GOCE

The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was the first of <a href="/facts/European_Space_Agency/L8YRNV0C">ESA</a>'s <a href="/facts/Living_Planet_Programme/7P8m6W3K">Living Planet Programme</a> <a href="/facts/Satellite/PTX8c68t">heavy satellites</a> intended to map in unprecedented detail the <a href="/facts/Earth%2527s_gravity_field/IXe9Bh8k">Earth's gravity field</a>. The spacecraft's primary instrumentation was a highly sensitive gravity <a href="/facts/Gravity_gradiometry/GJExevM4">gradiometer</a> consisting of three pairs of <a href="/facts/Accelerometer/xxrXzrlI">accelerometers</a> which measured gravitational gradients along three <a href="/facts/Orthogonal/JVIjYPog">orthogonal</a> axes.
Launched on 17 March 2009, GOCE mapped the deep structure of the Earth's <a href="/facts/Mantle_(geology)/RpDdtjCr">mantle</a> and probed hazardous volcanic regions. It brought new insight into ocean behaviour; this in particular, was a major driver for the mission. By combining the gravity data with information about <a href="/facts/Sea_surface_height/mEsQ4ERT">sea surface height</a> gathered by other satellite altimeters, scientists were able to track the direction and speed of <a href="/facts/Geostrophic_current/5DgWsEl4">geostrophic ocean currents</a>. The low orbit and high accuracy of the system greatly improved the known accuracy and spatial resolution of the <a href="/facts/Geoid/6aR04HQl">geoid</a> (the theoretical surface of equal gravitational potential on the Earth).
The satellite's unique arrow shape and <a href="/facts/Fins/H2Rjvfo3">fins</a> helped keep GOCE stable as it flew through the <a href="/facts/Thermosphere/uhG50e2V">thermosphere</a> at a <a href="/facts/Low_Earth_orbit/rq1TwayJ">comparatively low altitude</a> of 255 kilometres (158 mi). Additionally, an <a href="/facts/Ion_propulsion/cjt6M89p">ion propulsion</a> system continuously compensated for the variable deceleration due to air <a href="/facts/Drag_(physics)/vdl4jF7I">drag</a> without the vibration of a conventional chemically powered <a href="/facts/Rocket_engine/XT5gaFAb">rocket engine</a>, thus limiting the errors in gravity gradient measurements caused by non-gravitational forces and restoring the path of the craft as closely as possible to a purely <a href="/facts/Inertial/1U6TrdG3">inertial</a> trajectory.
After running out of propellant, the satellite began dropping out of orbit and made an uncontrolled re-entry on 11 November 2013.

GOCE open-in-new

GOCE