The MODTRAN MODerate resolution atmospheric TRANsmission computer code is widely used throughout the Department of Defense DoD, in many other Federal Government departments and agencies, and worldwide by research scientists in many fields for the prediction and analysis of optical measurements through the atmosphere. The code is embedded in many DoD operational and research sensor and data processing systems, particularly those involving the removal of atmospheric effects, commonly referred to as atmospheric correction, in remotely sensed multi- and hyperspectral imagery. These MODTRAN calculations are the most time-consuming part of the atmospheric correction process. Given the ever increasing capabilities of spectral sensors to quickly generate enormous quantities of data, combined with the need for image analysts to provide actionable information to the Warfighter in a timely manner, significantly speed up of MODTRAN processing was desired. Furthermore, MODTRAN was written in an outdated programming style and language Fortran77, making it time-consuming and costly to upgrade and maintain, and difficult to integrate with other software. To address these limitations, SSI has developed the NextGen MODTRAN code MODTRAN6, with a focus on current Air Force needs related to remote sensing applications used for Wide Area Surveillance.