Robert D. Kubik

Tilt modulation of high resolution radar backscatter cross sections: unified full wave approach

The unified full wave approach is used to determine the tilt modulation of the like- and cross-polarized (high-resolution) radar backscatter cross sections for the rough sea surface. Real or synthetic aperture radars (SARs) with small effective footprints (resolution cells) are considered. Since the unified full-wave approach accounts for Bragg scattering as well as specular point scattering in a self-consistent manner, it is not necessary to adopt a two-scale model for the rough sea surface. The sea surface slope probability density function is assumed to be Gaussian. The backscattering cross sections are evaluated for all angles of incidence (normal to grazing). For tilts in the plane of incidence, the modulation of all the cross sections is largest at angles of incidence of 10 degrees . The cross-section modulation due to tilts perpendicular to the plane of incidence critically depends on the incident and scattered polarizations. The effective filtering of the large-scale spectral components of the rough sea surface by the high-resolution radar is accounted for, and the dependence of the cross-section tilt modulation on the size of the effective footprint is determined. >

Computations of the Mueller matrix elements for scattering from layered structures with rough surfaces, with applications to optical detection

A full-wave method is used to evaluate the Mueller matrix elements for scattering from layered structures with random rough surfaces. These provide a database for applications in optical detection over a broad range of rough surface statistical parameters. They can be used to determine the optimal frequencies and incident angles that provide most reliable measurements for optical detection. The elements of the Mueller matrix that are most sensitive to medium parameters of the layered structures can also be identified. Contributions from individual terms of the full-wave solutions are shown to have distinct physical interpretations.

Like‐ and cross‐polarized transmission scatter cross sections for random rough surfaces: Full wave solutions

The full wave expressions for the transmission scatter cross sections for two-dimensional random rough surfaces are obtained using the full wave approach. The solutions are compared with published numerical results based on Monte Carlo simulations of rough surfaces.

SCATTERING BY LAYERED STRUCTURES WITH ROUGH SURFACES : COMPARISON OF POLARIMETRIC OPTICAL SCATTEROMETER MEASUREMENTS WITH THEORY

A laboratory model of a layered structure with a rough upper surface (a glass microscope slide cut with a diamond saw) is used to obtain optical polarimetric data. Scatterometer measurements were made of all the Mueller matrix elements associated with light scattered in arbitrary directions. (A preliminary measurement of scattering from a smooth opaque gold film on a silicon wafer was used to validate the calculation of the Mueller matrix elements.) These measurements are compared with corresponding analytical solutions based on the full-wave approach. Physical interpretations of the analytical solutions that account for scattering upon reflection and transmission across rough interfaces are given in a companion paper. The agreement between calculations and measurements suggests that the full wave, polarimetric solutions can provide a reliable database for electromagnetic detection of rough surfaces in remote-sensing applications.

Electromagnetic fields scattered from irregular layeredmedia

Full-wave expressions are presented for the electromagnetic fields scattered from a layered structure consisting of a planar surface coated by a dielectric material of irregular thickness. Each term of the full-wave expansion for the vertically or horizontally polarized electromagnetic fields scattered by the irregular stratified media has a physical interpretation. The full-wave solutions satisfy the reciprocity and duality relationships in electromagnetic theory. The slope-dependent surface scattering coefficients are invariant to coordinate transformations. The expression for the zero-order scattered field reduces to that of a specularly reflected wave from an unperturbed parallel stratified medium. The analysis is relevant to problems of communication in irregular stratified media and remote sensing of stratified media and for interpretation of ellipsometric data from irregular layered media.

Radar polarimetry applied to scattering from irregular layered media

Full-wave expressions are derived for the Mueller matrix elements that provide a complete polarimetric characterization of the electromagnetic fields scattered from irregular layered media consisting of dielectric coatings over dissipative substrates. The upper interface between free space and the coating material and the substrate is a two-dimensionally random rough surface, and the bottom interface between the substrate and the coating material is a planar surface. Each term of the full-wave expression for the vertically or horizontally polarized electromagnetic fields scattered by the irregular stratified media is shown to have a clear physical interpretation. The full-wave solutions satisfy the reciprocity and duality relationships in electromagnetic theory and are invariant to coordinate transformations. The expressions for the scattered fields reduce to that for the specularly reflected wave when the layered structure is a parallel stratified medium. The Mueller matrix or the modified Mueller matrix are measurable quantities that are used to relate the scattered Stokes vector to the incident Stokes vector. The elements of these matrices are related to commonly measured quantities in remote sensing and in ellipsometry. The analysis is relevant to problems of communication in irregular stratified media, remote sensing of irregular stratified media, and interpretation of ellipsometric data obtained from layered media.

