The fate of two planned giant telescopes in Hawaii and Chile rests with the director of the National Science Foundation (NSF), after a review of the U.S.-led projects, each vying for $1.6 billion in NSF funding, did not pick a clear favorite. The review panel concludes that both projects are ready to move to the final phase of assessment but highlights how funding even one of them would threaten NSF’s support of other telescopes and astronomy research in general. The panel’s report could give NSF Director Sethuraman Panchanathan reason to nix backing either proposal or let them languish if Congress does not provide considerable extra funding.
“Without augmentation [from Congress], NSF can’t do this,” said panel member Kelvin Droegemeier, an atmospheric scientist at the University of Illinois Urbana-Champaign and former vice chair of NSF’s governing board, at a briefing for journalists on 6 December.
The report is “a bitter disappointment,” says astrophysicist Richard Ellis of University College London, and “falls short of guiding the NSF director to make this very important decision.” Michael Turner, an astrophysicist at the University of Chicago (UC), is more positive: “They basically have put the ball in the court of NSF and Congress.”
So-called extremely large telescopes (ELTs)—with mirrors as big as baseball diamonds—are the next step in ground-based optical astronomy. By capturing faint light from immense distances, they would let astronomers look farther back in time toward the formation of the universe’s first stars, galaxies, and black holes, as well as scrutinize Earth-like planets around other stars in unprecedented detail.
With steady funding from 16 member states, the European Southern Observatory is marching ahead with its ELT, having passed the halfway mark of construction last year at its mountaintop site in Chile. It aims to finish construction of the 39-meter-wide scope in 2028 for an estimated cost of $1.5 billion. The two U.S.-led projects, the $2.5 billion Giant Magellan Telescope (GMT), a 25-meter scope in Chile, and the $3.9 billion Thirty Meter Telescope (TMT) in Hawaii, are funded by consortia of wealthy academic institutions and international partners. But they have stumbled in their fundraising efforts.
In 2018, the two longtime rival projects called on NSF to support a joint program incorporating both telescopes, dubbed US-ELT, that would give the wider astronomy community access. The “decadal survey” for astrophysics, a community priority-setting exercise that guides funding agencies and Congress, gave its blessing in 2021, naming the US-ELT as its top priority in ground-based astronomy and saying NSF should contribute $1.6 billion to gain 25% shares in both telescopes.
NSF began its usual process for assessing new large infrastructure projects and both telescopes passed the first hurdle, the preliminary design review. Entering the next stage, final design, almost invariably leads to construction, and NSF leadership paused before taking that step. As the costs of the two projects emerged, it wasn’t clear that $1.6 billion from NSF would be enough to complete one of the telescopes, let alone support both, which have a combined cost of more than $6 billion. But in February, the National Science Board (NSB) asked NSF to come up with a plan to select and support one of the two candidates.
To aid his decision, Panchanathan appointed an external panel of five senior scientists. None are astronomers, but some were former NSB members and all have experience of building major scientific infrastructure. The panel was tasked with assessing the fitness of the two project organizations and the risks to NSF of moving forward. It identified some problems, such as the questions hanging over the TMT’s chosen site, but said money remains the biggest challenge. “The biggest risk is securing appropriate funding,” said panel chair Dan Arvizu, former chancellor of New Mexico State University and a former NSB chair, at the briefing.
The panel authors write that having such a mammoth optical telescope is vital to maintain a leading position for U.S. astronomy. “Failure by the U.S. to support a US-ELT will have a domino effect and exacerbate the already problematic funding in the country for fundamental research,” the report says.
The report notes that the TMT has already received $700 million from its partners and has commitments that total $2 billion of its total estimated cost of $3.9 billion. Even if it wins the full $1.6 billion from NSF, the TMT would need at least $300 million more from elsewhere. The GMT has commitments of $850 million with most already paid. The full funding from NSF would be enough to complete construction, according to the GMT.
The report was particularly critical of the TMT’s handling of risk over its site. The TMT has always planned to build on Mauna Kea, a mountain in Hawaii that is home to many other telescopes. But some Native Hawaiians and other groups who consider the summit sacred have bitterly opposed a huge new facility. Protesters blocked the access road to the summit in 2015 and 2019 and the TMT has been unable to do any site preparation. The TMT has identified a backup option of building in the Canary Islands, but the panel says those plans are not well developed. “The panel finds [the TMT’s] mitigation strategy for this risk, taken as a whole, to be inadequate,” the report says, adding, “until this issue is resolved, it would be impossible for [the TMT] to complete [final design].”
Giving $1.6 billion to either project would have a severe impact on the NSF budget, the panel found. Construction of large infrastructure projects comes out of a budget called MREFC which, over the past 10 years has averaged at $187 million annually. Each telescope project would require annual MREFC funding of $200 million for many years. NSF’s budget requests for FY2025 onward aim to ramp up the MREFC budget to $500 million by FY2030. But even if Congress fulfils those requests, the report says, devoting much of the MREFC budget to just one of the giant telescopes would potentially cause delays or cancellations of other high priority NSF projects, including a next-generation radio telescope array, a cosmology telescope, a gravitational wave detector, and a neutrino observatory.
Operating either of the telescopes would also strain the budget of NSF’s astronomy division, which funds the running costs of facilities and provides grants to researchers. That budget is $79 million in the FY2025 budget request, but either telescope would consume $60 million per year. Even putting them through the final design phase—which comes from the same budget—would be prohibitively expensive at $103 million for the GMT and $144 million for the TMT over 2 or 3 years. “The idea of advancing both projects into [final design] without a clear path for future funding presents risk to NSF’s reputation within the community,” the panel says.
The panel notes that, although NSF usually wins bipartisan support in congress, that doesn’t always lead to generous appropriations in government funding bills. “The Panel is extremely concerned about the risk to NSF and to the nation’s research and education enterprise more broadly if this trend continues in the context of an US-ELT award,” the report says.
With all the uncertainty associated with President-elect Donald Trump’s new administration, it may be some time before astronomers learn what NSF decides to do next. Panchanathan, who was appointed by Trump in 2019, appears to be willing to bide his time. “NSF agrees with the panel’s findings that the success of the US-ELT program hinges on securing the necessary resources from Congress,” he said in a statement following the report’s release.
But Wendy Freedman, an astrophysicist at UC, hopes NSF isn’t going to give up. “Let’s hope that one or both projects will be supported and that the U.S. does not have to cede its leadership in astronomy, a position that it has held for a century,” she says. “It is hard to imagine just how hard a blow that would be.”
