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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 is part of the United States ELT Program (US-ELTP) which received the top ranking in the National Academies' ASTRO2020 Decadal Survey. The GMT Project continues to proceed with design, fabrication, and site construction. Our schedule responds to evolving programmatic factors and we are engaged in a process to obtain US federal support for part of the construction and operations scope. Of the seven 8.4m diameter mirror segments comprising the primary mirror, three have been completed with two in storage and with the third undergoing optical testing to demonstrate figure control with the GMT test mirror cell. The remaining four primary mirror segments have been cast and are in various stages of fabrication. The final design of the telescope mount is complete and fabrication is underway. The first off-axis adaptive secondary mirror system is being tested. Results to date from two adaptive optics and phasing testbeds have demonstrated the GMT phasing strategy and continue to be used for risk reduction and component qualification of our wavefront sensing and control strategy. The first generation science instruments are in various stages of development, from design to early fabrication. Hard rock excavation of the foundations for the enclosure and telescope pier is complete, as is the final design of the enclosure. Residence buildings and other facilities and infrastructure needed to support construction at the Las Campanas site in Chile are complete and in operation.
Burgett et al. (Wed,) studied this question.