Sunday, October 20, 2013

Space Junk Satellite To Fall To Earth: GOCE Update

GOCE Satellite.  Image Credit: ESA


UPDATE:  GOCE Has Fallen To Earth

Around 7:00 PM EST on Sunday, November 10, 2013, ESA’s GOCE satellite reentered Earth’s atmosphere on a descending orbit pass that extended across Siberia, the western Pacific Ocean, the eastern Indian Ocean and Antarctica.

The European Space Agency estimates that a satellite weighing 2,425 pounds (1,100 kilograms) will begin its orbital decay sometime this week and then hurl back to Earth in an uncontrolled descent from an orbital height of about 139 miles (224 kilometers).  

On October 18, the ESA reported that the pressure in the satellite's fuel system had dropped below 2.5 bar, which is the pressure needed to fire the ion engine.  It was estimated then that there was about 350g of xenon left in the fuel tank. If the engine continues to function until the tank is empty, orbital decay would start around October 26, 2013. However, ESA controllers expect the ion engine to terminate well before that.

The ESA cautioned that, while most of the satellite will disintegrate in the atmosphere, several parts might reach Earth’s surface.  Exactly when and where the space junk debris will crash cannot yet be predicted, but the affected area will be narrowed down by ESA scientists closer to the time of re-entry.  Re-entry is expected to happen about three weeks after the fuel is depleted. 

Because two-thirds of Earth is covered by oceans and vast land areas are thinly populated, the ESA reasoned that danger to life or property is very low.  An international campaign is monitoring the descent, which includes the Inter-Agency Space Debris Coordination Committee.  The situation is being continuously watched by ESA’s Space Debris Office, which will issue reentry predictions and risk assessments.  The ESA will also keep its Member States and the relevant safety authorities permanently updated.

The satellite, named Gravity field and steady-state Ocean Circulation Explorer or "GOCE", has spent more than four years mapping Earth’s gravity.  To accomplish this scientific task, GOCE has been orbiting Earth since March 2009 at the lowest altitude of any research satellite.

Dubbed the ‘Ferrari of space’ because of its sleek, aerodynamic design to minimize atmospheric drag, GOCE has mapped variations in Earth’s gravity with extreme detail.