From Phase to Current: A Unified Error Framework for Dual-Beam ATI-SAR Ocean Current Retrieval

Abstract

Dual-beam along-track interferometric synthetic aperture radar (DBATI-SAR) is a promising technique for retrieving two-dimensional ocean surface currents from two squinted radial-velocity observations. Its retrieval accuracy, however, is affected by heterogeneous error sources arising from wind-field uncertainty, geolocation offsets, beam- and attitude-control deviations, projection-geometry perturbations, and random phase noise. This article develops a unified joint-error modeling framework to describe how these perturbations propagate from the phase and radial-velocity domains into the retrieved current-vector domain. Analytical expressions are derived for the individual error terms and their combined propagation, providing a consistent basis for mission-level performance assessment and tolerance allocation. Full-chain simulations using representative Ku-band DBATI-SAR parameters show that the proposed model can predict retrieval errors under simultaneous multisource perturbations. The results indicate that wind-field uncertainty and attitude-induced cross-track residuals are the dominant contributors, whereas geolocation errors, projection-matrix perturbations, and random phase noise are generally secondary under the considered configurations. A real-data consistency assessment using DBATI-SAR measurements acquired over the Chudao coastal test site near Weihai, China, together with CMEMS and HYCOM reference fields, further supports the physical plausibility of the modeled error range under practical observation conditions. Overall, the developed framework can provide quantitative accuracy constraints and tolerance indicators for DBATI-SAR system design, offering theoretical support for future spaceborne ocean-current observation missions.