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GOCE

The primary objective of the GOCE mission was to provide global and regional models of the Earth's gravity field and the geoid, its reference equipotential surface, with high spatial resolution and accuracy.

Launch: 17 March 2009 (Rockot, from Plesetsk Cosmodrome in north-western Russia)

End: 21 October 2013 (re-entry occurred on 11 November 2013)

Mission Duration: 1700 days - 20 months nominal mission, >30 months extended mission.

On-board sensors
EGG Electrostatic Gravity Gradiometer Provided gravity gradients in the gradiometer reference frame
SSTI Satellite-to-Satellite Tracking Instrument Provided GPS observations of the GOCE orbit
LRR Laser Retro-Reflector Passive optical reflector; enabled satellite laser ranging by ground-based stations

Configuration: Octagonal structure with fixed solar wings, 5.3 m long, cross-section of 0.8 m2; winglets for aerodynamic stabilisation; ultra-stable CFRP structure, EGG instrument structure in carbon-carbon; no moving parts; modulated ion propulsion system for along-track drag-free control; drag sensing done by EGG instrument; attitude sensing in drag-free mode by star trackers and EGG instrument; attitude actuation by magnetic torquers; 8 days full autonomy.

Stabilisation: 3-axis stabilised; controlled to local orbit reference frame.

Mass: 1150 kg Beginning of Life, including 41 kg Xenon and 12 kg Nitrogen.

System budgets
Power GaAs triple junction cells with maximum power point tracker, 1600 W EOL; battery 78 Ah
TM-band S-band @100 Mbit/s
TC-band S-band @4 Mbit/s
On-board storage 4 Gbit solid state recorder; up to 72h of data

Mission orbit: Sun-synchronous; 96.7 deg inclination; mean altitude approximately 263 km; orbit period 90 min; mean local solar time at ascending node 18:00 hrs.

Ground stations: Kiruna 15 m (single station mission baseline); Svalbard.

Mission operations: Flight operations from ESOC; satellite maintenance from ESTEC; payload data ground processing at ESRIN; distributed higher level data processing by scientific consortium; data dissemination from ESRIN; user services from ESRIN.