Analysis of satellite drag

Precision radar tracking data were used to evaluate atmospheric density models at 275, 780, and 1500 km. All models give the same average performance at the two lower altitudes, although all of them exhibit significant departures from the actual density. There are physical variations in the atmosphere that are not modeled by any of the current atmospheric models. The inclusion of the precipitation index in future atmospheric models is recommended since significant correlation is found between the precipitation index and the scale factor at 275 and 780 km.