Relativistic analysis of the LISA long range optical links

TL;DR

This paper provides a detailed relativistic analysis of the optical links in the LISA mission, focusing on accurately modeling light propagation and relativistic effects to improve gravitational wave detection.

Contribution

It systematically derives relativistic effects on light propagation between spacecraft in Schwarzschild spacetime, enhancing data processing accuracy for LISA.

Findings

Rigorous evaluation of the Sagnac effect.

Quantitative analysis of gravitational redshift.

Improved modeling of light delays in relativistic context.

Abstract

The joint ESA/NASA LISA mission consists in three spacecraft on heliocentric orbits, flying in a triangular formation of 5 Mkm each side, linked by infrared optical beams. The aim of the mission is to detect gravitational waves in a low frequency band. For properly processing the science data, the propagation delays between spacecraft must be accurately known. We thus analyse the propagation of light between spacecraft in order to systematically derive the relativistic effects due to the static curvature of the Schwarzschild spacetime in which the spacecraft are orbiting with time-varying light-distances. In particular, our analysis allows to evaluate rigorously the Sagnac effect, and the gravitational (Einstein) redshift.