This artist's rendering shows the Thirty Meter Telescope sitting atop Mauna Kea. Credit: TMT International Observatory

Hawaii’s supreme court has ruled in favour of building the Thirty Meter Telescope (TMT) atop the mountain Mauna Kea. The decision removes the last legal hurdle preventing the US$1.4-billion project from resuming construction on Hawaii’s Big Island.

“This clears the way for the TMT to begin construction,” says Doug Simons, executive director of the Canada-France-Hawaii Telescope, which is located on Mauna Kea. “So yeah, it’s a really big deal.”

For years, the next-generation astronomical observatory has been mired in public protests and legal challenges. Some Native Hawaiians say that building the mega-telescope would further desecrate a sacred mountain that is already home to multiple observatories. In April 2015, protesters blocked the road to Mauna Kea’s summit as construction of the TMT was set to begin. That December, the state supreme court revoked the project’s construction permit, saying that the state government had granted it before opponents of the telescope could have their full say.

Hawaii’s Board of Land and Natural Resources issued a fresh construction permit in September 2017, prompting opponents to appeal. The latest ruling upholds that permit.

“It is a tremendously important and significant decision that provides secure legal grounds to restart construction of this transformative facility,” says Michael Balogh, an astronomer at the University of Waterloo in Canada who chairs an advisory committee that represents Canadian astronomers' interests in the TMT.

﻿A separate legal issue, involving the University of Hawaii’s sublease of land on Mauna Kea for the TMT site, was resolved in August. The state supreme court ruled in the project’s favour in that case, as well.

Next steps

Telescope opponents have few legal options left; they include petitioning the US Supreme Court.

One of the groups opposing the TMT, the environmental advocacy organization KAHEA in Honolulu, said it was “disappointed” by the new ruling. “Thousands of Hawaiian cultural practitioners have affirmed the sacredness of the entirety of Mauna Kea,” the group said in a statement.

﻿TMT officials have been considering an alternative site for the telescope, in Spain’s Canary Islands, in case they cannot resolve the obstacles to building in Hawaii. It could take months before project leaders decide whether to go ahead in Hawaii, now that they have the supreme court’s backing. Among the issues they face is how to restart construction on Mauna Kea, given the protests that broke out the last time they tried to do so.

“We remain committed to being good stewards on the mountain and inclusive of the Hawaiian community,” said Henry Yang, chair of the TMT International Observatory board of governors, in a statement.

The TMT is one of three planned mega-telescopes that would push astronomy into a new era of ground-based observing. The other two — the Giant Magellan Telescope and the European Extremely Large Telescope — are both under construction in Chile. The TMT is a multinational project involving two universities in California, plus the governments of Canada, China, India and Japan.

In Hawaii, the battle over how Mauna Kea is used may soon shift from the TMT to the University of Hawaii's master lease, which covers all the land on the mountain that is used for astronomical observatories. These include the Keck, Subaru and Gemini North telescopes. The lease expires in 2033, and Shelley Muneoka, a representative of KAHEA, says that the group is considering whether to challenge the lease's renewal.