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New On-Orbit Calibration Approach of SNPP VIIRS Reflective Solar Bands Using the Full Profile of Direct Solar Illumination of Solar Diffuser
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2019
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Source: IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 10, pp. 7704-7717, Oct. 2019
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Journal Title:IEEE Transactions on Geoscience and Remote Sensing
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NOAA Program & Office:
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Description:A methodological variant of the standard on-orbit calibration of reflective solar bands (RSBs) is presented for the Visible Imaging Infrared Radiometer Suite (VIIRS) housed in the Suomi National Polar-orbiting Partnership (SNPP) satellite. The new variant uses the full profile of direct solar illumination of the solar diffuser (SD), including both full and partial illuminations, to characterize the on-orbit gain change of the RSBs, differing from the standard approach that uses a smaller “sweet spot” subinterval within the full-illumination stage. The extended incident angular range of the solar light requires a new characterization analysis of the impact of the transmission function of the SD screen, SD bidirectional reflectance factor (BRF), and other affected calibration steps. Instead of the standard a priori derivation of the known characterization functions for the wider range, this analysis directly characterizes their manifested impact in the instrument data through a step-by-step extraction from a selected three-year period to build up a series of intermediate functions that are applicable mission-long. This newly adopted procedure presents a significant simplification as well as more clarity of the characterization analysis. The new RSB calibration coefficient of the full-profile approach is extracted for all 14 RSBs of SNPP VIIRS and is shown to be stable and smooth at the level of 0.1%. For bands M5 and above, the full-profile result achieves excellent agreement with the standard result, whereas results for bands M1-M4 diverge, in particular up to 2% for band M1, the shortest wavelength RSB at 410 nm. The finding elucidates a key challenge of the on-orbit RSB calibration arising from the nontrivial angular dependence of the on-orbit degradation of SD that introduces calibration error into any SD-based approach, such that the on-orbit RSB calibration result is not stable with different choices of the angular range of incident and outgoing light with respect to the SD. A detailed discussion of the nontrivial angular dependence in SD degradation is provided in the context of the known on-orbit RSB calibration results and recent findings, including discrepancy with the lunar-based calibration for bands M1-M4.
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Source:IEEE Transactions on Geoscience and Remote Sensing, vol. 57, no. 10, pp. 7704-7717, Oct. 2019
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Rights Information:Accepted Manuscript
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