# JWST/NIRCam Coronagraphy: Commissioning and First On-Sky Results

**Authors:** Julien H. Girard, Jarron Leisenring, Jens Kammerer, Mario Gennaro, Marcia Rieke, John Stansberry, Armin Rest, Eiichi Egami, Ben Sunnquist, Martha Boyer, Alicia Canipe, Matteo Correnti, Bryan Hilbert, Marshall D. Perrin, Laurent Pueyo, Remi Soummer, Marsha Allen, Howard Bushouse, Jonathan Aguilar, Brian Brooks  
**arXiv:** [2208.00998](https://arxiv.org/abs/2208.00998)  
**Date:** 2022-08-01  
**Summary page:** https://www.summarizepaper.com/en/paper/2208.00998v1/

## Key points

- The James Webb Space Telescope (JWST) was launched in late 2021 and underwent a six-month commissioning period.
- The telescope reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics and extends the parameter space of high-contrast imaging in the near and mid-infrared.
- One of the key observing modes on JWST is the NIRCam Coronagraphy mode, which allows for the detection of fainter/redder/colder self-luminous exoplanets as well as other faint astrophysical signals in the vicinity of any bright object such as stars or galaxies.
- The NIRCam Coronagraphy mode was declared "science ready" on July 10, 2022, making it the last of the 17 JWST observing modes to be commissioned.
- Julien H. Girard et al. describe some of the steps and hurdles that were overcome by the commissioning team to achieve excellent performances with this mode.
- The team was able to produce firm detections at 3.35μm of the white dwarf companion HD 114174 B which is at a separation of approximately 0.5" and a contrast of approximately 10 magnitudes (10^4 times fainter than its K~5.3 host star).
- New NIRCam reference files were created that improve performance by accounting for non-linearities in detector response and optical distortions in coronagraphic images.
- With these improvements, they achieved better than expected contrast levels across all filters.
- The team investigated target acquisition (TA) repeatability and found that the TA process is highly repeatable with a precision of approximately 0.1" for all masks, which is well within the required accuracy.
- Overall, these results demonstrate the excellent performance of the NIRCam Coronagraphy mode on JWST and its potential to detect faint exoplanets and other astrophysical signals in the vicinity of bright objects.

## Summary

The James Webb Space Telescope (JWST or "Webb") was launched in late 2021 and underwent a six-month commissioning period. In a cold and stable space environment, the telescope reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics. It also extends the parameter space of high-contrast imaging in the near and mid-infrared. One of the key observing modes on JWST is the NIRCam Coronagraphy mode, which was declared "science ready" on July 10, 2022, making it the last of the 17 JWST observing modes to be commissioned. This mode allows for the detection of fainter/redder/colder self-luminous exoplanets as well as other faint astrophysical signals in the vicinity of any bright object such as stars or galaxies. In this contribution, Julien H. Girard et al. describe some of the steps and hurdles that were overcome by the commissioning team to achieve excellent performances with this mode. Specifically, they focus on the Coronagraphic Suppression Verification activity and provide information on how they succeeded with target acquisition using all five NIRCam focal plane masks and their four corresponding wedged Lyot stops. The team was able to produce firm detections at 3.35μm of the white dwarf companion HD 114174 B which is at a separation of approximately 0.5" and a contrast of approximately 10 magnitudes (10^4 times fainter than its K~5.3 host star). They compare these first on-sky images with their latest end-to-end simulations through the same pipeline. Additionally, new NIRCam reference files were created that improve performance by accounting for non-linearities in detector response and optical distortions in coronagraphic images. With these improvements, they achieved better than expected contrast levels across all filters. The team also investigated target acquisition (TA) repeatability and found that the TA process is highly repeatable with a precision of approximately 0.1" for all masks, which is well within the required accuracy. Overall, these results demonstrate the excellent performance of the NIRCam Coronagraphy mode on JWST and its potential to detect faint exoplanets and other astrophysical signals in the vicinity of bright objects.