Results and Issues of Atmospheric Density Correction

Abstract

The unpredictable effects of atmospheric drag are the dominant error source in orbit determination and prediction of low altitude satellites. One prospective direction for increasing the accuracy of position prediction for these satellites is the organization of an upper atmosphere monitoring service. This would be the analog of the weather service in the lower atmosphere. For this purpose drag estimates associated with cataloged inactive payloads and debris were used. At any given time there are several hundred such drag-perturbed space objects. The element sets for these space objects are updated as an ordinary routine operation by the space surveillance systems a few times per day in near-real time. With the drag data operative corrections to the modeled atmosphere density can be constructed without significant additional costs. The drag data for the space objects used in this study were obtained by using Two Line Element (TLE) sets as the observational data. The density corrections are expressed as a linear function of altitude. The time series for the density corrections were obtained with a one-day grid over a four-year interval. The effectiveness of this density correction process was evaluated by comparison of the orbit determination and prediction results obtained with and without the estimated density variations.