A Correlated-k Based Ultra-Fast Radiative Transfer (kURT) Method

A new sensor-specific correlated- k (c- k ) ultra-fast radiative transfer (RT) formalism, kURT, has been designed for fast broad-bandpass scene simulations from UV-visible to LWIR wavelengths. A higher resolution RT code (1 cm -1 MODTRAN) has been adapted to output 1 cm -1 correlated- k parameters for ozone, water, and the combined uniformly mixed species on a pressure-temperature grid, which are merged to form a compact c- k set incorporating the sensor bandpass response function. The compact set is used to compute bandpass transmittance and radiance in near-real time. Scattering parameters (molecular Rayleigh, clouds and aerosols), blackbody and solar functions are cast as compact k -dependent source terms and used in the radiance computations. Preliminary transmittance results for 3-5 and 8-12 micron bandpasses and visible-MWIR sensors yield results within 2% of a 1 cm -1 MODTRAN calculation with a two-orders-of-magnitude computational savings. Applications include near-earth broadband propagation and extinction calculations for target detection and recognition, mid-range tracking, and search and rescue operations from ground and low altitude aircraft.