The MICROSCOPE experiment, ready for the in-orbit test of the equivalence principle

Abstract

Deviations from standard general relativity are being intensively tested in various aspects. The MICROSCOPE space mission, which has recently been approved to be launched in 2016, aims at testing the universality of free fall with an accuracy better than 10 −15. The instrument has been developed and most of the subsystems have been tested to the level required for the detection of accelerations lower than one tenth of a femto-g. Two concentric test masses are electrostatically levitated inside the same silica structure and controlled on the same trajectory at better than 0.1Å. Any dissymmetry in the measured electrostatic pressures shall be analysed with respect to the Earth's gravity field. The nearly 300 kg heavy dedicated satellite is defined to provide a very steady environment to the experiment and a fine control of its attitude and of its drag-free motion along the orbit. Both the evaluations of the performance of the instrument and the satellite demonstrate the expected test accuracy. The detailed description of the experiment and the major driving parameters of the instrument, the satellite and the data processing are provided in this paper.

The ACES/PHARAO space mission

“…In scenarios like the runaway Dilaton model of Damour, Piazza, and Veneziano [45], fundamental physical constants, such as the fine structure constant or the electron to proton mass ratio, are no longer "constant", but evolve with time, and the Einstein Equivalence Principle is violated at some level. Therefore, precision tests of the gravitational redshift and the search for a possible drift of fundamental constants, as planned in the ACES mission, and Equivalence Principle tests, as planned in the MICROSCOPE mission [46] and STE-QUEST [44], will either set new, tighter constraints on these new particles and their coupling to matter, or uncover new physical effects. The quest for more and more precise tests of the fundamental laws of physics remains a fascinating goal!…”

Testing the Equivalence Principle in space with MICROSCOPE: the data analysis challenge

“…MICROSCOPE (Touboul 2009, Touboul et al 2012) is a drag-free microsatellite which aims to test the WEP by comparing the acceleration experienced by two free-falling test masses in the Earth gravity field. It embarks two ultrasensitive electrostatic differential accelerometers.…”

MICROSCOPE – fabricating test masses for an in‐orbit test of the equivalence principle

“…1. Proposed by the Observatoire de la Cote d'Azur and ONERA [3] in the frame of the CNES Myriad microsatellite programme, MICROSCOPE takes advantage of the best technologies currently available to perform the WEP test in space with an accuracy of at least 10 −15 [4]. Performing the WEP test in space allows limiting all gravitational disturbances due to seismic noise or human activity.…”