ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) Mission

The Earth's gravity field is the fundamental physical force for every dynamic process on its surface. With the Gravity Field and steady-state Ocean Circulation Explorer (GOCE) Mission as its first Earth Explorer core mission, the European Space Agency (ESA) is playing an important role in this `geopotential decade' by preparing for acquisition of a high quality, high spatial resolution gravity field and geoid for future scientific applications. GOCE combines an innovative new three-axis gravity gradiometer (EGG) instrument (comprising three x, y, z pairs of accelerometers with a baseline separation of 0.5 m) with a drag-compensating ion-propulsion system to measure for the first time the full gravity gradient tensor along its orbit at 250 km altitude. GOCE will carry a GPS satellite-to-satellite tracking navigation system for 3-dimensional positioning, star trackers for precise pointing knowledge, and a laser retroreflector for ground laser tracking. GOCE is specifically designed to make accurate and precise measurements of the stationary gravity field and gravity anomalies (to 1 mGal) at high spatial resolution (100 km). The data will facilitate the computation of a high spatial resolution (100 km) global geoid model to 1-2 cm accuracy. Applications of these products will be illustrated using examples in oceanography, solid-earth physics and geodesy. After a successful completion of the design consolidation phase, the construction phase for the GOCE satellite is presently underway, with an anticipated a launch in late 2006.