The sleek and sexy-looking GOCE spacecraft has been mapping Earth’s gravity for over four years, but soon its xenon fuel will run out and the satellite will end up re-entering our atmosphere. But no one can say for sure when or where the 1-ton satellite will fall.
The Gravity field and steady-state Ocean Circulation Explorer has been orbiting Earth at super-low orbits, mapping out variations in Earth’s gravity with extreme detail. Launched in March 2009, the GOCE spacecraft was designed to fly low and has spent most of its mission roughly 500 km below most other Earth-observing missions, at an altitude of 255 km (158 miles), but has recently been at the lowest altitude of any research satellite at 224 km (139 miles).
With its sleek, aerodynamic design, some have called it the ‘Ferrari of space,’ but we’ve just called it sexy, like a satellite straight out of a James Bond movie.
And the satellite has delivered with unique results of Earth’s ‘geoid’ — precise measurements of ocean circulation, sea-level change and ice dynamics, greatly improving our knowledge and understanding of the Earth’s internal structure. The mission has also been studying air density and wind in space. Its data also produced the first global high-resolution map of the boundary between Earth’s crust and mantle, called the Mohorovicic, or “Moho” discontinuity.
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Mission managers predict that in mid-October 2013 the spacecraft will run out of fuel and the satellite will begin its descent towards Earth. There will be no remaining fuel to guide its re-entry, and while most of GOCE is predicted to disintegrate in the atmosphere, several parts might reach Earth’s surface. Experts predict as much as 25% of the spacecraft will survive reentry, as many parts are made of advanced materials, such as carbon-carbon composites.
But when and where these parts might land cannot yet be predicted, ESA says.
As the re-entry time nears, better predictions will be made. Re-entry is expected to happen about three weeks after the fuel is depleted.
ESA says that taking into account that two thirds of Earth are covered by oceans and vast areas are thinly populated, the danger to life or property is very low.
Recently, other larger satellites have made uncontrolled re-entries, such as NASA’s 6-ton UARS spacecraft and Germany’s 2.4-ton ROSAT in 2011 and the 13-ton failed Russian Mars probe, Phobos-Grunt in 2012.
About 40 tons of human-made space debris reach the ground per year, but the spread and size mean the risk of an individual being struck is lower than being hit by a meteorite.
An international campaign will be monitoring the descent, involving the Inter-Agency Space Debris Coordination Committee. The situation is being continuously watched by ESA’s Space Debris Office, which will issue re-entry predictions and risk assessments.
ESA says they will keep the relevant safety authorities permanently updated.