Soon after joining the faculty of the University of Hawai`i Department of Physics in 1953, I began to think about the unique potential of Hawai`i’s high mountains for observations of the Sun, and it became my goal to establish a solar observatory on the top of one of the mountains. There were three possible sites: Mauna Loa (13,680 ft.), and Mauna Kea (13,784 ft.), both on the island of Hawai`i, and Haleakala (10,025 ft.) on the island of Maui. Mauna Loa was an active volcano with very difficult access and was deemed unsuitable. Mauna Kea, though volcanic in origin, as is all of Hawai`i, was considered dormant or extinct. But like Mauna Loa, it was very remote and without vehicular access or electric power. Haleakala, though significantly lower than Mauna Kea, was still quite high as compared with other solar observatories around the world. Only the High Altitude Observatory at Climax, Colorado, at 11,000 feet was slightly higher. The great advantage of Haleakala was its ease of access via a paved road and commercial power to the summit. Site testing was begun in 1955 with the assistance of graduate student John Little.
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Graduate student John Little using the sky-brightness photometer on Haleakala, 1955
The crucial parameter for solar coronal studies is the brightness of the sky immediately adjacent to the solar disk. The results of a year’s measurements with an Evans-type sky brightness photometer (8) showed that Haleakala was indeed an outstanding site, not only in terms of sky transparency but also in the number of clear days per year (9). But funds for planning and constructing an observatory were not readily available.
In the meantime, the forthcoming International Geophysical Year 1957-58 placed Hawai`i in a crucial position, both in terms of latitude and longitude, for a number of geophysical observations in a worldwide network. Thus, the IGY provided the impetus and some modest funds to begin various projects. A solar observatory in Hawai`i was crucial to the work of the IGY but there was neither time nor funds to develop one on Haleakala. If coronal studies were forgone, a sea-level site could be suitable, and thus a site on the Island of Oahu at Makapu`u Point, about 300 feet above sea level, was found and developed. Fortunately, a small concrete building abandoned by the telephone company was available, and several experiments were installed and operating by the official beginning of the IGY, July 1, 1957.
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The University of Hawai`i Solar Observatory at Makapu`u Point, Oahu, 1967. The solar radio noise 10-ft dish is at the left. The heliostat mirror is at the left end of the building. On the roof, covered by a tarp, is the old Kaimuki Observatory telescope.
The heliostat mirror, which tracks the Sun and directs the solar beam into the hole in the side of the building, and into the telescope.
The solar telescope mounted on a rigid optical bench inside the building. On the left is a prism directing the solar beam from outside down the optical bench. Near the center is the shutter, and to the far right is the 35-mm camera, directly in front of which is the 0.5-Ångstrom H-alpha filter.
A solar flare patrol telescope was set up on an optical bench inside the building with a heliostat outside the building directing a solar beam into the telescope through a hole in the wall. The telescope employed a Halle-Lyot 0.5-Ångstrom H-alpha filter and routinely took photographs of the Sun every two minutes on 35-mm film. These films were processed daily at the university campus and visually scanned in a microfilm viewer. Flares and prominences were measured and the data reported every evening via a military communications link to the World Data Center in Boulder, Colorado.
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Image of the Sun taken at the Makapu`u Point Solar Observatory on 29 February 1958, at 2110 UT, in hydrogen light (H-alpha)
An indirect flare detector (IFD) provided very useful data to complement the optical data or provide indications of flare activity when the telescope was clouded out. The IFD was an experiment of the High Altitude Observatory in Boulder, Colorado, designed and built by Robert Lee of that institution. It consisted of two radio receivers, one tuned to 18 kHz with a long wire antenna, and the other tuned to 18 MHz with a very directional antenna pointed towards the zenith. The low frequency receiver picked up natural radio noise generated in the Earth’s atmosphere by lightning and propagated great distances by reflections from the base of the ionosphere. During the onset of a flare on the Sun the increase in ultra-violet and x-radiation reaching the Earth’s atmosphere causes an increase in the degree of ionization in the ionosphere and hence an increase in its ability to reflect the atmospheric radio noise, resulting in an enhancement of the atmospheric radio noise received. The high frequency receiver detected radio noise from outside the Earth’s atmosphere, referred to as cosmic radio noise (10). In the event of a solar flare, the enhanced ionization in the ionosphere resulted in a greater absorption of the cosmic radio noise arriving at the antenna.
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The solar radio noise receiver. The equatorially mounted dish tracks the Sun and receives radio noise at 200 MHz generated by storms on the Sun.
The Sun is itself a generator of radio noise and a study of this radio energy is a useful tool for understanding solar activity. Professor Iwao Miyake of the University of Hawai`i Department of Physics built and operated for the IGY a 200 MHz radio receiver adjacent to the Makapu`u Point Solar Observatory. Starting with a surplus Navy radar dish about 10 feet in diameter, he mounted it in an equatorial drive system so that it could be made to track the Sun. Bursts of radio noise in the frequency range used here are generated by the rapid expulsion of material from the surface of the Sun up through the Sun’s highly ionized atmosphere, and thus are an indication of violent disturbances on the surface of the Sun.
In cooperation with Dr. Robert Brode and Dr. Edward Chupp of the Department of Physics, University of California at Berkeley, the Makapu`u Point Solar Observatory also operated cosmic ray neutron and mu-meson monitors. These were telescopes in a sense because their sensitivity was directional and they were designed to detect changes in the particle flux associated with solar activity. Only in the case of the neutron flux was any change ever noted – a so-called Forbush decrease – related to solar activity. Since these changes are related to the Earth’s magnetic field, it is the low latitude of Hawai`i that made it very unlikely to find such decreases.
The IGY elicited a great deal of public interest which, to a large extent, was due to the planned launching for the first time in human history of an artificial Earth satellite. The planners of the IGY were very concerned about their ability to locate and track the satellite once it was launched. To accomplish the acquisition of the satellite, a volunteer citizen corps was established called operation MOONWATCH. For the precise tracking of the satellite, a worldwide network of twelve Super-Schmidt tracking cameras was envisioned. In both of these operations Hawai`i was in a position to fill a crucial gap in the vast Pacific.
In early 1957 I organized a MOONWATCH team made up of interested volunteers from the community. The base of operation was made at the Makapu`u Point Observatory because of its relative remoteness from city lights and access to electric power and telephone and other conveniences of the observatory. MOONWATCH telescopes were fabricated in the Physics shop and the MOONWATCH volunteers set up a row of sturdy pedestals on which to mount them. After numerous training sessions and many delays of satellite launchings, a satellite did finally appear in our skies, albeit, designated as a “sputnik”! And so the volunteers were finally rewarded. It is quite likely that the greatest payoff of the operation was the opportunity for citizens to participate in an active role in this exciting new era, rather than be passive bystanders