Microscope—extreme stability requirements for femto-g measurements

Abstract

Microscope is a 200kg microsatellite which belongs to the CNES Myriad family. It is dedicated to a fundamental physics experiment. The satellite development is currently in Phase B. Launch is planned for 2011.The scientific objective of the mission is to test—for the first time in space—the equivalence principle (EP) with an accuracy 100 times better than that achieved in ground tests. The instruments developed by ONERA are composed of two differential electrostatic accelerometers operating at a finely stabilised temperature. Their resolution is as precise as 10-15g. Continuous measurements will be made over periods of weeks. Furthermore, the satellite motion and attitude are precisely controlled by a drag free system which uses 12 micro-thrusters developed by ESA.After summarising the basic principles behind the scientific measurements, this paper will present the mechanical and thermal architecture of the satellite, which exhibits significant modifications with respect to the standard Myriad design. The major specifications will be presented, and we will show how the spacecraft configuration has been designed to satisfy the payload interface requirements, particularly for mechanical stability, thermal insulation and micro-cracking avoidance. The performance validation test plan will be presented, with results of elementary tests already performed.Finally, we will briefly describe an original de-orbiting system which Microscope will carry in order to comply with the space debris code of conduct. It consists of a deployable wing made of light-weight aluminised kapton membrane, deployed by an inflatable mast, which will enhance the atmospheric drag of the satellite after the end of its mission.