ABSTRACT
Civilian Earth observation started with the launch of TIROS-1, carrying an electron beam imaging (TV camera) system. The need to cover larger spectral regions soon led to the replacement of electron beam imagers with systems using discrete detectors. In this arrangement, radiance from the scene is directed to the optics with the help of a mechanical scanner and, hence, such systems are known as optomechanical scanners. Because of the mode of scanning, they are also known as whiskbroom scanners.
