Spaceborne imaging radars probe `in depth'

A vast array of sensors have been placed in earth orbit in the last 10 years. Passive sensors in the optical, infrared, and microwave portions of the spectrum have been returning data on geological resources, land-use patterns, soil moistures, and sea and ice conditions. Since 1978, active microwave sensors - scatterometers and altimeters - have been measuring sea surface winds and sea roughness. But the newest "eyes" in space - synthetic-aperture radars, or SARs - utilized some of the most sophisticated sensor technology ever flown in orbit.