Abstract: Deep space bistatic radar measurements face several challenges in planetary exploration, including rapidly varying observation geometry, extremely low signal-to-noise ratios, and difficulties in calibrating channel gain and phase due to the absence of onboard calibration sources. To address these issues, this study develops a bistatic radar terrain inversion system tailored for deep space applications. Using the SPICE （Spacecraft Planet Instrument C-matrix Events） toolkit and focusing on echo data acquired under near-backscatter conditions, the system integrates geometry modeling, data calibration, and multiparameter inversion of surface characteristics. The analysis demonstrates that the proposed system successfully extracts electromagnetic indicators associated with potential water-ice deposits in the lunar south polar region, including enhanced echo power, locally elevated circular polarization ratios （CPR）, reduced dielectric constants, and disturbed cross-spectrum phase behavior. These combined features support the possible presence of polar water-ice deposits. The results further verify the effectiveness of deep space bistatic radar for surface and material inversion and provide a scalable technical pathway for future bistatic radar applications in deep space missions.