The original development of MODTRAN was driven by a need for higher spectral resolution and greater accuracy than that provided by the (much older) LOWTRAN series of band model algorithms. MODTRAN calculates atmospheric transmittance and radiance for frequencies from 0 to 50,000 cm−1 at moderate spectral resolution, primarily 2 cm−1 (20 cm−1 in the UV). The characteristics of these layers are either drawn from several internal model atmospheres (urban or rural, equatorial or arctic, etc.) or can be characterized by (user provided) radiosonde data collected about a specific atmosphere. This is accomplished by modeling the atmosphere as a set of homogeneous layers. It is a computationally rigorous radiation transfer algorithm that is used to model the spectral absorption, transmission, emission and scattering characteristics of the atmosphere. MODTRAN is an acronym for MODerate spectral resolution atmospheric TRANsmittance algorithm and computer model, which is developed by the Air Force Research Labs (AFRL) in collaboration with Spectral Sciences, Inc (SSI). Hyper-links are in blue while section and Figure references are in red. It should be noted that this is a “live” document and is full of hyper-links to various web pages, etc. Along the way, ENVI functions such as Spectral Math, Spectral Resampling and the Spectral Library Viewer will be utilized. The output will be examined and used to assemble a sensor-reaching radiance equation. This script will also, automatically, parse the MODTRAN output and subsequently convert it to an ENVI spectral library. The actual execution of the MODTRAN code will commence using a custom UNIX script written for the digital imaging and remote sensing (DIRS) laboratory. This card deck will be used to simulate an atmosphere over Rochester, NY during the summertime.

Using GUI software, tape5 input card decks will be modified with an explanation of relevant parameters. Carlson Center for Imaging Science Rochester Institute of Technology February 5, 2007Ībstract The purpose of this lab is to expose the individual to the utilization of MODTRAN and ENVI processing. Using MODTRAN Predicting Sensor-Reaching Radiance∗ Emmett J.

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