Satellite to crash down on Earth in two weeks

21 October 2013
By Tereza Pultarova
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ESA's gravity monitoring GOCE satellite has run out of fuel and will enter the Earth's atmosphere in about two weeks

ESA's gravity monitoring GOCE satellite has run out of fuel and will enter the Earth's atmosphere in about two weeks

Europe’s gravity monitoring satellite GOCE has run out of fuel today, starting to slip slowly from its 224km orbit and will re-enter the Earth’s atmosphere in two weeks with parts of the 1,100kg spacecraft probably hitting the ground.

While most of the satellite will burn during the fall through the atmosphere, its fuel tanks and magnetotorquers are the most likely to survive. According to the European Space Agency (ESA), who operates the spacecraft, the location of the impact of these parts is not known at this moment but the team will try to narrow the affected area as the re-entry approaches.

Data acquisition and satellite operations will continue for about two more weeks until GOCE’s systems stop working because of the harsh environmental conditions at such a low altitude. At this point, the satellite will be switched off, marking the end of activities for the GOCE flight control team.

An international campaign is 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 periodically issue re-entry predictions.

Having been launched in 2009, the GOCE satellite has been orbiting the Earth at an unprecedentedly low altitude, enabling it to measure tiny variations in the Earth’s gravity.

Equipped with a unique 3D measuring instrument – a gradiometer – the satellite has enabled scientists to create a unique model of the ‘geoid’, which is essentially the shape of an ideal global ocean at rest and therefore critical for accurate measurements of ocean circulation and sea-level change. 

GOCE has provided dynamic topography and circulation patterns of the oceans with unprecedented quality and resolution, improving the understanding of the dynamics of the world's oceans.

Scientists further exploited GOCE’s data to create the first global high-resolution map of the boundary between Earth’s crust and mantle – called the Moho.

The satellite also became the first seismometer in orbit when it detected sound waves from the massive earthquake that hit Japan on 11 March 2011.

Although the planned mission was completed in April 2011, the fuel consumption was much lower than anticipated because of the low solar activity, enabling ESA to extend GOCE’s life.

In August 2012, the control team began to lower the satellite’s orbit – from about 255 km to 224 km. Dubbed ‘GOCE’s second mission’, the lower orbit increased the accuracy and resolution of GOCE’s measurements, improving the view of smaller ocean features such as eddy currents.

“This innovative mission has been a challenge for the entire team involved: from building the first gradiometer for space to maintaining such a low orbit in constant free-fall, to lowering the orbit even further,” said Volker Liebig, ESA’s Director of Earth Observation Programmes.

“The outcome is fantastic. We have obtained the most accurate gravity data ever available to scientists. This alone proves that GOCE was worth the effort – and new scientific results are emerging constantly.”

GOCE will now join a group of satellites that have re-entered the Earth’s atmosphere in an uncontrolled manner, stirring up the attention of media, the expert community and the general public.

In 2011, parts of NASA's Upper Atmosphere Research Satellite (UARS) and the German Röntgensatellit ROSAT satellite came crashing down on the Earth’s surface, followed in 2012 by the failed Russian Phobos-Grunt mission.

As in previous cases, the debris is mostly likely to land in the ocean, which covers by far the largest area of the Earth’s surface.

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