In orbit nano-g measurements, lessons for future space missions

Abstract

The electrostatic space accelerometers mounted on board the three satellites of the two last geodesy missions, CHAMP [C. Reiberg, CHAMP a challenging micro-satellite payload for geophysical research and application, GFZ Final Report, Potsdam, Germany, 1995] and GRACE [E. Davis, et al., The GRACE Mission: Meeting the Technical Challenges, 50th International Astronautical Congress, IAF-99-B.2.05 Conference, AAS 90-034, 1999], respectively launched in 2000 and 2002, take continuous and accurate measurements of the satellite drag acceleration. At the altitude between 400 and 500 km, this drag is induced by the residual atmosphere and the Sun and Earth radiation pressures. With a resolution up to several pico-g, these data provide also a good survey of the satellite vibration behaviour and of the operation of the attitude and orbit control. Beside the scientific interest of both missions with the fine and global recovery of the Earth's gravity field, the analysis of the collected acceleration data is very interesting for the future space missions like GOCE [ESA, Gravity Field and Steady-State Ocean Circulation Mission, ESA SP-1233(1), Report for mission selection of the four candidate earth explorer missions, European Space Agency, 1999, p. 217], MICROSCOPE [P. Touboul, et al., C. R. Acad. Sci. Ser. IV 2 (9) (2001) 1271–1286] or LISA [LISA Study Team, LISA Laser Interferometer Space Antenna: a Cornerstone Mission for the Observation of Gravitational Waves, ESA-SCI(2000)11, European Space Agency, 2000] which envisage much more accurate acceleration measurements. The definitions of these missions and others in the domain of fundamental physics and solid Earth are all based on drag-free satellites and similar electrostatic inertial sensors. Benefits of the previous results are presented in parallel to the status of these developments.