www.esa.int ESA’s gravity mission GOCE The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) is an ESA satellite that was launched on March 17, 2009.[1] It is a satellite carrying a highly sensitive gravity gradiometer which detects fine density differences in the crust and oceans of the Earth. GOCE data will have many uses, probing hazardous volcanic regions and bringing new insight into ocean behaviour. The latter, in particular, is a major driver for the mission. By combining the gravity data with information about sea surface height gathered by other satellite altimeters, scientists will be able to track the direction and speed of geostrophic ocean currents. The low orbit and high accuracy of the system will greatly improve the known accuracy and spacial resolution of the geoid (the theoretical surface of equal gravitational potential on the Earth). The satellite’s arrow shape and fins help keep the GOCE stable as it flies through the wisps of air still present at an altitude of 260 km. In addition, an ion propulsion system will continuously compensate for the deceleration of air-drag without the vibration of a conventional chemically-powered rocket engine, thus restoring the path of the craft as closely as possible to a purely inertial trajectory. The craft’s primary instrument is three pairs of highly sensitive accelerometers which will measure gravitational gradients in three different axes. en.wikipedia.org
