Science team members and an astronaut from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) missions -- launched on the space shuttle Endeavour in April and October 1994 -- are presenting findings from the two highly successful flights today at the American Geophysical Union's fall meeting in San Francisco.
"Both flights succeeded in acquiring 100 percent of the planned science data," said Dr. Diane Evans, SIR-C project scientist at NASA's Jet Propulsion Laboratory. "In addition, mission planners were able to redirect the radars during each flight to take advantage of rapidly changing conditions on the ground."
During the April flight, observations were taken of flooding in the midwestern United States and in Germany, and three different views of tropical cyclone Odille were added to the mission plan. During the second flight, the Kliuchevskoi volcano erupted just hours after launch on September 30 and the SIR-C/X-SAR team was able to retarget upcoming data passes over the Kamchatka peninsula to acquire several views of the eruption.
"The Endeavour astronauts were among the first witnesses to the eruption," said JPL's Dr. Jeffrey J. Plaut, experiment scientist on the SIR-C/X-SAR team. "The crew tracked the progress of the eruption daily, providing us with the most detailed documentation of a large eruption ever obtained from orbit."
"In total, both crews took more than 20,000 photographs of Earth to capture environmental conditions and seasonal changes at the hundreds of radar targets around the globe," added Dr. Tom Jones, one of the astronauts aboard Endeavour.
In addition to recording dramatic environmental differences between the April and October flights, SIR-C/XSAR science team members experimented with the new technique of "interferometry" to produce three-dimensional images of the Earth's surface. In October, the radars were flown twice over nearly identical orbit passes to generate two long swaths of interferometric data at dozens of sites around the world. Digital elevation computer models were generated at all three radar frequencies to produce the 3-D effect.
SIR-C/ X-SAR data were acquired over most of the volcanoes currently being studied as part of an international research program known as the United Nations International Decade for Natural Disaster Reduction. Spaceborne radar is an ideal tool for volcano research because it provides a safe vantage point from which to look at hazardous and often inaccessible areas. Several of the volcanoes viewed by SIR-C/X-SAR included:
-- Mt. Pinatubo in the Philippines;
-- Mt. Nyiragongo in Zaire;
-- Mt. Rainier in Washington state;
-- The volcanoes on the Kamchatka peninsula, including Mt. Kluichevskoi;
-- A previously unknown volcano in Colombia that was discovered in imagery of the Andes volcanic arc.
Scientists are using SIR-C/X-SAR data to study how the Earth's global environment is changing. The SIR-C/X-SAR radar data provides information about how many of Earth's complex "systems" -- those processes that control the movement of land, water, carbon and heat -- work together to make this a livable planet. The science team is particularly interested in studying the amount of vegetation coverage, the extent of snow packs, wetlands areas, geologic features such as rock types and their distribution, volcanic activity, ocean wave heights and wind speed.
The international science team has already used the data to produce a variety of results, including:
-- Tree classification and vegetation biomass maps of the Raco, Michigan supersite, generated by investigators from the University of Michigan.
-- A map showing clear cutting and regrowth was also generated for the Landes Forest in southwestern France.
-- A map of flooding near Manaus, Brazil -- the first step toward improving models of both flooding and wetlands under dense forest canopies.
-- Detailed soil moisture maps of the Chickasha, Oklahoma, supersite showing how the area changed between April 12, shortly after about 2 centimeters of rain, and on April 15, following three days of drying.
-- A snow wetness map (showing free liquid water content in the snow pack) of Mammoth Mountain, Calif., was generated with data from the April flight by the University of California at Santa Barbara. Additional data from the October flight will be used for estimates of snow water equivalency (the amount of water stored in a snow pack).
-- Extensive wave energy information was collected over the Southern Ocean by an associated experiment provided by the Johns Hopkins Applied Physics Lab. These data will help scientists study how the Earth's climate is moderated by the ocean.
-- In October, data were collected in support of a controlled oil spill experiment conducted by Germany in the North Sea that was designed to measure the radar signature of different weights and types of oils.
-- Monitoring of changes in the glaciers of the Patagonian Andes in the far southern region of South America. These poorly studied glaciers are among the most rapidly advancing in the world and are thought to be sensitive indicators of global climate change.
In addition, several areas of cultural interest continue to be studied with the use of SIR-C/X-SAR data. Among those areas are:
-- The mountain gorilla habitat in central Africa;
-- The area around the ancient Silk Road in northwest China;
-- The lost city of Ubar on the Arabian peninsula;
-- Buried river channels under the Sahara Desert.
SIR-C/X-SAR is a joint mission of the United States, German and Italian space agencies. JPL built and manages the SIR-C portion of the mission for NASA's Office of Mission to Planet Earth.
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