Meris In-flight Spectral Calibration

This paper first describes the different activities conducted for MERIS regarding it’s spectral calibration. The onboard spectral calibration is based on the use of a panel which presents well defined absorption peaks. In this absorption bands, each MERIS detector is characterized in wavelength. Limitations of this method are in the near infra red because of the lack of absorption lines in the pink panel. The use of the Fraunhofer lines is complementary, giving information in the violet and near infra red. Specific spectral band settings where used in the Fraunhofer absorption lines during a limited number of orbits when observing the Earth. Spectral characterization is achieved within 0.1 nm accuracy, in accordance with most of the mission objectives. A specific spectral arrangement was also used in the oxygen bands. Two different approaches were conducted: one based of the pressure retrieval and one based on the shape of the oxygen absorption. They also quite well agree within an accuracy of 0.02 nm. We also describe how the MERIS spectral characteristics are accounted for in the level 2 algorithms.