Accelerometers for CHAMP, GRACE and GOCE space missions: synergy and evolution

The STAR ultra-sensitive space acceierometer, based on the accurate electrostatic levitation of a parallelepiped proof-mass, is integrated at the center of the mass of the CHAMP satellite to be launched in 1999. STAR will perform the measurement of the non-gravitational accelerations which perturb the low-altitude orbit to be finely determined from the on-board GPS receiver, aiming at the recovery of the Earth’ s gravity field. The operation, design and technology of the accelerometer are well suited foro ptimization of the measurements provided for different mission performance requirements and environments. The Super-STAR instrument is designed keeping in view the two GRACE satellites, with a reduced fu11-scale range, and a resolution ten times better, leading to 10-10 ms-2 over an 1 Hz bandwidth. The launching of the GRACE satellites is scheduled for 2001 and the GOCE project is a good candidate for a follow-on mission. The GOCE’ s on-board gradiometer can be composed of a very stable carbon-carbon structure with similar electrostatic accelerometers : taking advantage of the fine active thermal control of the instrument case and of the drag-free compensation system of the satellite, a few 10-3 Eötvös can be reached at an altitude as low as 250 km.