Orbital Tests of Relativistic Gravity using Artificial Satellites

TL;DR

This paper explores the potential of using advanced satellite orbital data to test relativistic gravity theories and measure possible deviations from general relativity with high precision.

Contribution

It proposes that future satellite missions with drag-free technology could significantly improve tests of relativistic gravity and the variability of Newton's constant.

Findings

Potential to measure (beta - 1) and (gamma - 1) at 10^-4 level

Can probe the time variation of G at 10^-13 yr^-1

Suggests dedicated drag-free satellite missions for optimal results

Abstract

We reexamine non-Einsteinian effects observable in the orbital motion of low-orbit artificial Earth satellites. The motivations for doing so are twofold: (i) recent theoretical studies suggest that the correct theory of gravity might contain a scalar contribution which has been reduced to a small value by the effect of the cosmological expansion; (ii) presently developed space technologies should soon give access to a new generation of satellites endowed with drag-free systems and tracked in three dimensions at the centimeter level. Our analysis suggests that such data could measure two independent combinations of the Eddington parameters (beta - 1) and (gamma - 1) at the 10^-4 level and probe the time variability of Newton's "constant" at the d(ln G)/dt ~ 10^-13 yr^-1 level. These tests would provide well-needed complements to the results of the Lunar Laser Ranging experiment, and of the presently planned experiments aiming at measuring (gamma -1). In view of the strong demands they make on the level of non- gravitational perturbations, these tests might require a dedicated mission consisting of an optimized passive drag-free satellite.