Perturbations in Perigee Height of Vanguard I

The effect of solar radiation pressure on the perigee height of satellite 1958ss(2) (Vanguard I) has been considered. Previous consideration of the effect of the third hairmonic and the lunar and solar gravitational perturbations left an unexplained discrepancy between the observed and calculated values of perigee height. The inclusion of the effect of radiation pressure leads to close agreement between the orbit data and the theoretical results for Vanguard I.