The Fast-Steering Secondary Mirror (FSM) of Giant Magellan Telescope (GMT) consists of seven 1.1m diameter segments with effective diameter of 3.2m. Each segment is held by three axial supports and a central lateral support with a vacuum system for pressure compensation. Both on-axis and off-axis mirror segments are optimized under various design considerations. Each FSM segment contains a tip-tilt capability for guiding to attenuate telescope wind shake and mount control jitter. The design of the FSM mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The design of the mirror cell assembly will be performed including sub-assembly parts consisting of axial supports, lateral support, breakaway mechanism, seismic restraints, and pressure seal. . In this paper, the mechanical results and optical performance results are addressed for the optimized FSM mirror and mirror cell assembly, the design considerations are addressed, and performance prediction results are discussed in detail with respect to the specifications

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Myung Cho, Youra Jun, Christoph Dribusch, Jieun Ryu, Gary Poczulp, Ming Liang, Sungho Lee, Jeong-Yeol Han, Ueejeong Jeong, Sanghyuk Kim, Bongkon Moon, Chang-Hee Kim, Yunjong Kim, Chan Park, Byeong-Gon Park, Il-Kwon Moon, Chan-Hee Lee, Wongi Lee, Ho-Sang Kim, Paul Gardner, Robert Bernier, Frank Groark, and Hugo Chiquito, "Design of the fast steering secondary mirror assembly for the Giant Magellan Telescope," Proc. SPIE 10706, Advances in Optical and Mechanical Technologies for Telescopes and Instrumentation III, 1070607 (Presented at SPIE Astronomical Telescopes + Instrumentation: June 10, 2018; Published: 10 July 2018); https://doi.org/10.1117/12.2313375.