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 Δv 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.