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Enhancing Direct Exoplanet Spectroscopy with Apodizing and Beam Shaping Optics

Calvin, Benjamin and Jovanovic, Nemanja and Ruane, Garreth and Pezzato, Jacklyn and Colborn, Jennah and Echeverri, Daniel and Schofield, Tobias and Porter, Michael and Wallace, J. Kent and Delorme, Jacques-Robert and Mawet, Dimitri (2021) Enhancing Direct Exoplanet Spectroscopy with Apodizing and Beam Shaping Optics. Publications of the Astronomical Society of the Pacific, 133 (1020). Art. No. 024503. ISSN 0004-6280. doi:10.1088/1538-3873/abdace.

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Direct exoplanet spectroscopy aims to measure the spectrum of an exoplanet while simultaneously minimizing the light collected from its host star. Isolating the planet light from the starlight improves the signal-to-noise ratio (S/N) per spectral channel when noise due to the star dominates, which may enable new studies of the exoplanet atmosphere with unprecedented detail at high spectral resolution (>30,000). However, the optimal instrument design depends on the flux level from the planet and star compared to the noise due to other sources, such as detector noise and thermal background. Here we present the design, fabrication, and laboratory demonstration of specially-designed optics to improve the S/N in two potential regimes in direct exoplanet spectroscopy with adaptive optics instruments. The first is a pair of beam-shaping lenses that increase the planet signal by improving the coupling efficiency into a single-mode fiber at the known position of the planet. The second is a grayscale apodizer that reduces the diffracted starlight for planets at small angular separations from their host star. The former especially increases S/N when dominated by detector noise or thermal background, while the latter helps reduce stellar noise. We show good agreement between the theoretical and experimental point spread functions in each case and predict the exposure time reduction (~33%) that each set of optics provides in simulated observations of 51 Eridani b using the Keck Planet Imager and Characterizer instrument at W. M. Keck Observatory.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Calvin, Benjamin0000-0003-4737-5486
Jovanovic, Nemanja0000-0001-5213-6207
Ruane, Garreth0000-0003-4769-1665
Echeverri, Daniel0000-0002-1583-2040
Porter, Michael0000-0003-3168-5586
Wallace, J. Kent0000-0001-5299-6899
Delorme, Jacques-Robert0000-0001-8953-1008
Mawet, Dimitri0000-0002-8895-4735
Additional Information:© 2021. The Astronomical Society of the Pacific. Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 November 4; accepted 2021 January 12; published 2021 February 10. This work was supported by the Heising-Simons Foundation through grants #2019-1312, #2017-318, and #2015-129. Support was provided by the Simons Foundation grant "Planetary Context of Habitability and Exobiology". G. Ruane was supported by an NSF Astronomy and Astrophysics Postdoctoral Fellowship under award AST-1602444. W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA). The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Part of this work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA.
Group:Astronomy Department
Funding AgencyGrant Number
Heising-Simons Foundation2019-1312
Heising-Simons Foundation2017-318
Heising-Simons Foundation2015-129
NSF Astronomy and Astrophysics FellowshipAST-1602444
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Astronomical instrumentation – High resolution spectroscopy – Exoplanets
Issue or Number:1020
Record Number:CaltechAUTHORS:20210212-140005713
Persistent URL:
Official Citation:Benjamin Calvin et al 2021 PASP 133 024503
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108050
Deposited By: Tony Diaz
Deposited On:12 Feb 2021 23:20
Last Modified:16 Nov 2021 19:08

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