Microwave remote sensing

Microwave remote sensing is rapidly reaching the stage af maturity enjoyed by optical and infra-red systems. The value of microwaves is that the atmosphere is almost transparent within this band. Microwaves therefore offer a view of the earth surface that is completely unobstructed by clouds. Both passive and active microwave systems have been utilized for measuring several geophysical phenomena. Microwave radiometers have, for example, measured ocean temperature and salinity, winds over the ocean, soil moisture through vegetation, and the age of arctic ice. Active microwave systems (scatterometers, short pulse altimeters, and imaging radars) have proven their capability to measure wind speed and direction over the ocean, ocean wave height, the topography of the earth, and the conditions of crops. Numerous other applications can be found in the recent technical literature. As detailed examples of the value of microwave remote sensing, this article describes two systems which are approaching an operational stage.