Tilt-to-length coupling in the grace follow-on laser ranging interferometer

Abstract

The Laser Ranging Interferometer onboard the Gravity Recovery and Climate Experiment Follow-On satellites is the first laser interferometer in space measuring satellite-to-satellite distance variations. One of its main noise sources at low frequencies is the so-called tilt-to-length coupling, caused by satellite pointing variations. This error is estimated by fitting a linear coupling model, making use of the so-called center-of-mass calibration maneuvers. These maneuvers are performed regularly for the original purpose of center-of-mass determination. Here, the results of the tilt-to-length estimations for the Laser Ranging Interferometer are presented in terms of coupling factors, which are all within 200 μm ⋅ rad−1 and thus meet the requirements. From these parameters, estimations of nadir and cross-track components of the spacecraft center-of-mass positions with respect to the interferometer reference point are derived, providing an additional method to track center-of-mass movement over time.