Variations in the atmospheric neutral density at 145km

A least-squares multiple linear regression is performed on orbital decay density data obtained from precise orbital analysis of 22 low-perigee (130–160 km) Air Force satellites. Variations related to solar activity, the semi-annual effect, geomagnetic activity, and the zenith angle of the Sun are in agreement with the model of Jacchia (1971). Density variations in longitude and latitude are also deduced and compared with recent results from other investigations within this altitude regime.