Submitted to: Methods of Soil Analysis
Publication Type: Book / Chapter
Publication Acceptance Date: June 27, 2000
Publication Date: N/A
Technical Abstract: Passive microwave remote sensing instruments are capable of measuring the surface soil water content and can be implemented on trucks, aircraft, and spacecraft for repetitive large area observations. The amount of water present in a soil determines its dielectric properties. The dielectric properties, along with other physical characteristics, determine the microwave measurement. Efforts have been underway for sometime to develop passive microwave remote sensing as a tool for measuring and mapping surface soil water content. It was recognized early on in research in this field that instruments operating at low frequencies (less than 6 GHz) provide the best information. At low frequencies there are fewer problems with the atmosphere and vegetation, the instruments respond to a deeper soil layer, and there is a higher sensitivity to soil water content. The footprint of a passive microwave sensor will increase as frequency decreases. Current and near future satellite systems can provide only coarse resolution data (greater then 50 km). New antenna technologies under development will improve this resolution to 10 km within the next decade. The existing data interpretation algorithms for passive data are well tested for bare soil and vegetation and can be applied to a wide range of conditions. In this section, the basis of the method, soil water content retrieval methods, and examples of its application are presented.