Reassessment of the error modelling of non-gravitational perturbations on LAGEOS II and their impact in the Lense ?Thirring determination. Part I

The perturbative e ects due to both direct solar radiation pressure and Earth albedo radiation pressure have been investigated on LAGEOS II.In particular,the e ects on the eccentricity vector excitations,in the argument of perigee,and also in the inclination and node excitations have been studied.This study has been done both analytically and numerically,integrating the perturbative equations over 5 years.Conclusions regarding the use of LAGEOS II for general relativistic measurements are given.In particular we veri ed that:(i)the numerical integration results con rm the analytic predictions;(ii)the necessity of considering the eclipses modelling is more important in the case of inclination and node excitations rather than in eccentricity excitations and perigee rate e ects;(iii)LAGEOS II node and argument of perigee are good observable quantity for Einstein ’s geometrodynamic tests and measurements.