GRACE Follow-On Laser Ranging Interferometer Measurements Uniquely Distinguish Short-Wavelength Gravitational Perturbations

Abstract

We examined the first-ever laser ranging interferometer (LRI) measurements of inter-satellite tracking acquired by Gravity Recovery and Climate Experiment (GRACE) Follow-On satellites. Through direct along-orbit analysis of instantaneous inter-satellite measurements, we demonstrate the higher sensitivity of LRI (than K-band microwave ranging [KBR]) to anomalies associated with the Earth static gravity field at high spatial resolutions of 100–200 km. We found that LRI captures gravitational signals as small as 0.1 nm/s2 at 490 km altitude, improved by 1 order of magnitude from KBR. This allows LRI to uniquely detect un-/mis-modeled short-wavelength gravitational perturbations. We employed all LRI data in 2019 to validate various state-of-the-art global static gravity field models and show that LRI measurements, even over 1 month, can distinguish subtle differences among the models computed from ~15 years of GRACE KBR and ~4 years of Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) gradiometry data. Ultra-precise LRI measurements will be yet another critical data set for future gravity field model development.