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 Myriade line of product, weights 300 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.
To achieve this, two concentric cylindrical test masses made of different materials?one titanium and one a platinum-rhodium alloy?will be minutely controlled to maintain them motionless with respect to the satellite inside independent differential electrostatic accelerometers. If the equivalence principle is verified, the two masses will be subjected to the same control acceleration. If different accelerations have to be applied, the principle will be violated: an event that would shake the foundations of physics.
The experiment is flown on a 303 kg microsatellite – heavier than a usual 100-150 kg microsatellite – built around CNES?s Myriade bus and equipped with cold-gas microthrusters capable of compensating for the tiniest trajectory perturbations that might otherwise skew its results.
Some involved technologies shall prepare the participation of european team to the future more ambious EP experiment in space: STEP mission.
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