Degradation of Uv Earth Albedo Observations by Gome

Degradation of optical components in space is a problem affecting many remote sensing instruments. In the Global Ozone Monitoring Experiment (GOME) on board ERS-2, the light backscattered by the Earth’s atmosphere follows a different optical path through the spectrometer than solar irradiance. GOME has been therefore designed to monitor degradation of performance not only for the solar irradiance observation mode, but also for Moon radiance, which is occasionally measured. The performance of GOME for Earth albedo measurements, i.e. the observation mode necessary for the measurement of trace gases, is however not straightforward. This is caused by the difficulty of defining a stable calibration target: a first approach for wavelengths 295 nm is presented in [1]. Following that approach, the degradation of Earth albedos is here analyzed over the five years of GOME operations.