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Laser-only Adaptive Optics Achieves Significant Image Quality Gains Compared to Seeing-limited Observations over the Entire Sky

Howard, Ward S. and Law, Nicholas M. and Ziegler, Carl A. and Baranec, Christoph and Riddle, Reed (2018) Laser-only Adaptive Optics Achieves Significant Image Quality Gains Compared to Seeing-limited Observations over the Entire Sky. Astronomical Journal, 155 (2). Art. No. 59. ISSN 1538-3881. http://resolver.caltech.edu/CaltechAUTHORS:20180112-132754777

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Abstract

Adaptive optics laser guide-star systems perform atmospheric correction of stellar wavefronts in two parts: stellar tip-tilt and high-spatial-order laser correction. The requirement of a sufficiently bright guide star in the field-of-view to correct tip-tilt limits sky coverage. In this paper, we show an improvement to effective seeing without the need for nearby bright stars, enabling full sky coverage by performing only laser-assisted wavefront correction. We used Robo-AO, the first robotic AO system, to comprehensively demonstrate this laser-only correction. We analyze observations from four years of efficient robotic operation covering 15000 targets and 42000 observations, each realizing different seeing conditions. Using an autoguider (or a post-processing software equivalent) and the laser to improve effective seeing independent of the brightness of a target, Robo-AO observations show a 39% ± 19% improvement to effective FWHM, without any tip-tilt correction. We also demonstrate that 50% encircled energy performance without tip-tilt correction remains comparable to diffraction-limited, standard Robo-AO performance. Faint-target science programs primarily limited by 50% encircled energy (e.g., those employing integral field spectrographs placed behind the AO system) may see significant benefits to sky coverage from employing laser-only AO.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-3881/aa9abaDOIArticle
http://iopscience.iop.org/article/10.3847/1538-3881/aa9abaPublisherArticle
https://arxiv.org/abs/1711.04375arXivDiscussion Paper
ORCID:
AuthorORCID
Howard, Ward S.0000-0002-0583-0949
Law, Nicholas M.0000-0001-9380-6457
Ziegler, Carl A.0000-0002-0619-7639
Baranec, Christoph0000-0002-1917-9157
Riddle, Reed0000-0002-0387-370X
Additional Information:© 2018. The American Astronomical Society. Received 2017 August 9; revised 2017 November 8; accepted 2017 November 12; published 2018 January 15. We thank Rebecca Jensen-Clem for helpful discussions on the project. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013), and the NumPy, SciPy, and Matplotlib Python modules (Jones et al. 2001; Oliphant 2007; Millman et al. 2011; Hunter 2007; van der Walt et al. 2011). This work was partially supported by NASA XRP Grant NNX15AC91G. The Robo-AO system is supported by collaborating partner institutions, the California Institute of Technology and the Inter-University Centre for Astronomy and Astrophysics, and by the National Science Foundation under grant Nos. AST-0906060, AST-0960343, and AST-1207891, by the Mount Cuba Astronomical Foundation, and by a gift from Samuel Oschin. C.B. acknowledges support from the Alfred P. Sloan Foundation. We are grateful to the Palomar Observatory staff for their support of Robo-AO on the 1.5 m telescope, particularly S Kunsman, M Doyle, J Henning, R Walters, G Van Idsinga, B Baker, K Dunscombe, and D Roderick. This research was carried out on the traditional lands of the Occaneechi, Haw, and Eno Native American tribes in Orange County, NC, and on the traditional lands of the Luiseño, or Payómkawichum, at Palomar Observatory, CA. Finally, we would like to thank the anonymous referee who graciously gave their time to make this the best version of this work.
Group:Infrared Processing and Analysis Center (IPAC)
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
NASANNX15AC91G
CaltechUNSPECIFIED
Inter-University Centre for Astronomy and AstrophysicsUNSPECIFIED
NSFAST-0906060
NSFAST-0960343
NSFAST-1207891
Mt. Cuba Astronomical FoundationUNSPECIFIED
Samuel OschinUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:atmospheric effects; instrumentation: adaptive optics; instrumentation: high angular resolution; techniques: high angular resolution; techniques: image processing
Record Number:CaltechAUTHORS:20180112-132754777
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20180112-132754777
Official Citation:Ward S. Howard et al 2018 AJ 155 59
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:84306
Collection:CaltechAUTHORS
Deposited By: George Porter
Deposited On:16 Jan 2018 16:33
Last Modified:16 Jan 2018 16:33

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