[Source: ESA GOCE Home page, http://www.esa.int/esaLP/ESAYEK1VMOC_LPgoce_0.html
Launched on 17 March 2009, ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) was developed to ... bring about a whole new level of understanding of one of Earth's most fundamental forces of nature – the gravity field.
Dubbed the 'Formula 1' of satellites, this sleek high-tech gravity satellite embodies many firsts in its design and use of new technology in space to map Earth's gravity field in unprecedented detail. As the most advanced gravity space mission to date, GOCE will realise a broad range of fascinating new possibilities for oceanography, solid Earth physics, geodesy and sea-level research, and significantly contribute to furthering our understanding of climate change.
Although invisible, gravity is a complex force of nature that has an immeasurable impact on our everyday lives. It is often assumed that the force of gravity on the surface of the Earth has a constant value, but in fact the value of 'g' varies subtly from place to place. These variations are due to a number of factors such as the rotation of the Earth, the position of mountains and ocean trenches and variations in density of the Earth's interior.
Over its life of about 20 months, GOCE will map these global variations in the gravity field with extreme detail and accuracy. This will result in a unique model of the 'geoid', which is the surface of equal gravitational potential defined by the gravity field – crucial for deriving accurate measurements of ocean circulation and sea-level change, both of which are affected by climate change. GOCE-derived data are also much needed to understand more about processes occurring inside the Earth and for use in practical applications such as surveying and levelling.