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.
Note
This article has not yet been updated to include in-flight performance.
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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 1.5.1. 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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Imager
Table 1.MIRI imager bright source limits (for Ngroups = 5)
Filter | Full Frame (mJy) | SUB64 subarray (mJy) |
---|---|---|
F560W | 3.47 | 133.61 |
F770W | 2.93 | 95.79 |
F1000W | 5.38 | 175.77 |
F1130W | 20.96 | 684.53 |
F1280W | 10.10 | 330.04 |
F1500W | 11.46 | 374.17 |
F1800W | 19.35 | 631.76 |
F2100W | 21.85 | 713.38 |
F2550W | 43.41 | 1417.39 |
Table 2.MIRI imager subarray bright source limits (for Ngroups = 5)
Subarray | Brightness limit in F560W (mJy) | Brightness limit in F2550W (mJy) |
---|---|---|
FULL | 0.12 | 12.2 |
BRIGHTSKY | 11.16 | 139.28 |
SUB256 | 32.18 | 401.59 |
SUB128 | 81.15 | 1012.42 |
SUB64 | 133.61 | 1417.39 |
Low-resolution spectrometer (LRS)
Medium-resolution spectrometer (MRS)
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