Satellite decay computation and impact point prediction

Abstract

This paper presents a new method that has been developed to accurately model satellite orbit decay, approximate re-entry trajectories and predict the impact point. At higher altitudes, the model consists for efficiency reasons of a numerical integration of the drag effect computed along an analytical representation of the satellite orbit. Four different models for atmospheric density (J71, DTM77, MSIS77 and MSIS90) have been evaluated here. During the final decay phase, the method switches to a purely numerical integration until impact to assure maximum accuracy. NORAD Two-Line Elements are used as observational data for this study. Advantages of this technique are the relative simplicity of the method, the computational speed and the general availability of the data. The method has shown to be able to predict spacecraft impact epochs with an accuracy of better than 10 % of the prediction length for 4 of the recently decayed 5 satellites that have been used here.