The University of Hawaii Hoku Kea telescope is one step closer to being decommissioned following the publishing of final environmental assessment and finding of no significant impact documents.

UH Hilo’s teaching telescope is one of five Mauna Kea telescopes originally planned to be removed from the mountain in exchange for development of the landmark Thirty Meter Telescope.

The latest Mauna Kea Master Plan calls for a maximum of nine observatories atop Hawaii’s tallest mountain by the time the Mauna Kea Science Reserve lease expires in 2033. There are currently 13 telescopes, with four to be decommissioned, and if the TMT is built, a fifth would be taken out of operation.

The only other telescope close to being formally decommissioned is the Caltech Submillimeter Observatory, which is tentatively scheduled to be completed in late 2023.

The environmental documents describing the Hoku Kea’s decommissioning were published June 23 in The Environmental Notice.

The EA prepared by SSFM International Inc. identifies potential impacts the decommissioning project would have on the area’s resources and proposes measures to minimize those impacts.

The proposal would see the removal of two buildings and associated infrastructure, along with the restoration of the site to its original state as much as possible.

With the EA complete, the state Department of Land and Natural Resources can now review UH’s application for a conservation district use permit and present it to the Board of Land and Natural Resources for its consideration and approval.

If the permit is issued, the university can begin the removal of the observatory and site restoration, tentatively scheduled for completion by late 2023.

Located on the southeastern side of the 528-acre astronomy precinct at the summit of Mauna Kea, the Hoku Kea site was built by the U.S. Air Force in 1970 and was one of the first observatories on the mountain before it was handed off to UH Hilo.

During its heyday the Air Force 24-inch telescope conducted pioneering observations of objects in the solar system, including asteroids and the outer planets. As larger and more powerful telescopes took up residence on Mauna Kea, the small telescope remained relevant with UH Hilo faculty and students using it to collect data for more than a dozen published research projects since 1995, according to the university.

The Air Force telescope was removed in 2008, and the facility was outfitted with a larger dome and mirror in 2010 and named the Hoku Kea telescope.

UH now plans to install a new state-of-the-art, 0.7-­ meter teaching telescope in a small structure at the Halepohaku midlevel facility on Mauna Kea.

As for the $2.65 billion TMT, it remains on hold while its nonprofit developers search for additional funding and work to forge a partnership with the National Science Foundation, which is considering investing hundreds of millions of dollars in the project.

A decision on NSF funding is not expected until 2023.