“We’ve been working up to this for many years now,” says Bruce Bigelow, site enclosure specialist for the Giant Magellan Telescope (GMT). “We’ve developed a statement of work and the request for proposals package, and it all comes to a head with our industry briefing on November 3 to 4.”

At the briefing in Los Angeles, the team will be meeting with potential global contractors to tackle the complex task of building the telescope’s enclosure. Spanish-based IDOM completed final design work in 2024, and the National Science Foundation completed a rigorous review of the entire project in mid 2025. The approval secured from NSF is the key recommendation for further funding from the U.S. Congress. A consortium of academic and scientific organizations across the U.S. and around the world is building the telescope, with participants from South America, Europe and East Asia.

After the industry briefing in November, the goal is to have the finalized Request for Proposals package released in late March or early April 2027. The proposal preparations and evaluations would continue through 2027, with a goal to identify a contractor by the end of 2027 and begin construction in 2028.

“This is a very specialized procurement, and it will take an industry leader able to work out in the middle of nowhere,” says Ryan Kallabis, director of communications for the GMT.

The project, located on a mountaintop in Chile’s Atacama Desert, involves a 22-story enclosure for the telescope’s mirror array, with the upper 18 stories able to rotate 360° with complete precision. Site and utility work is complete, and the heavily detailed project documents go far beyond typical design documentation, says Bigelow.

Looking for quick answers on construction and engineering topics?
Try Ask ENR, our new smart AI search tool. Ask ENR →

“The level of design detail in these specs and the BIM is different according to discipline—we’re particularly attuned to the local Chilean contracting community, where contractors don’t do any design work at all and expect to know where every nut and bolt is—so it’s more detailed than in typical North American designs.”

Rendering of interior of telescope enclosure. Tan area shows tilt axis of moveable central mirror array.
Graphic courtesy Giant Magellan Telescope

While the GMT team expects the selected contractor to employ local Chilean firms, workers and subcontractors, they’re not limiting where they can come from. They expect the winning firm will come from a country involved in the GMT’s development, but may go further afield if there are good candidates.

The GMT team is also taking a slight departure from the project delivery of other large telescopes, opting to hire an outside construction manager rather than have the project team manage construction directly. “We’re in the hiring process right now for [a CM] and they will manage the contract with the general contractor and the GMT CM team,” explains Will Burgett, GMT project manager.

The decision to go with an external CM was not easy but the scale of the record-size telescope demanded it, says Bigelow. “We’ve crossed a threshold on size, we can’t run this internally with six to ten people.”

MEP detail of BIM rendering of telescope enclosure showing mechanical systems complexity.
Rendering courtesy of Giant Magellan Telescope

Project sequencing will be key, especially when to place concrete and in what order to erect the structural steel of the rotating enclosure. Bigelow likens it to an enormous puzzle.

“If you look at the history of how large telescope enclosures are built, there is always substantial falsework the whole time it is going up—same as in stadiums—you need that temporary support in case of an earthquake during construction,” he says. “And that’s a key part we’ll be looking for during proposals: how do you build this safely and timely with the associated risks?”

Bigelow adds that there are existing, smaller rotating telescopes built with falsework where the rotating components would eventually go, which were swapped in once the larger enclosure structure had firmed up. As Burgett points out, IDOM considered these issues during the design phase.

“Bruce was very careful to put constructability issues at the forefront of design, and led the constructability review of this design a couple of years ago,” he says, adding that IDOM will be retained as an engineering and architectural consultant during the construction phase to address submittals and change requests.

Since the GMT is one of the largest Extremely Large Telescopes ever built, Bigelow says it is an opportunity to show the best of modern construction practices.

“Are we building with a late-20th century mindset or a 21st century mindset?," he says. "We are trying to step beyond what’s been done in observatory construction.” With a fully detailed BIM and digital-driven project delivery, the goal is to have a full 3D digital twin to hand over for operation when the project completes.

“We are trying to set a standard for observatory construction, melding together areas of best practices to make the whole more than the sum of its parts,” says Burgett. “So not just best construction practices, systems engineering, the best technology through BIM, but the GC must demonstrate a safety record as good as it gets in construction.”

He adds that while sustainability goals are not as heavily touted in construction as they were a few years ago, respecting the environment and minimizing the impact to the surrounding region is another requirement for the project's contractor. 

Said Burgett: “The Chilean government has allowed us to be guests in their country, and given us access to their skies, and we want the GC to appreciate that.”