Cross-pol InSAR coherence degradation due to wave penetration into layered, anisotropic media

We numerically study degradation in the cross-polarized, complex-valued Interferometric Synthetic Aperture Radar (InSAR) coherence's magnitude (correlation) and phase due to electromagnetic (EM) wave penetration and guidance within planar-layered, (effectively) electrically anisotropic (i.e., electric field direction dependent) geophysical media. Specifically, we examine scenarios involving subsurface layers exhibiting electrical response given by deviated anisotropic tensors exhibiting low loss and high inter-layer dielectric contrast (i.e., strong subsurface wave guidance), as well as predominantly cross-pol specular interface scatter (XSIS)-based subsurface backscatter. We hypothesize that this scenario can occur within myriad layered geophysical structures containing media hosting a distribution of sub-wavelength, non-spherical inclusions with mean non-vertical orientation. Guidance-enhanced, XSIS-based backscatter we predict can dominate cross-pol InSAR observations (particularly at lower frequencies such as P-band) concerning these types of structures, leading (in the limit of stronger wave guidance) to rapid, inverse-quadratic degradation of correlation versus InSAR spatial baseline, as well as high and linearly divergent phase bias. Modeling the dominant cross-pol backscatter mechanisms adds another tool for Polarimetric InSAR (PolInSAR) data interpretation and inversion concerning sea ice and other complex layered geophysical structures which can contain media possessing effective anisotropic dielectric response.