L-band radar fading statistics vs. resolution

Radar-signal variability was investigated as a function of the size of the resolution cell from 25 m×25 m to 6400 m×6400 m, using L-band data from the Shuttle Imaging Radar-B (SIR-B). Scenes treated were from Illinois farmland, Amazon rain forest, and Japanese mountains. Fading ranges (5% to 95%), means, and medians were determined for each SIR-B scene and for composites of each area and of the entire set. It is shown that L-band radar signals from the ground vary over a 9-10-dB range at 25-m resolution, but that the variation is reduced to about 2 dB for 6.4-km footprints. For the homogeneous Amazon rain forest the variation is somewhat less than average, and for a combination of mountains, farmland, and cities in Japan it is slightly more than average. This information should be useful to radar designers in determining required system dynamic range and the range of clutter that must be discriminated against