Comparison of Different Calibration Approaches in S-NPP CrIS Full Spectral Resolution Processing

The Cross-track Infrared Sounder (CrIS) on Suomi National Polar-orbiting Partnership Satellite (S-NPP) is a Fourier transform spectrometer. It provides a total of 1305 channels in the normal mode for sounding the atmosphere. CrIS can also be operated in the full spectral resolution (FSR) mode, in which the MWIR and SWIR band interferograms are recorded with the same maximum path difference as the LWIR band and with spectral resolution of 0.625 cm-1 for all three bands (total 2211 channels). NOAA will operate CrIS in FSR mode in December 2014 and the Joint Polar Satellite System (JPSS). Up to date, the FSR mode has been commanded three times in-orbit (02/23/2012, 03/12/2013, and 08/27/2013). Based on CrIS Algorithm Development Library (ADL), CrIS full resolution Processing System (CRPS) has developed to generate the FSR Sensor Data Record (SDR). This code can also be run for normal mode and truncation mode SDRs with recompiling. Since CrIS is a Fourier transform spectrometer, the CrIS SDR need to be radiometrically and spectrally calibrated. The current calibration approach does the radiometric calibration first, and then applies the correction matrix operator (CMO), which includes the post calibration filter, spectral resampling, self-apodization removal and residual ILS removal, to the spectral calibration. In order to select the next calibration algorithm for JPSS-1, different calibration approaches are being implemented in the ADL full resolution code. In this study, comparison results from different calibration approaches will be presented and the ringing effect observed in CrIS normal mode SDR will be discussed.