Spatiotemporal Ambiguity-Driven System Parameter Design Method for Moon-Based SAR

Moon-based synthetic aperture radar (SAR) offers a vantage point for continuous, hemispheric-scale Earth observation. However, existing research primarily focuses on individual performance metrics or geometric coverage, lacking an effective system design methodology that jointly accounts for spatial coverage, timing constraints, and ambiguity performance. This article addresses the challenges of performance analysis and parameter design for Moon-based SAR. First, the spatiotemporal evolution of range and azimuth ambiguities is investigated. By incorporating the dynamic Earth-Moon geometry, this study analyzes the fluctuation amplitudes of range and azimuth ambiguities, which reach up to 18 and 11 dB, respectively, and explains their periodic degradation mechanisms. Second, an iterative framework for system parameter design and performance evaluation is proposed. This methodology addresses the complex trade-offs among system variables, establishing a pulse repetition frequency selection mechanism to enable the constrained joint selection of critical parameters such as antenna dimensions and beam position allocation. Finally, the proposed framework is validated through distinct C-band Moon-based ScanSAR design scenarios: a wide-swath mode (5000 km, 30 m resolution) and a high-resolution mode (1000 km, 3 m resolution). The evaluation of imaging metrics, including the noise equivalent sigma zero under average transmitted power constraints, demonstrates the applicability of the design method to diverse Earth observation missions.