SBIR-STTR Award

A new radiometric vicarious calibration approach for the Suomi NPP VIIRS Day/Night Band’s (DNB) high gain stage (HGS) is proposed that will complement traditional, extended source, radiance-based calibrations, which are based on natural lunar illumination and not as accurate as desired. The proposed research will produce affordable, field-deployable, NIST-traceable point source lamps that can achieve HGS DNB radiance per pixel with a long-term, post-correction source stability of better than 1%. Using radiative transfer modeling and VIIRS DNB characteristics, the top-of-atmosphere absolute radiometric accuracy will be better than 5% under clear sky conditions. The artificial source’s spectral distribution can be made similar to that of natural lunar illuminated scenes to ensure this new approach is compatible with ongoing lunar illumination-based vicarious radiometric calibrations. Other spectral distributions can also be produced if needed. To increase energy efficiency and reliability, the source will be remotely controlled and monitored. The source will only turn on during the VIIRS DNB site overpass, when observation conditions are optimal. Built-in lamp sensors will provide lamp health information and auxiliary sensors will provide site environmental conditions. This new approach should be applicable to other nighttime imagers and will help calibrate other point sources observed by VIIRS.

This project’s aim is to develop an Accurate Active Light Source (AALS) that can be fielded at selected calibration sites to address NOAA’s unmet needs and improve the calibration of the Suomi NPP VIIRS Day Night Band (DNB) operating in the high gain stage (HGS) under low light level conditions. The DNB HGS has extreme low-light sensitivity that enables a new generation of nighttime imaging. Many of these emerging applications’ utility however depend on absolute radiometric accuracy and sensor stability. Currently the DNB HGS calibration hinges on transferring calibration from the low and medium gain stages to the HGS using a solar diffuser, which is more than seven orders of magnitude brighter than many of the faintly lit targets imaged using the HGS. As a result, the HGS absolute calibration accuracy under extreme low light may be too low to provide quantifiable information and detect change. Our new AALS will improve our small target radiometry/point source understanding. Combining our national standards-traceable AALS with a sensitive VIIRS nighttime imaging capability has the potential to create game changing new commercial and military applications. Key to commercialization and economic viability is the ability to design and field a cost-effective AALS.