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Caltech's Submillimeter Observatory Has Been Removed from Maunakea

The final components of the Caltech Submillimeter Observatory (CSO), including its foundation, silver geodesic dome, and on-site buildings, have been removed from a valley atop Maunakea in Hawai‘i, and the land at the site has been restored. This officially concludes the physical decommissioning of CSO, a process that was initiated in 2015 and began in earnest in 2022 in accordance with the State of Hawai‘i's 2010 Decommissioning Plan for the Maunakea Observatories. For the next three years, the site will be monitored to document passive natural repopulation by summit flora and fauna and the results reported.

"The physical site decommissioning was undertaken with great care by our prime deconstruction contractor, with constant oversight by local cultural, archeological, environmental, and construction monitors as well as the Center for Maunakea Stewardship (CMS)," says Caltech physics professor and CSO Director Sunil Golwala.

CSO, which operated from 1987 to 2015, opened a new window to studying submillimeter wavelengths of light, which fall between infrared and radio on the electromagnetic spectrum. Its discoveries spanned a wide range of objects, including comets, planet-forming disks around stars, distant galaxies, and more. New detector technologies were also pioneered for use at CSO, and those technologies went on to play key roles in space and ground-based observatories.

Currently, the CSO telescope is packed in shipping containers in a harbor on the island of Hawai‘i, where it awaits a new purpose in Chile as the Leighton Chajnantor Telescope. The name honors both the inventor of the telescope, the late Caltech professor Robert B. Leighton (BS '41, PhD '47), and the planned site for the observatory on the high Chajnantor Plateau. The reincarnated telescope will make real-time observations of cosmic eruptions, which have gone largely unexplored at submillimeter wavelengths, and it will continue to observe planetary and stellar nurseries as well as the most distant galaxies. The telescope components will ship to Chile for assembly in the coming year, and first observations are expected in 2027.

More in-depth details about the decommissioning process can be found at the CSO site. A feature story about the history, science, and future of CSO is also online. The Gordon and Betty Moore Foundation and Caltech provided funds for the decommissioning. The Heising-Simons Foundation provided support for the removal of the telescope for reuse in Chile.

"Caltech thanks the people of Hawai'i for the opportunity to explore the universe from the CSO on Maunakea. It has been an honor to continue our relationship with the mauna and its people through this decommissioning effort," Golwala says.

Whitney Clavin
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