Angles-only navigation in the proximity of a binary asteroid system

This paper investigates the possibility to navigate one or more spacecraft in the proximity of an asteroid binary system using only optical measurements. The approach proposed in this paper assumes only limited prior knowledge of the shape and orbital parameters of the two asteroids. In particular it is shown that the knowledge of the semi-major axis of the orbit of the secondary with respect to the primary is critical to guarantee a sufficient level of navigation accuracy. A method is proposed to allow for the inclusion of the orbital parameters of the secondary asteroid in the estimation process. It is shown that the inclusion of the estimation of the orbital parameters of the secondary provides the required information to allow navigating in the proximity of the binary system at the Lagrange point L4. The paper then demonstrates that the same method can be used to navigate a small formation of two spacecraft at L4 provided that intersatellite position and velocity vectors can be measured with sufficient accuracy. In this case the formation can be controlled even if the optical sensor on board one of the spacecraft partially fails