Interpretation and Application of Spaceborne Imaging Radar Data to Geological Problems

Three synthetic aperture radars (SARs) sponsored by NASA have been flown in space. SEASAT in 1978, SIR-A in 1981 and SIR-B in 1984. Spaceborne radar image interpretation is different from airborne radar image interpretation, principally due to the wide swath and constant image geometry. Spaceborne SAR constitutes a high precision image data set in the sense that large areas are imaged under near-uniform illumination conditions. Thus spaceborne SAR images are ideally suited to geological studies of a regional nature. For spaceborne radar images a low incidence angle is probably preferable in areas of modest topography. Multifrequency observations area also needed for certain terrain-type distinctions. Subsurface imaging can occur in arid and semi-arid terrains provided that very restrictive conditions are simultaneously met. Despite the limitations sub-surface imaging has important applications in geology, hydrology, archaeology and other disciplines. Analysis of SEASAT images of a tropical terrain (Jamaica) reveals that SEASAT can provide unique information on structure and rock-type distribution on a regional scale in an environment which is not favourable for visible sensors. Possible future NASA radar missions such as SIR-B reflight, SIR-C and Space Station will provide new data from different incidence angles, frequencies and polarizations in the coming years.