RENDEZ-VOUS NEAR THE L_1 - L_2 LAGRANGE POINTS FOR THE FRESNEL TELESCOPE

摘要

The use of a diffractive array instead of classical mirrors and lens has proven its performances in laboratories so that it could provide from a significant improvement in space telescope. Based on the latter innovation, the FRESNEL project is designed to prepare missions such as DARWIN or the newt JWST. It is a two-spacecraft Formation-Flying telescope. In order to benefit from low gravity gradients, the vicinity of lagrangian points L_1 or L_2 is chosen, and particularly Halo or Lissajous orbits. Once injected by the launcher on dedicated trajectories leading to final orbits targeted by the spacecraft, two satellites are guided to a formation-flight. Thus the challenge is to manage a two-spacecraft formation in the vicinity of a lagrangian point.The goal of this paper is to propose models of the relative dynamics of the vehicles: a non-linear model based on the Circular Restricted Three Body Problem, a Linear Time Variant model and a Linear Time Invariant model. Two different approaches are considered: the impulse and the continuous thrusts. Three optimization methods are studied: one based on the Pontryagin theorem, the simplex method and the mean square method. This paper gives arguments explaining that the mean square method is the most adapted for on-board implementation. Such method would help to schedule as autonomously as possible, even through on-board algorithm implementation, the effective manoeuvres leading to the rendez-vous.