The most volcanically active region in the world -- the Pacific Rim -- is center stage for a comprehensive Earth- observing mission being conducted over the next 2 1/2 months by NASA and a team of scientists from several research institutions.

The ambitious program to collect data in more than 15 countries around the Pacific Ocean got underway today with the deployment of NASA's DC-8 Flying Laboratory from NASA's Dryden Flight Research Center at Edwards, Calif. Operated by the Airborne Science Directorate at NASA Dryden, the highly modified aircraft is carrying a suite of precision instruments to document geographic and atmospheric factors throughout the Pacific Rim area on its scientific odyssey.

Among the areas where data will be collected during the Pacific Rim 2000 mission conducted by NASA's Earth Science Enterprise are Cambodia's Angkor Wat Temple, French Polynesia, Papua New Guinea, the Philippines and the Australian coastal wetlands.

"The mission of PacRim 2000 includes gathering geographic and atmospheric data for coastal analysis and oceanography, forestry, geology, hydrology and archaeology," said Ellen O'Leary, PacRim 2000 mission coordinator at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This mission will provide a great deal of valuable information to each of the countries in which we are gathering data."

The primary PacRim 2000 instrument is the Airborne Synthetic Aperture Radar (AIRSAR), designed and built by JPL. AIRSAR is NASA's radar technology testbed and is used to demonstrate technology for spaceborne radar missions, such as the Shuttle Radar Topography Mission that flew on Space Shuttle mission STS- 99 in February 2000, according to Dr. David Imel, JPL's AIRSAR project manager.

AIRSAR also collects data for Earth science research and is an all-weather imaging tool, able to see through clouds and collect data at night. Radar's ability to collect data of the Earth's surface, even in cloud-covered regions, makes it a particularly valuable tool for the tropical areas around the Pacific Rim that are often covered with clouds. The instrument's longer wavelengths can also penetrate into the forest canopy, providing scientists with data at different levels in the forest.

The AIRSAR radar antenna panels are mounted on the outside of the aircraft and the instrument looks to the side of the flight path. The radar transmits microwaves and the return signal is collected after the Earth reflects it. Rough areas, such as cities, mountains and forests, have more surfaces for the signal to reflect off; they therefore return more of the radar signal to the antenna and appear brighter on the resulting radar image.

In contrast, smooth areas, such as deserts, roads and water surfaces, return less of the radar signal and appear darker on the radar images. Trees with differing branch and leaf structures will also return different amounts of the radar signal to the antenna. The resulting data can be used for forest and land-cover classification purposes.

In addition to collecting data about the roughness characteristics of the surface, AIRSAR can also collect data that is processed to high-resolution digital elevation models, which are three-dimensional topographic maps of the surface.

A third type of AIRSAR data is used to measure motion of currents and waves. Digital elevation model data are particularly important to disaster managers around the Pacific Rim who are responsible for developing plans to mitigate and respond to natural hazards such as typhoons, earthquakes and volcanic eruptions, which affect nearly everyone around the Pacific Rim "Ring of Fire."

Also onboard the DC-8 is the MASTER instrument, which is the MODIS/ASTER airborne simulator. The Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) are two instruments on NASA's Earth Observing System (EOS) Terra satellite launched in December 1999. The MASTER instrument is used to obtain detailed maps of land surface temperature, emissions and reflectance.

PacRim 2000 is the first mission to operate both the AIRSAR and MASTER instruments simultaneously on the DC-8. Michael Fitzgerald, manager of EOS simulation data production for the Airborne Sensor Facility at NASA's Ames Research Center, Moffett Field, Calif., anticipates exciting results from combining AIRSAR and MASTER data collected over the same site. For example, MASTER data can be draped over digital elevation model data generated by AIRSAR, providing scientists with additional insight on how topography affects the vegetation and land surface temperature as seen in the MASTER data.

NASA's DC-8 Flying Laboratory is a former long-range jetliner that has been converted into a world-class airborne scientific laboratory. It can carry 30,000 pounds (13,600 kilograms) of scientific instruments and equipment along with scientists and experimenters, cruising at altitudes up to 42,000 feet (12,800 meters). Its range is 5,400 nautical miles (10,000 kilometers) and it has a flight duration of up to 12 hours. The aircraft is scheduled to return to NASA's Dryden Flight Research Center on October 23.

A map of the flight plan is available at:

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Alan Brown, NASA Dryden Flight Research Center (661) 276-2665