Giant Magellan Telescope

The Giant Magellan Telescope joins seven 8.4-meter mirrors into one 25.4-meter telescope, with construction waiting on NSF

The Giant Magellan Telescope (GMT) is a 25 m class optical and infrared telescope: seven 8.4 m primary mirrors and seven 1 m deformable secondary mirrors, for an aperture of 25.4 m and a collecting area of 368 square meters. GMTO says its images will be 10 times sharper than Hubble's. Its science aims include finding habitable exoplanets.

GMTO Corporation, a nonprofit, builds it for a consortium of 15 institutions in the US, Australia, Brazil, Chile, Israel, South Korea and Taiwan (end of 2024); MIT joined in September 2025. Daniel T. Jaffe of UT Austin became president on 13 January 2026, and Taft Armandroff chairs the board. Partners have put in more than $1 billion, mostly from donors. The total to build and operate was about $2.54 billion in a 2024 estimate and over $2 billion in an April 2026 report.

The GMT entered the NSF Major Facilities Final Design Phase in June 2025 and is the one US Extremely Large Telescope Program project at that stage; NSF capped its giant-telescope budget at $1.6 billion in 2024. The FY2026 spending report of January 2026 told NSF to move both the GMT and the Thirty Meter Telescope to final design review. The NSF FY2027 request has no design funds, because GMTO said it can finish final design without new NSF money. The sources disagree on when the final design review falls: June 2026, mid-2027 or late 2027. In April 2026 about 40% of the components were in fabrication and assembly; full construction would start in FY2028 if NSF and Congress fund it, for science in the 2030s.

The site is Las Campanas Observatory in the Atacama Desert of Chile, at 2,516 m, owned by the Carnegie Institution for Science since 1960 and already home to the twin 6.5 m Magellan Telescopes. The telescope was moved slightly before excavation after wind modeling, and its foundations are dug. See the Giant Magellan Telescope listing, the largest optical telescopes and more observatories in Chile.

The Arizona Mirror Lab has cast all seven primary mirrors from Japanese glass, and three are finished

The Richard F. Caris Mirror Lab at the University of Arizona casts and polishes the primaries. Each mirror is 8.417 m across and weighs 17 t. The glass is Ohara E6 low-expansion borosilicate, melted in Japan; the Mirror Lab bought 20 t of it for the seventh segment. A GMTO caption from December 2024 calls the melt site the Chiba Kogaku glass factory, and no source found ties that name to Ohara.

The first mirror was cast in November 2005 and the seventh in October 2023, with an eighth planned as a spare. GMTO's latest count, from its 2024 status paper, is three mirrors complete, two in storage and one in optical testing, and four in fabrication; neither GMTO nor the Mirror Lab has published a 2026 count. In October 2024 a finished mirror went into the prototype test cell of its support system.

Each mirror floats on a pneumatic support of about 160 actuators, about 200 actuators and sensors in all. The instrumentation lab at Texas A&M University assembled and tested 160 prototype actuators from 2019 to 2021; production starts in 2027, and the production supplier is not publicly named. OHB Italia finished the first of seven mirror covers in April 2023.

Component	Supplier	Country	Role	Status	Note
Seven 8.4 m primary mirrors, casting and polishing	Richard F. Caris Mirror Lab, University of Arizona	US	Manufacturer	In production	All seven cast (seventh Oct 2023); three complete and four in fabrication per GMTO SPIE 2024 status paper; no 2026 count published
E6 borosilicate glass for primary mirror casting	Ohara Corporation	Japan	Manufacturer	Delivered	Ohara lists GMT among E6 customers; Mirror Lab team bought 20 t of Ohara E6 for segment seven; melted in Japan
Primary mirror pneumatic support actuators, 160 assembled and tested	Texas A&M University instrumentation lab	US	Manufacturer	Delivered	Prototype set for the test cell, 2019 to 2021; production actuator supplier not public
Mirror covers, first of seven	OHB Italia S.p.A.	Italy	Manufacturer	Delivered	First unit finished April 2023

