Entwicklung von Simulations- und Analysemethoden zur Modellierung von Störkräften im Rahmen der Satellitenmission MICROSCOPE

Abstract

In fundamental physics, a condition for the validity of the general theory of relativity is constantly being put to test: the weak equivalence principle. The satellite mission MICROSCOPE (MICRO-Satellite a trainee Compense pour la Observation du Principe da Equivalence) shall set a new milestone, aiming at a measurement result with an accuracy of 1e-15 and thus improving previous results by two orders of magnitude. The experiment is carried out with a differential accelerometer in which two test masses of different material are held on the same trajectory by means of electrostatic forces. Therefor the mass centres of these test masses, which are concentric hollow cylinders, must coincide. Any difference in the required forces would indicate a violation of the weak equivalence principle. The desired measurement accuracy places high demands both on the measuring instrument and on the satellite, which must ensure undisturbed environmental conditions for the experiment. In order to avoid material deformation, high temperature stability is required. In addition, the satellite should protect the experiment from external disturbing forces resulting from its interaction with environmental conditions in space. For this purpose, a special attitude control system is used, which compensates for these non-gravitational forces and thus ensures a purely gravitational trajectory. The MICROSCOPE data analysis is a very complex process, as a large number of possible error sources must be taken into account including the non- gravitational forces which act on the satellite. Their influence on the measurement result cannot be completely excluded. The modelling of these disturbing forces is a central topic of this work. For this purpose, a calculation method has been implemented that can take into account complex satellite geometries by decomposing the surface using finite elements. This method enables the assignment of different material properties and the affected area can be very well determined. The calculation of the disturbance forces requires the time-dependent calculation of the satellitea s orbit and attitude. For this purpose, a simulation tool is used, which was in part developed in the framework of this work. Furthermore an analysis tool that is used to process and analyse MICROSCOPE measurement data was designed. It is used in conjunction with the disturbance force simulation and analysis to support the evaluation process of the MICROSCOPE data. In addition, the analysis tool is used to validate simulation results.