A rendering of the Cornell Caltech Atacama Telescope, to be built on Chile's Cerro Chajnantor to replace CSO. Photo courtesy Caltech

Caltech seeks to dismantle Mauna Kea observatory

By T. Ilihia Gionson / Ka Wai Ola Loa

In the latest twist in the discussion over the future of astronomy on Mauna Kea, the California Institute of Technology announced plans to decommission its Caltech Submillimeter Observatory atop the mountain by 2018.

CSO, one of 12 observatories on the Mauna Kea summit, is one of three that measures waves in a range between infrared and visible light.

"CSO has found the distance of far-off galaxies, the composition of celestial bodies and of space itself, water in comets and spatial debris. … CSO has done a terrific service, but in so doing made itself redundant," CSO director Tom Phillips said. Using technology for studying submillimeter waves developed at CSO, the Atacama Large Millimeter Array will make the same kinds of observations that CSO does using 60 12-meter telescopes in a Chilean desert. The array will be more powerful than CSO, making it obsolete.

"At Caltech, you have to be the best in the world or you won't get very far," Phillips said. The decommissioning of CSO is planned "in recognition that we won't be the best in the world once ALMA is operational."

ALMA is not a project of Caltech, but the university is planning a submillimeter observatory near the ALMA site on Cerro Chajnantor, a peak 2,500 feet above the plain on which ALMA will be located. The 25-meter Cornell Caltech Atacama Telescope will complement ALMA, not be in competition with it. CCAT should be operational before CSO's planned decommissioning.

Tom Soifer, director of the Caltech's Spitzer Science Center, expressed the institution's gratitude to the community for the years CSO has been on Hawai'i Island. "Thanks to the people of Hawai'i for allowing us to put CSO on this wonderful site, Mauna Kea," he said. "We're extremely grateful."

Mauna Kea's Caltech Submillimeter Observatory shows off its 10.4 meter primary mirror in this undated photo. Photo courtesy Caltech

CSO subleases its site for $1.00 a year plus telescope time from the University of Hawai'i's Institute for Astronomy, which leases most of the summit of Mauna Kea from the state Department of Land and Natural Resources for no charge.

Bob McLaren, associate director of the Institute for Astronomy, is sad to see CSO go, but he said that the departure is in line with IFA's strategy for Mauna Kea. "More than 20 years ago, when CSO came to Mauna Kea, submillimeter was considered the last frontier of ground-based astronomy. The folks back then were real pioneers," he said. "We're a little sad to see the news that they'll be leaving but we understand why. By the time ALMA is operational, CSO will no longer be in the top rank of submillimeter astronomy. Their decision is in keeping with the University's wish that when it comes to astronomy on Mauna Kea, we'd like only the highest and best use up there."

Although Native Hawaiians and environmentalists have called for the removal of telescopes from Mauna Kea, there are regulatory hurdles that CSO must clear before beginning to decommission the observatory.

Because the summit is a conservation district, any land use – construction or decommissioning, for example – requires a conservation district use permit, among other documents.

Soifer said at a press conference in Hilo on April 30 that he believes that decommissioning is covered in existing documents. CSO's sublease with the University of Hawai'i does provide for complete removal of the facility and restoration of the site as an option at the termination of the sublease. However, said activity would need to be covered in a conservation district use permit. A Ka Wai Ola review of CSO's existing conservation district use application and permit did not find any references to decommissioning in the 1983 documents.

The court decision that mandated the creation of the Mauna Kea Comprehensive Management Plan stipulated that there can be no new permits for land use until a plan is in place. Although the CMP was conditionally accepted by the Board of Land and Natural Resources in April, six petitions contesting the decision could delay acceptance of a plan for years as the decision could go to court.

CSO officials said that they had no contingency plans in the event the CMP is not accepted by 2016, the planned beginning of the decommissioning process.

Caltech operates CSO, and is a partner in the W.M. Keck Observatory also on Mauna Kea. Caltech is also a partner in the planned Thirty Meter Telescope, for which Mauna Kea is one of two proposed sites.