Conference Agenda

Unlike surface, double-bounce, or volume scattering, helical scattering conveys the target's structural chirality and phase asymmetry, which can only be captured through full-polarimetric SAR systems. The study investigates helical scattering using full polarimetric C-band data from ISRO's EOS-04 satellite over general land cover types over Shadnagar, Telangana state, India to understand spatial distribution of different scattering mechanisms. ISRO’s Earth Observing Satellite (EOS-04) launched in 2022 is a follow-on Radar Imaging Satellite (RISAT-1) intended to serve operational users with an objective to provide high-quality quantitative data with extended swath coverage and spatial resolutions. EOS-04 is equipped with on-board Hybrid polarimetric architecture and Full polarimetry apart from conventional single/dual polarization to support land and ocean applications.

Methodology: The primary objective was to examine the traceability of the helical component within full-pol data, specifically to identified helical scattering directly from the covariance (COV) matrix instead of performing conventional polarimetric decompositions. The scattering mechanism viz surface (POdd), double-bounce (PEven), volume (PVol), and helical (PHelix) scattering powers within predefined Areas of Interest to identify regions with potential structural complexity and asymmetric features from Yamaguchi four-component decomposed images. The same AOIs were also applied to the corresponding Level-1C covariance product to ensure spatial consistency and direct comparison between decomposition-derived helical power (PHelix) and covariance-derived cross-polar terms. By mapping PHelix values from decomposed products against HHHV values from covariance products using the same AOIs, can establish direct spatial and numerical correspondence.

Results and Discussion: Statistical Correlation analysis revealed strong positive correlations between PHelix and specific covariance elements. This consistent pattern across all AOIs confirms that the HHHV element is the strongest statistical indicator of asymmetric scattering in the raw COV input. The covariance matrix structure for helical scattering exhibits specific properties: C₁₁ = C₃₃ (co-polarized symmetry), C₂₂ = 2(C₁₁+C₃₃) (cross-polarized dominance exceeding that of volume scattering), and purely imaginary off-diagonal elements C₁₂ and C₂₃ representing ±j phase relationships. The high correlation coefficients confirm that helical scattering power originates directly from the imaginary cross-polarized covariance terms (r approximately +0.79 to +0.82) that capture depolarization and phase quadrature relationships and negative correlations between PHelix and co-polarized intensity channels (HHHH)mean [r ≈ -0.32] and (VVVV)mean[r ≈ -0.29] confirms poor correlation. The imaginary components Im(C₁₂) and Im(C₂₃), which represent 90° phase shifts characteristic of circular polarization, serve as the mathematical precursors to helical scattering. Moreover, the calculated helical fraction (fc) also quantified the relative contribution of asymmetric scattering across different land covers supporting multiple physical mechanisms generating helical scattering at C-band frequencies. The core finding of this preliminary research is the definitive proof that PHelix is traceable from the covariance matrix.