A purely empirical model of penumbra based on star-photometry data calibrations applied to the orbital motion of geodetic satellites

The present work analyzes all the possible geometrical and physical causes of penumbra which could affect the budget of surface forces acting on Earth satellites. In particular some new solutions recently proposed are merged using a new approach to model atmospheric extinction and deflection. The new approach is based on extinction and refraction of star-light through the atmosphere. The model of penumbra so built is well-suited to assess the real effects of penumbra on the orbital motion of GPS satellites. (C) 1997 COSPAR. Published by Elsevier Science Ltd.