NIRCam Coronagraphy Calibration Status
The overall calibration status and estimated accuracy of NIRCam coronagraphy are described in this article; please also see the article on known issues affecting NIRCam data.
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Astrometric accuracy
Date:
Shortwave channel: Uncertainties for both round and bar occulting masks are generally on the order of 5–10 mas in the area covered by the coronagraph optical mount (COM). Outside the COM, the uncertainties are 3–6 mas.
Longwave channel: Uncertainties for both round and bar occulting masks are generally >10 mas both in and outside of the COM area.
Updated astrometric distortion files for coronagraphy are expected in the spring of 2024.
Photometric calibration
Updated:
An updated flux calibration for coronagraphy was released in CRDS on November 1, 2023 (pmap 1146).
The absolute flux calibration uncertainties are <1.5% for the round masks and the short wavelength bar mask (SWB). For the long wavelength bar mask (LWB), the uncertainties are <2% for most filters, but are higher for F277W (6%), F250M (13.5%), and F300M (12.5%) because the standard star was partially obscured by the mask. These numbers should improve when Cycle 2 data are incorporated.
Target acquisition performance
Date:
Table 1. Target acquisition global uncertainties
| Module A | SW as prime (F210M) | LW channel as prime (F335M) | |||
|---|---|---|---|---|---|
| Mask | MASK210R | MASKSWB | MASK335R | MASK430R | MASKLWB |
BRIGHT (ND) TA | SR offset: +0.007, -0.002 | SR offset: +0.000, -0.015 Global error: < 15 mas (1σ) | SR offset: -0.010, +0.006 Global error: ~15 mas (1σ) | SR offset: +0.017, -0.015 Global error: ~20 mas (1σ) | SR offset: +0.000, +0.031 Global error: > 0.5 pixel |
| FAINT TA | SR offset: -0.001, +0.011 Global error: TBD | TBD | SR offset: -0.006, +0.002 Global error: ~15 mas (1σ) | SR offset: +0.014, -0.019 Global error: TBD | TBD |
Table notes:
- SR offsets are the special requirements offsets (in arcsec) currently needed (in APT) to compensate for imperfect distortion compensation and updated mask positions.
- SR offsets will be discontinued when distortion corrections are updated (winter 2023/2024).
- Values in orange need confirmation (further analysis and/or more data).