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Scientists, Students Dig High and Low for 'Dirt' on Soil Moisture

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Old July 11th 03, 09:37 PM
Ron Baalke
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Default Scientists, Students Dig High and Low for 'Dirt' on Soil Moisture


Alan Buis (818) 354-0474
Jet Propulsion Laboratory, Pasadena, Calif.

Steve Roy (256) 544-0034
Marshall Space Flight Center, Huntsville, Ala.

NEWS RELEASE: 2003-097 July 11, 2003

Scientists, Students Dig High and Low for 'Dirt' on Soil Moisture

A water-sensing satellite orbits high above Earth. Airplanes packed
with research instruments, including one from NASA's Jet Propulsion
Laboratory, Pasadena, Calif., circle 25,000 feet above three U.S.
states and Brazil. Scientists, college students and other volunteers
troop into the countryside, armed with sensors and notepads. It's all
about "getting the dirt." In this case, collecting detailed
information about the soil.

The objectives are two-fold - validating soil moisture data gleaned
from satellites and working to find the optimum instrument for
conducting soil moisture remote sensing. By
learning how to better gauge the amount of moisture in the soil,
scientists are pursuing the long-range goal of eventually helping to
improve the accuracy of weather forecasts and better estimate crop
yields through remote-sensing methods.

Led by Dr. Thomas Jackson of the U.S. Department of Agriculture, Soil
Moisture Experiments in 2003 is a collaboration between NASA, the U.S.
Department of Agriculture's Agricultural Research Service, the
Brazilian Agricultural Research Corporation, several U.S. universities
and the Center for Hydrology, Soil Climatology, and Remote Sensing of
Alabama A&M University in Huntsville. The campaign began June 22 in
Huntsville and gathered data in Alabama and Georgia through July 2.
It is continuing in Oklahoma through July 19 and concludes in Brazil
Sept. 16-26.

"By gathering comprehensive soil moisture data from space, air and
land, we hope to better understand how these measurements correlate
and how the data can help farmers, weather forecasters and others who
depend on Mother Nature for their livelihood," said Dr. Charles
Laymon, a hydrologist and remote sensing scientist with Universities
Space Research Association at the Global Hydrology and Climate Center
in Huntsville.

For example, an improved understanding of soil moisture could aid
irrigation, allowing farmers to irrigate when and precisely where
necessary. This is important, Laymon said, because simple ground
observations don't always tell the whole story. That's why scientists
leading the campaign will look skyward for much of their data.

Aqua, a NASA satellite launched in May 2002, will fill in part of the
puzzle. Orbiting 692 kilometers (430 miles) above Earth, its sensors
collect information about Earth's water cycle -- including water vapor
in the atmosphere, clouds, precipitation, and snow and ice cover. The
Advanced Microwave Scanning Radiometer for Earth Observing System, a
National Space Development Agency of Japan instrument, is the Aqua
instrument scientists hope can provide information about soil

A challenge will be taking the "big picture" offered by that Aqua
radiometer instrument and filling in the gaps. "Aqua's Advanced
Microwave Scanning Radiometer for Earth Observing System was designed
primarily to monitor oceans and polar ice," Laymon said. "So the
sensor provides a very broad view of terrestrial soil moisture. To get
a more detailed look at soil moisture, we will use information from
this campaign to fine-tune the radiometer's results, and more
importantly, correlate the satellite data to measurements gleaned by
airborne instruments in the sky and by people on the ground."

The research aircraft are NASA's P-3B turboprop and DC-8 jet. Equipped
with a suite of remote sensing instruments developed for airborne
observations in support of satellite validation, including JPL's
Airborne Synthetic Aperture Radar instrument, or Airsar, they will
document patterns of surface moisture by measuring microwave energy in
units of brightness temperature and power reflected off the surface.

On the ground, teams of scientists, college students and volunteers --
rain or shine -- will disperse into the countryside daily, taking
measurements that include soil moisture and temperature, ground cover
type and plant height.

One proposed soil moisture mission that the campaign will assist in
the development of is the JPL-led Hydros remote global soil moisture
and freeze-thaw state observing system. Hydros would provide soil
moisture observations every three days or less over most of Earth's
unfrozen, non-forested regions (dense vegetation limits the ability to
sense the underlying soil moisture). The data would be used to better
understand how water, energy and carbon are exchanged between Earth's
land and atmosphere.

Dr. Eni Njoku, a JPL scientist and co-organizer of the Aqua radiometer
validation and Hydros development campaign components, said Airsar
data will be combined with ground data on soil and vegetation
conditions to develop the problem-solving procedures Hydros will use
for generating global soil moisture maps. "We hope to be able to
answer key questions, such as how well Hydros will be able to collect
soil moisture data in vegetated areas," he said. "We also expect to
gain insight into how to best combine radar and radiometer data to get
the most accurate soil moisture maps possible."

Participating NASA centers include the Marshall Space Flight Center in
Huntsville, Goddard Space Flight Center, Greenbelt, Md., and JPL.
Campaign aircraft are based at NASA's Wallops Flight Facility, Wallops
Island, Va., and Dryden Flight Research Center, Edwards, Calif. See
http://hydrolab.arsusda.gov/smex03/ for more information. JPL is
managed for NASA by the California Institute of Technology, Pasadena.



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