MICROSCOPE

The MICROSCOPE (Microsatellite à traînée Compensée pour l’Observation du Principe d’Equivalence) mission has been selected at end of 1999 by the French space agency Cnes for a launch scheduled for late 2004. The MICROSCOPE satellite developed by CNES within its new line of product, weights 140 kg and is compatible with a low cost launch like ASAP Ariane-5.

The scientific objective of the mission is the test of the Equivalence Principle (EP) up to an accuracy of 10-15 with its well known manifestation, the universality of free fall. This principle, at the origin of general relativity, is only consolidated by experimental results and presently with an accuracy of several 10-13.

Some involved technologies shall prepare the participation of european team to the future more ambious EP experiment in space : STEP mission.

The satellite is rather compact with no deployable solar panel to insure a high rigidity : any mass motion on board is avoided and no momentum wheel is used during the experiment operation. A peculiar attention is paid for the thermo-elastic behaviour of the satellite, the structure of which is realised with aluminium honeycomb and plates. The three solar panels will be mounted on three faces of the bus. High efficiency AsGa solar cells will be used in order to obtain available power of 80 W, equally shared for the payload, the electrical propulsion and the satellite module. Moreover, to limit magnetic disturbances due to test-mass susceptibility, the magnetic moments on-board the satellite shall be limited and steady, variations less than 0.1 Am2 in the EP frequency vicinity and at 30cm from the instrument are specified. This concerns particularly the magneto-torquers or the batteries.