Objectives of LARES satellite
I. Ciufolini ; A. Paolozzi ; G. Sindoni ; et al. ; - ASI Sponsor
Jan - 2009

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type: Conference Proceedings

Einstein general relativity states that mass and energy as well as mass currents produce spacetime curvature (F igure 1). In a recent paper [1] has indeed been verified that the Earth angular momentum produces an additional spacetime curvature. It is the Lense-Thirring (LT) effect that induces the node orbital motion of a laser ranged satellite. In the measurement presented in [1] the two LAGEOS satellites were used to confirm the LT effect with an accuracy of the order of 10\%. The node motion due to LT is very small and classical perturbations mask this effect by a factor of several millions times. However the accurate knowledge of the Earth gravitational field (improved GRACE models), the launch of a third laser ranged satellite (LARES) to be used together with the LAGEOS and LAGEOS 2, and a proper design of this new satellite will give the opportunity to measure LT effect with an accuracy of the order of 1\% . LARES was first presented as a response to a call for proposal issued by ASI in 1997 [2-4]. It is an evolution of the LAGEOS 3 proposal (1986)[5]. In February 2008 ASI signed a contract with Carlo Gavazzi Space to build the LARES system to be launched with the VEGA maiden flight in December 2009. 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 cancel out, providing a direct measurement of the Relativistic Lense-Thirring effect (if all the other perturbations are well modelled). The availability of the VEGA maiden flight was an opportunity to use an alternative approach. In fact, even if VEGA would have the capability to reach a 6000 km orbit with a lower payload weight, the flight envelope for qualification reaches only 1500 km. Now considering 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 foreseen orbit is now 1450 km altitude with an inclin ation of about 71 degrees and the three satellites are the two LAGEOS and LARES. In the paper it will be describ ed how to combine the orbital motion of the three laser ranged satellites to reach the main scientific objec tive of LARES mission and the status of the program with some details on: ground segment, launch system and space segment (LARES system).

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