15 May 2023
The main purpose of the MICROSCOPE satellite, launched in April 2016, was to test the validity of the Weak Equivalence Principle (WEP) in space. According to this principle, all bodies should fall in the same way in a gravitational field. The final results of the mission gave an accuracy of about 3 x 10^-15 [1]. This earth orbiting satellite contains as main instrument 2 concentric cylindrical test masses of different composition (Pt and Ti) whose relative acceleration is measured.
In the analysis [1], the bodies can fall with a different acceleration but keeping an identical direction of fall according to the direction of the gravity field. Other models of deflection at WEP are possible. One of them is the Standard Model Extension (SME). In the SME, the isotropy of space is broken by oriented fields that bathe the universe. 2 bodies of different composition can then fall in a different direction that is not necessarily that of the gravitational field [2]. This model contains many parameters, which can be experimentally constrained by quantifying the associated physical effects. This search is usually done by searching for periodic daily and annual deviation signals.
A first analysis of the MICROSCOPE mission data for an SME test has been performed at SYRTE during the thesis of Hélène Pihan-Le Bars. A functional analysis software, written in Python, has been developed and tested for the standard WEP test, as well as for the SME test. For the standard WEP test, our analysis pipeline has validated the results obtained by the consortium. The values obtained are consistent with the results of [1], which allows us to validate the different data analyses. For the SME test, the analysis of part of the Microscope data allowed us to obtain an improvement of up to 3 orders of magnitude compared to the state of the art [2].
We now wish to continue this analysis using the whole mission data set that is now available and to develop a finer statistical approach that would take into account more precisely the numerous slippages in the data.
Contacts: Aurelien Hees, Peter Wolf, Christine Guerlin
Footnotes
[1] P. Touboul et al, MICROSCOPE Mission: Final Results of the Test of the Equivalence Principle, Phys. Rev. Letters 129, 121102, 2022
[2] H. Pihan-Le Bars, et al, New Test of Lorentz Invariance Using the MICROSCOPE Space Mission, Phys. Rev. Letters 123, 231102, 2019