Measuring the Relativistic Perigee Advance with Satellite Laser Ranging

The pericenter advance of a test body by a central mass is one of the classical tests of General Relativity. To day this effect is measured with radar ranging by the perihelion shift of Mercury and other planets, in the gravitational field of Sun, with a relative accuracy of the order of 10–10. In this paper we explore the possibility of a measurement of the pericenter advance in the gravitational field of Earth by analyzing the laser-ranged data of some orbiting, or proposed, laser-ranged geodetic satellites. Such a measurement of the perigee advance would place limits on hypothetical, very weak, Yukawa-type components of the gravitational interaction with a finite range of the order of 10 km. Thus, we show that, at the present level of knowledge of the orbital perturbations, the relative accuracy, achievable with suitably combined orbital elements of LAGEOS and LAGEOS II, is of the order of 10. With the corresponding measured value of 2+2γ−β 3 , by using η = 4β−γ−3 from Lunar Laser Ranging, we could get an estimate of the PPN parameters γ and β with an accuracy of the order of 10 − 10. Nevertheless, these accuracies would be substantially improved in the near future with the new Earth gravity field models by the CHAMP and GRACE missions. The use of the perigee of LARES (LAser RElativity Satellite), with a suitable combination of orbital residuals including also the node and the perigee of LAGEOS II, would also further improve the accuracy of the proposed measurement.