MODTRAN Source Overview

The following page helps you understand the stakes of using a MODTRAN source in Speos simulations.

Note: The MODTRAN Source feature is in BETA mode for the current release.

Description

Atmospheric models are used to simulate the behavior of electromagnetic radiation as it interacts with the Earth's atmosphere. This is because the atmosphere can attenuate, emit, scatter, and refract light, affecting the accuracy of sensor signal acquisition.

In this context, MODTRAN (Moderate Resolution Atmospheric Transmission) is a software and computer model used to simulate radiative transfer in the Earth's atmosphere, developed by Spectral Sciences Inc. (SSI) and validated by the Air Force Research Laboratory (AFRL). MODTRAN models the transmission of light through the atmosphere and solves the radiative transfer, taking into account molecular and particulates effects as absorption, scattering, emission by atmospheric gases, aerosols, clouds, ground surface reflections and emission, and solar and lunar illumination.



Thus, Speos can take advantage from various characteristics that MODTRAN can offer such as:
  • The possibility to set and simulate atmospheric properties such as pressure, temperature, humidity, aerosols, gases
  • The possibility to consider a complete spectrum from ultraviolet (UV) to far-infrared (FIR)
  • The possibility to consider spatial variation

As a consequence, Speos can permit fast atmospheric simulation thanks to the combination of HPC tools , and thorough atmospheric simulation analysis.

Important:
  • MODTRAN sources are compatible with:
    • CPU Inverse simulations
    • CPU HPC
  • MODTRAN sources are not compatible with:
    • Direct simulations
    • Interactive simulations
    • GPU simulations
    • Live Preview

Generic Workflow

  1. In the MODTRAN software:
    1. define the atmospheric conditions and information and the sensor information
    2. generate a radiance map out of the parameters defined.

  2. In Speos, create a MODTRAN source in which you will input the generated radiance map file (*.tp5, *.json).

    This is the map file that determines all the characteristics of the atmosphere.

  3. Compute the MODTRAN source.

    This operation can take time.

  4. Create a MODTRAN Radiance sensor and link it to the MODTRAN source.
  5. Create an Inverse simulation and input the MODTRAN source, the Radiance sensor, and all features and geometries you want to simulate.
  6. Run the simulation and take advantage of the different Speos analysis tools available in the Labs to analyze your results.
Figure 1. Speos and MODTRAN relationship during the definition and updating processes of an ambient source with MODTRAN