Decommissioning the Caltech Submillimeter Observatory on Mauna Kea is set to begin next summer with final removal of the telescope before year’s end. The green light for decommissioning the telescope comes after the Hawaii Board of Land and Natural Resources issued a key permit last month.

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The telescope on the Big Island has served as one of the world’s most important instruments in the field of astronomy since 1987. It’s one of 13 telescopes located at the summit of Mauna Kea, a dormant volcano considered sacred by many Native Hawaiians.

The telescope, known as CSO and housed in a compact dome, has been used by hundreds of scientists, researchers and students from all over the world. Among other things, it allowed them to observe light emitted from celestial objects, enabling discoveries about star formation and the evolution of the universe.

“Discoveries made at the facility include the elucidation of the role of atomic carbon in the space between stars, a new phase of stellar evolution for red giant stars, the first ground-based detection of heavy water in a comet, and more,” according to Caltech.

The telescope’s functional life has been waning for years, with astronomical instruments removed from it in 2015.

The Caltech Submillimeter Observatory is one of two telescopes on Mauna Kea set to be decommissioned in the next two years. Screenshot: California Institute of Technology

The state land board paved the way for the telescope’s decommissioning on Jan. 14 by unanimously approving a conservation district use permit.

To receive the permit, the telescope’s operators had to conduct a slew of studies. These included an archeological assessment, a cultural setting analysis, a hydrogeological evaluation, a biological inventory, biological and traffic setting analyses, and a survey of asbestos, lead paint and mold, according to the University of Hawaii, which manages the land upon which the telescope sits.

The telescope’s removal could not come soon enough for those trying to protect the mountain as a sacred site. But they also want to make sure the process is done correctly.

“Removing telescopes can be just as destructive as putting them up,” said Kealoha Pisciotta, president of Mauna Kea Anaina Hou.

“The main thing that we are always concerned about is that all of the telescopes are built above the aquifers that are the main aquifers of Hawaii island,” she said. “We’ve been extensively concerned about their use of toxic chemicals and the human waste (in cesspools).”

In addition to sharing Pisciotta’s concerns about cleanup and what she considers a lack of scientific understanding of the summit’s hydrology, Deborah Ward of the Sierra Club says she would like more transparency about the costs of decommissioning and wants guarantees that the public won’t get stuck with unpaid expenses. Those details have been shrouded in secrecy, in Ward’s view.

“We need to understand what the entire decommissioning process costs and what it’s going to entail as far as the taxpayer commitment,” she said.

The cost of removing the telescope and remediating the site is estimated at around $4 million and is expected to be paid for by Caltech.

CSO is one of two Mauna Kea telescopes currently in the final stages of the decommissioning process. The other is UH Hilo Hoku Kea Telescope which is slated for removal and site remediation in 2023. The process is guided by the Mauna Kea Master Plan which sets a limit of nine operating astronomy facilities on Mauna Kea by 2033. The plan was adopted by the University of Hawaii Board of Regents on Jan. 20.

Greg Chun, executive director of the UH Hilo Center for Maunakea Stewardship, described the decommissioning of the two telescopes as “milestones in the stewardship of the mauna.”

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