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Characterizing vibrations at the Subaru Telescope for the Subaru coronagraphic extreme adaptive optics instrument

Lozi, Julien and Guyon, Olivier and Jovanovic, Nemanja and Takato, Naruhisa and Singh, Garima and Norris, Barnaby and Okita, Hirofumi and Bando, Takamasa and Martinache, Frantz (2018) Characterizing vibrations at the Subaru Telescope for the Subaru coronagraphic extreme adaptive optics instrument. Journal of Astronomical Telescopes, Instruments, and Systems, 4 (4). Art. No. 049001. ISSN 2329-4124. https://resolver.caltech.edu/CaltechAUTHORS:20181204-070800444

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Abstract

Vibrations are a key source of image degradation in ground-based instrumentation, especially for high-contrast imaging instruments. Vibrations reduce the quality of the correction provided by the adaptive optics system, blurring the science image, and reducing the sensitivity of most science modules. We studied vibrations using the Subaru coronagraphic extreme adaptive optics instrument at the Subaru Telescope as it is the most vibration-sensitive system installed on the telescope. We observed vibrations for all targets, usually at low frequency, below 10 Hz. Using accelerometers on the telescope, we confirmed that these vibrations were introduced by the telescope itself, and not the instrument. It was determined that they were related to the pitch of the encoders of the telescope drive system, both in altitude and azimuth, with frequencies evolving proportionally to the rotational speed of the telescope. Another strong vibration was found in the altitude axis of the telescope, around the time of transit of the target, when the altitude rotational speed is below 0.12  arc sec  /  s. These vibrations are amplified by the 10-Hz control loop of the telescope, especially in a region between 4 and 6 Hz. We demonstrate an accurate characterization of the frequencies of the telescope vibrations using only the coordinates—right ascension and declination—of the target and provide a means by which we can predict them for any telescope pointing. This will be a powerful tool that can be used by more advanced wavefront control algorithms, especially predictive control that uses information about the disturbance to calculate the best correction.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1117/1.JATIS.4.4.049001DOIArticle
ORCID:
AuthorORCID
Lozi, Julien0000-0002-3047-1845
Guyon, Olivier0000-0002-1097-9908
Martinache, Frantz0000-0003-1180-4138
Additional Information:© 2018 The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. Paper 18021 received Apr. 6, 2018; accepted for publication Aug. 16, 2018; published online Sep. 12, 2018. The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research Nos. 23340051, 26220704, and 23103002), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation and the directors contingency fund at Subaru Telescope. G. Singh would also like to acknowledge her appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory, California Institute of Technology, administered by Universities Space Research Association under contract with NASA. 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.
Funders:
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)23340051
Japan Society for the Promotion of Science (JSPS)26220704
Japan Society for the Promotion of Science (JSPS)23103002
National Institutes of Natural Sciences of JapanUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Subaru TelescopeUNSPECIFIED
NASA Postdoctoral ProgramUNSPECIFIED
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:extreme adaptive optics; vibrations; control; accelerometers; encoders
Issue or Number:4
Record Number:CaltechAUTHORS:20181204-070800444
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20181204-070800444
Official Citation:Julien Lozi, Olivier Guyon, Nemanja Jovanovic, Naruhisa Takato, Garima Singh, Barnaby Norris, Hirofumi Okita, Takamasa Bando, Frantz Martinache, "Characterizing vibrations at the Subaru Telescope for the Subaru coronagraphic extreme adaptive optics instrument," J. Astron. Telesc. Instrum. Syst. 4(4) 049001 (12 September 2018)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:91413
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:04 Dec 2018 19:44
Last Modified:09 Mar 2020 13:19

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