New Observability Criteria Based on Covariance Matrix for Angles-Only Navigation against Non-Cooperative Targets

Angles-Only Navigation (AON) is an efficient method for relative orbit determination but suffers from fundamental unobservability along the line-of-sight (LOS) without proper maneuvers. This paper proposes a new observability criterion based on the maximum eigenvalue of the position covariance matrix, directly constraining estimation accuracy rather than LOS angle changes. Using covariance propagation and the Sherman–Morrison formula, the criterion is reformulated as a simple quadratic inequality on relative position, enabling computationally efficient onboard optimization. A guidance strategy that minimizes ΔV while satisfying the proposed observability constraint is developed and validated through rendezvous simulations for JAXA’s Next Generation Sample Return mission targeting 289P/Blanpain. Demonstration result shows the practical applicability of the proposed approach for deep-space AON-based navigation.