Goce

Gravity Field and Steady State Ocean Circulation Explorer

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General

Designation	34602 / 09013A
Launch date	17 Mar 2009
Country of origin	Europe
Mission	Scientific: Earth gravity field measurement
Perigee/Apogee	263 km, sun-synchronous
Inclination	96.7°
Period
Launch vehicle	Rokot #14

Initially planned for launch in 2005. Exploitation started on 23 Nov 2009.

The gravity gradiometer (main instrument) measures the terrestrial gravitational field thanks to a set of 6 ultra-sensitive capacitive sensors. The gradiometer is combined with a precise GPS instrument.

Part of ESA's Living Planet program.

Within 2 years, it successfully mapped the Earth's gravity.

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End of life

End of life	01 Oct 2012
Decay	11 Nov 2013

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External resources

http://www.esa.int/goce

sat-index articles

Technical data

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Specifications

Prime contractor	Alenia Spazio (Thales Alenia Space)
Platform	From Astrium
Mass at launch	1052 kg
Dry mass
Dimension
Solar array
Stabilization
DC power	EOL: 1300 W
Design lifetime	20 months

The main payload instrument is a state-of-the-art Electrostatic Gravity Gradiometer incorporating six highly sensitive accelerometers, mounted in pairs along three perpendicular axes on an ultra-stable carbon-carbon structure. The mission will measure not gravity itself but the tiny differences in gravity between the accelerometer pairs 50 cm apart.
The data collected will yield accuracy of 1 to 2 cm in the geoid altitude and 1 mGal for the detection of gravity-field anomalies (mountains, for instance, usually cause local gravitational variations ranging from tens of milligals to approximately one hundred). The spatial resolution will be improved from several hundreds or thousands of kilometres on previous missions to 100 km with GOCE.

The spacecraft incorporates two low-power xenon ion engines, one primary and one backup, each able to deliver 1 to 20 mN of thrust. These thrusters are used to make real-time compensation for atmospheric drag, based on the mean acceleration detected by the two accelerometers mounted along the velocity axis. The system actually works and enabled a drag-free flight.

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