MODTRAN® (MODerate resolution TRANsmission model) is the DoD standard atmospheric infrared/visible/ultraviolet radiance and transmission band model for lower altitudes, developed and maintained by SSI and the US Air Force Research Laboratory. MODTRAN rapidly predicts the atmospheric emission, thermal scatter, and solar scatter for arbitrary, refracted paths above the curved earth, incorporating the effects of molecular absorbers and scatterers, aerosols, and clouds. MODTRAN's radiances and vertical fluxes, at 0.2 cm-1 spectral resolution in the latest version (MODTRAN6), have been extensively validated over the full spectral range from 1 to 50,000 cm-1 (0.2 - 10,000 microns). For information about the MODTRAN code and how to obtain it, please visit the official MODTRAN web site.
kURT (k-distribution based Ultra-fast Radiative Transfer) is a MODTRAN-based package of transmittance and radiance routines designed for highly efficient scene simulation. kURT leverages a pre-calculated correlated-k database to achieve several orders of magnitude improvement in computation speed compared to MODTRAN for broad optical bandpasses and multiple lines-of-sight.
Half-limb view from 15 km altitude.