Mar 25, 2011

SumbandilaSat winging its way past snags

Estimated Article Reading Time: 3 min.

SA’s first low-orbit satellite has problems but is making a point, writes Sarah Wild

DESPITE being called a “crippled ship”, SA’s first low-orbit satellite, SumbandilaSat, is doing what it was designed to do: take images of earth from space.

Orbiting at about 500km from the earth’s surface, the satellite transmits earth observation imagery that can inform decision makers on matters such as water and land use, as well as air quality.

But, at heart, the satellite is a “pathfinder, a technology demonstrator (to show that) we can put a satellite into orbit and it can function”, says Department of Science and Technology deputy director-general Val Munsami.

Built by SunSpace, a microsatellite company started by a team of Stellenbosch University graduates, the satellite was launched in September 2009 from the Baikonur Cosmodome in Kazakhstan. The total cost of the satellite — including construction, transportation to launch site, the launch itself, tracking the satellite’s received data, and maintenance — is not available. The R26m paid by the Department of Science and Technology for the construction of SumbandilaSat is — in satellite terms — very cheap.

“They made cost compromises because it wasn’t built for longevity. It was built as a prototype to show that SA has the capacity. It doesn’t have the back-up systems a fully functioning satellite would have,” says the Democratic Alliance’s shadow minister for science and technology, Marian Shinn.

“It’s cheap because we’ve done away with dual redundancy,” Mr Munsami says. With dual redundancy, a satellite has two sets of components, so that there is a back-up if one of them fails.

Dual redundancy would have complicated the design and made it more costly, he says. “We wanted it to be as simple as possible, that’s why it was so cheap and that’s why it has problems.”

And the problems are real.

One set of the satellite’s reaction wheels has stopped working. The wheels stabilise the satellite, and ensure it — and its onboard camera — point in the correct direction. But since there was no redundancy plan, SumbandilaSat “tumbles” forward.

“The tumbling issue has been around for a long time. It means the satellite is slightly unstable. It’s not ideal, but it works,” says Eugene Avenant, telemetry, tracking, and commanding manager at the CSIR’s Satellite Application Centre , which is responsible for satellite maintenance, and comprises three staff members dedicated to the project, as well as SunSpace on standby to help with problems.

“It tumbles, but as it passes over the area where they want to take the images, they slow the satellite down. It takes an image … and it carries on,” says Mr Munsam i. “This is the first time this has ever been done; it’s very innovative.”

The main reason for SA putting a satellite into space was to take images. “One licence (to source images from international satellites) can cost R80m over three years, and that’s just for one licence,” Mr Munsami says. “Going forward, we require six to seven data sets from different satellites. Each one would normally require its own licence .”

Mr Avenant says: “At the moment, we’re taking images of anything that gets requested. We did an image of the earthquake area in Japan.”

The satellite’s main client is the government. Requests are made through the CSIR, after which the unit gets clearance from the Department of Science and Technology. “We’re honouring most of the requests that come in,” Mr Avenant says.

But Ms Shinn does not believe the satellite is living up to expectations. “It is not delivering on its full potential as designed and paid for by the taxpayer,” she says. “It isn’t out of control, it’s delivering on some of what it was supposed to. What it isn’t delivering — which was promised — are some university research experiments (that were attached to the satellite)”.

These experiments include an amateur radio; a radiation experiment by the University of Stellenbosch; a forced vibrating string experiment by Nelson Mandela Metropolitan University; and a very low frequency radio experiment by the University of KwaZulu-Natal.

However, Mr Mun sami says two of the experiments are working. “The amateur radio is working, and Stellenbosch’s radiation (experiment) is working and they’ve taken a few results.”

Despite the potholes on SA’s road to full satellite capability, the country has plans to send up another satellite.

“We’re looking at the next step in terms of technological development, which will probably cost a lot more, but it’s on the … road map,” Mr Munsami says. With Sapa