Space test of the equivalence principle: First results of the MICROSCOPE mission

Pierre Touboul, Gilles Métris, Valerio Cipolla, Thibault Damour, Pascale Danto, Pierre Yves Guidotti, Emilie Hardy, Alain Robert, Pieter Visser, More Authors

Research output: Contribution to journalArticleScientificpeer-review

18 Citations (Scopus)


The weak equivalence principle (WEP), stating that two bodies of different compositions and/or mass fall at the same rate in a gravitational field (universality of free fall), is at the very foundation of general relativity. The MICROSCOPE mission aims to test its validity to a precision of 10-15, two orders of magnitude better than current on-ground tests, by using two masses of different compositions (titanium and platinum alloys) on a quasi-circular trajectory around the Earth. This is realised by measuring the accelerations inferred from the forces required to maintain the two masses exactly in the same orbit. Any significant difference between the measured accelerations, occurring at a defined frequency, would correspond to the detection of a violation of the WEP, or to the discovery of a tiny new type of force added to gravity. MICROSCOPE's first results show no hint for such a difference, expressed in terms of Eötvös parameter (both 1 uncertainties) for a titanium and platinum pair of materials. This result was obtained on a session with 120 orbital revolutions representing 7% of the current available data acquired during the whole mission. The quadratic combination of 1 uncertainties leads to a current limit on of about.

Original languageEnglish
Article number225006
Number of pages34
JournalClassical and Quantum Gravity
Issue number22
Publication statusPublished - 18 Oct 2019


  • drag-free
  • equivalence principle
  • experimental gravitation
  • general relativity
  • microsatellite
  • space accelerometers


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