LATOR Covariance Analysis

TL;DR

This paper analyzes the covariance of the proposed LATOR mission, demonstrating its potential to precisely measure gravitational parameters and test general relativity with high accuracy using laser interferometry in space.

Contribution

It provides a covariance study showing the expected measurement precisions of PPN parameters, solar quadrupole moment, and second-order post-PPN parameter for the LATOR mission.

Findings

Uncertainty in PPN parameter γ is 2.4 × 10⁻⁹.

Solar quadrupole moment J₂ can be measured to 6 × 10⁻⁹.

First measurement of second-order post-PPN parameter δ to about 10⁻³.

Abstract

We present results from a covariance study for the proposed Laser Astrometric Test of Relativity (LATOR) mission. This mission would send two laser-transmitter spacecraft behind the Sun and measure the relative gravitational light bending of their signals using a hundred-meter-baseline optical interferometer to be constructed on the International Space Station. We assume that each spacecraft is equipped with a $ < 1.9 \times 10^{-13} \mathrm{m} \mathrm{s}^2 \mathrm{Hz}^{-1/2} $ drag-free system and assume approximately one year of data. We conclude that the observations allow a simultaneous determination of the orbit parameters of the spacecraft and of the Parametrized Post-Newtonian (PPN) parameter $\gamma$ with an uncertainty of $2.4 \times 10^{-9}$. We also find a $6 \times 10^{-9}$ determination of the solar quadrupole moment, $J_2$, as well as the first measurement of the second-order post-PPN parameter $\delta$ to an accuracy of about $10^{-3}$.