Simulation of Pol-SAR Imaging and Data Analysis of Mini-RF Observation From the Lunar Surface

• Published in: IEEE transactions on geoscience and remote sensing 2022, Vol.60, p.1-11
• Main Authors: Liu, Niutao, Jin, Ya-Qiu
• Format: Article
• Language: English
• Subjects: Circular polarization; Circular polarization ratio (CPR); Components; CP SAR; Data analysis; decomposition; Digital Elevation Models; Digital imaging; Echoes; Horizontal polarization; Ice; Incidence angle; Lunar craters; Lunar surface; miniature radio frequency (Mini-RF); Moon; Polarimetry; Polarization; Radar; Radar clutter; Radar echoes; Radar imaging; Radio frequency; Ray tracing; Rough surfaces; SAR (radar); Scattering; Simulation; Statistical analysis; Statistical methods; Surface roughness; Synthetic aperture radar; Titanium dioxide; Vertical polarization; water ice
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2021.3064091

High circular polarization ratio (CPR) characteristics were found in permanently shaded regions (PSRs) near the lunar poles. High CPR was regarded as a water ice index. The compact-polarimetric (CP) miniature radio frequency (Mini-RF) radar transmits left-circularly polarized signals and receives horizontally polarized ( S_{\text {HL}} ) and vertically-polarized ( S_{\text {VL}} ) echoes from the lunar surface. Statistics of the CPR data show its relations with the relative phase ( \delta ) between S_{\text {HL}} and S_{\text {VL}} and the degree of polarization ( m ) but few interpretations were provided. The average CPR data reach the maximum and minimum at \delta =\pm 90^{\circ } , respectively. As m becomes very small, the CPR approaches 1. It has been found that CPR is also affected by surface roughness and incidence angle of radar waves. The CPR is now expressed in CP mode to explain the Mini-RF observation. Full-polarimetric radar echoes and CP parameters of the lunar surface are numerically simulated using the bidirectional analytic ray-tracing method. Single-bounce and multiple-bounce scattering components are included in the simulation. Radar images of the lunar crater are simulated with the digital elevation model (DEM) data. The H-\alpha decomposition derived from the full-polarimetric simulation is presented to analyze \delta and m . Simulated radar images with different surface roughness are analyzed statistically to study the functional dependences of \delta , {m} , and CPR on incidence angle and roughness. Relationships a