In Gravity Recovery and Climate Experiment (GRACE) Follow-on (GRACE-FO) mission, similar to its predecessor GRACE, the twin satellites are equipped with three-axis accelerometers, measuring the non-gravitational forces. After one month in orbit, during the in-orbit-checkout phase, the noise on GRACE-D accelerometer measurements elevated and resulted in systematical degradation of the data. For this reason, the GRACE-D data need to be replaced by synthetic data, the so-called transplant data, officially generated by the GRACE-FO Science Data System (SDS). The SDS transplant data are derived from the GRACE-C accelerometer measurements, by applying time and attitude corrections as well as adding modeled thruster responses.
We introduce an alternative approach to recover the GRACE-D Level-1B accelerometer data (ACT1B) by incorporating non-gravitational force models acting on the satellite. The alternative ACT product contributes to an improved estimation of higher degrees of the recovered monthly gravity field solutions, as well as low zonal degrees 2 and 3. The estimates of the C30 coefficients represents a significant improvement with respect to SLR-derived values, with which the GRACE-FO values are recommended to be substituted.
The generated monthly ACT1B products can be accessed through our FTP server: