The James Webb Space Telescope (JWST) will revolutionize the field of high-contrast imaging and enable both the direct detection of Saturn-mass planets and the characterization of substellar companions in the mid-infrared. While JWST will feature unprecedented sensitivity, angular resolution will be the key factor when competing with ground-based telescopes. Here, we aim to characterize the performance of several extreme angular resolution imaging techniques available with JWST in the 3–5 µm regime based on data taken during the instrument commissioning. Firstly, we introduce custom tools to simulate, reduce, and analyze JWST NIRCam and MIRI coronagraphy data and use these tools to extract companion detection limits from on-sky NIRCam round and bar mask coronagraphy observations. Secondly, we present on-sky JWST NIRISS aperture masking interferometry (AMI) and kernel phase imaging (KPI) observations from which we extract companion detection limits using the publicly available fouriever tool. Scaled to a total integration time of one hour and a target of the brightness of AB Dor (W1 ≈ 4.4 mag, W2 ≈ 3.9 mag), we find that NIRISS AMI and KPI reach contrasts of ∼ 7–8 mag at ∼ 70 mas and ∼ 9 mag at ∼ 200 mas. Beyond ∼ 250 mas, NIRCam coronagraphy reaches deeper contrasts of ∼ 13 mag at ∼ 500 mas and ∼ 15 mag at ∼ 2 arcsec. While the bar mask performs ∼ 1 mag better than the round mask at small angular separations ≲ 0.75 arcsec, it is the other way around at large angular separations ≳ 1.5 arcsec. Moreover, the round mask gives access to the full 360 deg field-of-view which is beneficial for the search of new companions. We conclude that already during the instrument commissioning, JWST high-contrast imaging in the L- and M-bands performs close to its predicted limits and is a factor of ∼ 10 times better at large separations than the best ground-based instruments operating at similar wavelengths despite its < 2 times smaller collecting area.
In less than a year, the James Webb Space Telescope (JWST) will inherit the mantle of being the world’s pre- eminent infrared observatory. JWST will carry with it an Aperture Masking Interferometer (AMI) as one of the supported operational modes of the Near-InfraRed Imager and Slitless Spectrograph (NIRISS) instrument. Aboard such a powerful platform, the AMI mode will deliver the most advanced and scientifically capable interferometer ever launched into space, exceeding anything that has gone before it by orders of magnitude in sensitivity. Here we present key aspects of the design and commissioning of this facility: data simulations (ami_sim), the extraction of interferometeric observables using two different approaches (IMPLANEIA and AMICAL), an updated view of AMI’s expected performance, and our reference star vetting programs.
KEYWORDS: Point spread functions, Sensors, Interferometry, Planets, James Webb Space Telescope, Exoplanets, Space telescopes, Astronomy, Aerospace engineering, Data modeling
JWST/NIRISS has a non-redundant aperture mask (NRM) for use with its F380M, F430M, F480M and F277W filters. In addition to high-resolution imaging with moderate contrast, the NRM provides better astrometric accuracy over a wide field of view than regular imaging. We investigate the accuracy achievable with the NRM by using an image-plane algorithm to analyze the PSFs of a point source that were obtained at a fixed pixel location with sub-pixel dithers during the second Cryo-Vacuum test campaign of the Integrated Science Instrument Module at NASA’s Goddard Space Flight Center. Astrometry of brown dwarfs with the NRM will be sensitive to the presence of terrestrial planets and can be used to probe the architecture of planetary systems around these objects.
KEYWORDS: Image segmentation, James Webb Space Telescope, Point spread functions, Wavefront sensors, Space telescopes, Telescopes, Mirrors, Sensors, Cameras, Wavefronts
We present several engineering and algorithmic aspects of non-redundant masking (NRM) as they pertain to the James Webb Space Telescope (JWST). NRM's fundamental data structures have multiple uses in wavefront sensing as well in as high resolution imaging. Kernel phases are a full aperture generalization of NRM applicable to moderate and high Strehl ratio images. Eigenphases, the complement to kernel phases, provide wavefront sensing with single in-focus images. Thus this set of phases is relevant to wavefront sensing with routine science images on any Nyquist-sampled science camera on JWST. We attempt to organize these apparently diverse aspects of such Fizeau interferometry into an inter-related picture in order to facilitate their development and potential use on JWST and future space telescopes.
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