The GOCE satellite, developed by an industrial consortium of 45 companies distributed over 13 European countries, embodies many world-firsts in its design and use of new technology in space to map Earth’s gravity field in unprecedented detail.

In order to achieve its very challenging mission objectives, the slender, five-metre long satellite is designed to orbit at a very low altitude of just 260 km because the gravitational variations are stronger closer to Earth.

To measure gravity, there can be no disturbances from moving parts so the entire spacecraft is actually one extremely sensitive measuring device. It is the first space mission to employ ‘gradiometry’ – the measurement of gravitational differences between an ensemble of test masses inside the satellite.

Sunny side of GOCE

The octagonal, 1100-kg satellite with a cross-sectional area of only 1m² is configured to keep aerodynamic drag and torque to an absolute minimum. GOCE is symmetrical about its flight direction and two winglets provide additional aerodynamic stability.

While the sleek aerodynamic design helps GOCE cut though what remains of the atmosphere at its exceptionally low altitude, an electric ion thruster at the back continuously generates tiny forces to compensate for any drag the satellite experiences.

In orbit, the same side of the satellite always faces the Sun. This side carries four body-mounted and two wing-mounted solar panels capable of tolerating temperatures as high as 160C and as low as –170C.

Solar-panel inspection

The internal equipment is protected against the high temperatures by multi-layer insulation blankets positioned between the solar panels and the main body of the satellite. The cold side that faces away from the Sun is used extensively as a radiator to dissipate heat into space.

The solar panels provide the necessary power for the satellite. At times when the solar array is not illuminated by the Sun, a lithium-ion battery delivers the power required.

An S-band communication antenna is mounted on each wing. One faces upwards and one downwards so that full spherical coverage is achieved in order to measure the spacecraft's position more accurately.