(BIVN) – Opponents of the Thirty Meter Telescope, the billion dollar observatory proposed for Maunakea but stalled in development, have once again declared that the project will not be built on the Hawaiʻi island mountain.
On July 15th, a “Notice to Cease and Desist” was issued by Puʻuhonua o Puʻuhuluhulu to the TMT International Observatory (TIO). Puʻuhonua o Puʻuhuluhulu was established in 2019 by kiaʻi with the support of the Royal Order of Kamehameha ʻEkahi during the most recent attempt to build the TMT on Maunakea.
The notice was sent to TIO, with copies sent to media and various government officials and institutions, including the Mauna Kea Observatories, University of Hawaiʻi, UH Hilo-Center for Maunakea Stewardship, and Mauna Kea Stewardship and Oversight Authority.
“This serves as a notice to TMT International Observatory (TIO) LLC to immediately cease and desist any and all efforts to construct the Thirty Meter Telescope (TMT) on Mauna Kea,” the notice stated. “Thousands of Native Hawaiians have demonstrated their rejection of the proposed project and have never given their free, prior, informed consent to construct the TMT on Mauna Kea.”
In recent months, the project has been relatively quiet compared to seven years ago, when the effort to construct the observatory on the northern plateau of Maunakea was delayed by the opposition who mobilized on the Mauna Kea Access Road.
In a May 2026 presentation to the University of Hawaiʻi Board of Regents, TMT project manager Dr. Fengchuan Liu said that TIO is considering other possible sites on Maunakea, such as the recently decommissioned site for the Caltech Submillimeter Observatory (CSO).
“We have taken a preliminary look of whether we can possibly build TMT on decommissioned sites, scientifically, engineering-wise, technically. This is very preliminary, of course. And we believe we can,” Liu told the Regents. “TMT is bigger than CSO, for example, and it would require more space than CSO, but we believe there’s enough space in that area.” Liu said the footprint of the observatory would be reduced in size, which would also lower construction costs.
The TIO is also considering a possible alternative site La Palma on the Canary Islands.
“Changing (the) site is a major, major decision. We take it very seriously, our board, and do all our due diligence, and it requires unanimous decision to change the site,” Liu said.
TMT opponents make a case against any site on Maunakea in their cease and desist notice.
“All available legal remedies will continue to be pursued to protect Mauna Kea from further overdevelopment and desecration,” the notice from Puʻuhonua o Puʻuhuluhulu stated. “Furthermore, the TMT project would be subject to the enforcement of environmental review and protections under federal and state statutes, jurisdictional issues related to the Mauna Kea Access Road, complications involving expiring leases, and the governance uncertainties of Mauna Kea as a whole.”
“The enclosed petition containing more than 500,000 signatures opposing the TMT project on Mauna Kea reflects the sustained and widespread opposition to the proposed development and reinforces the message repeatedly conveyed to TIO for the last 15 years: TMT will not be built on Mauna Kea,” the declaration stated.