Seven adaptive secondary mirrors, 2 millimeters thick, carry 4,725 actuators between them

The GMT corrects the atmosphere at its secondary mirror. Each of the seven adaptive secondary mirror (ASM) segments is a thin Zerodur shell about 1 m across and 2 mm thick, pushed by 675 voice coil actuators, 4,725 in all. AdOptica, the Italian partnership of A.D.S. International and Microgate, builds this fourth-generation ASM. SCHOTT supplied the Zerodur blank and Safran Reosc ground and polished the off-axis shell under a July 2021 contract, with about 10 times the asphericity of its earlier shells. KRISS in South Korea co-produced the reference body with the University of Arizona, and A.D.S. built the prototype hexapod positioner. Two off-axis face sheets arrived in May 2025.

Phasing without edge sensors

Seven separate mirrors must be phased to a fraction of a wavelength, and the GMT does it optically rather than with edge sensors. The acquisition, guiding and wavefront sensing system (AGWS) and the natural guide star wavefront sensor (NGWS), tested with INAF Arcetri, are joined by a holographic dispersed fringe sensor; the Smithsonian Astrophysical Observatory built a dispersed fringe sensor prototype and demonstrated closed-loop phasing. Assembly of the GAPS phasing testbed began in Pasadena in December 2025. The makers of the real-time adaptive optics computers are not publicly named.

Component	Supplier	Country	Role	Status	Note
Adaptive secondary mirror (ASM) system, seven segments	AdOptica (A.D.S. International and Microgate)	Italy	Integrator	In production	Fourth-generation ASM; 675 voice coil actuators per segment, 4,725 total; Safran Reosc shell and SCHOTT blank under AdOptica; segment assembly ready for Phasing Testbed by Dec 2025
ASM design (AdOptica member)	Microgate	Italy	Designer	In production	AdOptica member; contactless voice coil technology; 675 actuators per segment, 4,725 total
ASM prototype hexapod positioner actuator	A.D.S. International	Italy	Manufacturer	Delivered	Also received the first off-axis thin shell in 2024
ASM off-axis thin shell, 1 m class, 2 mm thick, ground and polished	Safran Reosc	France	Manufacturer	Delivered	Contract July 2021 under AdOptica; asphericity about 10 times its prior shells
Zerodur blank for ASM thin shell	SCHOTT AG	Germany	Manufacturer	Delivered	Named in GMT SPIE 2024 status paper
ASM reference body, co-producer	Korea Research Institute of Standards and Science (KRISS)	South Korea	Manufacturer	Delivered	Co-produced with University of Arizona
Natural guide star wavefront sensor prototype testing	INAF Arcetri	Italy	Designer	In production	Tested in the HCAT testbed at University of Arizona
Dispersed fringe sensor prototype and closed-loop phasing demonstration	Smithsonian Astrophysical Observatory	US	Designer	Delivered	Segment phasing; GMT has no published edge-sensor supplier

Ingersoll is building the 2,100-metric-ton mount in Illinois, and the enclosure still has no builder

The mount stands 39 m tall on a 22 m concrete pier and weighs 2,100 t with its optics. OHB Digital Connect of Germany, formerly MT Mechatronics, designed it, and Ingersoll Machine Tools, part of Italy's Camozzi Group, builds and tests it in Rockford, Illinois, under a $135 million contract signed in October 2019. Fabrication began in August 2024 and runs about six years; the 2019 plan had the mount in Chile by the end of 2025. Teledyne in Huntsville, Alabama rough-machines the azimuth track sections and Dynasty Fab near Detroit makes the azimuth disk sections.

