Mission Design for the Laser Astrometric Test Of Relativity

TL;DR

The LATOR mission aims to precisely measure light deflection near the Sun using laser interferometry between spacecraft and a space-based interferometer, testing general relativity with unprecedented accuracy.

Contribution

This paper presents a novel mission design employing a space-based optical interferometer on the ISS for high-precision tests of relativistic gravity.

Findings

Achieves measurement of the PPN parameter γ to 1 part in 10^8

Plans to measure solar quadrupole moment J2 with high precision

Will test effects like Lense-Thirring precession and non-linear gravity contributions

Abstract

This paper focuses on the mission design for the Laser Astrometric Test Of Relativity (LATOR). This mission uses laser interferometry between two micro-spacecraft whose lines of sight pass close by the Sun to accurately measure deflection of light in the solar gravity. The key element of the experimental design is a redundant geometry optical truss provided by a long-baseline (100 m) multi-channel stellar optical interferometer placed on the International Space Station (ISS). The spatial interferometer is used for measuring the angles between the two spacecraft and for orbit determination purposes. The geometric redundancy enables LATOR to measure the departure from Euclidean geometry caused by the solar gravity field to a very high accuracy. Such a design enables LATOR to improve the value of the parameterized post-Newtonian (PPN) parameter $\gamma$ to unprecedented levels of accuracy of 1 part in 10$^{8}$; the misison will also measure effects of the next post-Newtonian order ($\propto G^2$) of light deflection resulting from gravity's intrinsic non-linearity. The solar quadrupole moment parameter, $J_2$, will be measured with high precision, as well as a variety of other relativistic effects including Lense-Thirring precession. LATOR will lead to very robust advances in the tests of Fundamental physics: this mission could discover a violation or extension of general relativity, or reveal the presence of an additional long range interaction in the physical law.