Application of solar radiation pressure to formation control near libration points.

摘要

In this dissertation, the use of solar radiation pressure (SRP) for spacecraft formation control near one of the collinear Sun-Earth or Earth-Moon libration points is investigated. Specifically, we consider whether formation spacecraft that are equipped with Sun-facing reflective surfaces (solar sail or sun shield) can exploit the solar radiation force that acts on them to perform gradual relative maneuvering.The relative motion between formation spacecraft with solar sail or sun shield near libration point is analyzed. A set of linearized equations of relative motion for libration point formations under differential solar radiation forcing is derived, with the sun shield or solar sail off-pointing angle taken as the control input variable.These equations are firstly used to study the formation reconfiguration problem. With this model, we study the existence and properties of solution trajectories that take the spacecraft from a given initial formation geometry to a desired final one in the Sun-Earth system. The existence of time-optimal transfer trajectories is also investigated.The problem of formation keeping using solar radiation pressure in the Sun-Earth system is then discussed. Since the amplitude of the SRP force is constrained by the area of sun shield and the permissible maximum off-pointing angle, the theory of regulator with constrained control is applied to design the formation-keeping controller in order to use the capacity of on-board sun shield more efficiently. A subtopic of adaption of frequency of out-of-plane relative motion using SRP is also presented.Finally, we extend the investigation to the Earth-Moon system. The modeling of relative motion with SRP in the vicinity of the translunar libration point is examined. A formation-keeping controller based on a set of equations of relative motion is developed.