Robust mascon estimation from spherical harmonics
Abstract
Time-variable gravity estimates from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On missions are most commonly resolved as either spherical harmonic coefficients or mass concentration (mascon) cells. The missions' Science Data System teams deliver official Level-2 unconstrained monthly spherical harmonic solutions from the Jet Propulsion Lab (JPL), University of Texas at Austin's Center for Space Research (CSR), and the German Research Centre for Geosciences (GFZ), while other centers deliver similar products matching the processing standards and quality of these official solutions (e.g., the Graz University of Technology's ITSG-Grace2018 monthly solution). The science application of these products requires expertise in post-processing methods to appropriately handle correlated and uncorrelated noise and account for signal leakage across boundaries of studied regions. In order to provide high-quality user-friendly products that remove many post-processing burdens from users, teams at NASA Goddard Space Flight Center (GSFC), JPL, and CSR have developed constrained monthly mascon solutions that resolve surface mass changes across discrete cells. These solutions use a variety of regularization strategies to attempt to best localize and capture surface mass change while minimizing noise and leakage. These solutions have helped make GRACE data more accessible to non-experts, but analysis of these solutions must be done in the context of the regularization choices made by each center. Additionally, the estimation of these types of solutions has only been possible at centers capable of processing GRACE Level-1B inter-satellite ranging measurements. We present a new method of regularized mascon estimation from spherical harmonics. Provided that the full normal equations for these coefficients are available, this method allows for a mathematically equivalent mascon estimate to those from a single iteration of Level-1B observations, but at a fraction of the computational cost. We use the ITSG-Grace2018 solution and full normal equations to produce a new mascon solution of comparable quality to current solutions. We then use this method to perform a trade study comparing regularization strategies and the tradeoffs made by the three primary mascon solutions to date.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMG002.0006C
- 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