PyIMCOM: Image combination package

This is the Python implementation of Image Combination (PyIMCOM) package being developed for the Roman Space Telescope "Cosmology with the High Latitude Survey" Project Infrastructure Team.

Documentation on this site

See also the readthedocs page.

Requirements

PyIMCOM runs with Python 3.12 and higher.

Required dependencies should install when you run pip. Pip will automatically install the C kernel furry-parakeet. There are optional dependencies for some features:

• If you are running coaddition with PyIMCOM with Piff input files for the PSF (instead of FITS images), you need to install piff. Roman (including interfacing with PyIMCOM) is supported from the main branch (starting June 2026), or starting with v1.7 (when available).

  (Note that Piff is not required to read PyIMCOM output files, even if they were made using Piff.)

Installing PyIMCOM

Conda

conda install -c conda-forge --file requirements.txt
pip install .

Pip

pip install .

Overview of PyIMCOM concepts

• Hierarchy of input and output information

Running PyIMCOM

• How to build a mosaic in PyIMCOM
• How to write a PyIMCOM configuration file
• Input file formats
• Image destriping
• PSF splitting
• How to compress PyIMCOM output files
• How to generate a report after running PyIMCOM

Post-processing of PyIMCOM outputs

• Options for interacting with the PyIMCOM output files
• Instructions for using the meta post-processing module

Information relevant to various runs we have done in the past

• Preparing the PSFs for the OpenUniverse simulation

References

• Optimal linear image combination. Rowe et al. ApJ 741:46 (2011)
• Simulating image coaddition with the Nancy Grace Roman Space Telescope - I. Simulation methodology and general results. Hirata et al. MNRAS 528:2533 (2024)
• Simulating image coaddition with the Nancy Grace Roman Space Telescope - II. Analysis of the simulated images and implications for weak lensing. Yamamoto et al. MNRAS 528:6680 (2024)
• Analysis of Biasing from Noise from the Nancy Grace Roman Space Telescope: Implications for Weak Lensing. Laliotis et al. PASP 136:124506 (2024)
• Simulating image coaddition with the Nancy Grace Roman Space Telescope: III. Software improvements and new linear algebra strategies. Cao et al., ApJS 277:55 (2025)
• OpenUniverse2024: A shared, simulated view of the sky for the next generation of cosmological surveys. OpenUniverse et al. MNRAS 544:3799 (2025)
• Simulating image coaddition with the Nancy Grace Roman Space Telescope. IV. Hyperparameter Optimization and Experimental Features. Cao et al. ApJ, 998:304 (2026)
• Removing correlated noise stripes from the Nancy Grace Roman Space Telescope survey images. Laliotis et al. PASJ, 78:810 (2026)