Low-SNR Doppler Data Processing for the InSight Radio Science Experiment

Buccino, Dustin [ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA] Border, James S. [ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA] Folkner, William M. [ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA] Kahan, Daniel [ Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA] Le Maistre, Sébastien [UCL]

Radio Doppler measurements between the InSight lander and NASA’s Deep Space Network have been acquired for measuring the rotation of Mars. Unlike previous landers used for this purpose that utilized steerable high-gain antennas, InSight uses two fixed medium-gain antennas, which results in a lower radio signal-to-noise ratio (SNR). Lower SNR results in additional thermal noise for Doppler measurements using standard processes. Through a combination of phase averaging and traditional data compression, the increased thermal noise due to low SNR can be removed for most of the signal of interest, resulting in more accurate Doppler measurements. During the first 900 days of InSight operations, Doppler measurements were improved by ~25% on average using this method.