Evaluation of the Ozone Monitoring Instrument's pre-launch radiometric calibration using in-flight data

Launched on 15 July 2004 aboard the EOS AURA satellite, the Ozone Monitoring Instrument (OMI) is intended as the successor to the Total Ozone Mapping Spectrometer (TOMS). OMI's improved horizontal spatial resolution and extended wavelength range (264-504nm) will provide total column ozone, surface reflectance, aerosol index, and ultraviolet (UV) surface flux as well as ozone profiles and tropospheric column ozone, trace gases, and cloud fraction and height. We present results from a variety of calibration techniques that have been developed over the years to assess the calibration accuracy of backscatter UV sensors. Among these are comparisons of OMI solar measurements with external solar reference spectra and radiances measured over Antarctica and Greenland. OMI UV measured irradiances show wavelength dependencies and spectral features on order of 5% when compared to external solar spectra while all channels exhibit a nearly wavelength independent 1% seasonal goniometric error. No instrument throughput degradation has been identified beyond this level and has been confirmed through ice radiance comparisons. A 3% OMI radiance cross-track swath dependence is seen when comparing radiances over ice fields to radiative transfer results. Reflectances derived at low latitudes show the same cross-track swath dependence with an additional 5% offset.