Mauna Kea Observatories: Site Measurements and Early Observing Facilities

The observatories on Mauna Kea, in the high mountains of Hawaiʻi Island, developed through several stages: measuring site conditions, securing land use, installing telescopes and conducting observations. A key original document from 1968 is General Lease S-4191, signed by the State of Hawaiʻi's Board of Land and Natural Resources and the University of Hawaiʻi. It is dated 21 June 1968 and lists an expiry date of 31 December 2033.

The lease defines the land's purposes as scientific facilities, including an observatory, and a scientific reserve, with a buffer area against activities that could interfere with observations. An important part of 1968's significance was therefore a land-use arrangement permitting sustained development.

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Early advocates included University of Arizona astronomer Gerard Kuiper and John Jefferies of the University of Hawaiʻi. The official 1983 development plan recounts that, after a rough summit road was built, Kuiper's team tested seeing on the Puʻu Poliʻahu cinder cone in 1964. Jefferies's team continued night-by-night surveys in 1965–1966. In mid-1965, the University of Hawaiʻi began collaborating with NASA on a large reflecting telescope, making site surveys directly relevant to where funds and equipment would be committed.

A 1972 National Radio Astronomy Observatory design report includes nine months of water-vapour measurements from 1965–1966. Precipitable water ranged from about 0.3 to 5.1 millimetres, with a warning that the lowest values were difficult to measure precisely. Millimetres here express the depth of liquid water equivalent to the vapour in an atmospheric column, not local rainfall on a particular day.

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NASA's 1969 Planetary Program Review treated ground-based telescopes and spacecraft as complementary research tools. It explained that much thermal radiation from planets and many absorption features of their atmospheric molecules occur in infrared wavelengths. Observations must first pass through Earth's atmosphere, however, where water vapour and carbon dioxide obscure some signals.

At nearly 14,000 feet, Mauna Kea's dry air reduces water-vapour absorption, so the planned 88-inch telescope was directed particularly towards planetary infrared spectroscopy. The report also listed a new University of Texas telescope, showing that the project formed part of a larger planetary-research programme. In that 1969 report, the 88-inch telescope was still being installed.

References: [3]

While large instruments remained under construction, smaller equipment brought the site into practical use. An architectural survey sheet attached to the formal 2021 environmental assessment confirms intermittent operation of the Air Force-funded 24-inch facility in 1968, initially powered by generators. Jefferies and University of Hawaiʻi astronomer William Sinton helped advance this early group of facilities.

The survey quotes Jefferies's recollection that the Air Force wanted infrared sky mapping to distinguish artificial targets from celestial radiation sources. A small aperture therefore did not imply an absence of research tasks: it served observations of specific wavelengths and targets. The 1972 radio-observatory report already identified the 88-inch reflector as the site's principal instrument and dated its completion to 1970.

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Lease S-4191 explicitly identifies interference from light, dust and certain electrical or electronic facilities as concerns to be prevented. The university could construct buildings and other improvements, but construction and layout plans required prior approval by the land authority. Subleasing or transferring rights also required written consent. Astronomy was thus connected with roads, engineering layout and land management.

The lease also required clean, orderly land, proper maintenance of facilities and arrangements for removal or disposition of buildings when the lease ended. It prohibited damage, removal or excavation of antiquities, prehistoric remains and monuments of historical value, and restricted unauthorized introduction of plants. Good skies were a natural condition, but stable operation depended on continuing maintenance. The radio-observatory site study also noted that strong winds, low oxygen at high altitude and remote access complicated operation and repair of large equipment. Suitability for infrared observation did not make the location equally convenient for every type of telescope.

References: [1] [4]

Subsequent growth occurred through new cooperative arrangements. The 1983 plan records that Canadian, French and Hawaiian partners agreed in 1973 to build a 3.6-metre telescope, which entered operation in 1979. Infrared facilities built by the United States and United Kingdom also belonged to this later expansion, turning the early base into a group of observatories involving several institutions.

References: [1] [2] [3] [4]