The Soviet Union

The possibility of using radio to determine the distance of the Moon from Earth had been seriously considered by the Soviet radio physicists Leonid Mandel'shtam and Nikolai Papaleski as long ago as 1925, before accepting that it was not possible with the equipment available at that time.(1) However in 1943 they revisited the situation and concluded that radar observations of the Moon were then feasible. But researchers in the USA and Hungary were the first to succeed in making them three years later.

Papaleski had also considered the possibility of carrying out radar observations of the Sun and around the end of 1945 he asked Vitaly Ginzburg, of the P. N. Lebedev Physical Institute (LPI), to theoretically analyse the reflection of radio waves by the Sun. In the following year Ginzburg concluded from his subsequent analysis that radio waves from Earth would not reach the Sun's photosphere as they would be absorbed by either its chromosphere or corona.(2) Simultaneously and independently Iosif Shklovskii, of the Sternberg Astronomical Institute of Moscow State University, showed that solar thermal radiation in the metre waveband, discovered by the British army during the war, could not be emitted by the solar photosphere or chromosphere but must be emitted by the solar corona.(3) Also independently, in Australia David Martyn concluded in the same year that the solar emission measured by Joe Pawsey in the metre waveband must be coming from high in the solar corona as the corona would be opaque at those wavelengths, so it could not be coming from lower down in the solar atmosphere (see Section 16.1). These theoretical conclusions of Ginzburg, Shklovskii and Martyn were proved to be correct in the following year by a Soviet expedition led by A. A. Mikhailov and Semion Khaikin to observe a total solar eclipse in Brazil. The expedition found that the intensity of radio emission at a wavelength of 1.5 m (frequency 200 MHz) was, at totality, still about 30% of its level out of eclipse.

On his return Khaikin submitted a proposal to study radio wave propagation in the Earth's atmosphere using extraterrestrial sources, such as the Sun, Moon and other discrete radio sources covering the wavelength range from 3 m to 3 cm. This information was required by the military for the radio navigation of rockets,(4) and consequently the proposal was rapidly approved.

US Naval Research Laboratory

Just after the end of the Second World War John Hagan, the head of the Centimeter-Wave Research Branch of the US Naval Research Laboratory (NRL), was looking for a new field of research in which to use his branch's experience. As a result he hit on the idea of observing astronomical sources of radio emission. Consequently Hagen and his deputy, Fred Haddock, decided to observe the Sun, not only because of its effect on the Earth's atmosphere, but because it was probably the only astronomical source observable with their type of equipment.

For their first solar observations Hagen and Haddock used parabolic antennae up to 10 ft (3 m) in diameter with receivers operating at wavelengths of 8.5 mm, 3.2 cm and 9.4 cm (frequencies of 35, 9.4 and 3.2 GHz respectively). Then in 1947 they went further and used an 8 ft diameter antenna to observe a total solar eclipse at a wavelength of 3.2 cm from on board ship in the South Atlantic. As a result they were able to conclude that the Sun, at this wavelength, was only slightly larger than the optical Sun.(1)

Unfortunately Hagen and Haddock's equipment only enabled them to observe the emission from the Sun as a whole as it did not have enough resolution to locate the exact sources of radio emission. It was clear that to locate these sources they would need a much larger dish. And if they managed to procure one they may also be able to observe other cosmic sources, as well as detecting thermal radio emission from the planets. So in the late 1940s Hagen and Haddock managed to persuade the US Navy to provide $100,000 for its purchase and, as a result, they were able to acquire a 50 ft (15 m) parabolic reflector from the Collins Radio Company designed by Ned Ashton of the University of Iowa.

This 50 ft NRL dish was made of 30 aluminium sector castings which had been bolted together. The surface was then machined to its parabolic shape to enable it to be used at wavelengths as low as 1 cm.

