Robust Angles-Only Tracking of Cislunar Noncooperative Maneuvering Targets with Observation Gaps

This study investigates space-based angles-only orbit tracking of cislunar noncooperative maneuvering targets under the Earth–moon Circular Restricted Three-Body Problem. The problem is particularly challenging when impulsive maneuvers occur during observation gaps, owing to accumulated prior errors and weak radial observability. For angles-only tracking with conventional strong tracking filters (STFs), the lack of direct radial information can lead to excessive range corrections after measurement reacquisition. To address this challenge, a line-of-sight (LOS-)discriminated adaptive pointing vector (LD-APV) filter is developed. Variable range pointing vector residuals are transformed into the pointing frame, where radial and transverse fading-factor candidates are evaluated separately. The enlarged radial pseudomeasurement variance is excluded from the transverse tests; because the radial innovation is second order in small LOS mismatch while the transverse innovation is first order, the final scalar factor is generally transverse dominated under the derived condition. This factor is applied globally to the covariance, while weak radial regularization limits the LOS Kalman gain and mitigates aggressive radial corrections. Simulation results demonstrate that LD-APV exhibits enhanced robustness compared to existing STF methods, especially for challenging coorbital tracking where target maneuvers coincide with prolonged observation gaps.