The MICROSCOPE mission: first results of a space test of the Equivalence Principle

Abstract

According to the Weak Equivalence Principle, all bodies should fall at the same rate in a gravitational field. The MICROSCOPE satellite, launched in April 2016, aims to test its validity at the $10^{-15}$ precision level, by measuring the force required to maintain two test masses (of titanium and platinum alloys) exactly in the same orbit. A non-vanishing result would correspond to a violation of the Equivalence Principle, or to the discovery of a new long-range force. Analysis of the first data gives $\hat{I}´(\mathrm{Ti},\mathrm{Pt})=[-1\pm 9(\mathrm{stat})\pm 9(\mathrm{syst})]\times 10^{-15}$ (1$\ddot{I}ƒ$ statistical uncertainty) for the titanium-platinum Eötvös parameter characterizing the relative difference in their free-fall accelerations.

Typos corrected