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The MICROSCOPE mission was designed to test the weak equivalence principle (WEP), stating the equality between the inertial and the gravitational masses, with a precision of 10^{-15} in terms of the Eötvös ratio η. Its experimental test consisted of comparing the accelerations undergone by two collocated test masses of different compositions as they orbited the Earth, by measuring the electrostatic forces required to keep them in equilibrium. This was done with ultrasensitive differential electrostatic accelerometers onboard a drag-free satellite. The mission lasted two and a half years, cumulating five months worth of science free-fall data, two-thirds with a pair of test masses of different compositions-titanium and platinum alloys-and the last third with a reference pair of test masses of the same composition-platinum. We summarize the data analysis, with an emphasis on the characterization of the systematic uncertainties due to thermal instabilities and on the correction of short-lived events which could mimic a WEP violation signal. We found no violation of the WEP, with the Eötvös parameter of the titanium and platinum pair constrained to η(Ti,Pt)=[-1.5±2.3(stat)±1.5(syst)]×10^{-15} at 1σ in statistical errors.

International audience; The MICROSCOPE space mission aims at testing the Equivalence Principle with an accuracy of 1E-15. It will test for the first time in space this founding principle of General Relativity. Whether it confirms or not the Equivalence Principle, it will bring a major constrain on new theories aiming to unify Gravity to Quantum Physics.The payload developed by ONERA is composed of two double inertial sensors giving full 6-axis measurements to be processed with on board GPS and star-trackers collected data. The on ground data processing takes into account the fine datation of the measurement pick up and the position of the satellite along its orbit to correct for the effect of the Earth’s gravity gradient in the difference of the acceleration of two bodies in free-fall. Once corrected the data will be analyzed to extract a possible signal of violation which is proportional to the Earth’s gravity field.In April 2016, the MICROSCOPE satellite will be launched from Kourou, French Guyana. At the time of the presentation, only the flight commissioning phase will be undergone comprising the health check of the instrument. This first step, decisive for the mission success, will be presented.

International audience; The objective of the activity done by MECANO ID for the GRACE FO program was to perform the mechanical sizing of the electrostatic accelerometer developed and manufactured by ONERA (The French Aerospace Lab) and in particular the plates of its core, made of ULE glass (Ultra Low Expansion glass: a titanium silicate glass).This document describes the methodology employed and the results obtained to achieve this purpose.