August 22, 2010

Goce Gravity Satellite Suffers Computer Blow

A European gravity observation satellite has been hit by a second computer glitch and is not able to transmit its valuable data down to Earth.

Europe's Goce satellite, launched on 17 March, 2009, is a satellite carrying a highly sensitive gravity gradiometer which detects fine density differences in the crust and oceans of the Earth. Its main mission is to make the most precise maps yet of how gravity varies across the globe.

The satellite suffered a processor fault in February forcing operators to switch the satellite over to a back-up computer system.

The back-up system too has now developed an issue and engineers are scrambling to make the satellite fully functional again.

The European Space Agency (ESA) remains confident that the problem can be fixed, however. "There's no doubt about it: we're in a difficult situation, but we are not without ideas," Goce mission manager Dr Rune Floberghagen told BBC News.

The ESA lost use of an instrument on its Herschel space telescope last year, but engineers were still able to find a way to bring it back online even though they were separated from the hardware by more than 600,000 miles of space.

While engineers work to restore the problem, the instrument's data-gathering has been suspended and the satellite has been pushed higher into orbit.

The problem affects a communication link between the processor board in the B computer and a module that prepares telemetry for transmission to the ground. The B computer has been rebooted but the error still persists.

Some good news in the matter is that the operation team is making headway in getting some functionality back on the primary computer. They are hoping the primary computer can be made stable enough to handle telemetry tasks while the B unit is given the responsibility for processing.

"If we have just two half-computers, we can stitch them together and get Goce working again," Dr Floberghagen said.

Even if by chance the computers were not able to be recovered, Goce has collected around two-thirds of the gravity data originally expected from the mission since its launch last year.

The data will help with many different applications, especially in the area of climate studies by studying how gravity influences the way the ocean waters move and redistribute heat around the world.

A senior investigation team at ESA is looking into the root causes of the computer malfunctions, to understand the implications for other satellite missions.

"It's frustrating when you consider all the focus and effort that went into the building of the innovative parts of Goce, like its gradiometer - to see all that work perfectly, and then be faced with failures in elements that are really 'bread and butter' in any satellite mission," Dr Floberghagen observed.

The ESA expects the computer recovery to take until at least the middle of September.


Image Courtesy of ESA


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