TABLE OF CONTENTS Radar is a highly versatile sensor. It is an active device which beams electromagnetic energy into the space it observes, and detects the presence of objects by sensing a tiny part of the energy reflected by them. Radar technology has come a long way since the days of its early development preceding and during the Second World War, and the radar has been put to multifarious uses during the intervening decades. Currently radar systems range in size and complexity from huge ones that probe hundreds of millions of kilometres into space to small hand-held sets used in sports and traffic monitoring. The radar was first used for detecting incoming hostile aircraft during World War II, and it has subsequently been perfected in this role through sustained research and development. Aircraft and other radar targets of relatively small size are called point largets, and a majority of radars are used for detecting such targets.
Radars used for observing point targets in the atmosphere also receive the echo power scattered by any raindrops within their volume of observation. Rain echoes generally interfere with the radar's ability to observe the point targets, and are dismissed as clutter. In fact, the signal processors of such radars are specifically designed to maximally eliminate weather clutter and make the point target(s) stand out clearly against the background of the interfering weather echo signals.
It was, however, the observation of weather echoes in aircraft-detecting and ship-detecting radars that first suggested the idea...