The 200 inch (5.1 m) Hale Telescope

The early twentieth century had seen the emergence of the United States as the world leader in the construction of large optical telescopes. For example, two large solar telescopes had been built on Mount Wilson, California before the First World War. In addition, George W. Ritchey had also completed a 60 inch (1.5 m) reflector at the same observatory in 1908, and nine years later Ritchey and W. L. Kinney had completed the 100 inch (2.5 m) Hooker reflector there. As a result by the early 1920s Mount Wilson was also the premier observatory in the world.

No sooner had the 100 inch telescope been completed than George Ellery Hale, the director of the Mount Wilson Observatory, began to consider building an even larger instrument.(1) He mentioned his ideas to Francis Pease, who had recently joined the staff on Mount Wilson. By 1921 Pease, who by then had outlined the design for a 300 inch (7.5 m), was convinced that a 100 ft (30 m) telescope was feasible. But Hale was much more cautious, partly because of the difficulties that he had already experienced with building the 100 inch, and partly because of the difficulty he anticipated of raising the money to build such an enormous telescope. In fact, as he recognised, the time was not ripe for raising finances for even a 300 inch.

Nevertheless, Pease continued with designing his 300 inch. Then in 1926 he and Walter Adams took H. J. Thorkelson of the General Education Board of the Rockefeller Foundation on a tour of the Mount Wilson Observatory. During the tour, Pease showed him his design of the 300 inch. This design impressed Thorkelson so much that he mentioned it to Wickliffe Rose of the Rockefeller Foundation's International Education Board shortly afterwards.

Two years later Hale wrote an article for Harper's Magazine on ‘The Possibilities of Large Telescopes’ in which he outlined their importance. He also floated the idea of finding a donor to back the financing of a new large telescope, following on the path already trodden by Messrs Lick, Yerkes, Hooker and Carnegie in funding telescopes.

La Silla

European Southern Observatory's Early Telescopes

After the Second World War the most immediate priority in western Europe was to feed and house its people aided by the American Marshall Plan. Once that problem had largely been solved these western European countries began to consider how to ensure that such a European conflict could not happen again. One way of doing this was to work together in joint ventures. On the scientific side the first such initiative was in the field of nuclear physics which eventually resulted in the establishment of CERN in 1953.(1)

In the same year Walter Baade of the Mount Wilson and Palomar Observatories had been invited by Jan Oort to spend two months at the Leiden Observatory. During his visit Baade suggested that it would be a good idea if European astronomers considered establishing a joint European observatory. At that time the largest optical telescopes were in the northern hemisphere so it would be best if the suggested new observatory were built in southerly latitudes. A southern observatory would also be beneficial as the Magellanic Clouds and the central region of the Milky Way were best observed from well south of the equator. Baade suggested that the observatory's main instruments should be a 120 inch (3 m) reflector similar to that of the Lick Observatory and a 48 inch (1.2 m) Schmidt like that on Mount Palomar (see Section 1.2).(2) Using these existing designs as a basis should enable the European versions to be built more quickly and cheaply than if the telescopes had to be designed from scratch. Baade's idea was discussed shortly afterwards by a group of European astronomers who had gathered at Groningen, in the Netherlands, in June 1953 for a conference on galactic research. The meeting concluded that a meridian circle should be added to Baade's proposed instrument complement to undertake much-needed astrometric work in the southern hemisphere.

At the time South Africa was the envisaged location of the observatory in view of its known good observational conditions and the fact that a number of European countries already owned or used observational facilities there.

Early Australian Radio Astronomy

Solar Observations

The Australian Radiophysics Laboratory was created at Sydney in 1939 as a secret branch of the Council for Scientific and Industrial Research (CSIR). It was to undertake radar research and development during the Second World War in collaboration with British laboratories and the Australian military.(1) The laboratory was highly successful, but as the war was coming to an end in 1945 the Australian government began to consider how its role should be changed. To assist in the decision Edward G. (Taffy) Bowen, who was soon to take over as the head of the reconstituted Radiophysics Laboratory, assembled a series of papers for a meeting of the CSIR Council in July of that year. These resulted in a decision to concentrate future research in three areas, namely radio, vacuum, and rain and cloud physics. Bowen was to lead the rain and cloud physics group whilst Joe Pawsey, who had studied under John Ratcliffe at Cambridge in the 1930s, led the radio group. In October 1945, the radio group began to study the effect of the Sun on radio communications. This followed receipt of a report that a New Zealand military radar station on Norfolk Island had detected noise at 200 MHz (wavelength λ 1.5 m) that appeared to be connected with the Sun.

