Microwave remote sensing uses microwave radiation at wavelengths from about one centimeter to a few tens of centimeters. It enables observation in all weather conditions, rain or shine, and it does not rely on solar radiation. Indeed, microwave remote sensing can be used day or night, giving it an advantage over the visible and/or infrared remote sensing techniques. In addition, microwave remote sensing provides unique information about surface characteristics related to roughness and dielectric properties, such as sea wind and wave direction, and about subsurface features in arid environments. The two systems of microwave remote sensing most commonly used by the EPIF include synthetic aperture radar (SAR) and a P-band scatterometer.