Scatterometer

From Wikipedia, the free encyclopedia

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 particularly useful for monitoring hurricanes. Scatterometer data are being applied to the study of vegetation, soil moisture, polar ice, and global change. Non-terrestrial applications include study of Solar System moons using space probes. This is especially the case with the NASA/ESA Cassini mission to Saturn and its moons.

[edit] Contribution to Botany

Scatterometers helped to prove the hypothesis, dating from mid-19th century, of the anisotropic (direction dependent) long distance dispersion by wind to explain the strong floristic affinities between landmasses.

A work, published by Science journal in May 2004 with the title "Wind as a Long-Distance Dispersal Vehicle in the Southern Hemisphere", used daily measurements of wind azimuth and speed taken by the SeaWind scatterometer from 1999 to 2003. They found a stronger correlation of floristic similarities with wind connectivity than with geographic proximities, which supports the idea that wind is a dispersal vehicle for many organisms in the Southern Hemisphere.