The Giant Magellan Telescope (GMT) is one of three planned ground-based optical/IR Extremely Large Telescopes (ELTs) that will provide a generational leap in ground-based Optical/IR capability. The GMTO Corp. completed in 2019 a multi-stage acquisition process that led to the selection of OHB Digital Connect (formerly MT-Mechatronics or MTM) and Ingersoll Machine Tools (IMT) to supply the final design, fabrication, and installation of the GMT Mount. The ~2000 metric ton GMT Mount comprises the telescope structures, mechanisms, and utilities but does not include the optics and science instruments. This paper provides a general overview of the technical scope of the GMT Mount including the key and driving requirements, systems engineering framework, and planned design development. Due to the GMT site location in Chile, the Mount design must accommodate a challenging seismic environment. Major Mount subsystems are also described including the Hydrostatic Bearing System (HBS), Gregorian Instrument Rotator (GIR), and the Azimuth Track and its interface to the telescope Pier. In addition, a summary is presented of the design path forward to the Final Design Review (FDR) from the point of completing the Preliminary Design Review (PDR) in early 2021, including the current status of critical prototyping efforts. Finally, management processes are outlined that are necessary to execute the Mount design-build contract spanning the next 8-9 years.
The Giant Magellan Telescope will be a 25.4-m visible and infrared telescope at Las Campanas Observatory. The optical design consists of 7 8.4-m primary mirror segments that reflect light to 7 secondary mirror segments in a doubly-segmented direct Gregorian configuration. Each mirror pair must be coaligned and co-boresighted. During operations, the alignment of the optical components will deflect due to variations in temperature, gravity-induced structure flexure of the mount, and, on a scale relevant to phasing, vibrations. The doubly-segmented nature and size of the GMT will create a novel set of challenges for initial assembly, integration, and verification and maintaining high-precision alignment of the optical elements during operations. GMT is developing a Telescope Metrology System that uses 3D laser metrology systems to decrease the complexity of alignment and increase observatory efficiency. This paper discusses the 4 subsystems of TMS as well as their operational modes.
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