Wikipedia
MODTRAN (MODerate resolution atmospheric TRANsmission) is a computer program designed to model atmospheric propagation of electromagnetic radiation for the 100-50,000 cm (0.2 to 100 um) spectral range. This covers the spectrum from middle ultraviolet to visible light to far infrared.
The most recently released version of the code, MODTRAN5, provides a spectral resolution of 0.2 cm using its 0.1 cm band model algorithm.
Some aspects of MODTRAN are patented by Spectral Sciences Inc. and the US Air Force, who have shared development responsibility for the code and related radiation transfer science collaboratively since 1987. The acronym MODTRAN was registered as a trademark of the US Government, represented by the US Air Force, in 2008.
All MODTRAN code development and maintenance is currently performed by Spectral Sciences while the Air Force handles code validation and verification. MODTRAN may be obtained from Spectral Sciences, Inc.
MODTRAN5 is written entirely in FORTRAN. It is operated using a formatted input file. Third parties, including Ontar, have developed graphical user interfaces to MODTRAN in order to facilitate user interaction and ease of use.