Microwave and millimeter-wave radar remote sensing
Project Title: Retrieval of Soil Moisture and Roughness From the Polarimetric
Students: Yisok Oh, Tesn-Chie Chiu, Dan Zahn
Soil moisture, its temporal and spatial variations are influential parameters
in both climatic and hydrologic models. With the advent of synthetic
aperture radar (SAR) and radar polarimetry, radar remote sensing of
soil moisture has attained significant prominence in the past decade.
In this study, we are investigating the theoretical, numerical, and
experimental aspects of electromagnetic scattering from rough surfaces.
In the general case, the microwave backscatter from natural surfaces
is determined by three major factors: (1) the roughness statistics of
the soil surface, (2) soil moisture content, and (3) soil surface cover.
To develop an accurate inversion model for soil moisture we have conducted
an extensive experimental measurements of the radar polarimetric backscatter
from bare soil surfaces at 1.25, 5.3, and 9.6 GHz over a wide range
of moisture conditions and roughness scales. These data set is used
for two purposes: (a) evaluation of the prediction accuracy of theoretical
surface scattering models such as small perturbation, physical optics,
and geometric optic models, and (b) development of an accurate semi-empirical
model. Theoretical expressions for the bistatic scattering coefficients
of soil surfaces with slightly rough interface and stratified permittivity
profile are being developed. The scattering formulation is based on
a new approach where the perturbation expansion of the volumetric polarization
current instead of the tangential fields is used to obtain the scattered
field. In addition to these activities, novel numerical scattering code
for rough surfaces based on volumetric and surface integral equations
are under development.