MIRI Bright Source Limits
Bright source limits of JWST's Mid-Infrared Instrument (MIRI) are predicted by a saturation model that uses measurements obtained during ground testing.
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).
The values in the table and plots below were obtained from ETC 1.5. The JWST ETC assumes a safety margin when calculating when saturation occurs to account for pre-flight uncertainties in the overall responsivity and throughput of the observatory and instrument.
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Table 1.MIRI imager bright source limits (for Ngroups = 5)
|Filter||Full Frame (mJy)||SUB64 subarray (mJy)|
Table 2.MIRI imager subarray bright source limits (for Ngroups = 5)
in F560W (mJy)
in F2550W (mJy)
Low-Resolution Spectrometer (LRS)
Medium-Resolution Spectrometer (MRS)
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