STIPS - Space Telescope Imaging Product Simulator
The Space Telescope Imaging Product Simulator for the Nancy Grace Roman Space Telescope, or STIPS , is used to simulate realistic astronomical scenes for WFI similar to Level 2 (L2) data products from the exposure level pipeline, which are described in Data Levels and Products.
What is STIPS?
STIPS stands for Space Telescope Imaging Product Simulator, and is a tool crafted to generate simulated images for the Nancy Grace Roman Space Telescope's Wide Field Instrument (WFI). It can generate post-pipeline astronomical scenes for any number of Sensor Chip Assemblies (SCA), encompassing the entire 18-SCA WFI. STIPS includes instrumental distortion (if available), along with calibration residuals originating from flatfields, dark currents, and cosmic rays. Furthermore, it includes an estimate of Poisson and readout noise in the simulations, although it does not cover instrument saturation and non-linearity effects. The software obtains instrument and filter parameters for the WFI directly from Pandeia and approximates Point Spread Functions (PSFs) at any pixel location by interpolating over a grid of nine evenly-distributed, SCA-specific PSFs generated with WebbPSF , the PSF modeling software for the WFI. Generally, the resulting flux measurements are expected to be within ~10% of those generated by Pandeia .
Figure of STIPS M13 Demo
Top – Simulated color image of the globular cluster, M13, of all 18 SCAs in WFI generated with STIPS using the properties of individual stars from literature catalogs of positions and brightness. The simulated color image is a combination of the F106, F129, and F158 filters for WFI. Bottom – Zoom into the the M13 simulation to show a single SCA.
Current Software Version
This documentation is written for STIPS version 2.2.2 (released on December 16, 2024). The software can be obtained from the STScI-STIPS Github repository. Up-to-date development documentation is available in the STIPS readthedocs.
When to use STIPS?
STIPS is designed to quickly produce image simulations that are similar to the anticipated Level 2 (L2) data products from the WFI. STIPS is recommended for full-SCA or multiple-SCA image simulations, especially in cases when Pandeia , the Exposure Time Calculator for the WFI, does not provide a sufficiently large simulation area. While STIPS can add error residuals (representing the remaining uncertainty after pipeline calibration), it does not start with Level 1 (L1) data products to propagate instrumental calibrations through the output images and the output residuals have not been fully validated against the actual pipeline calibrations of L1 data products. Therefore, STIPS is not the ideal choice if high instrumental accuracy is needed. Moreover, STIPS outputs do not conform to the Roman datamodels and are therefore not suitable for use with the Romancal pipeline.
For applications that require high-accuracy simulations we recommend using
Pandeia
.
As described in the Caveats to Using STIPS for Roman, neither pixel saturation nor non-linearity residuals are currently supported.
Acknowledgements
STIPS was developed by Brian York (@york-stsci), Robel Geda (@robelgeda), and O. Justin Otor (@ojustino). Python ePSF code developed by Sebastian Gomez (@gmzsebastian) is based on Fortran software written by Andrea Bellini (@AndreaBellini).
For additional questions not answered in this article, please contact the Roman Help Desk at STScI.
References
In addition to this documentation, STIPS is described in the following references. Users are encouraged to cite this publication:
STIPS Development Team et al 2024, "STIPS: The Nancy Grace Roman Space Telescope Imaging Product Simulator", PASP 136 124502