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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIFORNIA 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov http://www.jpl.nasa.gov/

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 moisture.

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. 

-end-

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