Study of the Sun and Moon as Radiation Calibration Targets

This study determined the calibration accuracy when the Sun and the Moon were used as radiometric calibration targets for three spacebornspectrometers: Global Ozone Measurement Experiment (GOME), and partially MERIS and SCHIAMACHY. The most recent Sun measurement data was used to determine the Solar irradiance, variance and the suitable calibration Fraunhofer lines for the spectrometers. The most recent data of the Moon formed a database containing all the relevant information for using the Moon as a calibration target. Thefinal part of the study concentrating of utilising the Sun and Moon radiometric information in determining the effects of the satellite attitude errors, instrument pointing restrictions and the effects of the Sun and the Moon orbits in the calibration procedure. The Sun calibration can be performed during each orbit, with accuracy of 0.7%, were 0.6% arises from wavelength independent irradiance variations, and 0.17% from the satellite way-axis random errors. Calibration accuracy of 0.7% is acceptable and the Sun calibration will be used in GOME mission. The Moon calibration is possible about 20 times per year, with an accuracy only 14% per scan, where main error source is the variation in the Moon viewing time through the GOME slit, caused by the satellite roll-axis random error. If more than one Moon scan is used,the calibration acuracy can be improved. For seven consecutive Moon scans the accuracy will be 5%.