Multispectral remote sensing of the nighttime combustion sources
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 M10, centered at 1.6 um. Without solar input, the M10 spectral band record sensor noise, punctuated by high radiant emissions associated with gas flares, biomass burning, volcanoes, and industrial sites like steel mills. The secondary detection bands are M12 and M13, centered at 3.7 and 4.05 um. Low-temperature combustion sources can be detected as outliers on the M12-M13 probability density histogram. Planck curve fitting of the hot source and background radiances yield temperature (K) and emission scaling factor. Additional calculations are done to estimate source size (square meters), radiant heat intensity (W/m2) and radiant heat (MW). Nightfire successfully retrieved temperature estimates ranging from 600 to 6000 K. An intercomparison study found Nightfire radiant heat (MW) to be highly correlated to MODIS Fire Radiative Power (MW). Similar detection algorithm with Planck curve fitting can be applied at nighttime to the LANDSAT-8 bands 5, 6 and 7.