AMONG SPACE FUNDAMENTAL PHYSICS MISSIONS, MICROSCOPE, A SIMPLE CHALLENGING FREE FALL TEST

Description

Several space tests of gravity laws have already been performed but the MICROSCOPE mission is the first one to be fully dedicated to the test of the Equivalence Principle. The dedicated payload is now under qualification and the rather large micro satellite will be produced by Cnes for a launch at beginning of 2015. Each of the two differential accelerometers of the experimental device includes a pair of test-masses whose 720 km altitude orbital motions are constrained along the same purely gravitational trajectory. Evidence of an EP violation is provided by the comparison of the electrostatic configurations needed to maintain the two masses composed of different materials motionless relative to each other. Not only the servo-loop electronics must exhibit very weak level of noise but the geometrical and electrical configuration of the instruments must be very well optimised, accurate, cleaned and steady. Although the accelerometers are saturated on ground by normal gravity, they can be tested on board a free fall capsule in drop tower. These tests complete the fine verification of all mechanical and electrical functions. In addition, the present in flight results of the GOCE mission accelerometers are deeply analysed. Because the sensors of the gravity gradiometer exploits the same technologies, they provide confirmation of the MICROSCOPE instrument models used to extrapolate the in orbit performance and then estimate the expected mission accuracy.

Abstract

International audience

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