MIRISim: A Simulator for the Mid-Infrared Instrument on JWST

TL;DR

MIRISim is a Python-based simulator that models the on-orbit performance of JWST's MIRI instrument, aiding in commissioning and data analysis by generating realistic uncalibrated detector images.

Contribution

The paper introduces MIRISim, a comprehensive and publicly available simulator that accurately mimics MIRI's observational data and instrument behavior for the first time.

Findings

MIRISim successfully reproduces MIRI's detector images with realistic noise and distortions.

The software provides data compatible with JWST calibration pipelines.

MIRISim facilitates user training and instrument commissioning processes.

Abstract

The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST), has imaging, four coronagraphs and both low and medium resolution spectroscopic modes . Being able to simulate MIRI observations will help commissioning of the instrument, as well as get users familiar with representative data. We designed the MIRI instrument simulator (MIRISim) to mimic the on-orbit performance of the MIRI imager and spectrometers using the Calibration Data Products (CDPs) developed by the MIRI instrument team. The software encorporates accurate representations of the detectors, slicers, distortions, and noise sources along the light path including the telescope's radiative background and cosmic rays. The software also includes a module which enables users to create astronomical scenes to simulate. MIRISim is a publicly available Python package that can be run at the command line, or from within Python. The outputs of MIRISim are detector images in the same uncalibrated data format that will be delivered to MIRI users. These contain the necessary metadata for ingestion by the JWST calibration pipeline.