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We describe a new variant of the on-orbit calibration methodology for the reflective solar bands (RSBs) of SNPP VIIRS using the entire illumination interval of the solar diffuser (SD), instead of the smaller “sweet spot” within the illumination interval used by the standard procedure, to compute the calibration coefficients, or F-factors. The instrument response from the full-illumination profile per orbit over the whole mission is directly used to carry out a step-by-step fitting and characterization analysis to arrive at the new F-factors. The new F-factor result is compared with that of standard, lunar-based calibration, and Earth-scattered light approach, expectedly demonstrating very good agreement for bands of longer wavelength but also discrepancies for Bands M1 to M4, the four shortest wavelength bands. The difference is attributed to the angular-dependence in the degradation of the SD that is manifested by the different approaches having different angles of incidence of light to the SD. Thus this result demonstrates the inherent systematic and worsening error for all SD-based on-orbit RSB calibration methodologies to mitigate. On its own, the full-profile approach achieves remarkable stability and robustness on the level of 0.1%, making it a very competitive or better alternative to the current methodology.
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