Abstract
The Day–Night Band (DNB) imaging sensor of the Visible Infrared Imaging Radiometer Suite (VIIRS) adds nighttime monitoring capability to the Suomi National Polar-Orbiting Partnership and National Oceanic and Atmospheric Administration 20 weather satellite launched in 2011 and 2017, respectively. Nighttime visible imagery has already found diverse applications, but image quality is often unsatisfactory. In this study, variations in observed top-of-atmosphere (TOA) reflectance were examined in terms of nighttime bidirectional effects. The Antarctica Dome C ground site was selected due to high uniformity. First, variation of reflectance was characterized in terms of viewing zenith angle, lunar zenith angle, and relative lunar azimuth angle, using DNB data from 2012 to 2020 and Miller–Turner 2009 simulations. Variations in reflectance were observed to be strongly anisotropic, suggesting the presence of bidirectional effects. Then, based on this finding, three popular bidirectional reflectance distribution function (BRDF) models were evaluated for effectiveness in correcting for these effects on the nighttime images. The observed radiance of VIIRS DNB was compared with the simulated radiance respectively based on the three BRDF models under the same geometry. Compared with the RossThick-LiSparseReciprocal (RossLi) BRDF model and Hudson model, the Warren model has a higher correlation coefficient (0.9899–0.9945) and a lower root-mean-square-error (0.0383–0.0487). Moreover, the RossLi BRDF model and Hudson model may have similar effects in the description of the nighttime TOA over Dome C. These findings are potentially useful to evaluate the radiometric calibration stability and consistency of nighttime satellite sensors.
Highlights
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument [1] onboard the Suomi National Polar-Orbiting Partnership (S-NPP) and National Oceanic and Atmospheric Administration (NOAA) 20, launched on 28 October 2011, and 18 November 2017, respectively
When the viewing zenith angle (VZA) is in 50◦ –60◦ and relative lunar azimuth angle (RAA) is less than 30◦, and VZA is in 60◦ –70◦
The following conclusions can be drawn: (1) Only when the VZA is in 50°–60° and RAA is less than 30°, and VZA is in 60°–70° and RAA is in 30°–120°, the nighttime TOA reflectance is positively correlated with the lunar zenith angle (LZA)
Summary
The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument [1] onboard the Suomi National Polar-Orbiting Partnership (S-NPP) and National Oceanic and Atmospheric Administration (NOAA) 20 (formerly Joint Polar Satellite System-1, JPSS-1), launched on 28 October 2011, and 18 November 2017, respectively. To support highquality nighttime-visible imagery, the Day–Night Band (DNB), covering wavelengths from 500 to 900 nm on VIIRS, has a specified dynamic range spanning seven orders of magnitude, making it capable of detecting Earth scenes under illumination as dim as quarter moon. This range is achieved by a three-gain-stage charge-coupled device (CCD) with four arrays of imaging detectors: the low gain stage (LGS) for daytime, the medium gain stage (MGS). Calibration of DNB is complicated, due to its large dynamic range, ultra-high sensitivity, scan-angle-dependent field of view (FOV), and sensitivity to stray light contamination [3,4]. The calibration uncertainty of the LGS and MGS are 5–10% and 10–30%, respectively, while the uncertainty of the HGS is over
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