14 FEB. 2008
publication date
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Full name: Gravity field and steady-state Ocean Circulation Explorer
Launched: 17 March 2009 from the Plesetsk Cosmodrome, Russia
Duration: After 4 years and 8 months orbiting Earth, the mission came to an end on 11 November 2013, far exceeding its 20-month design life
Mission control: European Space Operations Centre (ESOC), Darmstadt, Germany
Data download: Kiruna (Sweden) and Svalbard (Norway) ground stations
Processing & archiving: ESA’s Earth observation centre in Italy (ESRIN) and the distributed High-level Processing Facilities
Number of instruments: 3
Mission cost: €350 million (including launcher and operations)
Orbit: about 260 km altitude, polar, Sun-synchronous
Mass: 1100 kg
Size: 5.3 m long, about 1 m body diameter
Propulsion tank: 40 kg of xenon
Mission objectives
– to determine gravity-field anomalies with an accuracy of 1 mGal (where 1mGal = 10–5 ms–2).
– to determine the geoid with an accuracy of 1-2 cm.
– to achieve the above at a spatial resolution better than 100 km.
Geoid accuracy: 1 - 2 cm vertically with 100 km spatial resolution
Gravitational acceleration at Earth’s surface is about 9.8 m/s², varying from a minimum of 9.788 m/s² at the equator to a maximum of 9.838 m/s² at the poles.
The six accelerometers (three pairs in three orthogonal directions) are some 100 times more sensitive than any previously flown in space.
Industrial Core Team
Thales Alenia Space (Italy) – satellite prime contractor
EADS Astrium GmbH (Germany) – platform contractor
Thales Alenia Space (France) – gradiometer
ONERA (France) accelerometer & system support
The Core Team led a consortium of 41 companies distributed over 13 European countries.
Technical details:
Satellite | |
|---|---|
Configuration | Minimum cross-section in the direction of motion (1.1 m2) Approx. 9 m2 solar array aligned in the orbit plane 1050 kg launch mass |
Structure | Several carbon fibre, reinforced plastic structural compartments; load-carrying external structure Structural dynamics: 110 Hz axial, 18 Hz lateral |
Thermal control | Passive with heaters High-thermal-stability gradiometer compartment (10 mK @ 5 mHz) |
Electrical power | 24-32 Vdc unregulated bus; protected and redundant lines Fixed Gallium Arsenide (GaAs) cell solar array, 1300 W Lithium Ion (Li-Ion) battery, 78 Ah, made of 52 strings with 8 cells each |
Attitude control | Nadir pointing Only magnetorquers for attitude control Wide-field star trackers hybridised with gradiometer angular acceleration measurement Coarse Sun sensors and magnetometer for acquisition and safe mode AOCS/DFACS application software run in central computer |
Drag control | Ion thrusters commanded in closed loop, based on gradiometer common-mode acceleration measurements |
Reaction Control System (RCS) | 20 mN Kaufman-type ion thrusters (2x) |
Data handling | Packet telemetry Flexible and reallocatable packet sizes High-rate (10 Hz) gradiometer-to-computer link via 1553 bus for drag control command synthesis |
Telemetry and Command | |
|---|---|
RF | S-band up- and down-link and ranging 2 hemispherical antennas on solar array edges |
Telecommand | 4 Kbits/s |
Telemetry | Up to 1.2 Mbps |
Media modal
Kiruna station
The Kiruna S- and X-band station supports 18 satellites, including many of ESA's flagship missions such as Aeolus, CryoSat, Integral, the Swarm trio, the Sentinel series of Earth Observation spacecraft, Cluster and CHEOPS. The station will also support SEOSAT and Sentinel-6A through their crucial Launch and Early Orbit phase. For the Estrack network, Kiruna hosts one 15- and one 13-m antenna. Both operate in S-band for uplink and downlink and X-band for downlink. The station is located at Salmijärvi, 38 km east of Kiruna, in northern Sweden.
ESOC
The European Space Operations
Centre in Darmstadt, Germany, is
where we control our missions and
build the systems on the ground
that manage our fleet of spacecraft
in orbit.
ESRIN
The European Space Research
Institute in Frascati, Italy, is
ESA’s centre for Earth observation
and home to the Vega space
transportation programme.
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