Performance evaluation of spaceborne iGNSS-R waveform re-tracking

Sea surface height inversion technology based on Global Navigation Satellite System Reflectometry (GNSS-R) has garnered increasing attention in ocean remote sensing due to its low cost and high spatiotemporal resolution. Despite significant advancements in spaceborne GNSS-R ocean altimetry, most existing studies remain limited to single-frequency signal waveform data obtained through the conventional (cGNSS-R) method. For the first time, this study systematically evaluates the applicability of existing re-tracking algorithms in multi-frequency, multi-system iGNSS-R altimetry scenarios, based on multi-frequency measured waveforms acquired via spaceborne interferometric GNSS-R (iGNSS-R) signal processing. Experimental results reveal significant differences in the altimetry performance of GPS L1/L5, BDS B1/B2, and Galileo E1/E5 signals across different re-tracking methods. Notably, the HALF method exhibits a mismatch with iGNSS-R waveform characteristics due to its fixed tracking coefficient (0.75). Through quantitative power ratio analysis, a dynamic tracking coefficient adjustment strategy is proposed, serving as a reference for optimizing spaceborne iGNSS-R altimetry algorithms.