NASA scientists are developing and using a variety of airborne and spaceborne remote-sensing tools to study potentially dangerous volcanoes that could one day threaten populated areas in the United States and around the world.

A number of domestic volcanoes are being studied, including Mount St. Helens and Mount Rainier in Washington; Mount Shasta and Lassen Peak in California; and Kilauea and Mauna Loa in Hawaii. Using information collected with the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR), the Airborne Synthetic Aperture Radar (AIRSAR), the Airborne Emission Spectrometer (AES), the Thermal Infrared Multispectral Scanner (TIMS), the airborne Laser Altimeter Facility, and the Shuttle Laser Altimeter, scientists create three-dimensional "flyover" video animation clips that help them study how the volcanoes are changing.

"Imaging radar is a particularly useful tool for studying volcanoes because the radar is able to see through the weather and volcanic clouds. It's a good tool for mapping new volcanic deposits because of the radar's sensitivity to texture such as ash and different types of lava flows," said Dr. Jeffrey J. Plaut, SIR-C experiment scientist at NASA's Jet Propulsion Laboratory. "We are using radar data to study the dormant lava domes in Long Valley, CA so we can understand how lava is placed during eruptions. Understanding the eruptive process helps us know where lava will flow and that has bearing on the hazards that are posed to the nearby communities, including the Mammoth Mountain ski areas."

"By combining the radar data with information from scanning laser altimeters, we are now tracking changes at the summits of Mount St. Helens and Mount Rainier that will document the impact of erosion, climate and other factors on the topography and stability of large volcanoes," said Dr. James B. Garvin, chief scientist for the Shuttle Laser Altimeter at NASA's Goddard Space Flight Center (GSFC), Greenbelt, MD. "These laser altimeters also have successfully measured the flank topography of volcanoes beneath their tree canopies. This is important because many of the most dangerous volcanoes are heavily vegetated, and the subtleties of their local relief must be known to accurately predict the path of their flows."

In recent months, AIRSAR, AES and TIMS were part of a cadre of scientific instruments onboard a NASA DC-8 aircraft that captured images of the Manam volcano within hours of an eruption on an island off the north coast of Papua New Guinea. "The airborne instrument helps us map the topography from a safe distance. The data over Manam were collected as a "target of opportunity" and the topographic data set will serve as a valuable baseline for studies about future changes to the volcano," said Ellen O'Leary, the AIRSAR science coordinator at JPL.

"We use the thermal infrared data to study volcanoes in three ways. The first is to map ground temperatures, which we can relate to geothermal phenomena. The second is to map variations in the composition of lava flows and the third is to map the sulfur dioxide in volcanic plumes," said Dr. Vincent J. Realmuto, TIMS experiment scientist at JPL. "TIMS data are useful for studying volcanoes because thermal infrared remote sensing is the only practical means of obtaining virtually instantaneous maps of dynamic phenomena such as the distribution of temperatures on the ground or sulfur dioxide in a plume. Such data are of great use in monitoring volcanoes, where changes in ground temperatures or sulfur dioxide emission can signal impending activity."

JPL's Digital Image Animation Laboratory (DIAL) turns the scientific data into three-dimensional video animations and other images. "These visualizations can range from the simple, such as the use of color to combine data sets, to the complex, such as simulated flights through the data. The basic objectives of data visualization are to give scientists new perspectives into complex data sets and to permit them to communicate their findings in a format that is both compelling and accessible," Realmuto said.

The DIAL is best known for visualizations of planetary data sets of Venus and Mars, but visualizations have been produced for a variety of volcanoes, such as Mount Rainier, the Long Valley caldera in the Mammoth Mountains of California, Mauna Loa, Mount Pinatubo and Taal in the Philippines, Mount Etna near Sicily, and the trans-Mexican volcanic belt. The most recent addition to this series is a simulated flight over Mount St. Helens that was created by combining TIMS data with a high-resolution digital elevation map.

AIRSAR is the airborne cousin of SIR-C/X-SAR that flew twice on the space shuttle Endeavour in 1994. AIRSAR also uses three radar wavelengths: L-band (24-cm), C-band (6-cm) and P-band (68-cm) and can collect data in both vertical and horizontal polarization. AIRSAR can also be used to collect three- dimensional topographic data in its TOPSAR mode to create digital elevation models.

TIMS collects image data in the thermal infrared portion of the spectrum. TIMS operates at six channels between 8 and 12 micrometers. For comparison, visible light extends from 0.4 to 0.7 micrometers. TIMS is a precursor to the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) that is scheduled to fly on the first Earth Observing System satellite (EOS AM-1) in 1998.

AES is a spectrometer that operates between 2.3 and 15.4 micrometers, and is a precursor to the Tropospheric Emission Spectrometer (TES). TES is scheduled for launch aboard the EOS CHEM-1 platform in 2002.

The GSFC Laser Altimeter Facility sensors are routinely flown aboard NASA Wallops Flight Facility aircraft such as the P-3 and T-39. The Shuttle Laser Altimeter (SLA) experiment flew on STS-72, and a second flight of SLA is scheduled for July 1997 as part of STS-85.

JPL manages the SIR-C/X-SAR, AIRSAR and AES missions for NASA's Office of Mission to Planet Earth, Washington D.C. TIMS and the DC-8 aircraft are maintained and operated by NASA's Ames Research Center, Moffet Field, CA. All of these instruments are part of NASA's Mission to Planet Earth, a coordinated research enterprise designed to study the Earth as a total system.

For more information: http://www.geo.mtu.edu/eos/

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