Atmospheric density determination using high-accuracy satellite GPS data

Atmospheric drag is the main source of error in the determination and prediction of the orbit of low Earth orbit (LEO) satellites; however, empirical models that are used to account for this often have density errors of around 15%-30%. Atmospheric density determination has thus become an important topic for researchers. Based on the relationship between the atmospheric drag force and the decay of the semi-major axis of the orbit, we derived atmospheric density along the trajectory of challenging mini-satellite payload (CHAMP) satellite with its rapid science orbit (RSO) data. Three primary parameters-the ratio of cross-sectional area to mass, the drag coefficient, and the decay of the semi-major axis caused by atmospheric drag-were calculated. We also analyse the source of the error and made a comparison between the GPS-derived and reference density. The result for December 2, 2008, showed that the mean error of the GPS-derived density could be decreased from 29.21% to 9.20%, if the time span adopted for the process of computation was increased from 10 min to 50 min. The result for the entire month of December indicated that a density precision of 10% could be achieved, when the time span meets the condition that the amplitude of the decay of the semi-major axis is much greater than its standard deviation.