关键词: 热层大气, 大气密度模式, 模式校准, 温度修正, 经验正交函数, 球谐分析

Abstract: The force produced by thermospheric density is the largest non-gravitational perturbation acting on low orbit space-crafts. It is difficult for existing atmospheric density models to satisfy space mission requirements because of the 15%-20% deviations in the models. With the NRLMSISE-00 empirical model as the density reference standard, an equation for temperature corrections and density is established by correcting the temperature parameters of Jacchia-Roberts empirical density model to calibrate density. The improved Gauss-Newton correction algorithm is chosen to avoid divergent solution of the equation in specific regions. The spatial-temporal characteristics of temperature corrections are captured by Empirical Orthogonal Function (EOF), and are then compared with the characteristics of temperature corrections captured by the traditional Spherical Harmonics (SH). Results show that more than 85% and 80% variations of temperature corrections are involved in the first 4 EOFs and the first 9 SH expansion functions. The first EOF reflects the overall bias of temperature corrections. The coefficients corresponding to the second to fourth EOF show that the temperature corrections have diurnal periodicity, and the coefficients obtained with the SH also have diurnal periodicity. Jacchia-Roberts model is calibrated by the reconstructed temperature corrections using the first 4 EOFs and the first 9 SH expansion functions, and the calibrated density deviations of Jacchia-Roberts reduce by 9.06% and 5.37%, respectively. It is confirmed that the EOF method has better efficiency than the SH method in temperature parameter correction and density model calibration.

Key words: thermosphere, atmospheric density model, model calibration, temperature correction, empirical orthogonal function, spherical harmonic analysis