GRACE Follow-On Gravity Field Recovery from Combined Laser and Microwave Measurements

Abstract:

GRACE-FO carries a Laser Ranging Interferometer (LRI) as a technology demonstration to provide measurements of inter-satellite range changes. This additional measurement technology provides supplementary observations, which improve the reliability of the range rate measurements and allow for a cross-instrument diagnostics with the K-band ranging (KBR) system. Although the in-orbit performance of the LRI is better than expected at high frequencies, the data exhibits systematic errors at frequencies lower than 60mHz, which, comparing to KBR, degrade the driven monthly gravity field solutions.

The aim of this study is to incorporating the two ranging systems (LRI and KBR) in the ITSG-Grace2018 gravity field recovery. The two observation groups are combined in an iterative least squares adjustment, with variance component estimation used to determine their estimated noise model and relative weights. The results leads to improvements within the LRI data calibration, which contributes to the overall accuracy of gravity field solutions.