Simulation Development Utilities
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. At present, the available tools include the following:
| 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. |
In this article, we provide a high-level summary of these tools with links to their documentation. The articles in this section (linked above) give further information specific to each tool including guidance on the use of the tool in the context of the Roman WFI.
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 present for, 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.
Bandpass information for the Coronagraph Instrument is not provided by STScI. Other tools may be available for the Coronagraph Instrument, and users should consult the Roman at IPAC page for more information.
For additional questions not answered in this article, please contact the Roman Help Desk at STScI.
References
- Sahlmann, J., Osborne, S., Cox, C., Proffitt, C. R., Law, D., Perrin, M., and Boyer, M. 2019, pysiaf, https://zenodo.org/record/3516964
- Lim, P. L. et al. 2016, synphot User's Guide (Baltimore, MD: STScI), https://doi.org/10.5281/zenodo.3673988