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Proceedings Paper

The opto-mechanical design of the GMT-consortium large earth finder (G-CLEF)
Author(s): Mark Mueller; Daniel Baldwin; Jacob Bean; Henry Bergner; Bruce Bigelow; Moo-Young Chun; Jeffrey Crane; Jeff Foster; Gabor Fűrész; Thomas Gauron; Dani Guzman; Edward Hertz; Andrés Jordán; Kang-Min Kim; Kenneth McCracken; Timothy Norton; Mark Ordway; Chan Park; Sang Park; William A. Podgorski; Andrew Szentgyorgyi; Alan Uomoto; In-Soo Yuk
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Paper Abstract

The GMT-Consortium Large Earth Finder (G-CLEF) is a fiber fed, optical echelle spectrograph that has been selected as a first light instrument for the Giant Magellan Telescope (GMT) currently under construction at the Las Campanas Observatory in Chile’s Atacama desert region. We designed G-CLEF as a general-purpose echelle spectrograph with precision radial velocity (PRV) capability used for exoplanet detection. The radial velocity (RV) precision goal of GCLEF is 10 cm/sec, necessary for detection of Earth-sized planets orbiting stars like our Sun in the habitable zone. This goal imposes challenging stability requirements on the optical mounts and the overall spectrograph support structures. Stability in instruments of this type is typically affected by changes in temperature, orientation, and air pressure as well as vibrations caused by telescope tracking. For these reasons, we have chosen to enclose G-CLEF’s spectrograph in a thermally insulated, vibration isolated vacuum chamber and place it at a gravity invariant location on GMT’s azimuth platform. Additional design constraints posed by the GMT telescope include: a limited space envelope, a thermal emission ceiling, and a maximum weight allowance. Other factors, such as manufacturability, serviceability, available technology and budget are also significant design drivers. All of the previously listed considerations must be managed while ensuring that performance requirements are achieved. In this paper, we discuss the design of G-CLEF’s optical mounts and support structures including technical choices made to minimize the system’s sensitivity to thermal gradients. A more general treatment of the properties of G-CLEF can be found elsewhere in these proceedings1. We discuss the design of the vacuum chamber which houses the irregularly shaped optical bench and optics while conforming to a challenging space envelope on GMT’s azimuth platform. We also discuss the design of G-CLEF’s insulated enclosure and thermal control systems which maintain the spectrograph at milli-Kelvin level stability while simultaneously limiting the maximum thermal emission into the telescope dome environment. Finally, we discuss G-CLEF’s front-end assembly and fiber-feed system as well as other interface challenges presented by the telescope, enclosure and neighboring instrumentation.

Paper Details

Date Published: 6 August 2014
PDF: 15 pages
Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91479A (6 August 2014); doi: 10.1117/12.2056440
Show Author Affiliations
Mark Mueller, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Daniel Baldwin, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Jacob Bean, The Univ. of Chicago (United States)
Henry Bergner, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Bruce Bigelow, GMTO Corp. (United States)
Moo-Young Chun, Korea Astronomy and Space Science Institute (Korea, Republic of)
Jeffrey Crane, Carnegie Observatories (United States)
Jeff Foster, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Gabor Fűrész, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Thomas Gauron, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Dani Guzman, Pontificia Univ. Católica de Chile (Chile)
Edward Hertz, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Andrés Jordán, Pontificia Univ. Católica de Chile (Chile)
Kang-Min Kim, Korea Astronomy and Space Science Institute (Korea, Republic of)
Kenneth McCracken, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Timothy Norton, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Mark Ordway, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Chan Park, Korea Astronomy and Space Science Institute (Korea, Republic of)
Sang Park, Harvard-Smithsonian Ctr. for Astrophysics (United States)
William A. Podgorski, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Andrew Szentgyorgyi, Harvard-Smithsonian Ctr. for Astrophysics (United States)
Alan Uomoto, Carnegie Observatories (United States)
In-Soo Yuk, Korea Astronomy and Space Science Institute (Korea, Republic of)


Published in SPIE Proceedings Vol. 9147:
Ground-based and Airborne Instrumentation for Astronomy V
Suzanne K. Ramsay; Ian S. McLean; Hideki Takami, Editor(s)

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