Measurements of general relativity precessions in the field of the Earth with laser-ranged satellites and the LARASE program

Abstract

The LAser Ranged Satellites Experiment (LARASE) is a new experiment whose main purpose is to provide precise and accurate measurements of gravitation in the weak-field and slow-motion (WFSM) limit of Einstein's theory of general relativity by means of a very precise laser tracking of geodetic satellites in orbit around the Earth. Beside the good quality of the tracking observations of the satellites orbit, guaranteed by the powerful Satellite Laser Ranging (SLR) technique of the International Laser Ranging Service (ILRS), also the quality of the dynamical models implemented in a software code plays a fundamental role in order to obtain precise and accurate measurements of relativistic physics. The models have to account for the perturbations provoked by both gravitational and non-gravitational perturbations in such a way to reduce as well as possible the difference between the observed range, from the tracking, and the computed one, from the models. In particular, LARASE is an experiment that aims to improve the dynamical models of the present best laser-ranged satellites in order to perform a precise and accurate orbit determination. This represents a first step towards new refined tests and measurements of GR in the field of the Earth. After a brief presentation of the main relativistic measurements which constitute the main goals of LARASE, the results obtained during last year will be discussed in terms of the improvements reached in the satellites orbit modelling and in their precise orbit determination.