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Calibration approaches and quality aspects for the ENVISAT Atmospheric-Chemistry instruments

Angelika Dehn(1), Thorsten Fehr(2), Fabrizio Niro(1), Lidia Saavedra de Miguel(1), Gilbert Barrot(3), Heinrich Bovensmann(4), Miguel Canela(5), Roland Gessner(6), Manfred Gottwald(7), Henri Laur(2), Pascal Lecomte(2), Gaetan Perron(8) and Piera Raspollini(9)

(1) Serco, Via Sciadonna 24-26, 00044 Frascati, Italy
(2) ESA/ESRIN, Via Galileo Galilei, 00044 Frascati, Italy
(3) ACRI-ST, Route du Pin Montard 260, 06904 Sophia-Antipolis, France
(4) IFE/University of Bremen, , 28334 Bremen, Germany
(5) ESA/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, Netherlands
(6) EADS ASTRIUM GmbH, Friedrichshafen, 88039 Friedrichshafen, Germany
(7) DLR-IMF, Münchner Str. 20, 82234 Oberpfaffenhofen, Germany
(8) ABB BOMEM, 585 Charest Blvd., Québec, Québec G1K9H4, Canada
(9) IFAC/CNR, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy


ENVISAT carries on-board, among others, three Atmospheric Chemistry instruments: GOMOS, MIPAS and SCIAMACHY. These three instruments use different measurement techniques and observation geometries for atmospheric remote sounding. All of them have in common that specific in-flight calibrations have to be applied not only to assign a physical unit to the raw measurements (e.g.: radiance, transmission) but also to correct for some instrumental effects (e.g. dark current). Theses calibrations are routinely performed with a well defined periodicity that allows to account for long term degradation of instrument performances or for short term variation of measurement conditions, e.g.: detector temperature changes. Detailed characterisation of the instruments on-ground before launch is important on the one hand side, on the other side an accurate calibration of in-flight measurements is crucial to obtain best data quality. This paper gives an overview on the most relevant calibration aspects over the three instruments and examples on improvements on data calibration resulting in improved data quality.