Initial Investigation of a GNSS-R Multiscale Rough Surface Forward Model at San Luis Valley Calibration/Validation Sites

A forward model for delay-Doppler maps (DDMs) of global navigation satellite system reflectometry (GNSS-R) from bare land surfaces with multiscale roughness is presented and investigated. The geometrical optics (GO) model of [1] for GNSS-R from rough sea surfaces has been extended to land applications in [2] by including a longwave component derived from the elevations and gradients of a digital elevation model (DEM) and a medium- wave component arising from surface gradients below the resolution of the DEM. Following [3], the present work improves the GO model by including an attenuation factor that accounts for shortwave diffraction. The proposed multiscale forward model has potential applications for the spaceborne monitoring of soil moisture and other biogeophysical parameters.