This page contains information related to low-level development tools and utilities that support simulations of the Roman Wide Field Instrument (WFI) data.

Introduction

Several tools are available for users who wish to create their own simulations of Roman Wide Field Instrument (WFI) observations. Here, we present complementary tools that such users may find useful, high-level summaries, links to additional documentation, and guidance on the use of the tools in the context of the Roman WFI.

Tool Name	GitHub Repository	Website	RDox Article Link	Purpose
pysiaf	pySIAF on GitHub	pySIAF ReadTheDocs	PySIAF for Roman	Transformations between detector, science, ideal, telescope, and sky coordinate systems for both the WFI and Coronagraph Instrument. Figures in this article provide context for the coordinate systems.
synphot	Synphot on GitHub	Synphot ReadTheDocs	Synphot for Roman	Synthetic observations and photometry in WFI bandpasses (both imaging and spectroscopic modes) of input source spectra.
Jupyter Footprint Viewer	Jupyter Footprint Viewer on GitHub	The Jupyter notebook on GitHub is the main website for the tool.	Jupyter Footprint Viewer for Roman	Uses pysiaf information to display an instrument footprint on the sky. Can additionally query an astronomical catalog with the instrument footprint.

pySIAF

The Science Instrument Aperture File (SIAF) is an XML-formatted file that describes the various coordinate systems used in the planning of WFI observations and creation of WFI data products. The SIAF itself contains a great deal of information necessary to set up these transformations, and  pysiaf (Sahlmann et al. 2019) provides the tools necessary to read the XML file and presents the transformations as Python-based functions and methods. For more information and examples, see the ReadTheDocs page for  pysiaf as well as the PySIAF for Roman page for Roman-specific information and installation instructions.

Synphot

The  synphot Python package (Lim et al. 2016) was developed for general-purpose synthetic observations and photometry of input source spectra, and is a direct replacement for Astrolib PySynphot. synphot convolves bandpass information from the WFI with input spectra to create synthetic observations, and then integrates over the bandpass to estimate the flux that would be measured by the WFI. Additional functions and methods are also available, including various metrics of the bandpasses themselves such as their pivot wavelength. More information may be found on the ReadTheDocs page for  synphot as well as the Synphot for Roman page for Roman-specific information and installation instructions.

Please note that additional support packages and reference data are necessary for  synphot to have access to WFI bandpass information. These include  webbpsf OR  stsynphot , as well as the Spectral Atlas Files for Synphot Software. Specific information on these dependencies are provided in the installation instructions on the Synphot for Roman page.

Jupyter Footprint Viewer for Roman

This Jupyter notebook created by MAST takes instrument footprint information from pysiaf and provides the Python code needed to both overlay the instrument footprint on survey data and query astronomical catalogs within the footprint. The footprint viewer is flexible enough to use many different instrument footprints, but tips and instructions for use with the Roman WFI footprint are provided on the Jupyter Footprint Viewer for Roman page. 

For additional questions not answered in this article, please contact the Roman Help Desk at STScI.

References

1. Sahlmann, J., Osborne, S., Cox, C., Proffitt, C. R., Law, D., Perrin, M., and Boyer, M. 2019, pysiaf, https://zenodo.org/record/3516964
2. Lim, P. L. et al. 2016, synphot User's Guide (Baltimore, MD: STScI), https://doi.org/10.5281/zenodo.3673988