This data set contains measurements of Global Positioning System (GPS) signals reflected from the Earth's surface and collected on an airborne platform. The measurements were taken over the Soil Moisture Experiment 2003 (SMEX03) regional study areas of Brazil and Alabama, Georgia, and Oklahoma, USA. The primary objective was to collect land reflections for sensitivity of the reflected GPS power to temporal and spatial soil moisture and foliage attenuation. The measurements are a form of bistatic radar and can be used to estimate the surface scattering coefficient, such as roughness and/or dielectric properties, as well as path delays between the direct and reflected GPS signals. Scattering coefficients can then be used to estimate changes in surface soil moisture. The reflections collected were from agricultural land in Brazil, Alabama, and Georgia, along with grassland in Oklahoma. Data were collected on 24, 25, 27, 30 June 2003 and 2, 3, 5, 7, 12-15, 17, 18 July 2003.
These data were collected as part of a validation study for the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E). AMSR-E is a mission instrument launched aboard NASA's Aqua Satellite on 04 May 2002. AMSR-E validation studies linked to SMEX are designed to evaluate the accuracy of AMSR-E soil moisture data. Specific validation objectives include assessing and refining soil moisture algorithm performance; verifying soil moisture estimation accuracy; investigating the effects of vegetation, surface temperature, topography, and soil texture on soil moisture accuracy; and determining the regions that are useful for AMSR-E soil moisture measurements.