The Thirty Meter Telescope scored a significant victory Thursday when a federal report ranked the proposed cutting-edge observatory and its U.S.-led cousin, the Giant Magellan Telescope, planned for Chile, among its top priorities for U.S. government funding.

The decadal survey report is recommending that the two facilities — now planned to work together as the U.S. Extremely Large Telescope Program — share at least $1.6 billion.

TMT officials welcomed the recommendations of the panel of astronomers assembled by the National Academy of Sciences, Engineering and Medicine.

“We are grateful for the science community’s support for our project, and acknowledge it is just one step in a process,” said Henry Yang, board chairman of the TMT International Observatory. “We will review the full report carefully and evaluate our next steps.”

Three years in the making and designed to set federal funding guidelines for the next 10 years and beyond, the report describes both the TMT and the GMT as essential for keeping the U.S. in a leadership role in ground-based astronomy.

“These observatories will create enormous opportunities for scientific progress over the coming decades and well beyond,” the report says.

However, the report also acknowledges there are significant risks with each project, including the fact that there may not be enough funding to support both of them.

Even with the new federal funding, the TMT — now estimated to cost $2.65 billion — is looking at a shortfall of $310 million, according to the report, while the GMT faces an even larger deficit of $600 million.

The report calls on the National Science Foundation to assess the viability of the two projects before making a final decision about funding in 2023. And during that two-year period, the TMT must confirm its site — either on Mauna Kea or at its backup site on La Palma in the Canary Islands.

The report also recommends that if one of the proposed observatories (either the TMT or the GMT) turns out to be infeasible, then the money should go to the other one.

“The success of at least one of these projects is absolutely essential if the United States is to maintain a position as a leader in ground-based astronomy,” the report says.

Doug Simons, director of the University of Hawaii’s Institute for Astronomy, called the report’s recommendations “a shot in the arm.”

Simons said the report’s ranking will give the stalled project enough juice to help overcome any funding issues that may be plaguing the TMT now.

In addition, he said, if the National Science Foundation does elect to follow the funding recommendation, its involvement in Hawaii will help to carry the project over the line. “They bring so much new to the conversation, and that alone will help find a path forward,” he said.

Mauna Kea astronomer Thayne Currie agreed.

“They are capable of doing something the state government can’t,” Currie said. “And if trust is broken with the state, at least they will now being dealing with a different entity with formidable resources well beyond the state.”

Opponents, however, say they remain unimpressed and stand ready to defend the mountain whenever they have to.

Mauna Kea Hui leader Kea­loaha Pisciotta said that while the report laudably acknowledges faults in the astronomy community in dealing with Indigenous people, the bottom line is that it still suggests construction atop Hawaii’s tallest and most sacred mountain while likely allocating hundreds of millions of dollars for that purpose in the face of years of protest.

“As for the consent issue, they have sidestepped the answer they don’t want to hear,” Pisciotta said. “We have said no, and continue to say no. And no means no.”

Attorney Richard Naiwi­eha Wurdeman added, “If it isn’t clear by now, after the significant opposition that was demonstrated in 2015 and again in 2019, and the worldwide support for the kia‘i in opposition to the TMT project, there has certainly been unyielding and significant opposition to the TMT project and nothing indicates any change in the steadfast and significant opposition to the project in the future.”

Not every Hawaiian is opposed to the TMT. Among them is Jacqui Hoover, executive director of the Hawai‘i Island Economic Development Board, who says, “As a Native Hawaiian, I navigate through the gauntlet to reconcile past and present, and am trying to do so without sacrificing the future or the rich legacy including wayfinding that my ancestors bestowed on me.

“I’m energized by the idea of the community astronomy model, which prioritizes advancing scientific research while also respecting, empowering and benefiting local communities,” she said in a statement.

If the federal funding comes through for the TMT, the National Science Foundation is likely to begin a new environmental impact statement that complies with the National Environmental Policy Act, as well as conduct a formal consultation with Native Hawaiians as called for in Section 106 of the National Historic Preservation Act.

The 614-page report, “Pathways to Discovery in Astronomy and Astrophysics for the 2020s,” suggests there may be some disagreement about the La Palma alternative site among the TMT partners, which include the University of California and Caltech, and the science institutions of China, India, Japan and Canada.

According to the report, the panel reviewed the relevant metrics on site quality and found Mauna Kea the superior location. La Palma was deemed “acceptable,” with deficiencies in the thermal infrared and in the ultraviolet near the atmospheric cutoff.

“Despite this assessment, the choice of a site still poses a significant programmatic risk since it could adversely affect the partnership,” the report said.

An independent evaluation of the TMT and GMT found each of their timelines too aggressive, according to the report. The TMT is planning for a 10-year construction window, but the outside evaluation estimated 13 years. GMT is planning for 12 years, while the independent assessment estimated 13 years.

TMT, the report said, has the added risk that its site has not yet been selected, adding cost and schedule uncertainty.

“However, the biggest risk for both projects is the large gap between commitments in-hand from the partners, and what is required to complete the projects, even with a significant federal investment.”

GMT partners include the Carnegie Institution for Science, Smithsonian Institution, Harvard University, University of Chicago, University of Texas and Arizona State University.

While TMT and GMT were the top priority for ground-based astronomy, the report tabbed as its top space priority an $11 billion next-generation space telescope that wouldn’t be ready until the 2040s.