Stability of the Galileo Constellation, and Long Term Evolution of Disposal Orbits
Deleflie, F. J.¹; Valk, S.²; Guzzo, M.³; Lemaitre, A.^2
1OCA-GRGS; ²FUNDP; ³University of Padova

We detect the structure of the web of resonances for the Galileo-like satellites in a model accounting for the non spherical shape of the Earth and the luni--solar perturbations, and for the solar radiation pressure. In particular, we study to what extent the choice of the new nominal semi-major axis of the constellation (a=29600km) is much better than the previous one (a=29993km), because of a combination between periods involved in the motion of the Moon, the Sun, and the Earth.

Our study is based on the numerical integration of a set of equations of motion, where the influence of short periods has been removed in an analytical way. On a very long time scale, we analyse the impact on the long term evolution of the orbital elements, in view of studying the stability of diposal orbits. In particular, we will wonder if there is some chaos in that 4-body system (due to resonance effects...).

Finally, we will try to characterize the long term evolution of the semi-major axis and the eccentricity of Galileo-like orbits, and to understand the origin of the eccentricity's growth appearing in many MEO orbits. We will show that in some specific cases, this growth can be avoided, which could permit to define stable storage orbits.