumbandilaSat's manufacturing company, Stellenbosch-based SunSpace. Deloitte was to determine the size and cost of the shareholding by July 2011.”
Government's shareholding in the company will be held by Sansa.
Sansa says during the development of the Sumbandila prototype programme, a technology demonstrator satellite was designed and built from scratch in one year, at low cost, by South African engineers.
“It was launched and successfully commissioned. A world-class mission control system was developed in SA for the programme.”
Sansa Space Operations took over satellite operations from the satellite design authority, SunSpace, which is not the norm worldwide, and successfully operated the satellite over an extended period of time.
“The satellite is well-known by the amateur radio satellite society worldwide for the excellent results from its amateur radio payload.”
University research was part of the original motivation for the SumbandilaSat, but only one out of three projects was able to utilise the satellite.
Science and technology minister Naledi Pandor said it is due to the physical condition of the satellite that the payloads for the two remaining experiments have not been turned on and this situation will probably last until the end of the satellite's life.
“It's sad that the university experiments - that were part of the original motivation for using taxpayers' money to build SumbandilaSat - have been so severely compromised by the launch delays and operational difficulties of this satellite,” says Shinn.