VIIRS Nightfire: multispectral satellite pyrometry at night

The Nightfire algorithm detects and characterizes sub-pixel hot sources using multispectral data collected globally each night by the Suomi NPP Visible Infrared Imaging Radiometer Suite (VIIRS). The spectral bands utilized span visible, near-infrared (NIR), short-wave infrared (SWIR) and mid-wave infrared (MWIR). The primary detection band is in the SWIR, centered at 1.6 μm. Without solar input, the SWIR spectral band records sensor noise, punctuated by high radiant emissions associated with gas flares, biomass burning, volcanoes, and industrial sites like steel mills. Planck curve fitting of the hot source radiances yields temperature (K) and emission scaling factor (ESF). Additional calculations are done to estimate source size (m2), radiant heat intensity (W/m2) and radiant heat (MW). Nightfire retrieved temperature estimates for sub-pixel hot sources ranging from 600 to 6000 K. The IR sources can be ranked worldwide to reveal a list of top 100 largest gas flaring sites. An intercomparison study of biomass burning in Sumatra from June 2013 found Nightfire radiant heat (MW) to be highly correlated to MODIS Fire Radiative Power (MW).