NIRCam Coronagraphy was declared ready for science in the early summer 2022. Several impactful science results have since been obtained using the NIRCam coronagraphs, mainly on known exoplanetary systems. In this contribution we give an update on all improvements we have implemented to make this mode more efficient and perform better. With tight timing constraints in commissioning, we focused on the long wavelengths occulter MASK335R. Here we describe how we improved the target acquisition for all five masks, the distortion correction and global alignment, the absolute flux calibration, etc. We also implemented the default dual channel operations mid-Cycle 1 (simultaneous short and long wavelengths). While not trivial, this new capability improves the efficiency and the impact NIRCam Coronagraphy can have in the field of exoplanets. We discuss the current on-sky contrasts and astrometric performances which are now better understood and can be compared to other high contrast facilities. We demonstrate that NIRCam Coronagraphy is transformative in characterizing known objects but also discovering colder and/or more mature exoplanets.
KEYWORDS: Signal to noise ratio, Near infrared, Point spread functions, Telescopes, Stars, Calibration, Distortion, Coronagraphy, Exoplanets, Astronomical instrumentation, Astronomical imaging, Target acquisition, Direct methods, James Webb Space Telescope
In a cold and stable space environment, the James Webb Space Telescope (JWST or ”Webb”) 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. Launched in late 2021, JWST underwent a six month commissioning period. In this contribution we focus on the NIRCam Coronagraphy mode which was declared ”science ready” on July 10 2022, the last of the 17 JWST observing modes. Essentially, this mode enables the detection of fainter/redder/colder (less massive for a given age) self-luminous exoplanets as well as other faint astrophysical signal in the vicinity of any bright object (stars or galaxies). Here we describe some of the steps and hurdles the commissioning team went through to achieve excellent performances. Specifically, we focus on the Coronagraphic Suppression Verification activity. We were able to produce firm detections at 3.35µm of the white dwarf companion HD 114174 B which is at a separation of ' 0.500and a contrast of ' 10 magnitudes (104 fainter than the K∼5.3 host star). We compare these first on-sky images with our latest, most informed and realistic end-to-end simulations through the same pipeline. Additionally we provide information on how we succeeded with the target acquisition with all five NIRCam focal plane masks and their four corresponding wedged Lyot stops.
KEYWORDS: Signal to noise ratio, Point spread functions, Stars, Calibration, Coronagraphy, Exoplanets, Space telescopes, James Webb Space Telescope, Device simulation, Visibility
The James Webb Space Telescope (JWST) and its suite of instruments, modes and high contrast capabilities will enable imaging and characterization of faint and dusty astrophysical sources1-3 (exoplanets, proto-planetary and debris disks, dust shells, etc.) in the vicinity of hosts (stars of all sorts, active galactic nuclei, etc.) with an unprecedented combination of sensitivity and angular resolution at wavelengths beyond 2 μm. Two of its four instruments, NIRCam4, 5 and MIRI,6 feature coronagraphs7, 8 for wavelengths from 2 to 23 μm. JWST will stretch the current parameter space (contrast at a given separation) towards the infrared with respect to the Hubble Space Telescope (HST) and in sensitivity with respect to what is currently achievable from the ground with the best adaptive optics (AO) facilities. The Coronagraphs Working Group at the Space Telescope Science Institute (STScI) along with the Instruments Teams and internal/external partners coordinates efforts to provide the community with the best possible preparation tools, documentation, pipelines, etc. Here we give an update on user support and operational aspects related to coronagraphy. We aim at demonstrating an end to end observing strategy and data management chain for a few science use cases involving coronagraphs. This includes the choice of instrument modes as well as the observing and point-spread function (PSF) subtraction strategies (e.g. visibility, reference stars selection tools, small grid dithers), the design of the proposal with the Exposure Time Calculator (ETC), and the Astronomer's Proposal Tool (APT), the generation of realistic simulated data at small working angles and the generation of high level, science-grade data products enabling calibration and state of the art data-processing.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.