Angles-Only Navigation of a Formation in the Proximity of a Binary System

Abstract

This paper will focus on the navigation and station keeping of one or more spacecraft around the dynamic equivalent of the Lagrange point L4 of a binary asteroid system. This location can be conveniently used by a spacecraft equipped with a small scale laser to demonstrate laser ablation as a viable asteroid deflection technology and to extract and analyse surface and subsurface material. This paper proposes an approach using optical navigation only and exploiting the knowledge of the dynamics of the secondary asteroid around the primary. Each spacecraft is equipped with only a camera, a good attitude determination and control system and an inter-satellite link that allows sharing information with other spacecraft in the formation and provides a complete spacecraft-to-spacecraft position vector.Two scenarios will be considered in this study: one in which a single spacecraft uses only information from a camera observing both the primary and the secondary asteroid, in the other, a small formation of spacecraft autonomously navigates using only cameras and an intersatellite link. Measurements and dynamics are processed in a form of Unscented H-infinity Filter that can effectively estimate the state of the system and allows maintaining the formation at L4.

Angles-Only Navigation in the Proximity of a Binary Asteroid System

“…In this paper, however, we consider the use of optical cameras operating in the visible range, we study the sensitivity to the knowledge of the orbital parameters of the secondary and we propose a state estimation process that simultaneously improves the knowledge of the motion of the secondary. The work in this paper extends previous studies by the authors on navigation in the proximity of single and binary asteroids [16,17,25,26] and on asteroid deflection [27,28]. The approach investigated in this paper uses the pointing vectors of the cameras to the primary and secondary asteroids in combination with the knowledge of the motion of the secondary asteroid around the primary to obtain an estimation of the position of the spacecraft with respect to the primary asteroid via a triangulation technique.…”

“…In this last test case, the effect of malfunctioning cameras on the estimation process is investigated, similarly to what already presented in a previous work [26]. The scenario starts as in the previous test case.…”

“…As stated in Section III.C, the efficacy of the triangulation model depends on the knowledge of the motion of the secondary asteroid around the primary. In a previous work [26] it was shown how inaccuracies on the knowledge of the inclination or the initial true anomaly of the asteroid can lead to large errors in the state estimation of the spacecraft.…”

“…In this new scenario, both spacecraft are provided with the inter-spacecraft measurement described in Section III.D. In a previous work it was demonstrated that the use of the relative position vector could improve the estimation process and also allow a spacecraft to continue navigating even when the cameras became unavailable [26].…”