Comparison and Accuracy Assessment of Semi-Empirical Atmosphere Models through the Orbital Decay of Spherical Satellites

Abstract

A detailed comparison and assessment of the accuracy of semi-empirical atmospheric density models (JR-71, MSIS-86/90, TD-88) were carried out by analyzing the orbital decay of nine spherical satellites in the 150-1500 km altitude range. The orbital decay data used were distributed over a full solar activity cycle (1987-1999). The drag coefficients which were estimated by fitting the observed semimajor axis evolution with a high accuracy orbit propagator were compared with those computed by theoretical analysis. While MSIS-86/90 proved to be the best model to compute the air density below 400 km, in low solar activity conditions, JR-71 was more accurate at greater altitudes and/or solar fluxes. TD-88, defined below 700 km, was quite accurate (10%) only during periods of moderate solar activity. Between 350 and 800 km, the average accuracy of JR-71 and MSIS-86/90 was generally better than 15% and, sometimes, even better than 10%. However, at 1500 km and during low solar activity conditions, both models underestimated the air density by 60%, while below 350 km, still during low solar activity conditions, they overestimated the air density by 20-25% and 10-20%, respectively.