The successful launch of the Suomi National Polar‐orbiting Partnership Satellite on 28 October 2011 with the key instrument Visible Infrared Imaging Radiometer Suite signifies a new era of moderate‐resolution imaging capabilities following the legacy of AVHRR and Moderate‐Resolution Imaging Spectroradiometer (MODIS). After a year and half of calibration and validation, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is performing very well. By early 2013, the sensor data records have achieved provisional maturity status and have been used in the routine production of more than 20 environmental data records by users worldwide. Based on comparisons with MODIS, the VIIRS reflective solar band radiometric uncertainties are now comparable in reflectance to that of MODIS Collection 6 equivalent bands (within 2%) although radiance differences could be larger for several bands, while an agreement on the order of 0.1 K has also been achieved for the thermal emissive bands, except for bands with significant spectral differences or certain bands at extreme temperatures (below 200 K or above 343 K). The degradation in the VIIRS rotating telescope assembly mirrors is gradually leveling off after reaching ~30% and thus far has limited impact on instrument performance and products. Environmental data record users are generally satisfied with the VIIRS data quality which meets the product requirements. While the specific technical details are documented in other papers in this special issue and in Cao et al. (2013a), this paper focuses on the major findings of VIIRS calibration and validation since launch, radiometric performance validation, and uncertainties, as well as lessons learned.

Power outages after a major storm affect the lives of millions of people and cause massive light outages. The launch of the Suomi National Polar-orbiting Partnership satellite with the Visible Infrared Imaging Radiometer Suite (VIIRS) significantly enhances our capability to monitor and detect light outages with the well-calibrated day/night band (DNB) and to use light loss signatures as indication of regional power outages. This study explores the use of the DNB in quantifying light outages due to the derecho storm in the Washington DC metropolitan area in June 2012 and Hurricane Sandy at the end of October 2012 on the East Coast of U.S. The results show that the DNB data are very useful in detecting power outages by quantifying light loss, but it also has some challenges due to clouds, lunar illumination, and straylight effect. Comparison of light outage and recovery trend determined from DNB data with power company survey shows reasonable agreement, demonstrating the usefulness of DNB in independently verifying and complementing the statistics from power companies.

On-orbit radiometric performance of the Suomi National Polar-Orbiting Partnership (Suomi-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) is studied using the extended simultaneous nadir overpass (SNO-x) approach. Unlike the traditional SNO analysis of data in the high latitudes, this study extends the analysis to the low latitudes-in particular, over desert and ocean sites with relatively stable and homogeneous radiometric properties-for intersatellite comparisons. This approach utilizes a pixel-by-pixel match with an efficient geospatial matching algorithm to map VIIRS data into the Moderate Resolution Imaging Spectroradiometer (MODIS). VIIRS moderate-resolution bands M-1 through M-8 are compared with Aqua MODIS equivalent bands to quantify radiometric bias over the North African desert and over the ocean. Biases exist between VIIRS and MODIS in several bands, primarily because of spectral differences as well as possible calibration uncertainties, residual cloud contamination, and bidirectional reflectance distribution function (BRDF). The impact of spectral differences on bias is quantified by using the Moderate Resolution Atmospheric Transmission (MODTRAN) and hyperspectral measurements from the Earth Observing-1 (EO-1) Hyperion and the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS). After accounting for spectral differences and bias uncertainties, the VIIRS radiometric bias over desert agrees with MODIS measurements within 2% except for the VIIRS shortwave infrared (SWIR) band M-8, which indicates a nearly 3% bias. Over ocean, VIIRS agrees with MODIS within 2% by the end of January 2013 with uncertainty less than 1%. Furthermore, VIIRS bias relative to MODIS is also computed at the Antarctica Dome C site for validation and the result agrees well within 1% with the bias estimated using SNO-x over desert.

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