Pre-launch characterization of the Ozone Monitoring Instrument transfer function in the spectral domain

A new method and experimental measurement setup to accurately characterize instrument transfer function in the spectral domain for hyperspectral spectrometers in the ultraviolet - visible wavelength range are described. The application to the on-ground calibration of the Ozone Monitoring Instrument on board of the Earth Observation System Aura satellite is presented and discussed. With this method and setup, based on an echelle grating, the sampling of the instrument transfer function in the spectral domain can be selected and is not limited by the spectral resolution and sampling of the spectrometer that is being characterized. The importance of knowing the OMI instrument transfer functions in the spectral domain accurately for in-flight DOAS retrievals and the wavelength calibration is discussed. The analysis of the OMI measurement data is presented and shows that the instrument transfer functions in the spectral domain as a function of wavelength and viewing angle can be determined with high accuracy.