Refinements in determining satellite drag coefficients - Method for resolving density discrepancies

The discrepancies in atmospheric densities deduced from satellites of compact and long cylindrical shapes can be used to improve our knowledge of drag coefficients. Constraints on the accommodation coefficient imposed by experiments in space and in the laboratory make it possible to resolve the discrepancies and gain information on the angular distribution of molecules reemitted from satellite surfaces. We present a sample calculation based on some limited published data. If the published nominal length-to-diameter ratio of the cylindrical satellites is the actual ratio, then we can conclude that the assumption of a diffuse angular distribution of reemitted molecules is adequate (at least near 200-km altitude), even for the long cylindrical sides where most of the molecules strike at grazing incidence. The method can be used with detailed orbital data and precise satellite shapes to infer reflection characteristics and drag coefficients for a range of altitudes and perigee velocities.