Radio holographic principle for observing natural processes in the atmosphere and retrieving meteorological parameters from radio occultation data

The radio holographic principle is briefly described and tested by using radio occultation data of the GPS/MET and MIR/GEO experiments. Sub-Fresnel spatial resolution similar to 12 m/pixel was achieved using focused synthetic aperture radio holographic approach, and direct evidence of multibeam propagation effects in the atmosphere was obtained. The achieved instrumental accuracy in angular distance measurements was near 0.004 milliradian/pixel, and observed angular distance between different rays was equal to 0.3 milliradians. The angular resolution of the radio holographic method depends on the wavelength as lambda (1) compared to lambda (1/2) in conventional methods. In general case the principal limit of the vertical resolution may be determined using focused synthetic aperture antenna theory and may achieve a value similar to 20-40 m under assumptions of spherical symmetry and quiet atmospheric conditions. Wave structures were discovered in the altitude distribution of the gradient electron density at a height interval of 60-95 km with spatial period 1-2 km and vertical resolution 300-500 m. Good correspondence was found between the temperature profiles revealed by radio holographic analysis and those obtained by traditional retrieval using UCAR GPS/MET data.