View on GitHub


A Virtual Radio Interferometer application

The Friendly Virtual Radio Interferometer

The Friendly Virtual Radio Interferometer (VRI) is designed to simulate astronomical observations using linked arrays of radio antennas in a technique called earth rotation aperture synthesis. As the successor to the original Java-based VRI, it focuses on simulating the effect of combining different antenna layouts.

fVRI Control Window

fVRI Plot Window


Click on the ‘View on GitHub’ link at the top of the page and then the ‘Clone or download’ button to fetch the package code. The Friendly VRI is written in Python to work with both Python 2.7.x and 3.x. The recommended way to install is via an Anaconda environment. Run the following command to create an environment called vri:

conda env create -f environment.yml.

Once all required modules are installed, activate the environment:

conda activate vri


Start the application by executing python on the command line from within the friendlyVRI/ directory. The interface is (hopefully) very intuitive and is split into a control window and a plotting window. The plotting window can be maximised and buttons at the lower-right enable jumping quickly between the two windows. The control window allows you to:

The plotting window shows inputs, outputs and intermediate steps in the process: model image, fast Fourier transform (FFT) of the model, plot of uv-coverage, filtered model FFT, synthesised beam and final observed image.

See HELP or the help menu in the application for step-by-step instructions.

Note that the calculations underlying the graphical application are split into the file to facilitate use with alternative interfaces. See CALCULATIONS for a simple example.

Defining Custom Arrays

The location and layout of antennas in each array configuration is defined in ASCII files under the arrays/ directory. You can define your own arrays by copying the existing templates and supplying a list of coordinate offsets in the East and North directions, in units of meters. The software will read these on start-up and they will appear in the list of available arrays. Note that the combination of ‘telescope’ + ‘array’ name must be unique.


This software is designed to be a simple ‘quick-look’ tool and ignores lots of effects such as non-co-planar arrays, time averaging, multi-frequency synthesis etc. It also sets the sampling grid in the Fourier domain from the extent and pixel spacing of the input image, which can result in under-sampled synthesised beams and artefacts. At the moment, the observing simulations are assumed to be noise-free and no attempt is made at calculating sensitivities. Tasks to perform robust simulations of an interfometric observation exist in CASA, MIRIAD and AIPS, but are more difficult to use.

Other VRI Software

Other excellent virtual interfeometer software has been developed by staff at observatories around the world:

Credits and Contact Information:

The Friendly Virtual Radio Interferometer tool was written by Cormac Purcell and Roy Truelove at Macquarie University, Sydney. Questions, comments, feature requests and bug reports should be directed to ‘cormac.purcell (at)’.


Copyright (c) 2017 - 2022 Cormac R. Purcell and Roy Truelove.

Released under the MIT licence.