In the beginning of 2002, SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) was launched successfully onboard ENVISAT. It measures scattered, reflected, and transmitted light of the Earth atmosphere in the UV-Vis-NIR wavelength region. Occultation measurements are one of three major observation modes performed by SCIAMACHY. An introduction will be given to the requirements of sun-synchronous orbits like that of ENVISAT. Orbit parameters affect strongly the measurement conditions, especially for occultation geometry.
The second part of the presentation will focus on first validations of NO2 and O3 vertical profile retrievals. Furthermore, recent improvements of the retrieval algorithm will be discussed concerning corrections for tangent heights and Fraunhofer lines in the solar spectra respectively. Since solar occultation measurements are expected to be very accurate compared to other measurement geometries, there is a great demand for data products with high and reliable accuracies.