GOCE's 5 × 1.1 m (16 × 4 ft) frame had fixed
solar panels covering its sun-facing side, which produced 1,300
watts of power.
[37] The panels were shaped to act as fins, stabilising the spacecraft while it orbited through the residual air in the
thermosphere.
The
ion propulsion electric engine, designed and built at
QinetiQ's space centre in Farnborough, England, ejected
xenon ions at velocities exceeding 40,000 m/s (140,000 km/h; 89,000 mph), which compensated for the orbital decay losses. GOCE's mission ended when the 40 kg (88 lb) xenon fuel tank emptied.
[7] The dual Kaufman-type ion thrusters could produce up to 20
millinewtons (0.0045 lbf) of thrust.
[38]
Although its predicted lifetime was 20 months, an ESA report in June 2010 suggested that unusually low solar activity (meaning a calmer upper atmosphere, and hence less drag on the craft) meant the fuel would last longer than its predicted 20 months—possibly into 2014. In reality, the end of mission was formally declared on 21 October 2013 after 55 months, with the final 11 months in a lower orbit (with greater air density and therefore greater fuel use).
[39]
