Testing fundamental physics with satellite laser ranging: perspectives and goals of the Larase experiment

Passive laser-ranged satellites, launched for geodynamics and geophysics purposes, not only have contributed to significant measurements in space geodesy [1,2], but also provided an outstanding test bench to fundamental physics. Significant examples are represented by the measurement of the Lense-Thirring precession on the combined nodes of the two LAGEOS satellites [3], and by the measurement of the total relativistic precession of the argument of pericenter of LAGEOS II [4,5]. Indeed, the physical characteristics of such satellites and of their orbit, and the availability of high-quality tracking data provided by the International Laser Ranging Service (ILRS) [6], allow for precise tests of gravitational theories. The aim of LARASE (LAser RAnged Satellites Experiment) is to go a step further in the tests of the gravitational interaction in the field of Earth (i.e. in the weak-field and-slow motion (WFSM) limit of general relativity (GR)) by the joint analysis of the orbits of the two LAGEOS satellites and that of LARES [7]. To reach such a goal a key ingredient is to provide high-quality updated models for the perturbing non-gravitational forces acting on such satellites. A large amount of Satellite Laser Ranging (SLR) data of LAGEOS and LAGEOS II has been analyzed using a set of dedicated models for their dynamics, and the related post-fit residuals have been analyzed. A parallel work is ongoing for LARES that, due to its much lower altitude, is subject to larger gravitational and non-gravitational effects; the latter are in part mitigated by its much lower area-to-mass ratio. Recent work on the data analysis of the orbit of such satellites will be presented together with the development of some new refined model to account for the impact of the subtle non-gravitational perturbations.