TABLE OF CONTENTS In this chapter, sea clutter is described in terms of its observed characteristics. These observations will provide the foundations upon which the themes of subsequent chapters are developed.
Radars operating in a maritime environment inevitably encounter backscattered radar signals from the sea surface, usually referred to as sea clutter. For some applications, such as remote sensing systems, the reception of this backscattered signal may be the main purpose of the radar. Space-borne synthetic aperture radars, with spatial resolutions of a few meters, are used for oceanographic studies, gathering data on waves and currents, sea ice and so on. Scatterometers measure average backscatter over hundreds of square kilometres to measure wind speed and direction over the sea surface.
For most other applications, the backscatter from the sea is unwanted and may interfere with the radar's operation. For example, almost all airborne radar operation over the sea encounters sea clutter, whether the radar is used for long range surveillance of shipping, detection of other aircraft or detecting very small targets such as submarine periscopes. Similarly, ship-borne radars, whether used for navigation or surveillance of the air and sea, must contend with unwanted sea clutter.
The characteristics of sea clutter over this range of applications may vary extremely widely. The radar system designer needs to understand these characteristics in order to develop suitable signal processing strategies and to predict performance under different conditions. An important step in achieving these goals is the development of accurate statistical models of the clutter return.
