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Technological advancements in detectors, cryocoolers, infrared spectrometers and optical materials enables hyperspectral infrared atmospheric sounding in a CubeSat. Legacy instruments such as NASA Atmospheric Infrared Sounder (AIRS) and the Cross-track Infrared Sounder (CrIS) measure the upwelling spectrum to retrieve temperature profiles and atmospheric water vapor. These data are assimilated by National Weather Prediction (NWP) centers worldwide and had significant positive impact to the operational forecasts. NASA and NOAA have sponsored technology demonstration of a hyperspectral IR sounder packaged in a 6U CubeSat at JPL. The instrument is called the CubeSat Infrared Atmospheric Sounder (CIRAS). Like AIRS, CIRAS uses a grating spectrometer that senses spatial information in one dimension and spectral in the other, but CIRAS uses a 2-dimensional Focal Plane Assembly (FPA), while AIRS uses multiple linear arrays to produce one spectrum. For CIRAS, if the dispersion direction is not aligned with the rows and columns of the detectors, spectral and spatial mixing can cause radiometric errors if uncorrected. This paper discusses a method to resample the signals from the detector array while viewing a spectral and spatial calibration source and produce a spectrally and spatially corrected image. The correction, or ‘Electronic Alignment’ can be performed pre-flight during Integration and Test, or in-flight using a combination of on-board and ground processing systems. Results are presented for simulated misalignments and errors consistent with design requirements using real scenes from the legacy sounders. The method works reasonably well with highest errors around sharp absorption features for cold scenes. Residual radiance errors from the simulation can be used in a larger simulation of the retrieval of geophysical parameters from hyperspectral IR instruments.
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