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An Improved Scanner Model for Sciamachy

R.C. Snel(1) and J.M. Krijger(1)

(1) SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands


An improved model of the SCIAMACHY scanner unit is presented. The model is used for combination of the on-ground ambient and thermal vacuum calibration data, and removes errors initially introduced into the calibration key data as a result of ambiguities in the polarisation frame definitions used during on-ground calibration and in 0-1 data processing. The scanner model builds on the Fresnel equations and describes limb, nadir and sun over ESM diffuser geometries. It is possible to add up to two dielectric layers with arbitrary thickness on any of the modeled mirror or diffuser surfaces. On-ground and in-flight measurements were used to verify the model output. The possibility of modeling contamination of the mirror and diffuser surfaces allows future investigation of certain aspects of instrument degradation, such as scan angle dependent degradation and UV transmission loss.