Assessment of conservative force models from GRACE accelerometers and precise orbit determination

• Main Authors: Calabia A., Jin S.
• Other Authors: Zonguldak Bülent Ecevit Üniversitesi
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Masson SAS 2016
• Subjects: Accelerometers; Conservative forces; Precise Orbit Determination (POD) GRACE; Principal Component Analysis (PCA); Canada; Greenland; Indian
• Online Access: https://hdl.handle.net/20.500.12628/4368; https://doi.org/10.1016/j.ast.2015.11.034

The accuracy of the conservative force-models is not clear and the new space accelerometers provide a unique opportunity for their validation. In this paper, the conservative-force model deficiencies are investigated via Principal Component Analysis (PCA) using 4 years of GRACE measurements (2006-2009). The deficiencies are assessed by comparing the accelerometer readouts with the differences between the conservative force-model and the precise orbit accelerations. Within this scheme, the spatiotemporal data analysis is synthesized in a time-series of grids whose latitudinal and longitudinal variations are respectively influenced by the half orbital period and the equatorial orbit shift. With maximum amplitude of 50 nm/s2, the mean map shows a positive overestimation in Canada and Brazil and negative in Greenland. Explaining the 74% of the variability, the two first pairs of PCA modes show un-modeled patterns with amplitudes maxima of 80 nm/s2 and 50 nm/s2. Their periodic behavior and wave-length of degree-6 and degree-11s spherical harmonics strongly suggest an additional modeling and improvement. As for the long-term variations, our results show a latitudinal variation of 15 nm/s2 maximum amplitude correlated with the day-night periods. Performing a combined analysis of ascending and descending orbits, a trend of 3 nm/s2yr in the Indian Ocean is also observed. Our new approach for orbital force-models validation can be considered crucial for the current state-of-the-art of precise orbit determination (POD) and Time-Varying Gravity (TVG) modeling. © 2015 Elsevier Masson SAS. Science and Technology Commission of Shanghai Municipality: 12DZ2273300 National Basic Research Program of China (973 Program): MOST 973, 2012CB72000 National Natural Science Foundation of China: 11173050, 11373059 National Natural Science Foundation of China This work was supported by the National Keystone Basic Research Program ( MOST 973) (Grant No. 2012CB72000 ), National Natural Science Foundation of China (NSFC) Project (Grant ...