Suomi NPP VIIRS Near Constant Contrast (NCC) Imagery
NCC is one of twelve VIIRS Imagery Environmental Data Record (EDR) products. It is produced by converting the observed Day/Night Band (DNB) radiance values into reflectance-like values. NCC is a product of the most innovative and advanced VIIRS band, the DNB, a broadband visible channel with a heritage that began with the Defense Meteorological Satellite Program (DMSP) Operational Line Scan System (OLS). The DNB provides spatial resolution as good as the best OLS imagery (approximately 750 m) but much better sensitivity than OLS (down to 10-7 W•m-2•sr-1).
The VIIRS Imagery and Visualization Team has been working with Northrup Grumman Aerospace Systems to fix the software that produces the NCC product. The complex NCC software combines radiance values from the three gain stages of the DNB, along with modeled solar and lunar radiance values to calculate a pseudo-albedo. This conversion from radiance to reflectance reduces the dynamic range of DNB observations (which may span more than 7 orders of magnitude between day and night) and produces imagery with nearly constant contrast from day to night, particularly in scenes straddling the terminator. In this way, visible-wavelength imagery is produced that has a similar appearance from day to night for all phases of the moon.
A major issue with NCC imagery was the lack of production under lower-light conditions, a problem that has now been solved. The fix for another issue, that of stray light contamination in the DNB, is currently being tested and will soon be implemented in the VIIRS operational processing.
Numerous examples of NCC imagery will be shown and contrasted with the DNB from which it is produced. NCC imagery can also be combined with other VIIRS M-band imagery, being that NCC is mapped into the same 750 m resolution Ground Track Mercator (GTM) grid used for VIIRS M-band imagery. The NCC image and its use in combination with other VIIRS bands are important new tools for the weather satellite user community.
Disclaimer: The views, opinions, and findings contained in this article are those of the authors and should not be construed as an official National Oceanic and Atmospheric Administration (NOAA) or U.S. Government position, policy, or decision.