riassunto2

Speaker_	Lucchesi, David M.
Co-autors	Peron Roberto
Talk_	LAGEOS satellites pericenter: a tool to constrain a Yukawa interaction in Earth’s field
Abstract_	The deviations from the usual 1/r law for the gravitational potential, as in the hypothesis of a fifth–force of nature, would lead to new weak interactions between macroscopic objects. Very significantly, these supplementary interactions may be either consistent with Einstein Equivalence Principle (EEP) or not. The characteristic of such very weak interactions, which are predicted by several theories, is to produce deviations for masses separations ranging through several orders of magnitude, starting from the sub–millimeter level up to the astronomical scale. These interactions are usually described through a Yukawa–like potential with strength \alpha and range \lambda. Among the several techniques useful for the search of this additional physics at the various scales, the accurate measurements of the pericenter shift of a binary system may be used to test for a New–Long–Range–Interaction (NLRI) with a characteristic range comparable with the system semimajor axis. The LAGEOS satellites, thanks to the very accurate determination of their orbit by the Satellite Laser Ranging (SLR) technique (with a precision of a few mm in the so–called normal points), could be considered the best candidates for the study of a possible NLRI with a characteristic range close to the Earth radius. We focus on the constrain we can obtain today for a possible Yukawa interaction from the accurate analysis of the argument of pericenter of the two LAGEOS satellites. We consider, in order to estimate a reliable error budget, the impact of the main systematic errors due to the gravitational and non–gravitational perturbations. In particular, with regard to the gravitational perturbations, we analysed the most recent gravity field models from CHAMP and GRACE space missions. Indeed, thanks to these dedicated missions, the systematic errors from Earth’s gravitational field uncertainties have been strongly reduced with respect to the previous multi–satellite models. Therefore, only the subtle effects of the non–gravitational perturbations will be effective in biasing the measurement of the strength \alpha of a possible Yukawa–like interaction with respect to the 10^(-11) value that can be in principle constrained with an accurate analysis of LAGEOS satellites orbit.