The enclosure is about 65 m tall, 60 m wide and 4,800 t, with 92 wind vents and 24 seismic pendulums that let it move 700 mm in an earthquake. It turns a full circle in about four minutes by one account and a little over three by another. M3 Engineering of Tucson was named as its designer in 2019; IDOM of Spain won the final design in March 2022, passed the final design review in June 2024, and is Designer of Record. Boeing and RWDI modeled the wind loads. WSP has been construction manager since January 2018. In October 2026 GMTO was preparing to select a contractor, and the enclosure construction contractor is not publicly named.

Component	Supplier	Country	Role	Status	Note
Telescope mount design, 39 m tall, 2,100 t with optics	OHB Digital Connect (formerly MT Mechatronics)	Germany	Designer	Delivered	Contract Oct 2019, USD 135 million with Ingersoll
Telescope mount manufacture, assembly and factory test	Ingersoll Machine Tools (Camozzi Group)	US	Manufacturer	In production	Fabrication began Aug 2024 in Rockford IL; about six years of work
Azimuth track sections, rough machining	Teledyne (Huntsville AL)	US	Manufacturer	In production	Named in GMT SPIE 2024 status paper
Azimuth disk sections	Dynasty Fab	US	Manufacturer	In production	Near Detroit MI
Enclosure final design, 65 m tall, 4,800 t	IDOM	Spain	Designer	Delivered	Designer of Record; final design review passed June 2024; no construction contractor named as of Nov 2026 (GMTO preparing contractor selection Oct 2026)
Earlier enclosure design	M3 Engineering	US	Designer	Delivered	Tucson firm named in 2019 as having designed the enclosure
Wind loading fluid dynamics modeling	Boeing	US	Designer	Delivered	With RWDI
Wind loading fluid dynamics modeling	RWDI	Canada	Designer	Delivered	With Boeing
Construction manager	WSP	Canada	Integrator	Contracted	Awarded January 2018

G-CLEF, GMACS and GMTNIRS will be the first instruments

G-CLEF, an optical echelle spectrograph from the Center for Astrophysics, Harvard and Smithsonian, is in fabrication; its vacuum chamber was nearly complete in December 2025. GMACS, a visible multi-object spectrograph from the CfA with the Steiner Institute in Sao Paulo, is in final design and will be the second instrument commissioned. GMTNIRS, a near-infrared spectrograph from UT Austin and the Korea Astronomy and Space Science Institute (KASI), will be the first diffraction-limited instrument; its gratings and first cameras were delivered by December 2025. GMagAO-X and GMTIFS are in final design and MANIFEST is near the end of conceptual design. GMTO's 2024 status paper names no detector supplier.

Component	Supplier	Country	Role	Status	Note
G-CLEF optical echelle spectrograph	Center for Astrophysics, Harvard and Smithsonian	US	Designer	In production	Vacuum chamber nearing completion Dec 2025
GMTNIRS near-infrared spectrograph	University of Texas at Austin	US	Designer	In production	With KASI; gratings and first cameras delivered by Dec 2025
GMTNIRS near-infrared spectrograph	Korea Astronomy and Space Science Institute (KASI)	South Korea	Designer	In production	With UT Austin
GMACS visible multi-object spectrograph	Center for Astrophysics, Harvard and Smithsonian	US	Designer	Planned	In final design as of June 2024; with Steiner Institute, Sao Paulo

NOIRLab will write the software astronomers use to request GMT observations

NSF NOIRLab is to provide the observatory software that external astronomers use to request and define observations, and GMTO manages its requirements in IBM DOORS. The Operations Plan passed external review in October 2025. The real-time computers, the data center and any AI or machine-learning program are not publicly named.

Component	Supplier	Country	Role	Status	Note
Observatory software for observation requests	NSF NOIRLab	US	Designer	Planned	Named in 2022 status paper
Requirements management tool (DOORS)	IBM	US	Manufacturer	In service	Manages GMT requirements

Las Campanas runs daytime tours, but whether they include the GMT site is not stated

Las Campanas Observatory offers daytime tours booked through its visit site, a form for arranging visits and a virtual night tour. Its pages do not say whether tours include the GMT site, or give fees and hours.