TheSASS^{1}scattering coefficientσ° algorithm

This paper describes the algorithms used to convert engineering unit data obtained from the Seasat-A satellite scatterometer (SASS) to radar scattering coefficients (
\sigma\deg
) and associated supporting parameters. A description is given of the instrument receiver and related processing used by the scatterometer to measure signal power backscattered from the earth's surface. The applicable radar equation used for determining
\sigma\deg
is derived. Sample results of SASS data processed through current algorithm development facility (ADF)
\sigma\deg
algorithms are presented which include
\sigma\deg
values for both water and land surfaces,
\sigma\deg
signatures for these two surface types are seen to have distinctly different characteristics. As expected,
\sigma\deg
values for water show strong dependence on both incidence angle and wind speed. For land,
\sigma\deg
values are relatively independent of incidence angle above
20\deg
and have values in the range
-14 < \sigma\deg < -6
dB.
\sigma\deg
measurements of the Amazon rain forest indicate the usefulness of this type of data as a stable calibration reference target. Using this Amazon data, relative biases between all four antennas and both polarizations are shown to be less than 0.4 dB.