Angles-only navigation state observability during orbital proximity operations

Angles-only navigation during proximity operations suffers from a well-documented range-observability problem when a single camera is assumed to be at the center of mass of the host vehicle. Inspired by this range-observability problem, this paper explores relative-position/-velocity observability when a single camera is offset from vehicle center of mass. Within the context of the Clohessy-Wiltshire dynamics, it is shown that relative position and velocity are generally observable when the camera offset is included in the problem formulation, enabling a range observability without Δν requirements. Although special cases are identified when the state is unobservable, the conclusion is that the relative state is generally observable even in the case of v-bar station keeping during attitude hold when the angle measurements are constant. The thesis that state observability results when the motion of the camera does not obey the Clohessy-Wiltshire dynamics is presented.