Active microwave sensing of the Earth's surface--A mini review

Radar has been used for remotely sensing the surface of the land and sea since the middle of World War II, but only since the mid-1960's has this technique become widely used for civil purposes. The nature of radar backscatter and theoretical models that have been used to describe it are briefly described. The state of knowledge of radar return from both land and sea is summarized. The principal radar remote sensing instruments are briefly described. A summary is presented of applications of sidelooking radar to observing the land and of various radar sensors (SLAR, scatterometers, altimeters) to observing the sea. Finally, the future of this technique is assessed both in terms of the applications and instruments to be expected during the remainder of the 1970's and the following decade and in terms of research that is needed for radar remote sensing to realize its full potential.