Remote sensing of the earth with spaceborne imaging radars

Recent scientific and technological developments are reviewed in the field of earth observation with spaceborne imaging radars. Such developments, beginning with Seasat in 1978 and continuing with the Space Shuttle in 1981 and 1984, were made possible by the use of new large spaceborne lightweight planar array antennas (2 x 10 m) with printed radiating elements. Transmitters were solid-state 1-kW peak power units operating at L-band (1.2 GHz). Images were obtained to monitor sea ice, soil moisture, and geologic, biologic and oceanographic features. Optical and digital processing was done to achieve high resolution (25 to 40 m). More advanced systems are under development, including multispectral, multipolarization imaging radar systems for flight in the late 1980s. An overview of planned activities in the 1980s is given.