To map in detail the Earth's gravity field from a satellite orbit, GOCE’s primary instrumentation was a highly sensitive gravity gradiometer consisting of three pairs of accelerometers which measured gravitational gradients along three orthogonal axes. And doing this with an unprecedented accuracy of 10^-5 m·s^-2 (1 mGal), GOCE was able to determine the geoid (the theoretical surface of equal gravitational potential on the Earth) with an accuracy of 1 to 2 cm! Among the main goals of the project are: (1) a better understanding of the physics of the Earth's interior to gain new insights into the geodynamics associated with the lithosphere, mantle composition and rheology, uplift and subduction processes; (2) a better understanding of the ocean currents and heat transport; (3) a global height-reference system, which can serve as a reference surface for the study of topographic processes and sea-level change; (4) better estimates of the thickness of polar ice-sheets and their movement.