Scientific Aspects of LARES mission

LARES was first presented as a response to a call for proposal issued by ASI in 1997. It is an evolution of the LAGEOS 3 proposal (1986). In February 2008 ASI provided financial support to build the LARES system that will be launched with the VEGA maiden flight in year 2010. Altitude at 6000 km with an inclination of 70 degrees (supplementary to LAGEOS I satellite) was the original proposal. With this orbit, the contribution of all the even zonal harmonics of the Earth gravitational field to the node motion of the orbit of the satellite would have been cancelled out, providing a direct measurement of the Relativistic Lense-Thirring effect (provided that all the other perturbations are well modeled). The availability of the VEGA maiden flight was an opportunity to use an alternative approach. In fact, the compromise between the scientific objectives and the launch vehicle objectives in its qualification flight was selected of a circular orbit with an altitude of 1450 km and inclination of 71 degrees. Taking into consideration that the major source of error, in the experiment, is given by the first two even zonal harmonics it is possible to combine the orbital motion of three laser ranged satellites to eliminate the uncertainties induced by those two harmonics: The candidates are the two LAGEOS and LARES. In this paper there will be described the status of the program with some details on both scientific objectives and engineering aspects: ground segment, launch system and space segment (LARES system).