Ballistic coefficient estimation of satellite in low Earth orbit and atmosphere model error analysis

An inversion method is introduced to study the variations of the ballistic coefficient for orbital satellites with different geometrical characteristic. Using satellite tracking data and NRLMSISE00 empirical model of the atmosphere, ballistic coefficients B of the selected satellites are compiled out with this new method. The "true" values of B (B_t) were computed by averaging the 31 years of B values obtained for each satellite. These true B values were validated by comparing the B_t values of two spheres and by comparing the B_t values obtained for a pair of satellites having very similar size, shape and mass. The estimated ballistic coefficients B' variations for a number of selected satellites were then averaged over each year, and compared with solar indices. Some interesting results are found. Firstly, there does not appear to be a bias in the B_t values computed using the 31 years' time period. Secondly, the large similarity between the time series of B ratios is apparent and solar activity related variations in the thermosphere increase in amplitude with increasing height, as do the errors in the NRLMSISE00 model. Thirdly, the anti-correlations of B' variations with the F_10.7 variations were found in short periods. Finally, the NRLMSISE00 model has failed to produce the low thermospheric density during the 2008 solar minimum. The variations in B' point out that the scaling factor is required to correctly predict the true densities from empirical atmosphere models, especially in solar maxima and minima. It is also shown that changes in B ratios during some major geomagnetic storms cannot be explained by atmosphere model.