Determination of SCIAMACHY LOS Misalignments

Kurzfassung

Certain geolocation parameters derived in the early analyses of SCIAMACHY's limb measurements deviated from the expected values. After a corrective action in the ENVISAT flight operation segment the situation improved significantly. However small inconsistencies persisted. These concern a still existing bias and a left-right asymmetry in the limb tangent heights. We speculate that the inconsistencies originate in additional small line-of-sight misalignments between SCIAMACHY and the platform. This view is supported by azimuth/elevation features observed in solar occultation and sub-solar measurements around times when scanner control is switched from prediction to Sun Follower. In a model approach we use these specific measurements of SCIAMACHY to quantitatively determine potential extra misalignments in pitch, roll and yaw. The approach uses the features in elevation and azimuth to simulate misalignment effects. Initial results agree well with observations.