GRACE-FO Laser Ranging Interferometer (LRI) Data Processing Improvements and Resulting Gravity Fields
Abstract
The GRACE Follow-On mission includes the Laser Ranging Interferometer (LRI) technical demonstration element, which has produced data functionally equivalent to the usual dual-band microwave ranging data for most of the mission's operation to date. While the LRI data theoretically enjoys approximately two orders of magnitude better measurement precision, due to temporal aliasing errors the unconstrained spherical harmonic gravity field solutions using the LRI data were only comparable in quality to those using the microwave ranging data. Early 2020 communications with the Albert Einstein Institute (AEI) highlighted a need to significantly overhaul our LRI processing in several ways. First, we improved our methodology for removing phase jumps or "glitches" in the phase measurements, mainly correlated with roll attitude maneuver thruster activations, both of normal magnitude (of order 10 cycles) and so-called `mega-jumps' (of order 10^5 Cycles). We did this first within our previous approach of handling each spacecraft's LRI piston phase time series separately, and then taking advantage of time-delayed manifestation of the same features in both transponder and master time series. Our improved de-glitching led to improved LRI scale factor estimation and eliminated the need for tedious manual clean-up editing of the LRI data. We also adjusted our compression and differentiation algorithm settings to suppress high-frequency numerical noise in the time-of-flight (ToF) correction to LRI range acceleration, without negatively impacting ToF correction to LRI range and range rate. Various other minor changes were made to both LRI housekeeping and main LRI science data products, and all changes went through careful validation. After this we reprocessed all LRI data products since mission start for an intermediate rl04.5 release. We here detail the resulting monthly (time-varying) and mean (multi-month) gravity fields to degree and order 180 obtained therewith.
©2020 California Institute of Technology. Government sponsorship acknowledged.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMG002.0002F
- Keywords:
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- 1217 Time variable gravity;
- GEODESY AND GRAVITY;
- 1218 Mass balance;
- GEODESY AND GRAVITY;
- 1225 Global change from geodesy;
- GEODESY AND GRAVITY;
- 1240 Satellite geodesy: results;
- GEODESY AND GRAVITY