Bright source limits of JWST's Mid-Infrared Instrument (MIRI) are predicted by a saturation model that uses measurements obtained during ground testing.


Introduction

Parent page: MIRI Predicted Performance

The performance of MIRI has been measured directly at both the component and system level using the fully assembled MIRI flight model in a flight-like radiative environment with a well characterized radiometric source (Glasse et al. 2015).  Results of these JWST throughput measurements have been integrated into a sensitivity model, which includes the following components: (1) background, (2) photon conversion efficiency (PCD), (3) encircled energy, and (4) detector performance  (Pontoppidan 2016).

Users should ultimately use the Exposure Time Calculator (ETC) for all bright limit calculations.



Values

Tables 1 and 2, and Figure 1 show bright source limits assuming a five group integration. The values shown represent the fluxes at which the detector reaches 70% of the pixels' full-well capacity.

Imager

Table 1.MIRI imager bright source limits (for Ngroups = 5)

FilterBright source limit (mJy)
full frame
Bright source limit (mJy)
64 × 64 subarray
F560W4.1134
F770W3.6118
F1000W7.8255
F1130W331077
F1280W13.6444
F1500W17.6575
F1800W31.71035
F2100W31.81038
F2550W95.33112



Table 2.MIRI imager subarray bright source limits (for Ngroups = 5)
SubarrayBrightness
limit in F560W
(mJy)
Brightness
limit in F2550W 
(mJy)
FULL 14.195
BRIGHTSKY13306
SUB25638882
SUB128962222
SUB641343111




Figure 1. MIRI bright source limits (for Ngroups = 5)

MIRI imager bright source limits for all modes, assuming FULL frame.







References

Glasse, A. et al. 2015, PASP, 127, 686
The Mid-Infrared Instrument for the James Webb Space Telescope, IX: Predicted Sensitivity

Pontoppidan, K. 2016, Proc of SPIE, 9910, 16
Pandeia: a multi-mission exposure time calculator for JWST and WFIRST 

JWST technical documents





Last updated

Updated September 6, 2018

  • Updated Bright Source graph according to correct arrays used


Updated February 7, 2018

  • Updated Bright Source graph to reflect current values used


Updated February 2, 2018

  • Updated Bright Source Imager numbers to reflect current values used.


Published December 30, 2016


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Updated April 05, 2017

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Published March 02, 2017