Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 12 2006 10.5194/acp-6-5347-2006 http://www.atmos-chem-phys.net/6/5347/2006/ http://www.atmos-chem-phys.net/6/5347/2006/acp-6-5347-2006.html http://www.atmos-chem-phys.net/6/5347/2006/acp-6-5347-2006.pdf 5347 5367 2006-11-28 SCIAMACHY Level 1 data: calibration concept and in-flight calibration G. Lichtenberg guenter.lichtenberg@dlr.de Q. Kleipool J. M. Krijger G. van Soest R. van Hees L. G. Tilstra J. R. Acarreta I. Aben B. Ahlers H. Bovensmann K. Chance A. M. S. Gloudemans R. W. M. Hoogeveen R. T. N. Jongma S. Noël A. Piters H. Schrijver C. Schrijvers C. E. Sioris J. Skupin S. Slijkhuis P. Stammes M. Wuttke SRON National Institute of Space Research, Utrecht, The Netherlands Royal Netherlands Meteorological Institute (KNMI), de Bilt, The Netherlands Institute of Remote Sensing (IfE), University of Bremen, Germany TNO Science and Industry, Delft, The Netherlands DLR-DFD/IMF, Weßling, Germany Harvard-Smithsonian Center for Astrophysics (SAO), Cambridge, USA now at: Royal Meteorological Institute Netherlands (KNMI), de Bilt, The Netherlands now at: DLR-DFD/IMF, We{ß}ling, Germany now at: Deutsches Elektronen-Synchrotron (DESY), Notkestr. 85, 22607 Hamburg, Germany The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board ENVISAT in February 2002. While SCIAMACHY's functional performance is excellent since launch, a number of technical difficulties have appeared, that required adjustments to the calibration. The problems can be separated into three types: (1) Those caused by the instrument and/or platform environment. Among these are the high water content in the satellite structure and/or MLI layer. This results in the deposition of ice on the detectors in channels 7 and 8 which seriously affects the retrievals in the IR, mostly because of the continuous change of the slit function caused by scattering of the light through the ice layer. Additionally a light leak in channel 7 severely hampers any retrieval from this channel. (2) Problems due to errors in the on-ground calibration and/or data processing affecting for example the radiometric calibration. A new approach based on a mixture of on-ground and in-flight data is shortly described here. (3) Problems caused by principal limitations of the calibration concept, e.g. the possible appearance of spectral structures after the polarisation correction due to unavoidable errors in the determination of atmospheric polarisation. In this paper we give a complete overview of the calibration and problems that still have to be solved. 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