The purpose, plan, and progress of the Giant Magellan Telescope primary mirror off-axis segment test cell

Barbara M. Fischer; Trupti Ranka; Francisco Aguayo; Dave Ashby; Erich Bugueno; Austin Everman; John Ford; Zaven Kechichian; Kurt Kenagy; Tomas Krasuski; Gary Muller; Wylie Rosenthal; David Schwartz; Jose Soto; Hector Swett; Divya Thanasekaran; Abhijit Wadhavkar

doi:10.1117/12.2561694

13 December 2020 The purpose, plan, and progress of the Giant Magellan Telescope primary mirror off-axis segment test cell

Barbara M. Fischer, Trupti Ranka, Francisco Aguayo, Dave Ashby, Erich Bugueno, Austin Everman, John Ford, Zaven Kechichian, Kurt Kenagy, Tomas Krasuski, Gary Muller, Wylie Rosenthal, David Schwartz, Jose Soto, Hector Swett, Divya Thanasekaran, Abhijit Wadhavkar

Author Affiliations +

Proceedings Volume 11445, Ground-based and Airborne Telescopes VIII; 114451H (2020) https://doi.org/10.1117/12.2561694
Event: SPIE Astronomical Telescopes + Instrumentation, 2020, Online Only

Abstract

Large aperture telescopes require active control to maintain focus, collimation, and correct figure errors in the Primary Mirror (M1) due to gravity and thermal deformations. The Giant Magellan Telescope (GMT) M1 active optics subsystem consists of the hardware and software that controls the shape, position, and thermal state of each mirror segment. Pneumatic force actuators support the weight and control the surface figure while linear position actuators control the six solid-body degrees of freedom of each mirror segment. A forced convection system comprised of fan-heat exchanger units control the mean temperature and thermal gradient of each mirror segment. The M1 Subsystem design leverages existing technology and employs innovations driven by more demanding requirements compared to heritage systems. These differences led to the identification of three key GMT project risks: determining if the vibration environment induced by the fan-heat exchanger units and the error in the applied influence functions required to shape the mirror are within image quality budget allocations. The third risk is incorporating damping to the force actuators to meet the seismic requirements. GMT is currently mitigating these risks by integrating a fully functional off-axis M1 Test Cell at the University of Arizona’s Richard F. Caris Mirror Lab. This paper summarizes our requirements and design presented at the M1 Subsystem Preliminary Design Review in June 2019, describes our risk burn-down strategy for the M1 Subsystem, and presents our integration and test progress of the M1 Test Cell.

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Barbara M. Fischer, Trupti Ranka, Francisco Aguayo, Dave Ashby, Erich Bugueno, Austin Everman, John Ford, Zaven Kechichian, Kurt Kenagy, Tomas Krasuski, Gary Muller, Wylie Rosenthal, David Schwartz, Jose Soto, Hector Swett, Divya Thanasekaran, and Abhijit Wadhavkar "The purpose, plan, and progress of the Giant Magellan Telescope primary mirror off-axis segment test cell", Proc. SPIE 11445, Ground-based and Airborne Telescopes VIII, 114451H (13 December 2020); https://doi.org/10.1117/12.2561694

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KEYWORDS

Mirrors

Telescopes

Off axis mirrors

Actuators

Active optics

Collimation

Control systems

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