Improving Orbit Propagation of LEO Satellites Using Atmospheric Drag Analysis   

The variability of the atmospheric drag force on satellites is influenced by several factors, which include neutral density and gas composition, solar activity, and the orientation and shape of the satellite. During periods of geomagnetic activity, changes in these properties contribute to significant variations in the drag force, impacting the satellite trajectory. Therefore, the atmospheric drag force is considered as one of the largest sources of error in the orbit estimation for Low Earth Orbit (LEO) satellites. The methods presently used for satellite orbit determination define a constant term to represent the drag force, which can result in significant errors in long-term propagation and prediction of satellite positions. This work aims to improve SGP4 orbit propagation method by updating the drag term at regular intervals. The estimation of the drag term implements atmospheric drag analysis, which involves calculating the satellite drag coefficients using different Gas-Surface Interaction (GSI) models and neutral density data from Global Ionosphere Thermosphere Model (GITM) to estimate the mean motion derivative. The results demonstrate improved orbit propagation and estimation of orbital decay for the Gravity Recovery and Climate Experiment (GRACE) and Communication/Navigation Outage Forecasting System (C/NOFS) satellites during selected periods containing quiet and storm times.