Microscope: A Microsatellite for Equivalence Principle Measurement in Space

The MICROSCOPE mission is developed in the frame of the CNES Myriade micro satellite family. The project is currently ending its Phase B, the Preliminary Design Review has been held in March 2011 and the launch is planned in 2015. The scientific objective of the mission consists in a test of the Equivalence Principle (EP) between gravitational mass and inertial mass with a relative accuracy of 10-15; the payload is composed of a set of two 6-axis differential accelerometers developed by ONERA. To achieve this goal, a drag free control of the satellite has to be achieved in order to limit the non-gravitational accelerations on the payload below 3.10-10 ms-2*Hz-1/2. This paper begins with a introduction of the mission and the payload, explaining how mission requirements and payload I/F strongly constrain the design of spacecraft (drag free, microperturbation and stability). The functional chains of the satellite are presented in detail with an emphasis on mechanical and thermal architecture, Acceleration and Attitude Control System (AACS) and Cold Gas Propulsion System (CGPS). It is shown how the design of the satellite is optimized, melting new advanced technology (Payload, AACS, CGPS) and low cost, well proven methods and equipment of Myriade family.