Direct Density Correction Method: review of results
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The primary source of errors in orbit determination and prediction for Low Earth Orbit (LEO) space objects (SOs) is the inaccuracy of the upper atmosphere density models. The existing models do not represent the actual density variations with an acceptable accuracy. A review of results obtained recently by the Direct Density Correction Method (DDCM) is presented. For the last few years we have employed the DDCM to construct the atmosphere density corrections using the Two Line Element (TLE) sets as the input observational data. The density corrections for the GOST and NRLMSIS-OO models were generated with a one-day grid over a four-year interval from December 1999 through November 2003. The density corrections were generated from the smoothed ballistic factors resulting from the secondary data processing. The effectiveness of this density correction process was evaluated by comparison of the orbit determination and prediction results obtained with and without taking into account the estimated density variations. A preliminary comparison of the obtained results with the High-Accuracy Satellite Drag Model (HASDM), an alternative approach to density correction, was performed. The statistical characteristics of the observed density corrections and their correlations with different factors were investigated. Approaches for forecasting the density corrections are proposed.
