NASA's airborne imaging radar system is set to its first major campaign of 1998, a three-week series of missions involving 11 flights from April 17 through May 1 focusing on 13 imaging and data-collection Earth science experiments.
The highly modified jetliner is one of three specialized aircraft in NASA's Airborne Science Program based at NASA's Dryden Flight Research Center, Edwards, CA. The DC-8 serves as a platform for multiple experiments at altitudes up to 42,000 feet.
The current campaign centers on the remote imaging and data- collection capabilities of the Airborne Synthetic Aperture Radar (AIRSAR) system developed at NASA's Jet Propulsion Laboratory. Two AIRSAR antenna systems mounted on the DC-8's left rear fuselage, assisted by an integrated Global Positioning System/Inertial Navigation System, allow for precision measurement of the resulting high-resolution digital elevation models.
According to Chris Jennison, Dryden's mission manager for this campaign, the primary objective of this series of flights is to obtain data for use in topographic mapping, geologic research and hydrology.
"Because it produces such a wide variety of data, the synthetic aperture radar can be used to interpret many different environmental and natural phenomena, such as moisture content and soil studies," he said. "We fly at a very specific altitude and a very precise speed. By accurately measuring the time between when a radar pulse is sent out and when it's returned to the antenna, the radar can produce a very fine resolution image."
AIRSAR was developed more than a decade ago by JPL radar scientists and engineers. It is an all-weather imaging device that can penetrate clouds, forest canopies and, in dry areas, thin sand and dry snow packs. AIRSAR sends and receives radar waves that are sensitive to the material on Earth's surface such as geologic features, vegetation and water content.
Experiments are being flown over mountains in the Pacific Northwest, the Missouri River floodplain, the Gulf Coast, several locations in the Southwest and a number of geologic sites in California. Individual missions are being flown from McChord Air Force Base, Tacoma, WA.; Kelly Air Force Base, San Antonio, TX; and Dryden at Edwards Air Force Base in Southern California.
One flight over the Pacific Northwest is focused on a multi- altitude forestry study over Oregon's Santiam Pass as well as data collection over Blue Glacier in Washington's Olympic Mountains.
"Data collection at three different altitudes allows the study of the varying degrees of radar penetration into the forest canopy. This will shed light on the use of interferometry to estimate the vertical characteristics within a forest," said Ellen O'Leary, AIRSAR science coordinator at JPL. Interferometery is a technique that collects three-dimensional images of the surface.
Three flights from Dryden will target AIRSAR on 11 different geologic sites around California. These studies range from sites of surface deformations due to earthquake activity and oil and water extraction, to evaluation of the radar's ability to estimate snow properties and the amount of water released during melting. Study locations extend from the Geysers Natural Area and the Hayward Fault in Northern California to the Santa Cruz and Monterey Bay coastal areas, the Sierra Nevada range and the Santa Monica and San Gabriel Mountains in the southern part of the state.
The AIRSAR science mission is managed by JPL, a division of the California Institute of Technology, for NASA's Office of Earth Sciences, Washington, DC.
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