MIRSL
AND MICROWAVE REMOTE SENSINGan Introduction
Tools for
studying the environment have been with us for centuries, but only
recently have technologies enabled scientists to study the environment
on a global scale. Traditional sensors such as thermometers,
anemometers, and rain gauges, do not provide a view of geophysical
processes over large areas of the earth. Today, such views are obtained
through microwave sensors mounted on aircraft, spacecraft, and
satellites. MIRSL has been developing a wide range of microwave
sensors to remotely sense many different kinds of geophysical processes.
One
example of MIRSL's ongoing research is their creation of microwave
sensors to gather data on clouds. Atmospheric scientists are interested
in clouds because they have a direct effect on earth's energy budget.
Clouds reflect incident sunlight back into space, while at the same
time forming a blanket over the earth below, restraining the rate of
heat radiation from the earth. This results in the minimization of wide
fluctuations in temperature on the earths' surface.
Typical
data that can be collected by millimeter-wave radar includes cloud
dimensions and the freeze and melt regions within clouds. Most of
MIRSL's millimeter-wave radars also have the capability to measure Doppler shifts,
allowing the determination of cloud motion relative to the point of
observation.
The
remote sensing of surface winds over the ocean using microwave radars
and radiometers has also been a focus of MIRSL research.
Measurement of these winds from high altitudes is possible because
surface roughness and foaming cause changes in the surface's microwave
"signature" as a function of wind speed.
MIRSL has
also been using millimeter-wave frequencies to study the scattering and
radiating characteristics of vegetation, particularly leaves. MIRSL's
objective has been to collect extensive data as a function of
wavelength, viewing angle, and polarization in order to develop
empirical and analytical models to identify moisture content and
vegetation type throughout the growing season. Such information is
valuable to assess the health of plants and for crop inventory.
Passive
microwave radiometers are also being used by MIRSL to study soil
because they are highly responsive to changes in soil's water content.
Soil moisture is a primary factor in crop yield, so the U.S. Department
of Agriculture has been very interested in MIRSL's research programs.
These are
only a few of the projects MIRSL is engaged in. For more detailed
information about MIRSL's ongoing projects, see the research section of this web site.
