Space Shuttle

New geologic information in remote tropical, arid, and heavily vegetated areas was acquired by JPL's imaging radar on NASA's second space shuttle flight in November 1981, as reported in the Dec. 3, 1982, edition of Science magazine.

The experiment, called Shuttle Imaging Radar-A (SIR-A), penetrated cloud cover, varying degrees of vegetation, and dry desert sand to provide new geologic information in poorly surveyed regions.

For example, U.S. Geological Survey and JPL scientists studying SIR-A data found that the radar had penetrated beneath the extremely dry Selima Sand Sheet dunes and drift sand of the Arbain (CQ) desert in the Sudan and Egypt to reveal ancient, buried stream beds, geologic structures, and probable Stone Age habitation sites.

In inaccessible, cloud-covered regions of the Amazon, SIR-A data has provided cartographers with detailed images for more complete mapping.

The imaging radar also revealed new geologic detail in the southeastern Egyptian desert. Radar images show linear features immediately west of the Red Sea that may be hundreds of millions of years older that the Red Sea Rift, and may have guided the orientation of the rift.

In the mountainous regions of western Guyana in South America, the radar uncovered significant geologic structural detail, despite complete rainforest cover. Lineaments and other major surface features are clearly visible in the images. Field surveys are required in this poorly surveyed region before the features may be interpreted conclusively.

In the Great Kavir salt desert in Iran, SIR-A images complemented imagery from the Landsat geologic satellite and were found to be useful in identifying different surface rock and soil types, and helped determine whether the surface was altered by erosion or fracturing of the surface salt crust. In some areas, strata of the folded Miocene Era (26 million years old) bedrock were visible through the surface, feature usually obscured from view in ground surveys.

SIR-A acquired data over approximately 10 million square kilometers (3.8 million square miles) of Earth. In conjunction with other experiments on NASA's first scientific shuttle payload, SIR-A demonstrated the shuttle's useful role as platform for scientific investigations.

The sensor was returned from space in fully opera tional status. It is being modified and upgraded for second shuttle flight as SIR-B in summer 1984. SIR-B will be a fully digital system, will have higher resolution than SIR A, and will carry an antenna that can be tilted at variable angles for studying different ground and ocean features.

Principal investigator of SIR-A is Dr. Charles Elachi of Caltech's JPL. Co-investigators are from JPL; the U.S. Geological Survey, Flagstaff, Ariz.; the University of Kansas; NASA's Johnson Space Center, Houston, Tex.; the University of Arkansas; Hunting Geology and Geophysics Ltd., U.K.; the French Space Agency; and the Chevron Oil Field Research Co., Calif.

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