Satellite gravimetry is a technique of surveying the earth’s gravity and geoid and their changing signal. The data are used in geodesy science
environment monitoring
seismic
hydrology
and ocean science.An accelerometer is a core payload in the satellite-to-satellite tracking model or satellite gravity gradiometry and is used to sense non-gravity forces. An accelerometer cannot survey a non-conservative force absolutely for its bias
drift
scale
and second-order terms. Parameters change with the environment
status
and time. Thus
the accelerometer should be calibrated and validated.The accelerometer STAR is loaded on the Challenging Mini-Satellite Payload for Geophysical Research and Application (CHAMP) satellite and has an accuracy of 10-8—10-9 m/s2. The SuperStar accelerometer is loaded on the Gravity Recovery And Climate Experiment (GRACE) satellite
and its accuracy is improved to 10-9—10-10 m/s2. The GRADIO accelerometer is loaded on the Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite
and its accuracy is 10-11—10-12 m/s2. With the improving accuracy
additional requirements are needed to calibrate the accelerometer.In terms of data type
the three calibration methods are as follows: The first method is direct calibration
where non-gravity force model data are used to compare the output of the accelerometer. The second is the dynamic method
where GNSS data are used to determine the satellite orbit and the accelerometer bias parameters together. The third is the integrated method
where all data are used to determine the total coefficients of the gravity model and the bias of the accelerometer. In addition
the energy domain
the cross point
and the gravity up-continue methods are used to calibrate the accelerometer. The energy domain method is based on persistence energy. The dissipative energy is deduced by the satellite position and velocity. Then
the parameters of the accelerometer are evaluated from the dissipative energy. Its accuracy is not better because the dissipative energy cannot be calculated precisely given the error of the satellite position and velocity. The cross point method is based on the hypothesis that the force of satellite
which crosses a point twice
is equivalent. Evidently
it is an inaccurate method. The gravity up-continue method is used to calibrate the gravity gradiometer. All these methods have been used to calibrate the accelerometer on CHAMP and GRACE. Results indicate that the dynamic and integrated methods are appropriate for external calibration. A new calibration method called the acceleration domain method is proposed. The calibration method is discussed
and the mathematic model is deduced.The acceleration domain method is used to calibrate the GRACE accelerometer. Results indicate that the total calibration accuracy is 10-8—10-9 m/s2. The best calibration is that of the X-axis parameters
followed by the Z-axis parameters
and then the Y-axis.The acceleration domain method effectively determines the accelerometer parameters. The calibration method is affected by the prior earth gravity model. Thus
iterative procedures should be applied. The accuracy of total acceleration
which is calculated from GNSS data
is related to the position sample rate. Thus
if the GNSS data rate is increased
then the calibration accuracy is improved. If the GNSS data rate is 1 s
State Key Laboratory of Remote Sensing Science, Aerospace Information Research Institute, Chinese Academy of Sciences
Shanghai Aerospace Electronic Technology Institute
Key Laboratory of Radiometric Calibration and Validation for Environmental Satellites, China Meteorological Administration (LRCVES/CMA) and National Satellite Meteorological Center
First Institute of Oceanography,State Oceanic Administration