MODTRAN

MODTRAN
Name	MODTRAN
Developer	Air Force Research Laboratory; Spectral Sciences, Inc.
Initial release	1980s
Operating system	Microsoft Windows
Genre	Radiative transfer model
License	Proprietary

MODTRAN MODTRAN is a computerized radiative transfer model used for simulating atmospheric transmission and radiance in the ultraviolet, visible, and infrared portions of the electromagnetic spectrum. The software supports remote sensing, atmospheric science, and defense applications by modeling interactions among solar irradiance, atmospheric constituents, surface reflectance, and instrumental effects. MODTRAN is widely employed by research institutes, government agencies, and industry partners for sensor design, calibration, and environmental monitoring.

Overview

MODTRAN computes spectral radiance and transmittance through layered atmospheres, combining molecular absorption, aerosol scattering, and cloud effects to produce outputs usable for Landsat-class sensor simulation, SPOT missions, and instrument teams at NASA. The model incorporates databases and parameterizations developed by experts at SRI International, Air Force Research Laboratory, and Spectral Sciences, Inc. to support users from NOAA, USGS, and defense laboratories. MODTRAN interfaces are used in workflows alongside tools from Jet Propulsion Laboratory, European Space Agency, and academic groups at Massachusetts Institute of Technology and University of Colorado Boulder.

History and Development

MODTRAN originated from radiative transfer efforts in the 1980s at research groups including Air Force Geophysics Laboratory and collaborators at SRI International and was further developed with contributions from scientists affiliated with Harvard University and University of Oxford. Historical improvements paralleled developments in atmospheric spectroscopy from initiatives at California Institute of Technology and instrument teams at NASA Goddard Space Flight Center. Subsequent versions integrated line-by-line and band models influenced by work at National Center for Atmospheric Research and spectroscopic compilations maintained by Institute of Physics-affiliated researchers. Over decades, stewardship shifted among contractors and government laboratories such as Lincoln Laboratory and Lawrence Livermore National Laboratory as sensor demands from Department of Defense programs and civil agencies evolved.

Core Models and Algorithms

The model employs correlated-k approximation, multiple scattering solvers, and parameterized aerosol and cloud schemes that trace conceptual lineage to numerical methods developed at Princeton University and Stanford University. MODTRAN’s radiative transfer engine couples discrete-ordinate and two-stream approximations, utilizing molecular absorption coefficients derived from spectroscopic compilations like those compiled by Harvard-Smithsonian Center for Astrophysics contributors and international collaborations associated with World Meteorological Organization committees. Line-shape treatments reference community standards promulgated by groups at National Institute of Standards and Technology and incorporate pressure- and temperature-broadening algorithms developed in laboratory programs at Argonne National Laboratory. The software’s inversion and forward-modeling workflows are used alongside retrieval algorithms from teams at University of Oxford and Imperial College London.

Spectral Databases and Atmospheric Inputs

MODTRAN relies on spectral line databases and continuum models originating from the HITRAN community and experimental datasets maintained by National Aeronautics and Space Administration laboratories and university spectroscopy groups such as University of Cambridge. Standard atmospheric profiles derive from climatologies produced by NOAA and reanalysis products from European Centre for Medium-Range Weather Forecasts, while aerosol models reference studies from NASA Jet Propulsion Laboratory and field campaigns like those run by Scripps Institution of Oceanography and Desert Research Institute. Surface reflectance libraries and emissivity catalogs used in simulations incorporate measurements from USGS and airborne campaigns led by University of Alaska Fairbanks and Colorado State University research teams.

Applications and Use Cases

MODTRAN supports sensor design for satellite programs including projects coordinated by NASA, European Space Agency, and national laboratories such as Sandia National Laboratories. Defense-oriented use spans modeling for electro-optical systems evaluated by Defense Advanced Research Projects Agency contractors and operational units within the United States Air Force. Environmental science applications include trace gas retrievals for studies conducted by National Oceanic and Atmospheric Administration and field experiments organized by National Center for Atmospheric Research and university consortia like Purdue University and University of Illinois Urbana-Champaign. The model underpins validation campaigns for instruments on Terra and Aqua platforms and supports calibration for hyperspectral sensors developed by teams at Ball Aerospace and Rutherford Appleton Laboratory.

Validation and Performance

Validation of MODTRAN outputs uses measurements from ground-based networks such as AERONET and spectroradiometer campaigns executed by groups at National Renewable Energy Laboratory and NIST. Comparative studies benchmark MODTRAN against line-by-line models produced by researchers at University of Toronto and laboratory spectrometers at Max Planck Institute for Meteorology. Performance assessments consider computational cost on platforms from Intel Corporation-based workstations to high-performance clusters at Oak Ridge National Laboratory. Intercomparison exercises have been organized by panels involving World Meteorological Organization, Committee on Space Research, and academic consortia at University of Bremen.

Licensing and Distribution

MODTRAN is distributed under proprietary licensing arrangements managed by commercial entities and government contractors, with usage governed by agreements involving U.S. Department of Defense programs, civilian agencies such as NASA, and academic licensees at institutions like Massachusetts Institute of Technology and University of Michigan. Access pathways include site licenses for laboratories such as Los Alamos National Laboratory and purchasable developer licenses used by companies including Lockheed Martin and Raytheon Technologies. Training and user support are provided through workshops hosted by organizations like SPIE and conference sessions at American Geophysical Union meetings.

Category:Radiative transfer models