文档介绍：214 MICROWAVE REMOTE SENSING THEORY
image processing techniques, molecular theory of microwave
radiation of gases, etc.
The scattering effects of geophysical terrain can be charac-
terized by random rough surface scattering and volume scat-
tering from inhomogenities of the medium. In rough surface
scattering, the rough surface has many peaks and valleys and
the height profile can be described by random processes (1–3).
In volume scattering, there are many particles that interact
with microwaves. The positions of these particles are random.
Such volume scattering effects are described by random dis-
tribution of wave scattering (2,4–6). This article studies the
wave scattering by random rough surfaces and random dis-
crete scatterers and their applications to microwave interac-
tion with geophysical media in the context of microwave re-
mote sensing. At microwave frequency, the size of the
scatterers and the rough surface heights in a geophysical ter-
rain parable to microwave wavelengths. Thus, the use
of the wave approach based on solutions of Maxwell’s equa-
tions is essential.
First, we review the basic principles of microwave interac-
tion in active remote sensing and passive remote sensing.
Next, we describe vector radiative transfer theory (2,7), which
treats volume scattering and the small perturbation method
for treating rough surface scattering. With the advent of mod-
puters and the development putation methods,
recent research in scattering problems emphasizes Monte
Carlo simulations of solutions of Maxwell’s equations. These
consist in generating samples or realizations of rough surface
and random discrete scatterers and then using numerical
methods to solve Maxwell’s equations for such boundary
value problems. In the final section, we describe the results
of such approaches.
BASICS OF MICROWAVE REMOTE SENSING
Active Remote Sensing
We first consider the radar equation for scattering by a