Einstein's theory of general relativity (GR) represents the best theory we have at our disposal for the description of the gravitational interaction, both at the high and low energy scales, and it is the pillar of modern cosmology to understand the universe that we observe through a number of different techniques. Indeed, after 100 years, GR has passed a wide number of experimental verifications and it is currently considered the "Standard Model" for  gravitational physics.

The experiment denominated LARASE (LAser RAnged Satellites Experiment) represents a new experiment whose main goal is to provide accurate measurements for the gravitational interaction in the weak field and slow motion (WFSM) limit of GR by means of the laser tracking of satellites orbiting around the Earth. In fact, thanks to the very precise measurements provided by the powerful Satellite Laser Ranging (SLR) technique, down to a few mm in root-mean-square of the so-called Normal Points ― which represent the station-to-satellite distances averaged over a suitable (and short) time period ― we are able to reconstruct the orbital elements of each satellite with an accuracy of a few cm over weekly arcs.

Indeed, among the various ingredients needed two of them play a very significant role: i) the quality of the tracking observations of the orbit, and ii) the quality of the dynamical models. The dynamical models are implemented in a software code whose goal is to minimize, opportunely, an observable function and solve for the unknowns in which we are interested. These models have to account for both gravitational and non-gravitational forces in such a way to reduce as better as possible the difference between the observed range and the computed (from the models) one. Of course, the better the minimization process through the orbit data reduction from one side and the better the estimate of the systematic error sources from the other, more precise and accurate will be the a posteriori reconstruction of the satellite orbit.

The test masses of the LARASE experiment are spherical in shape and fully passive laser-ranged satellites with a generally low area/mass ratio in order to minimize the non-gravitational accelerations.

In this family, the two LAGEOS and the recently launched LARES will be the most important to consider because of the high accuracy of their orbit determination thanks to the very precise measurements of the SLR technique. The older LAGEOS (LAser GEOdynamic Satellite) was launched by NASA on May 4 1976, LAGEOS II was jointly launched by NASA and ASI on October 22 1992, finally LARES (LAser RElativity Satellite) was launched by ASI on February 13 2012.

Therefore, LARASE aims to improve the dynamical models of the current best laser-ranged satellites, as well as to improve the error budget estimates of the several perturbations, both  gravitational and non-gravitational, that influence their geodesic motion around the Earth.

This  will allow to test in a reliable way Einstein's theory of GR with respect to other metric and non-metric theories for the gravitational interaction and to go beyond with respect to the present measurements as well as to the kind of tests carried out so far.

LARASE is funded by the Italian National Institute for Nuclear Physics (INFN), Astroparticle Physics Experiments of National Scientific Committee 2 (CSN2). Leaded by David Lucchesi, it is carried out by IAPS/INAF, ISTI/CNR and University of Tor Vergata (Rome).