Hybrid Lyot coronagraph for WFIRST-AFTA: coronagraph design and performance metrics

Trauger, John T.; Moody, Dwight; Krist, John; Gordon, Brian

doi:10.1117/1.jatis.2.1.011013

Cited by 84 publications

(63 citation statements)

References 22 publications

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“…We investigate the observability of a sulfur haze and its impact on the detectability of various atmospheric chemical species using an updated version of the noise model described in Robinson et al (2016), which includes specific coronagraph designs that have been proposed for WFIRST, such as the Shaped Pupil Coronagraph (SPC; capable of both broadband imaging and spectroscopy; Kasdin et al 2004) and the Hybrid Lyot Coronagraph (HLC; imaging mode only; Trauger et al 2016). The baseline telescope and instrument parameter values corresponding to these coronagraphs are different from that of Robinson et al (2016;see their Table3).…”

Section: Wfirst Noise Modelmentioning

confidence: 99%

Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra

Gao

Marley

Zahnle

et al. 2017

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Recent work has shown that sulfur hazes may arise in the atmospheres of some giant exoplanets, due to the photolysis of H 2 S. We investigate the impact such a haze would have on an exoplanet's geometric albedo spectrum and how it may affect the direct imaging results of the Wide Field Infrared Survey Telescope (WFIRST), a planned NASA space telescope. For temperate (250 K<T eq <700 K) Jupiter-mass planets, photochemical destruction of H 2 S results in the production of ∼1 ppmv of S 8 between 100 and 0.1 mbar, which, if cool enough, will condense to form a haze. Nominal haze masses are found to drastically alter a planet's geometric albedo spectrum: whereas a clear atmosphere is dark at wavelengths between 0.5 and 1 μm, due to molecular absorption, the addition of a sulfur haze boosts the albedo there to ∼0.7, due to scattering. Strong absorption by the haze shortward of 0.4 μm results in albedos <0.1, in contrast to the high albedos produced by Rayleigh scattering in a clear atmosphere. As a result, the color of the planet shifts from blue to orange. The existence of a sulfur haze masks the molecular signatures of methane and water, thereby complicating the characterization of atmospheric composition. Detection of such a haze by WFIRST is possible, though discriminating between a sulfur haze and any other highly reflective, high-altitude scatterer will require observations shortward of 0.4 μm, which is currently beyond WFIRST's design.

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Section: Wfirst Noise Modelmentioning

confidence: 99%

Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra

Gao

Marley

Zahnle

et al. 2017

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“…Furthermore, the occulting spot in the Lyot coronagraph can be replaced by more complicated focal plane masks that involve a combination of phase shifting and apodization, such as the hybrid Lyot coronagraph (Kuchner & Traub 2002;Moody & Trauger 2007;Moody et al 2008;Trauger et al 2012;Trauger et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Polynomial Apodizers for Centrally Obscured Vortex Coronagraphs

Fogarty

Pueyo

Mazoyer

et al. 2017

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Several coronagraph designs have been proposed over the last two decades to directly image exoplanets. Among these designs, vector vortex coronagraphs provide theoretically perfect starlight cancellation along with small inner working angles when deployed on telescopes with unobstructed pupils. However, current and planned space missions and ground-based extremely large telescopes present complex pupil geometries, including large central obscurations caused by secondary mirrors, that prevent vortex coronagraphs from rejecting on-axis sources entirely. Recent solutions combining the vortex phase mask with a ring-apodized pupil have been proposed to circumvent this issue, but provide a limited throughput for vortex charges > 2. We present pupil plane apodizations for charge 2, 4, and 6 vector vortex coronagraphs that compensate for pupil geometries with circularly symmetric central obstructions caused by on-axis secondary mirrors. These apodizations are derived analytically and allow vortex coronagraphs to retain theoretically perfect nulling in the presence of obstructed pupils. For a charge 4 vortex, we design polynomial apodization functions assuming a greyscale apodizing filter that represent a substantial gain in throughput over the ring-apodized vortex coronagraph design, while for a charge 6 vortex, we design polynomial apodized vortex coronagraphs that have 70% total energy throughput for the entire range of central obscuration sizes studied. We propose methods for optimizing apodizations produced with either greyscale apodizing filters or shaped mirrors. We conclude by demonstrating how this design may be combined with apodizations numerically optimized for struts and primary mirror segment gaps to design terrestrial exoplanet imagers for complex pupils.

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“…The two concepts developed by the LUVOIR concept design team, LUVOIR-A with an on-axis 15 m primary mirror, and LUVOIR-B with an off-axis 8 m primary mirror, both segmented, have their exoplanet science yield driven by their coronagraph performan-ce (Stark et al 2019), which is greatly affected by the discontinuities in the pupil. Nonetheless, the last decade has seen an array of clever solutions to this problem (Mawet et al 2011(Mawet et al , 2013Pueyo & Norman 2013;Guyon et al 2014;Carlotti et al 2014;Mazoyer et al 2015;Ruane et al 2015aRuane et al , 2015bRuane et al , 2016Balasubramanian et al 2016;Trauger et al 2016;Zimmerman et al 2016), and the Exoplanet Exploration Program Office at NASA is currently funding several groups to address this technology challenge through the Segmented Coronagraph Design and Analysis study (Crill & Siegler 2017). For instance, a deformable mirror (DM) assisted vortex coronagraph (DMVC) is baselined for the LUVOIR-B coronagraph, in which the combined work of two DMs suppresses the diffraction from the segment gaps.…”

Section: Introductionmentioning

confidence: 99%

High-contrast Demonstration of an Apodized Vortex Coronagraph

Llop-Sayson

Ruane

Mawet

et al. 2020

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High-contrast imaging is the primary path to the direct detection and characterization of Earth-like planets around solar-type stars; a cleverly designed internal coronagraph suppresses the light from the star, revealing the elusive circumstellar companions. However, future large-aperture telescopes (>4 m in diameter) will likely have segmented primary mirrors, which cause additional diffraction of unwanted stellar light. Here we present the first high-contrast laboratory demonstration of an apodized vortex coronagraph, in which an apodizer is placed upstream of a vortex focal plane mask to improve its performance with a segmented aperture. The gray-scale apodization is numerically optimized to yield a better sensitivity to faint companions assuming an aperture shape similar to the LUVOIR-B concept. Using wavefront sensing and control over a one-sided dark hole, we achieve a raw contrast of 2×10 −8 in monochromatic light at 775nm, and a raw contrast of 4×10 −8 in a 10% bandwidth. These results open the path to a new family of coronagraph designs, optimally suited for next-generation segmented space telescopes.Unified Astronomy Thesaurus concepts: Exoplanets (498); Direct imaging (387); Space telescopes (1547)

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Hybrid Lyot coronagraph for WFIRST-AFTA: coronagraph design and performance metrics

Cited by 84 publications

References 22 publications

Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra

Sulfur Hazes in Giant Exoplanet Atmospheres: Impacts on Reflected Light Spectra

Polynomial Apodizers for Centrally Obscured Vortex Coronagraphs

High-contrast Demonstration of an Apodized Vortex Coronagraph

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