2009-03-23: Collection 3: improved level-1b data for OMI retrievals.

OMI retrievals of trace gases, clouds and aerosols depend critically on the quality of the observed radiance and irradiance data. The Ozone Monitoring Instrument is equipped with a CCD-camera that allows simultaneous Earth-viewing under 60 individual angles. In the first years of operation, this novel technique appeared susceptible to calibration offsets that changed with viewing angle. In a recent paper, Dobber et al. [2008] have significantly improved the calibration of the OMI level-1b data.
They show that with these improvements, the accuracy of the geophysically calibrated level 1b radiance and irradiance is much better in the collection 3 data. They also report that the in-orbit radiometric degradation since launch is smaller than 0.5% above 310 nm and increases to about 1.2% at 270 nm. Improvements in the spectral and spatial stray light corrections from collection 2 data to collection 3 data are presented and discussed. Collection 3 data are publicly available since 12 October 2007, and can be obtained through www.knmi.nl/omi.
(a) Irradiance viewing angle dependence calibration improvement from collection 2 (left) to (b) collection 3 (right).