# VIIRS Day/Night Band--Correcting Striping and Nonuniformity over a Very Large Dynamic Range
## 3 Results
### Survey of DNB Imagery
#### 3.1.3 Observations for Nighttime Scenes  
Nighttime DNB scenes are almost entirely relegated to the HGS (with the exception of some very bright gas flares and fires). Generally, nighttime HGS images contain stronger striping than MGS or LGS for two reasons: first, the HGS contains the non-uniformities produced by the LGS calibration as well as the two cross-calibrations; second, the HGS is the only stage where the dynamic range extends  
Figure 3: NCC twilight scene over Antarctica with striping from 22 September 2014 at 00:19 UTC. The image is 700 by 1100 pixels and is centered near nadir. The median radiance in this image is about \(1\times 10^{-5}\) W\(\cdot\)cm\({}^{-2}\)\(\cdot\)sr\({}^{-1}\).  
Figure 2: Near Constant Contrast (NCC) twilight scene with striping from 22 September 2014 at 00:19 UTC in a region of Antarctica. The image is 650 by 1000 pixels and the right edge is the end of scan. The blue line shows the transition between the Mid-Gain Stage (MGS) above the line and the Low-Gain Stage (LGS) below it. The median radiance in this image is about \(5\times 10^{-4}\) W\(\cdot\)cm\({}^{-2}\)\(\cdot\)sr\({}^{-1}\).  
into total darkness, so that offset errors appear prominently in the darkest scenes. Figure 4 shows a DNB scene during the new moon over the southeastern Atlantic Ocean. Here, the only source of ambient illumination is nightglow (chemiluminescent airglow) and all other natural illumination from sources other than the sun, the moon or auroras, including, stellar light and zodiacal light. [1; 3]. Even by this faint illumination which resides at 10% of the minimum required DNB radiance threshold, cloud features are easily distinguished in the image. However, noise and striping artifacts are prominent throughout the scene.  
Figure 5 was collected on 7 October 2014 showing Typhoon Vongfong around the time of its maximum intensity in the Pacific Ocean northeast of the Philippines while illuminated by a nearly full moon. As in Figure 1, gain striping dominates the image and shows that even with the brightest nighttime images, there is significant striping present. This storm had a remarkably concentric structure in ridges in this image--much more so than the daytime VIIRS overpass from 12 h before or after this overpass. Whereas visible imagery of storms reveal structural features that are not seen in the emissive IR imagery, striping makes it more difficult to interpret these fine features, particularly when the striping aligns with naturally occurring banded structures associated with storm dynamics. Furthermore, with striping it is more difficult to design new algorithms that can make use of moonlight reflectance combined with thermal emissive data to better understand such storm systems (e.g., the Dvorak technique [32]).  
Figure 6 shows an image of the Ross Sea and Antarctica on 25 June 2015 under quarter moon illumination. In areas where the stray light correction is applied (over approximately the lower two thirds of the image) there are significant residual nonuniformities that were not corrected by the stray light correction. These nonuniformities are likely at least partly due to changes in the stray light between the time that the correction tables were determined and when they were applied [1; 10; 22]. There is also striping in the upper third of the image similar to what appears in Figure 1.  
Figure 4: Image collected under new moon (_i.e._, nightglow illumination) conditions on from 28 May 2014 at 01:38 UTC in a region of the southeastern Atlantic. Radiances are plotted on a linear scale over the range of \(-1.0\times 10^{-10}\) to \(3.3\times 10^{-10}\) W\(\cdot\)cm\({}^{-2}\cdot\)sr\({}^{-1}\) black to white. The 1000 by 1900 pixel image is at start of scan.