Testing General Relativity within Global Navigation Satellite Systems

The European GNSS satellites Galileo 5 and 6 in eccentric orbits have recently allowed us, as well as a second independent group, to perform a sensitive test of the general relativistic gravitational redshift. This was based on an analysis of approximately three years of orbit and clock data from the onboard Passive Hydrogen Masers of these satellites. In this talk we will discuss some of the refinements that we have meanwhile done on our modelling of systematic uncertainties of this test. For this we will also consider further data that has since been taken. In the light of these results we also discuss the perspectives for other tests of General Relativity within the framework of GNSS. A crucial element in this is the modelling of non-gravitational orbit perturbations. Here we will present the current status of our modelling efforts for these perturbations, based on a geometrical Finite Element Model of the Galileo satellites.