TABLE OF CONTENTS Measuring waves and currents
Microwave scatterometry
Microwave altimetry
Synthetic aperture radar and its applications
The way radio waves scatter from the earth's surface can be used to investigate large-scale features of land and sea.
Random, noise-like processes are often interesting, but the surface of the sea has a particular fascination. People stare at it for hours. For a radar engineer, the challenge is first to find out how radio waves are scattered from the sea and then to turn the problem round and ask, How can we determine what is happening at sea from our radar observations? In some ways, this type of inverse problem is like being given an answer and having to find the question.
What is an ocean wave? We must answer this question before we can make any progress with the problem. Wave motion is carried by particles of water exhibiting circular motion as the wave travels past. This is easily demonstrated by floating a cork, or small piece of wood, on the sea and watching it move as a wave travels by. At the surface of the sea these circular motions can have quite large amplitudes, but they quickly die away with depth (see Fig. 11.1). Submarines soon avoid the effects of wave motion when they submerge.
Figure 11.1 shows why the shape of the wave itself is not a sinusoid but...
