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 Fall 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 ASW as prime (F210M)LW channel as prime (F335M)
MaskMASK210RMASKSWBMASK335RMASK430RMASKLWB

BRIGHT (ND) TA

SR offset: -0.004, -0.011
Global error: < 15 mas (1σ) 

TBD


SR offset: -0.006, -0.012
Global error: < 15 mas (1σ) 


SR offset: -0.006, -0.012
Global error: < 15 mas (1σ) 

TBD
FAINT TATBDTBD

Target Acquisition Offsets

This text file contains the most up to date list of special requirements (SR) offsets: NIRCam_Coronagraphy_SR_offsets.txt

Please always work with your assigned contact scientist to make sure you apply the latest SR offsets to your program. 


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.
  • Values in orange need confirmation (further analysis and/or more data).



Notable updates

  • Corrected Table 1 with latest values and added a dynamic link
Originally published