Rendez Vous Near the L1-L2 Lagange Points for the Fresnel Telescope
- Paper number
IAC-08.E2.2.8
- Author
Mr. David Flamenbaum, Supaéro - Ecole Nationale Supérieure de l'Aéronautique et de l'Espace , France
- Year
2008
- Abstract
“What are the conditions for planet formation and emergence of life?” or “How did the Universe originate and what is it made of?” : these scientific questions have led to do research on innovating telescopes which permit to peer at interstellar background. To fulfil this objective, the FRESNEL project is designed. FRESNEL capabilities rely on an interferometric imager that has a high resolution and enables at the same time to detect some dark points despite a dazzle due to brilliant objects. Although its spectrum is large, it will be particularly used in UV because of the intrinsic richness of physical phenomena in such short waves. In order to get a telescope with a very high angular resolution, the lens and the sensors have to be far away from each other - a few kilometres. Therefore a two spacecraft Formation-Flying telescope is needed: a leader with the interferometric lens and a follower with the sensor. As all classical space missions, the propellant mass of satellites has to be minimized in order to maximise the payload. Besides, this mission should last more than ten years, so that orbital corrections should be minimized also during the telescope’s life. Low gravity gradients are required where it would take place. The solution is to benefit from equilibrium Euler-Lagrange points L1 or L2. Although those points are linearly unstable, there are stable orbits in their vicinity: periodical orbits called “Halo orbits” and quasi-periodical orbits called “Lissajous orbits”. Moreover lagrangian points remain fixed with regard to both the Sun and the Earth. Located in L2, the telescope would take advantage to see the Sun, the Earth and the Moon on the same side. Consequently, only one face of each satellite would be enlightened. This provides a very stable thermal environment. The cold face would permit to observe the deep space with a high level of detection sensitivity. Furthermore, we are undergone to two optical constraints: first the distance to gather both spacecraft to form the telescope, secondly the pointing of precise zone of space. Thus the challenge is to manage a two spacecraft formation in the vicinity of a lagrangian point. Once injected by the launcher on dedicated trajectories leading to the final orbits targeted by the spacecraft, we have to guide the two vehicles’ motion to a formation-flight orbit. The goal of this paper is to propose an optimization method that would help to schedule as autonomously as possible, even through onboard algorithm implementation, the effective manoeuvres leading to the rendez-vous. First, general background knowledge on lagrangian points are presented through the Restricted Circular Three Body Problem. Then the article retails the models of the two spacecraft relative movement and the models of the manoeuvres’ optimization. It deals with a linearized analysis of the dynamics. Indeed, it gives a consistent approach of the follower spacecraft’s motion in the vicinity of the leader’s trajectory. Finally, the exhibited results of the simulations permit to provide two kinds of answers: on one hand the necessary propellant mass for the travel and on the other hand the reliability of the linearized models. Such a work brings a new contribution to the formation-flight knowledge and will have significant consequences on the FRESNEL project.
- Abstract document
- Manuscript document
IAC-08.E2.2.8.pdf (🔒 authorized access only).
To get the manuscript, please contact IAF Secretariat.