OIFITS Simulator

(c) Brian Kloppenborg, Fabien Baron (2015)

The OIFITS SIMulator is a tool to assist in observation planning or in reconstructed image artefact analysis. The program has the ability to either (1) simulate the data from an interferometer given a list of observational hour angles and a FITS image of what the source looks like, or (2) copy the UV coverage of an existing observation and simulate the data given a FITS image of the source.

OIFITS-SIM is developed by Brian Kloppenborg and licensed under the GPLv3. Originally based on the MROI simulator written by Fabien Baron, it does not include all its capabilities yet (though it does bring new ones).

This repository contains Fabien Baron's own version of OIFITS-SIM, developed for PFI.

To check out and build the current stable version of this software do:

git clone https://github.com/fabienbaron/oifits-sim.git
cd oifits-sim
git submodule init
git submodule update
cd build
cmake ..
make

The simulator operates in two primary modes:

In this mode the program will simulate observations from the interferometer and COPY the uncertainty estimates from an existing data file. This mode is useful if you are exploring artefacts in existing images as you can sample a model image and reconstruct the resulting OIFITS file. To use this mode the user needs to specify the target, target image, output file, input OIFITS file, array, combiner, and spectral mode of the combiner. In future versions the last three parameters will be determined (in as much as possible) from the OIFITS file but in the present version this wasn't possible.

oifits-sim -t target_file.txt -i image_file.fits -o output.oifits -d existing.oifits -a array -c combiner -m mode

The simulator attempts to find information about the array, combiner and spectral mode from the OIFITS file. If it fails, it will prompt you for more information.

For example (running from the bin directory), we can emulate CHARA-MIRC's observations of the 2010-10 model image of epsilon Aurigae via:

oifits-sim -t ../samples/target_epsAur.txt -i ../samples/2010-10.fits -o 2010-10_simulated.oifits -d ../samples/2010-10-eps_Aur-all-avg5.oifits -a CHARA -c MIRC -m LowH

In this mode the program will simulate observations from an interferometer and estimate the noise (see documentation for further description of noise estimation). This mode is useful during observing planning as the user can choose various array configurations and see the sampling that results from the configuration. The user may, of course, reconstruct images from the simulated data to see which configuration results in "better" images.

To use this mode the user must specify the target, target image, output file, array, combiner, spectral mode, and observations:

oifits-sim -t target_file.txt -i image_file.fits -o output.oifits -a array -c combiner -m spectral_mode -obs observations

Note: see the shortcut section below as arrays, combiners, and spectral modes may be abbreviated.

Example of Hour Angle usage:

oifits-sim -t ../samples/target_epsAur.txt -i ../samples/2010-10.fits -o 2010-10_simulated.oifits -a CHARA -obs ../samples/obs_ha_example.txt -c MIRC -m LowH

For the definitions of arrays, combiners, and spectral modes the software will automatically search the files in oifits-sim/etc for the presence of a similarly named file. Parameters in these files can be overridden (although they may not necessarily be used) on the command line via -parameter_name=value.

Currently implemented arrays:

CHARA

Currently implemented combiners and spectral modes

MIRC	: Low_H

Some (but not all) of the parameters in default configuration files can be manually overridden on the command line. To override one of these parameters specify the options IMMEDIATELY after the inclusion of the configuration file. For example the following command overrides the default value of r0 at CHARA (7.6 cm) and sets it to 3.1 cm:

oifits-sim -a CHARA --r0 0.031 -t foo.txt ...
...
r0 overridden from default value in array config file.  Now: 0.031

Conversely the following will do nothing as the --r0 parameter will be ignored.

oifits-sim -a CHARA -t foo.txt ... --r0 0.031

All parameters that can be overridden are mentioned below. See documentation for more details.

Array:
    --r0 double
    --wind_speed double

Target:
    --res double
    --mag double

Please use the issue tracker on GitHub

oifits-sim is free software, distributed under the GNU Lesser General Public License (Version 3).

If you use this software as part of a scientific publication, please cite the following work:

Kloppenborg, B.; Baron, F. (2012) "oifits-sim: an OIFITS-simulator" (Version 2). Available from https://github.com/fabiebaron/oifits-sim.