Design and development of a fast-steering secondary mirror for the Giant Magellan Telescope

Cho, Myung‐Haing; Corredor, Andrew; Dribusch, Christoph; Park, Kwijong; Kim, Youngsoo; Moon, Il-Kweon

doi:10.1117/12.892411

Cited by 9 publications

(6 citation statements)

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“…For the previous baseline segment depth of 140 mm [1] , the optical performance results indicated that the shading effect may cause an image degradation. In order to overcome the effect, we have looked at the following four options: (1) extended flange of the front sheet, (2) tapered back, (3) chamfered edge, and (4) combined with all 3 options.…”

Section: Fsm Mirror Configurationmentioning

confidence: 95%

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Development of the fast steering secondary mirror for the Giant Magellan Telescope

Cho

Corredor

Dribusch

et al. 2013

Optomechanical Engineering 2013

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The Giant Magellan Telescope (GMT) Fast Steering Secondary Mirror (FSM) is one of the GMT two Gregorian secondary mirrors. The FSM is 3.2 m in diameter and built as seven 1.06 m diameter circular segments. The conceiving philosophy used on the design of the FSM segment mirror is to minimize development and fabrication risks ensuring a set of secondary mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode, thereby mitigating risks associated with fabrication of the Adaptive Secondary Mirrors (ASM). This approach uses legacy design features from the Magellan Telescope secondary mirrors to reduce such risks. The final design of the substrate and support system configuration was optimized using finite element analyses and optical performance analyses. The optical performance predictions of the FSM are based on a substrate with a diameter of 1.058m (on-axis), 1.048m (off-axis), a depth of 120mm, and a face plate thickness of 20mm leading to a mass of approximately 90kg. The optical surface deformations, image qualities, and structure functions for the axial and lateral gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy in the focal plane. The mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of 20 Hz tip-tilt motion.

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Section: Fsm Mirror Configurationmentioning

confidence: 95%

“…of SPIE Vol. 8836 88360V-9Downloaded From: http://proceedings.spiedigitallibrary.org/ on 08/04/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx1) 43.64Hz…”

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confidence: 99%

Development of the fast steering secondary mirror for the Giant Magellan Telescope

Cho

Corredor

Dribusch

et al. 2013

Optomechanical Engineering 2013

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“…The requirement of the preload of the spring is one to three times of gravity force of mirror [7] . The mass of the mirror is nearly 100 kg and there are three axial support in the FSM [3], [4], [8] . The preload range for single BAS is from 333N to 999N.…”

Section: Breakaway Systemmentioning

confidence: 99%

“…It will also be used for seeing-limited observations at times when the ASM needs to be removed for maintenance or repair [2] . FSM segments are capable of producing rapid, small tip-tilt motions to compensate for wind-induced vibration and tracking jitter by adapting axial supports [3]- [5] . This tip-tilt capability thus enhances the performance of the telescope in the seeing limited observation mode.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of breakaway system for the fast-steering secondary mirror prototype of GMT

Lee

Kim

Han

et al. 2018

Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III

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The Fast-steering Secondary Mirror (FSM) of Giant Magellan Telescope (GMT) consists of seven 1.1 m diameter circular segments with an effective diameter of 3.2 m, which are conjugated 1:1 to the seven 8.4 m segments of the primary. Each FSM segment contains a tip-tilt capability for fast guiding to attenuate telescope wind shake and mount control jitter by adapting axial support actuators. Breakaway System (BAS) is installed for protecting FSM from seismic overload or other unknown shocks in the axial support. When an earthquake or other unknown shocks come in, the springs in the BAS should limit the force along the axial support axis not to damage the mirror. We tested a single BAS in the lab by changing the input force to the BAS in a resolution of 10 N and measuring the displacement of the system. In this paper, we present experimental results from changing the input force gradually. We will discuss the detailed characteristics of the BAS in this report.

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“…The FSM and ASM segments attach to the M2 Segment Positioners at a kinematic interface allowing the individual FSM and ASM Segments to be mounted in a repeatable manner. The FSM is composed of seven rigid segments each of which is mounted in an individual cell with tip/tilt actuators that provide pointing corrections at frequencies above the control bandwidth of the Telescope Mount [2] [3] . The main disturbance the FSM mitigates is image motion due to wind disturbances.…”

Section: Introductionmentioning

confidence: 99%

Development of the fast steering secondary mirror assembly of GMT

et al. 2016

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The Giant Magellan Telescope (GMT) will be featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM has an effective diameter of 3.2 m and built as seven 1.1 m diameter circular segments, which are conjugated 1:1 to the seven 8.4m segments of the primary. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter. This tip-tilt capability thus enhances performance of the telescope in the seeing limited observation mode. As the first stage of the FSM development, Phase 0 study was conducted to develop a program plan detailing the design and manufacturing process for the seven FSM segments. The FSM development plan has been matured through an internal review by the GMTO-KASI team in May 2016 and fully assessed by an external review in June 2016. In this paper, we present the technical aspects of the FSM development plan.

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Design and development of a fast-steering secondary mirror for the Giant Magellan Telescope

Cited by 9 publications

References 0 publications

Development of the fast steering secondary mirror for the Giant Magellan Telescope

Development of the fast steering secondary mirror for the Giant Magellan Telescope

Experimental study of breakaway system for the fast-steering secondary mirror prototype of GMT

Development of the fast steering secondary mirror assembly of GMT

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