The Giant Magellan Telescope project team is preparing to select a contractor to build the 22-story precision rotating enclosure for the record-breaking telescope located on a mountain in Chile.
With design reviews complete, the team plans an informational meeting for potential contractors in early November, with the goal of issuing a request for qualifications in early 2027.
“We’ve been working on this for many years,” says Bruce Bigelow, site closure specialist at the Giant Magellan Telescope (GMT). “We’ve developed a statement of work and request for proposal package, and it all comes to a head with our industry briefing on November 3-4.”
At the briefing in Los Angeles, the team will meet with potential global contractors to tackle the complex task of building the telescope enclosure. Spain-based IDOM completed final design work in 2024, and the National Science Foundation completed a rigorous review of the entire project. by mid-2025. NSF’s approval is the key recommendation for further funding from the US Congress. A consortium of academic and scientific organizations from the United States and around the world is building the telescope, with participants from South America, Europe and East Asia.
Following the industry briefing in November, the goal is to have the finalized RFP package released in late March or early April 2027. Proposal preparations and evaluations will continue through 2027, with the goal of identifying a contractor in late 2027 and beginning construction in 2028.
“This is a very specialized hire and will need an industry leader who can work in the middle of nowhere,” says Ryan Kallabis, GMT’s director of communications.
An unusual project with unusual challenges
The project, located atop a mountain in Chile’s Atacama Desert, includes a 22-story enclosure for the telescope’s mirror array, with the top 18 floors capable of rotating 360° with full precision. Site and utility work is complete, and the highly detailed project documents go well beyond typical design documentation, Bigelow says.
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“The level of design detail in these specifications and BIM is different by discipline; we’re particularly attuned to the local contractor community in Chile, where contractors don’t do any design work and expect to know where every nut and bolt is, so it’s more detailed than in typical American designs.”
Although the structure has been designed to exceed local Chilean building codes, it goes further in seismic design, being even more prescriptive than ASCE 7-22. This is due to the nature of the installation, with its array of sensitive mirrors and the need for the revolving enclosure to remain functional after a seismic event.
Representation of the interior of the telescope enclosure. The tan area shows the tilt axis of the moving central mirror array. Graphic courtesy of the Giant Magellan Telescope
While the GMT team expects the selected contractor to employ local Chilean companies, workers and subcontractors, they are not limiting where they can come from. They expect the winning company to come from a country involved in GMT development, but can go further if there are good candidates.
The GMT team also deviates slightly from the project delivery of other large telescopes, choosing to hire an external construction manager rather than having the project team manage construction directly. “We are in the process of hiring right now [a CM] and will manage the contract with the general contractor and the GMT CM team,” explains GMT Project Manager Will Burgett.
The decision to go with an external CM wasn’t easy, but the scale of the record-sized telescope demanded it, Bigelow says. “We’ve crossed a size threshold, we can’t run this internally with six or ten people.”
The unusual nature of the project will be another challenge for the contractor, but GMT officials hope it will also appeal to those looking for creative solutions. The closest analog would be movable stadium roofs, but Bigelow points out that they only need to be closed a few times a year. “We operate several times a day, when we need to turn and energize the venue. Someone who has done stadium ceilings has a leg up on the shutter doors, but the revolving part of the venue is very hard. The closest thing is a locomotive turntable, except our turntable is 22 stories high.”
MEP detail of the BIM representation of the telescope enclosure showing the complexity of the mechanical systems.Rendering courtesy of the Magellan Giant Telescope
Sequencing the project will be key, especially when to place the concrete and in what order the revolving enclosure’s structural steel is erected. Bigelow compares it to a huge puzzle.
“If you look at the history of how big telescope enclosures are built, there’s always substantial falsework all the way up, just like in stadiums, you need that temporary support in case of an earthquake during construction,” he says. “And that’s a key part that we’ll be looking for during proposals: How do you build it safely and in a timely manner with the associated risks?”
Bigelow adds that there are existing smaller rotating telescopes built with false works where the rotating components would eventually go, which were changed once the larger structure of the enclosure was solidified. As Burgett points out, IDOM considered these issues during the design phase.
“Bruce was very careful to bring constructability issues to the forefront of the design and led the constructability review of this design a couple of years ago,” he says, adding that IDOM will remain an engineering and architectural consultant during the construction phase to address submissions and change requests.
Because the GMT is one of the largest extremely large telescopes ever built, Bigelow says it’s an opportunity to showcase the best modern construction practices.
“Are we building with a late 20th century mindset or a 21st century mindset?” he says. “We are trying to go beyond what has been done in building the observatory.” With fully detailed BIM and digital-based project delivery, the aim is to have a full 3D digital twin to deliver to work when the project is complete.
“We’re trying to set a standard for building observatories, combining areas of best practice to make the whole greater than the sum of its parts,” says Burgett. “So not only the best construction practices, the systems engineering, the best technology through BIM, but the GC has to demonstrate a safety record as good as the construction.”
He adds that while sustainability goals are not as promoted in construction as they were a few years ago, respecting the environment and minimizing the impact on the surrounding region is another requirement for the project contractor.
Burgett said, “The Chilean government has allowed us to be invited into their country and given us access to their skies, and we want the GC to appreciate that.”
