Thirty Meter Telescope rejects La Palma as alternative host site
€1bn funding package has been turned down by the Thirty Meter Telescope International Organization The post Thirty Meter Telescope rejects La Palma as alternative host site appeared first on Physics World .
Members of the Thirty Meter Telescope (TMT) International Organization have declined Spain's €1bn offer to construct the telescope at the Roque de los Muchachos Observatory in La Palma. The funding proposal, presented in July, included contributions from the European Investment Bank and Spain's Official Credit Institute. As a result, Hawaii's Mauna Kea has emerged as the sole viable location for the telescope.
The TMT, once built, will utilize a segmented primary mirror, composed of 492 elements of zero-expansion glass, to create a 30-meter-diameter primary mirror. This will enable astronomers to observe the faintest and most ancient galaxies. TMT's members comprise the University of California, the California Institute of Technology, Canada, India, and Japan.
While the final construction cost remains undisclosed, it is anticipated to exceed $3bn, with $2bn already secured. In 2009, TMT chose Hawaii's Mauna Kea as its site; however, construction was delayed in 2015 due to protests from indigenous Hawaiians who consider the location sacred. In 2016, an alternative site, the Canary Island of La Palma, was proposed.
Although some astronomers raised concerns about the environmental conditions on La Palma, which might hinder the telescope's scientific potential due to its warmer climate and lower elevation compared to Mauna Kea, La Palma was still considered as a potential alternative. In 2024, the US National Science Foundation (NSF) restricted the TMT project to either the Giant Magellan Telescope (GMT) or the TMT, but not both.
Subsequently, the NSF opted for the GMT, which features seven primary and seven secondary mirrors, resulting in an optical surface of 25.4 meters. Construction on the GMT has already commenced at Chile's Las Campanas peak, with officials working towards a final design review. Later, in 2025, Spain offered €400m to join the TMT project if it were built in La Palma.
The European Investment Bank and Spain's Official Credit Institute subsequently pledged an additional €600m in loans for construction. However, TMT officials have now rejected this offer, stating that TMT members could not reach a consensus to accept the financial proposal. Despite this decision, the Astrophysics Institute of the Canaries (IAC), which operates the Roque de los Muchachos Observatory, remains committed to the scientific and technological advancement of the observatory.
The IAC plans to continue promoting the installation of new infrastructure, such as the Cherenkov Telescope Array Observatory and the European Solar Telescope.
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