Welcome to the Visibility Modeling Tool (VMT)

Version 2.0 - Release Date: 04/2009

VMT is a software application developed by the NASA Exoplanet Science Institute (NExScI) to allow prospective or experienced users of optical interferometers to model the interferometric observables for objects of interest using a simple interface. A new component in NExScI's getCal suite of observation planning utilities, VMT performs visibility amplitude predictions (and null depth as in the case of the KI), both for geometrical models constructed as combinations of elementary morphologies (point source, uniform disk or ring, and Gaussian) as well as for an arbitrary brightness uploaded as a FITS image. Data in the OI-FITS standard can also be uploaded, to be plotted alongside the VMT simulations.

  • For information on how to use VMT, please refer to the VMT User's Guide.
  • For any questions, comments, or bug reports, please visit the NExScI Help Desk.

    VMT can be run by either of these two methods:
  • Run the web applet, or
  • Download the executable application.

  • Visibility Modeling Tool Applet:

    You may be prompted to accept a certificate signed by "NExSci Multi-Mission Tools" to allow the applet unrestricted access to your computer. Please accept the certificate in order to run the applet.

    Wait for the button to appear below. Please be patient, this may take a few moments to download.

    When the "Start VMT Applet 2.0" button appears above, click it to start the applet.

    To avoid inadvertantly terminating your VMT session, it is recommended that you minimize this window after starting up the applet.


    • This applet requires JRE 1.4 or later be available on your computer. If you don't see the applet button above after a short period (or if you see a red X), you may need to install Java on your computer or enable your browser for Java with a Java Plug-in. There are many websites that can help determine which version of Java you are using as well as help in upgrading your Java version such as You can find more information in section 2 of the VMT User's Guide.

    Visibility Modeling Tool Executable Download:

    A downloadable version of the executable is available through the NExScI Download Portal.