SUN GLITTER RADIANCE AND RADAR CROSS-SECTION MODULATIONS OF THE SEA-BED

Aircraft and satellite-borne multispectral sensors such as ocean color scanners, spectrometers, and scanning Lidar's have proved to be effec tive in detecting submarine shallow-water bottom topography in clear c oastal waters. For such studies the blue-green band of the visible ele ctromagnetic spectrum (wavelength between 400 and 580 nm) is used, bec ause natural light in this range has the deepest penetration into the water column. However, if the water becomes turbid, the reflection fro m the submarine sea bed disappears. In this case the only possible mec hanism available in the optical range of the electromagnetic spectrum for detecting surface signatures of shallow water bottom topography is through the observation of direct sunlight specularly reflected from a roughened sea surface, known as sun glitter radiance. As the tidal f low over irregularities on the submarine sea bed creates surface rough ness variations, sun glitter imagery can be used to detect such featur es. In this paper a first-order theory of the sun glitter imaging mech anism of submerged sand waves is presented. The results of sun glitter radiance modulations are compared with simulations of P band radar cr oss-section modulations and with experimental data. Calculations of bo th the constant background sun glitter radiance and the sun glitter ra diance modulation show that these parameters are very sensitive to win d speed, to view angle with respect to acquisition time, and to observ ation geometry as a whole.