GEOMETRICAL MODEL FOR PREDICTING THE LONG-TERM LUNI-SOLAR EFFECTS ON GEOSYNCHRONOUS SATELLITES.

This paper presents the results of an investigation into the long-term orbit evolution of uncontrolled geosynchronous satellites under the lunar-solar gravitational effects. A simplified semi-analytical model, that averages the disturbing function over the mean anomalies of the satellite and of the perturbing bodies, has been developed and applied to the orbital prediction of the no-longer-controlled Italian satellite SIRIO. The results have shown a satisfactory agreement with corresponding orbital predictions obtained by numerical approaches normally employed during the spacecraft operational phase.