Caltech Submillimeter Observatory decommissioned

Two observatories have now been completely removed from the summit of Maunakea, fulfilling a commitment made by the University of Hawaiʻi. All site work for the decommissioning of the Caltech Submillimeter Observatory (CSO)was completed in June 2024 following the removal and site restoration of the UH Hilo Hōkū Keʻa Observatory in May 2024.

"The completion of the two decommissioning projects demonstrates our commitment to responsible stewardship of Maunakea. We remain devoted to our role as stewards of the Mauna, respecting its profound cultural and environmental significance," said UH Hilo Chancellor Bonnie D. Irwin.

Caltech Submillimeter Observatory decommissioned: Two observatories have now been completely removed from the summit of Maunakea

The UH Hilo Center for Maunakea Stewardship (CMS) oversaw both decommissioning projects. Both sites will be monitored over the next three years to assess species population and diversity.

"This is a significant milestone in the history of astronomy on Maunakea and shows that we have come a long way in our stewardship of the Mauna. This project required close, daily coordination between CSO, the contractors, and CMS. I want to commend the team for their commitment to problem solving and completing this project in a way that was pono," said Greg Chun, Executive Director of the UH Hilo Center for Maunakea Stewardship.

CSO dome site before and after the removal

Photo credit: National Astronomical Observatory of Japan)

The deconstruction phase of CSO began in August 2022 and included the removal and transport of the telescope, physical deconstruction of the building housing the telescope and site restoration. As with the Hōkū Keʻa Observatory, the project was completed in accordance with the decommissioning process required by the Mauna Kea Comprehensive Management Plan.

"The physical 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 CMS," said Caltech physics professor and CSO Director Sunil Golwala.

The Hawaiʻi State Legislature established the Maunakea Stewardship and Oversight Authority (MKSOA) in 2022. After a five-year transition period MKSOA will assume oversight and management of Maunakea in 2028, and as part of our shared management responsibilities during this transition period, the MKSOA has been briefed by CMS regarding the decommissioning project.