Testing General Relativity and gravitational physics using the LARES satellite

TL;DR

The LARES satellite's initial observations strongly support General Relativity by closely matching predicted geodesic motion, enabling precise gravitational physics tests and improved Earth gravity measurements.

Contribution

This study demonstrates that LARES exhibits the smallest deviations from geodesic motion among satellites, providing a new tool for testing fundamental physics and Earth's gravity.

Findings

LARES's orbit aligns closely with General Relativity predictions.

LARES improves accuracy in Earth's gravitational field measurements.

LARES shows minimal non-gravitational perturbations.

Abstract

The discovery of the accelerating expansion of the Universe, thought to be driven by a mysterious form of `dark energy' constituting most of the Universe, has further revived the interest in testing Einstein's theory of General Relativity. At the very foundation of Einstein's theory is the geodesic motion of a small, structureless test-particle. Depending on the physical context, a star, planet or satellite can behave very nearly like a test-particle, so geodesic motion is used to calculate the advance of the perihelion of a planet's orbit, the dynamics of a binary pulsar system and of an Earth orbiting satellite. Verifying geodesic motion is then a test of paramount importance to General Relativity and other theories of fundamental physics. On the basis of the first few months of observations of the recently launched satellite LARES, its orbit shows the best agreement of any satellite with the test-particle motion predicted by General Relativity. That is, after modelling its known non-gravitational perturbations, the LARES orbit shows the smallest deviations from geodesic motion of any artificial satellite. LARES-type satellites can thus be used for accurate measurements and for tests of gravitational and fundamental physics. Already with only a few months of observation, LARES provides smaller scatter in the determination of several low-degree geopotential coefficients (Earth gravitational deviations from sphericity) than available from observations of any other satellite or combination of satellites.