VJ202DNB - VIIRS/JPSS2 Day/Night Band Moderate Resolution 6-Min L1B Swath 750m

VJ202DNB is the short-name of the Joint Polar-orbiting Satellite System-2 (JPSS-2/NOAA-21; referred to hereafter as J2) platform-derived single NASA VIIRS panchromatic Day-Night band (DNB) calibrated radiance product. The DNB is one of the M-bands with an at-nadir spatial resolution of 750 meters (across the entire scan). The panchromatic DNB's spectral wavelength ranges from 0.5 µm to 0.9 µm. It facilitates measuring night lights, reflected solar/lunar lights with a large dynamic range between a low of a quarter moon illumination to the brightest daylight. The DNB attempts to maintain a nearly constant 750-m resolution over the entire 3060 km orbital swath by resorting to an on-board aggregation method, which also renders the calibration of the DNB a challenge. Stray-light and other sources of noise (lunar illuminance, twilight, clouds, noisy scan-edges, etc.) affect the DNB quality, and warrant correction. Considered a major advance in low-light imaging, the VIIRS DNB owes its heritage to the Operational Linescan System (OLS) visible sensors that were part of the Defense Meteorological Satellite Program (DMSP) platforms since the 1970s. The image dimensions of the 750-m DNB product measure 3232 lines by 4064 pixels.

Radiometric Calibration-specific changes
The J2 VIIRS radiometric calibration Level-1B reprocessing includes a few calibration updates for the reflective solar bands (RSB), but no significant changes for the day-night band (DNB) or thermal emissive bands (TEB). The RSB updates include the following:

1. An estimated time-dependent adjustment is applied to the VIS/NIR band solar diffuser (SD) F-factors before generating the F-Predicted LUTs to correct for the expected long-term drift in the SD calibration. The estimated adjustment is the average of the S-NPP and J1 (NOAA-20) adjustments derived from comparing SD and lunar trends for S-NPP and J1. This estimated approach is used since there is not yet enough J2 lunar data to derive an adjustment directly for J2.
2. The accuracy of the F-Predicted LUTs for the SWIR bands is improved in the reprocessed time series by fitting the measured SD F-factors (which show rapid gain changes for some SWIR detectors) to smooth functions to remove the forward-prediction errors.
3. A scale factor of 6.1% is applied to the M11 reflectance and radiance values consistently over the entire mission to improve the agreement between J1 and J2 reflectances at this wavelength.