Scatterometer
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A radar scatterometer is designed to determine the normalized radar cross section (sigma-0) of the surface. Scatterometers operate by transmitting a pulse of microwave energy towards the Earth's surface and measuring the reflected energy. A separate measurement of the noise-only power is made and subtracted from the signal+noise measurement to determine the backscatter signal power. Sigma-0 is computed from the signal power measurement using the distributed target radar equation.
The primary application of spaceborne scatterometry has been measurements near-surface winds over the ocean. By combining sigma-0 measurements from different azimuth angles, the near-surface wind vector over the ocean's surface can be determined using a geophysical model function (GMF) which relates wind and backscatter. Scatterometer wind measurements are partiularly useful for monitoring hurricanes. Scatterometer data is being applied to the study of tropical vegetation, polar ice, and global change.