This study assessed navigation performance for rendezvous and close approach applications where on-board navigation must be accomplished through the use of angles-only measurements by developing various relative motion orbital trajectories. Chaser vehicle maneuvers designed to enhance the estimator's observability of the downrange distance to the target are considered. The target vehicle is assumed to be non-maneuvering and in a near-circular orbit. The modeled system includes representative scenarios from the Orbital Express mission.nAlthough a wide array of angle measurement sensors are available, their use in orbital rendezvous is generally limited by the fact that they are unable to provide direct target ranging information which leads to significant downrange error accumulation in the navigation filter. These navigation problems inherent to angles-only measurements in a natural motion environment are first qualitatively studied both analytically and through linear covariance modeling.
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