New Calibration Method of Accelerometers in GRACE Satellites Based on Precise Solar Radiation Model

Adopting the precise radiation pressure model, we compute the real perturbation force caused by the solar radiation on the GRACE satellites and estimate the scale factors of accelerometer's y axis and z axis. Setting these scale factors constant and using the dynamical orbit determination (OD), we estimate the rest four calibration parameters, i.e. the scale factor of the x axis and the biases of three axes. On this basis, we obtain the daily calibration parameters from 2002 to 2014. The average values and standard deviations of scale factors of the x, y and z axes are 0.9435 ± 0.0187, 0.9393 ± 0.0444, 1.0371 ± 0.0391 for GRACE-A, and 0.9313 ± 0.0170, 0.9488 ± 0.0452, 1.0274 ± 0.0446 for GRACE-B, respectively. Compared with our previous work, this new method constrains the scale factors of the y and z axes with the precise radiation pressure model, which can reduce the influence of data errors on the weak-signal axes (y, z), as well as reduce the correlation between scale factors and biases, and eventually improve the stability of calibration parameters. Taking the y and z axes of GRACE-A as an example, the standard deviations of scale factors with this new method are about 0.0391-0.0444, while the previous results obtained by the unconstrained dynamical orbit determination were about 0.21-0.31. It is shown that the standard deviations of scale factors in this paper have been reduced by more than 78%, and those of biases have been reduced by more than 85%. Therefore, the calibration parameters estimated with the new method are more stable and will be of particular interest for the study on the rotation speed and wind field of the Earth's thermosphere.