Simulation of high resolution radar potarimetric images— unified full wave approach

Abstract The unified full wave approach is used to generate polarimctric images of composite rough surfaces illuminated by high resolution radar (i.e., real or synthetic aperture radars with small effective footprints). The unified full wave solutions account for Bragg scattering and specular point scattering in a self-consistent manner, therefore it is not necessary to decompose the surface into two surfaces with large and small roughness scales. The like and cross-potarized scattering cross-sections for the rough sea surface are tilt modulated due to the presence of swell or ship wakes. Hydrodynamic effects such as velocity bunching arc not considered here. The normal to an arbitrarily oriented mean plane associated with the illuminated resolution cell (pixel) is characterized by the tilt angles Q and t, in and perpendicular to, a fixed reference plane of incidence associated with the radar. The like and cross polarized backscatter cross sections of a tilted resolution cell are expressed in terms of the...

Real and imaginary index-of-refraction measurements for RP-1 rocket fuel

Complex index of refraction values of RP-1 liquid rocket fuel are reported at laser wavelengths of 0.193 micrometers (ArF excimer), 0.5145 micrometers (argon-ion), 0.532 micrometers (Nd-YAG, frequency doubled), 1.064 micrometers (Nd-YAG), and 10.5915 micrometers (CO2). The imaginary part of the index of refraction (k) was determined by the traditional transmission method. The real part (n-r)) is determined by reflectance measurements, critical angle, Mueller matrix, and Michelson interferometer techniques. Reflectance measurements are used to obtain nr at a wavelength of 0.193 micrometers . Critical angle method is used to determine nr at 0.5145 micrometers and 0.532 micrometers . The real part of the refractive index is obtained from Snells law by measuring the critical angle. The real part of the refractive index at 1.064 micrometers is derived based on elements of the Mueller matrix. Specular measurements were performed using a TMA scatterometer to obtain the Mueller matrix. A Michelson interferometer is used to determine nr at 10.5915 micrometers .

High Rsolution Radar Polarimetric Imaging Of The Ocean Surface Due To Tilt Modulation - Unified Full Wave Approach

The unified full wave approach is used to simulate polarimetric images of composite rough surfaces illuminated by a high resolution radar (i.e. real or synthetic aperture radars with small effective footprints). The unified full wave solutions account for Bragg scattering and specular point scattering in a selfconsistent manner, therefore it is not necessary to decompose the surface into two surfaces with large and small roughness scales. The like and cross polarized scattering cross sections for the rough sea surface are tilt modulated due to the presence of swell or ship wakes. Other hydrodynamic effects such as velocity bunching are not considered here. The normal to an arbitrarily oriented mean plane associated with the illuminated cell (pixel) is characterized by the tilt angles in and perpendicular to a fixed reference plane of incidence. The like and cross polarized backscatter cross sections of an individual tilted resolution cell is expressed in terms of the angle of incidence in the fixed reference coordinate system, the tilt angles of the resolution cell, and elements of the Phase (Mueller) matrix that completely characterizes electromagnetic scattering from an untilted resolution cell.

Complex index-of-refraction measurements for RP-1 liquid rocket fuel

Complex index-of-refraction values of RP-1 liquid rocket fuel are reported at laser wavelengths of 0.193 μm (ArF excimer), 0.4765 μm (argon ion), 0.488 μm (argon ion), 0.5145 μm (argon ion), 0.532 μm (Nd-YAG, frequency doubled), 0.6328 μm (He-Ne), 1.064 μm (Nd-YAG), and 10.5915 μm (CO 2 ). The imaginary part of the index of refraction ( k ) is determined by traditional transmission methods. The real part ( n r ) at the specific laser lines is determined using reflectance measurements, critical-angle measurements, Mueller matrix elements, and Michelson interferometric measurements. Reflectance measurements are used to obtain n r at a wavelength of 0.193 μm. The critical-angle method is used to determine n r at 0.4765, 0.488, 0.5145, and 0.532 μm: the real part of the refractive index is obtained from Snells law by measuring the critical angle. The real part of the refractive index at 0.6328 and 1.064 μm is derived from elements of the Mueller matrix, which are obtained using a TMA Technologies scatterometer. A Michelson interferometer is used to obtain phase shifts in a wedge cell, which are then used to calculate n r at 10.5915 μm. The need for many methods to measure the complex index of refraction is a result of the large changes in k over the wavelengths of interest.