Interferometry with GPS Low Earth Orbiters Occultations

GPS signals reflected off the Earth surface can be detected by receivers aboard occulting Low Earth Orbiters (LEO). The geophysical information contained in such reflected signal, has been partially clarified for using radioholographic analysis. After calibration, occultation geometry and the troposphere have the main contributions to the relative delay between direct and reflected signal. The reflected-to-direct relative delay is a function of the location of the reflecting surface as well as the different effect of the troposphere on both ray paths. Information can be obtained from precise measurements of the interferometric delay, and by separating the geometric from the atmospheric effect. This talk presents novel results with centrimetric precision in carrier-phase reflected-to-direct relative delay from GPS to LEO occultations. The separation techniques will be discussed and potential applications of the interferometric delay to Ice surface topography, super-refractivity layer determination, marine boundary layer height detection will be given. Detection of super-refractivity conditions by the interferometric signal can lead to further refinements in the retrievals of lower atmospheric refractivity profiles where biases are known to exist.