The Giant Magellan Telescope Mount: final design completion and start of fabrication

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 GMT Mount is the structural, mechanical, hydraulic, and electronic system that provides the overall framework for mounting and alignment of optics and science instruments, supports payloads and utilities, and provides the three main axes of motion consisting of azimuth, elevation, and Gregorian Instrument Rotator (GIR) rotations. The GMTO Corp. completed in 2019 a multi-stage acquisition process that led to the selection of OHB Digital Connect (ODC, formerly MT-Mechatronics or MTM) and Ingersoll Machine Tools (IMT) to supply the final design, fabrication, and installation of the GMT Mount. The Final Design Review of the Mount subsystem was successfully passed in June 2023. The fabrication of the Mount is split into two phases comprising first the rotating azimuth base structure and secondly the elevation and optical support moving structures. The Mount will be assembled and tested at the IMT factory to the largest feasible assembly state where all three motion axes and critical systems will be functionally tested. The Mount will then be disassembled, shipped, and reassembled and tested at the GMT’s Las Campanas site in Chile. The first phase of fabrication has begun starting with the Azimuth Track Segments. Full factory functional testing of the Hydrostatic Bearing System (HBS), the electric Direct-Drive System, the Earthquake Damping System (EDS), and the Azimuth cable wrap will be completed during the first phase of fabrication. This paper will describe the final design configuration of the Mount, major subassemblies, fabrication and test phasing, fabrication highlights to-date, and an overview of the prototype testing that validated the final design parameters.