The Mid-Infrared Instrument for the James Webb Space Telescope, IX: Predicted Sensitivity

TL;DR

This paper estimates the on-orbit performance of the JWST MIRI instrument, detailing its sensitivity, efficiency, and saturation limits based on testing data, to predict its capability for observing faint astronomical sources.

Contribution

It provides the first detailed sensitivity predictions for JWST's MIRI instrument, including algorithms and testing results that inform expected observational performance.

Findings

Estimated detection efficiency for MIRI systems.

Predicted sensitivity limits for faint source observations.

Saturation flux levels for bright targets.

Abstract

We present an estimate of the performance that will be achieved during on orbit operations of the JWST Mid Infrared Instrument, MIRI. The efficiency of the main imager and spectrometer systems in detecting photons from an astronomical target are presented, based on measurements at sub-system and instrument level testing, with the end-to-end transmission budget discussed in some detail. The brightest target fluxes that can be measured without saturating the detectors are provided. The sensitivity for long duration observations of faint sources is presented in terms of the target flux required to achieve a signal to noise ratio of 10 after a 10,000 second observation. The algorithms used in the sensitivity model are presented, including the understanding gained during testing of the MIRI Flight Model and flight-like detectors.