Abstract:
AbstractIn Gravity Recovery and Climate Experiment (GRACE) Followāon (GRACEāFO) mission, similar to its predecessor GRACE, the twin satellites are equipped with threeāaxis accelerometers, measuring the nonāgravitational forces. After 1Ā month in orbit, during the ināorbitācheckout phase, the noise on GRACEāD accelerometer measurements elevated and resulted in systematical degradation of the data. For this reason, the GRACEāD data need to be replaced by synthetic data, the soācalled transplant data, officially generated by the GRACEāFO Science Data System (SDS). The SDS transplant data are derived from the GRACEāC accelerometer measurements, by applying time and attitude corrections. Furthermore, modelābased residual accelerations due to thruster firings on GRACEāD were added, proven to improve the data quality in gravity field recovery. However, preliminary studies of GRACEāFO data during the single accelerometer months show that the low degree zonal harmonics, in particular C20 and C30, are sensitive to the current transplant approach. In this work, we present a novel approach to recover the GRACEāD ACT1B data by incorporating nonāgravitational force models and analyze its impact on monthly gravity field solutions. The results show the improved ACT1B data not only contributed to a noise reduction but also improved the estimates of the C20 and C30 coefficients. The application of this new approach demonstrates that the offset between Satellite Laser Ranging (SLR) and GRACEāFO derived C30 time series can be reduced by the use of the alternative accelerometer product.
