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State estimation of spacecraft formation near small asteroid

An autonomous navigation method is investigated to estimate the states of each spacecraft relative to the asteroid. Inter-spacecraft position measurements are then combined with the spacecraft-to-asteroid position measurements to improve the navigation accuracy. Two navigation schemes based on different combinations of measurements are constructed to evaluate the improvement in navigation performance. Unscented Kalman Filter is used to estimate the state for each spacecraft with respect to the asteroid. Results show that the navigation performance is significantly improved by adding the inter-spacecraft position measurements.