Spaceborne Imaging Radar Research in the 1990s: an Overview

The imaging radar experiments on Seasat (1978) and on the space shuttles (SIR-A in 1981 and SIR-B in 1984) have resulted in wide interest in the use of spaceborne imaging radars in earth and planetary sciences. The radar sensors provide unique and complementary information about what is acquired with visible and infrared imagers, including subsurface imaging in arid regions,I ,2 allweather observations of ocean-surface dynamic phenomena,3-5 structural mapping, 6-8 soil moisture mapping, 9 and stereo imaging and the resulting topographic mapping. 10 Until now, experiments have exploited only a very limited range of the generic capability of radar sensors. With planned sensor developments in the late 1980s and early 1990s, a quantum jump will be made in our ability to exploit fully the potential of these sensors. Developments include (Table 1) multiparameter research sensors such as SIR-C and X-SAR; long-term and global monitoring sensors such as the European ERS-l, the Japanese JERS-l, the Canadian Radarsat, and the proposed NASA programs EOS (Earth Observing System) and GLORI (Global Radar Imager), the spaceborne sounder; and planetary mapping sensors such as the Venus Magellan and Cassini/ Titan mappers, topographic three-dimensional imagers such as the scanning radar altimeter, and three-dimensional rain mapping. These sensors and their associated research are briefly described in this article.