Wind responses of Giant Magellan telescope

Irarrazaval, Benjamin; Buleri, Christine; Johns, Matt

doi:10.1117/12.2057130

Cited by 6 publications

(4 citation statements)

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“…Both secondaries can be used to correct small misalignments of the primary mirror segments, significantly relaxing the precision and bandwidth requirements for the M1 support system. Image blur due to windshake and telescope structure vibrations will also be compensated with the fast tip-tilt motion of the secondary segments 14 . The positioners are designed to have sufficient stroke to compensate for manufacturing and assembly tolerances of the structure, as well as thermal expansion and flexure as the telescope moves in elevation.…”

Section: Telescope Opticsmentioning

confidence: 99%

Overview and status of the Giant Magellan Telescope project

Bernstein

McCarthy

Raybould³

et al. 2014

SPIE Proceedings

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The Giant Magellan Telescope (GMT) is a 25.4-m diameter, optical/infrared telescope that is being built by an international consortium of universities and research institutions as one of the next generation of Extremely Large Telescopes. The primary mirror of GMT consists of seven 8.4 m borosilicate honeycomb mirror segments that are optically conjugate to seven corresponding segments in the Gregorian secondary mirror. Fabrication is complete for one primary mirror segment and is underway for the next two. The final focal ratio of the telescope is f/8.2, so that the focal plane has an image scale of 1.0 arcsec/mm. GMT will be commissioned using a fast-steering secondary mirror assembly comprised of conventional, rigid segments to provide seeing-limited observations. A secondary mirror with fully adaptive segments will be used in standard operation to additionally enable ground-layer and diffraction-limited adaptive optics. In the seeing limited mode, GMT will provide a 10 arcmin field of view without field correction. A 20 arcmin field of view will be obtained using a wide-field corrector and atmospheric dispersion compensator. The project has recently completed a series of sub-system and system-level preliminary design reviews and is currently preparing to move into the construction phase. This paper summarizes the technical development of the GMT sub-systems and the current status of the GMT project.

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Section: Telescope Opticsmentioning

confidence: 99%

Overview and status of the Giant Magellan Telescope project

Bernstein

McCarthy

Raybould³

et al. 2014

SPIE Proceedings

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“…The image quality of an astronomical telescope is affected by the alignment of the secondary mirror and the primary mirror. However, due to the gravity, wind vibration, and temperature, the secondary mirror of an astronomical telescope may be misaligned (Pottebaum & MacMynowski 2006;MacMynowski & Andersen 2010;Angeli et al 2011;Irarrazaval et al 2014;MacMartin & Vogiatzis 2014).…”

Section: Introductionmentioning

confidence: 99%

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Yu,

Wang,

Zhang

et al. 2023

Res. Astron. Astrophys.

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Thermal gradient is an important factor causing degradation in the image quality of telescopes. In order to ensure the accurate alignment of the primary focus unit and the primary mirror, the hexapod platform (as a corrector) is investigated in this paper. First, a ground-based telescope with 2.5 m aperture and 3.5 deg field of view is described. The telescope is under construction, and it is expected to be finished in 2023. Secondly, the hexapod platform with flexure hinges utilized to adjust the primary focus unit is proposed, which is applied as a corrector. Then, the inverse kinematics of the platform is established and an open-loop control system is built based on it. Finally, the cryogenic performance test for the hexapod platform is performed. The experimental results show that the resolution and repeatability of the translation for the hexapod platform can be achieved at the micro-meter level. The resolution and repeatability of the rotation can be achieved at the arc-second level. Therefore, the cryogenic performance of the hexapod platform can meet the optical imaging requirements of the wide-field ground-based telescope. The kinematic analysis and cryogenic performance tests in the paper provide a technical reference for the precise alignment of the primary focus unit and the primary mirror, which can improve the imaging quality of the telescope.

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“…In addition, they clarified that for motion in the azimuthal plane, frontal-direction wind had a greater effect than did sideor tail-direction winds. For the Giant Magellan Telescope (GMT) in Chile, which has a 25 m diameter reflector, Irarrazaval et al [7] proposed a finite element model (FEM) for the telescope structure and a computational fluid dynamics (CFD) model for wind loads. Zhang et al [8] analyzed the impact of the flexible oscillation of a reflective surface resulting from a stochastic wind disturbance on pointing accuracy using structural deformations derived from dynamic equations based on modal analysis.…”

Section: Introductionmentioning

confidence: 99%

Wind- and Operation-Induced Vibration Measurements of the Main Reflector of the Nobeyama 45 m Radio Telescope

Hashimoto

Chiba

Okada

et al. 2020

J. Vib. Eng. Technol.

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Purpose As deformations of the main reflector of a radio telescope directly affect the observations, the evaluation of the deformation is extremely important. Dynamic characteristics of the main reflector of the Nobeyama 45 m radio telescope, Japan, are measured under two conditions: the first is when the pointing observation is in operation, and the second is when the reflector is stationary and is subjected to wind loads when the observation is out of operation.Methods Dynamic characteristics of the main reflector are measured using piezoelectric accelerometers. Results and ConclusionWhen the telescope is in operation, a vibration mode with one nodal line horizontally or vertically on the reflector are induced, depending on whether the reflector is moving in the azimuthal or elevational planes, whereas under windy conditions, vibration modes that have two to four nodal lines are simultaneously induced. The predominant mode is dependent on the direction of wind loads.

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Wind responses of Giant Magellan telescope

Cited by 6 publications

References 0 publications

Overview and status of the Giant Magellan Telescope project

Overview and status of the Giant Magellan Telescope project

Design and Cryogenic Performance of a Hexapod Platform for a Large Ground-based Wide Field Survey Telescope

Wind- and Operation-Induced Vibration Measurements of the Main Reflector of the Nobeyama 45 m Radio Telescope

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