Direct and indirect solar radiation effects acting on LAGEOS satellite: Some refinements

Abstract The LAGEOS tracking data show that the residuals on the along track acceleration have a secular drag of about 3.4×10 12 m/sec 2 and signatures whose periods are represented by linear combinations of the longitude of the LAGEOS node and of the Sun. The direct solar radiation model is rediscussed when LAGEOS is going out from or entering the eclipse. In fact specular asymmetries of the eclipse figure with respect to the plane which is perpendicular to the orbit and including the Sun-Earth direction due to the Earths revolution are able to justify peaks on the Along Track of the pico-m/sec 2 order and very interesting behaviours along the radial and Out of Plane directions. Furthermore the paper refines the modelling of the Yarkovsky-Schach effect at the boundaries of the eclipses and performes, exploiting the phases of shadow too, a sort of least square fitting of the along track residuals where LAGEOS spin cosine directors and thermal inertia are the parameters to be recovered.