Autonomous Orbit Determination and Control in Constellations of Satellites

Abstract

The management of a satellite constellation needs a new approach on problems of orbit restitution and control. In fact, the large number of satellites in orbit at the same time does not allow to apply the classical technics associated to orbit measurement and control. The ground standard operations associated to orbit control must be highly reduced in order to be able to support a satellite constellation with a non oversized ground segment.These constraints lead to an increasing autonomy in the constellation management: autonomy of satellites for the orbit measurement, for the orbit control and maneuvers.The first part of the paper will present the different functions involved in “Autonomous Orbit Control” (A.O.C.): orbit and time determination, calculation of maneuvers in order to follow a reference orbit, realization of maneuvers, monitoring of maneuvers. The functional architecture will be addressed as the first step of the conception process.As a second part, the space dynamics aspects of each function will be pointed out. Particularly, the algorithms elaborated in order to realize the following functions will be explained: orbit determination, monitoring of maneuvers. We will focus on the validation of the algorithms based on theorical simulations and in-flight measurements analysis (comparison on-board/ground calculations on TOPEX and SPOT measurements).The use of positioning systems on satellite lead to the development of a specific on-board equipment called autonomous navigator. This equipment can be based on two kinds of location and synchronization systems (CNES System: DORIS and GPS solution). The navigator general material characteristics and its interfaces with the whole satellite will be shown (implantation of receiver, antennas, electrical consumption). An outlook on the development plan concerning such a sub-system and the qualification process associated will be described