TOMOGRAPHY OF THE EARTHS ATMOSPHERE BY THE SPACEBORNE OCCULTATION RADIOMETER ORA - SPATIAL INVERSION ALGORITHM

The occultation radiometer ORA was designed to perform measurements of O-3, NO2, H2O, number density, and aerosol extinction altitude profil es in the Earth's atmosphere through the occultation method viewing th e full solar disk. The experiment was mounted on the EURECA satellite and measured the relative transmission of light during about 7000 orbi tal sunsets and sunrises from August 11, 1992, to May 13, 1993. The sp atial inversion algorithm developed to retrieve the total extinction a ltitude profiles from these data is described here. It is shown that t he signal measured by an instrument having a large field of view can b e successfully processed to give a much better altitude resolution tha n the one related to the angular size of the Sun. The main difficultie s concern the inclusion of all refractive effects, the application of a new inversion scheme and its associated mapping strategy to refine t he aerosol layer detection. The algorithm applies to fully nonlinear o ccultation experiments requiring global and nonheuristic inversion sch emes.