Engineering Challenges of LARES Satellite, Designed to Test the Dynamics of General Relativity

With the successful flight of VEGA launcher, a passive laser-ranged satellite for testing general relativity has been put in orbit in 2012. LARES is an Italian Space Agency satellite specifically designed and developed for testing frame dragging, an intriguing prediction of general relativity. The fabric of spacetime is warped by the rotation of a body, e.g. by the Earth rotation that drags space and time around it and consequently the orbital plane of a satellite. This last effect is called Lense-Thirring effect and the LARES mission is aimed to measure it with an accuracy of about 1%. The main problem to be solved, in order to reach this objective, is to reduce and to model the classical perturbations, acting on the satellite, at a level well below the Lense-Thirring effect. This has been achieved with the use of a constellation of three laser ranged satellites, a challenging design of the satellite, an optimal choice of the altitude and inclination of the orbit and with the use of the most accurate determinations of the gravitational field of Earth. The paper will describe the mission focusing on the engineering challenges encountered during the development of the program. In particular the extremely high density of the satellite was a concern for the first natural frequency of the satellite and supporting structure that must be higher than 70 Hz