Radar signatures of terrain: Useful monitors of renewable resources

The development and utilization of techniques for civilian-oriented satellite remote sensing of the earth began in the early 1960's with the launch and operation of meteorological and weather satellites. Among the numerous sensing systems that have since been transported into space for experimental and operational purposes, the four satellites in the Landsat series have played a leading role in establishing remote sensing as an integral natural resource management tool in today's technological society. The Landsat systems-three of which were placed in orbit in the 1970's, and one in 1982-were equipped with multispectral optical scanners designed primarily for land applications. Despite their usefulness in a wide variety of geoscientific applications, the optical scanners do, nevertheless, have their limitations; the most serious of these is their inability to provide information about the surface of the earth when obscured by cloud cover. In the field of remote sensing, the decade of the 1980's will witness a new generation of space sensors; chief among them will be the synthetic-aperture radar (SAR). In addition to its cloud cover penetration capabilities, the SAR possesses many attributes in terms of its electro-magnetic response to surface features. As a result, the use of radar imagery, together with optical imagery, is expected to yield both greater amounts of and more accurate information about the earth's surface than has hitherto been possible. This paper endeavors to provide a general overview of the backscattering behavior of terrain surfaces, and to examine the potential use of radar in the monitoring of renewable resources.