MICROLAB-1 EXPERIMENT - MULTIPATH EFFECTS IN THE LOWER TROPOSPHERE

Interpretation of the Doppler-shifted radio frequencies from the proof -of-concept GPS/MET radio occultation experiment is impeded by the eff ects of multipath propagation caused by strong variations of atmospher ic refractivity. In this paper, we describe and validate a method of d eciphering the ray structure of the measured electromagnetic field in regions of multipath propagation. The method is based on diffraction t heory and the principles of the synthesized aperture, which allows for the refinement of the vertical resolution beyond the Fresnel scale as well as for the improvement of the signal/noise ratio. The validation of the method is based on artificial occultation data simulated using global fields from a NCEP analysis. An example of the application of the diffraction correction algorithm for the processing of real GPS/ME T data is given. The comparison of the inversion results with and with out diffraction correction indicates a very significant role of multip ath propagation in the lower troposphere, which suggests that the diff raction correction can significantly improve the quality of the data p rocessing.