NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

Käufl, H. U.; Kasper, Markus; Arsenault, Robin; Jakob, Gerd; Leveratto, Serban; Zins, G.; Fuenteseca, Eloy; Riquelme, M.; Siebenmorgen, R.; Sterzik, M.; Ageorges, N.; Gutruf, S.; Kampf, Dirk; Reutlinger, Arnd; Absil, Olivier; Carlomagno, Brunella; Guyon, Olivier; Klupar, Pete; Mawet, Dimitri; Ruane, Garreth; Karlsson, Mikael; Pantin, É.; Dohlen, Kjetil

doi:10.1117/12.2313395

Cited by 5 publications

(4 citation statements)

References 19 publications

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“…The rejection performances of these AGPMs and of the first-generation AGPM-N3 mask were measured on a thermal IR bench at ESO Garching. 13 The measured rejection rate of the new AGPMs ( 200 at 10.2 µm) was found to be inferior to the measured performance of the AGPM-N3 mask (∼ 400 at 10.2 µm). Based on these performance tests, the best AGPM mask among the new devices (referred to as AGPM-BT3) and the AGPM-N3 mask were sent to Paranal for integration in VISIR alongside the AGPM-N4 mask, whose intrinsic rejection rate was still mostly unknown.…”

Section: Mid-infrared Annular Groove Phase Masksmentioning

confidence: 76%

Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment

Maire

Huby

Absil

et al. 2020

J. Astron. Telesc. Instrum. Syst.

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Vortex coronagraphs have been shown to be a promising avenue for high-contrast imaging in the close-in environment of stars at thermal infrared (IR) wavelengths. They are included in the baseline design of the mid-infrared extremely large telescope imager and spectrograph. To ensure good performance of these coronagraphs, a precise control of the centering of the star image in real time is needed. We previously developed and validated the quadrant analysis of coronagraphic images for tip-tilt sensing estimator (QACITS) pointing estimator to address this issue. While this approach is not wavelength-dependent in theory, it was never implemented for mid-IR observations, which leads to specific challenges and limitations. Here, we present the design of the mid-IR vortex coronagraph for the new Earths in the α Cen Region (NEAR) experiment with the Very Large Telescope (VLT)/Very Large Telescope imager and spectrometer for the mid-infrared (VISIR) instrument and assess the performance of the QACITS estimator for the centering control of the star image onto the vortex coronagraph. We use simulated data and on-sky data obtained with VLT/VISIR, which was recently upgraded for observations assisted by adaptive optics in the context of the NEAR experiment. We demonstrate that the QACITS-based correction loop is able to control the centering of the star image onto the NEAR vortex coronagraph with a stability down to 0.015λ/D rms over 4 h in good conditions. These results show that QACITS is a robust approach for precisely controlling in real time the centering of vortex coronagraphs for mid-IR observations.

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Section: Mid-infrared Annular Groove Phase Masksmentioning

confidence: 76%

Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment

Maire

Huby

Absil

et al. 2020

J. Astron. Telesc. Instrum. Syst.

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“…The VLT Imager and Spectrometer for the mid-Infrared (VISIR) is an instrument that provides diffraction-limited imaging over the N (8-14 μm) and Q (17-28 μm) bands. In 2019, the New Earths in the Alpha Cen Region (NEAR) experiment was launched to search for rocky exoplanets in the habitable zone around Alpha Centauri A and B with VISIR 28 . To enable HCI with VISIR, it was upgraded with a new vortex coronagraph consisting of an AGPM and was installed at the VLT unit telescope 4 to use the adaptive optics facility there.…”

Section: The Vlt/visir Instrumentmentioning

confidence: 99%

Modeling the vortex center glow in the ELT/METIS vortex coronagraph

Shinde¹,

Delacroix²,

Xivry³

et al. 2022

Modeling, Systems Engineering, and Project Management for Astronomy X

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The Mid-infrared ELT Imager and Spectrograph (METIS) is among the first three scientific instruments commissioned at the ELT. It will implement vortex coronagraphy to achieve high-contrast imaging (HCI) at small angular separations from bright, nearby stars. An important unresolved problem with vortex coronagraphy is the vortex center glow (VCG) effect, where the thermal emission from the warm environment around the entrance pupil is partially diffracted into the image of the pupil by the vortex phase mask (VPM), which shows up as a diffuse bright spot in the center of the image. This effect has proven to be a significant nuisance in previous mid-infrared observations. Here, we use physical optics propagation to model the VCG for the first time and evaluate its strength with respect to the background flux in standard noncoronagraphic imaging in the context of ELT/METIS. Through our end-to-end simulations we find that the VCG peaks at about 70% of the standard background flux at an angular separation of 1 λ/D from the star and reduces to about 20% at 5 λ/D from the star. We apply the same method to model the VCG for the VLT/VISIR configuration, and show our model to be in agreement with the actual VCG measured in VISIR data, where the peak of the VCG is about twice as bright as the thermal background. In case the VCG turns out to be larger than anticipated in METIS, we propose two methods to mitigate it: (i) adding pupil stops in the pupil plane upstream to the VPM to block all of the thermal emission, and (ii) adding undersized Lyot stops in the image plane to block part of the diffracted light.

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“…77,132 Apodizers in the plane of the Lyot stop may also be designed to help suppress on-axis starlight 132 as well as diffraction from an off-axis stellar companion. 133…”

Section: Lyot Stopsmentioning

confidence: 99%

Review of high-contrast imaging systems for current and future ground- and space-based telescopes I: coronagraph design methods and optical performance metrics

Ruane¹,

Riggs

Mazoyer³

et al. 2018

Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave

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The Optimal Optical Coronagraph (OOC) Workshop at the Lorentz Center in September 2017 in Leiden, the Netherlands gathered a diverse group of 25 researchers working on exoplanet instrumentation to stimulate the emergence and sharing of new ideas. In this first installment of a series of three papers summarizing the outcomes of the OOC workshop, we present an overview of design methods and optical performance metrics developed for coronagraph instruments. The design and optimization of coronagraphs for future telescopes has progressed rapidly over the past several years in the context of space mission studies for Exo-C, WFIRST, HabEx, and LUVOIR as well as ground-based telescopes. Design tools have been developed at several institutions to optimize a variety of coronagraph mask types. We aim to give a broad overview of the approaches used, examples of their utility, and provide the optimization tools to the community. Though it is clear that the basic function of coronagraphs is to suppress starlight while maintaining light from off-axis sources, our community lacks a general set of standard performance metrics that apply to both detecting and characterizing exoplanets. The attendees of the OOC workshop agreed that it would benefit our community to clearly define quantities for comparing the performance of coronagraph designs and systems. Therefore, we also present a set of metrics that may be applied to theoretical designs, testbeds, and deployed instruments. We show how these quantities may be used to easily relate the basic properties of the optical instrument to the detection significance of the given point source in the presence of realistic noise.

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NEAR: New Earths in the Alpha Cen Region (bringing VISIR as a "visiting instrument" to ESO-VLT-UT4)

Cited by 5 publications

References 19 publications

Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment

Design, pointing control, and on-sky performance of the mid-infrared vortex coronagraph for the VLT/NEAR experiment

Modeling the vortex center glow in the ELT/METIS vortex coronagraph

Review of high-contrast imaging systems for current and future ground- and space-based telescopes I: coronagraph design methods and optical performance metrics

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