GRACE accelerometer data transplant

Abstract

In the last few months of GRACE (Gravity Recovery and Climate Experiment) mission operation, the accelerometer (ACC) aboard GRACE-B was turned off due to battery problems. In order to compute a gravity field model for these months, a data processing strategy was developed to retrieve the missing information, the so called Accelerometer data transplant. The ACC data transplant uses linear accelerations as measured by the GRACE-A accelerometer to generate the missing GRACE-B ACC data. A simple method of ACC data transplant was presented by Save et al. (2006), which only applies attitude and time correction due to orbit separation. In this paper we present an improved method of the ACC data transplant, which also includes thruster spike correction. The thruster spikes are residual linear accelerations occurring at each thruster firing caused by thruster imperfections and misbalance. We provide detailed description of the thruster spike model, which was derived analytically based on the ACC transfer function and 10 Hz ACC data. Using the transplanted ACC data we computed the gravity field models for the months with missing GRACE-B ACC data (November 2016-June 2017). We show that the gravity field model based on in the improved ACC data transplant has significantly reduced noise, especially for degrees beyond the first orbital resonance, when compared to the simple transplant method. The improved ACC transplant became therefore a part of the processing standards for the upcoming JPL RL06 gravity solution.

Improved Estimates of Geocenter Variability from Time-Variable Gravity and Ocean Model Outputs

“…The accelerometer onboard GRACE-B was turned off in September 2016 to reduce the battery load and maintain the operation of the microwave ranging instrument. Independent methods have been developed by the GRACE processing centers to spatiotemporally transplant the accelerometer data retrieved from GRACE-A for GRACE-B [66]. The increased uncertainty in the gravitational fields likely affects our ability to estimate the geocenter variability, particularly for the months with a single operating accelerometer.…”

Quantifying the Central European Droughts in 2018 and 2019 With GRACE Follow‐On

“…Some exceptions are notable, in particular during the early years of the GRACE mission. During the GRACE end‐of‐life months from November 2016 to June 2017, the data quality degraded due to the loss of the accelerometer data on one spacecraft (Bandikova et al., 2019), which leads to an increased spread among the series. Those months are therefore ignored in the following analysis.…”

Replacing GRACE/GRACE‐FO With Satellite Laser Ranging: Impacts on Antarctic Ice Sheet Mass Change

“…The accelerometers on each GRACE spacecraft operated nominally until October 2016 when the GRACE‐B accelerometer was turned off for six out of the seven final GRACE solution months (May 2017 excepted) in order to reduce the power load on the diminished battery. In an effort to mitigate the loss of this accelerometer, the Level‐1B team at the Jet Propulsion Laboratory (JPL) developed a sophisticated algorithm to “transplant” the GRACE‐A accelerometer measurements onto GRACE‐B, taking into account the flight time, orientation, and satellite‐specific thrusting events (Bandikova et al, ). Overall, this approach has been highly successful at extending the valuable data record of the GRACE mission by facilitating the production of monthly gravity solutions from November 2016 through June 2017 (the inter‐satellite ranging system was turned off for September and part of October 2016).…”