To study the Sun, Pawsey, Ruby Payne-Scott and Lindsay McCready initially used a Royal Australian Air Force wartime radar antenna on the coast at Collaroy 400 ft (120 m) above the sea near Sydney. It consisted of 40 half-wave dipoles operating at 200 MHz. After only three weeks of data they concluded that there was a close correlation between the total area of the Sun covered by sunspots and the magnitude of the radio noise which had varied by a factor of 30. Unfortunately the antenna could not be used to track the source in altitude but measurements of the noise along the horizon at sunrise and sunset clearly showed that it was associated with the Sun.(2)

Introduction

Although the Palomar Observatory had been very successful after the completion of its main instruments in the late 1940s, its existence had only exacerbated an underlying problem in the organisation of astronomy in the United States. This was because at that time the vast majority of telescopes were already owned by a limited number of prestigious universities or observatories. These had been paid for by private benefactors and their use had been generally limited to members of these institutions. As a result, astronomers at less wealthy universities had only access to instruments of more limited performance. There was no tradition of publicly funded observatories in the United States at that time, unlike that of many European countries.

The first major collaboration between two American universities in the provision of an optical observatory was instituted in 1932, when it was agreed that the new McDonald Observatory would be the joint responsibility of the universities of Texas and Chicago. Then in 1940 Otto Struve, McDonald's director, published an article ‘Cooperation in Astronomy’ in Scientific Monthly.(1) In this, he suggested setting up a collaborative observatory between a larger number of astronomical institutions. This would have provided the wider access required, although Struve was assuming, at the time, that the initial finance would be provided by a private benefactor, in this case either the Carnegie Institution or the Rockefeller Foundation. Unfortunately, this project had to be put on hold at the time because of the imminent involvement of the United States in the Second World War.

The Second World War saw a turning point in the funding of technology in general by the United States government. In both the United States and Europe large sums of money were spent on nuclear, radio and radar research, and in Germany, in particular, on the development of rockets like the V2. All of this was to have a major effect on the development of astronomy in the United States and elsewhere after the war. In the United States, in particular, it also had the effect of generating much more centralised government funding for all types of scientific research, both civil and military.

From Radar to Radio Astronomy

Bernard Lovell had begun his investigations into cosmic rays in 1937 at the University of Manchester in the UK where P.M.S. (Patrick) Blackett was professor of physics.(1) But two years later, at the outbreak of the Second World War, Lovell was posted to an operational radar station which was assigned to track enemy aircraft. Shortly after arriving he noticed that, in addition to observing reflections from aircraft, there were numerous short-lived echoes which the radar operators attributed to the ionosphere. Lovell wondered what the cause of these signals could be, and suggested to Blackett that they may be being produced by radar reflections from the ionisation produced by highly energetic cosmic ray showers. But the exigencies of war stopped him from investigating them further.

Lovell returned to Manchester immediately the war with the intension of investigating the transient radar echoes. To do this he borrowed an army 4.2 m wavelength mobile radar with a Yagi antenna that had been used to detect V2 rockets.(2) He immediately set up the system outside the university's physics department in the middle of Manchester. There, unfortunately, any radar signals were completely overwhelmed by interference from electric trams that ran nearby. Clearly a quiet location outside the city was required. Lovell considered a number of options before settling on a plot of land at Jodrell Bank about 25 miles (40 km) south of Manchester that belonged to the university's Botanical Gardens. He was given permission to locate his equipment there for a few weeks in December 1945.

Amazingly, Lovell observed several short-lived radar echoes from various distances on his first day of observations.(3) This was repeated on the next two days but, instead of the expected one or two echoes per day, he was detecting several per hour. This led Blackett to wonder whether Lovell was really detecting echoes caused by cosmic ray ionization or whether the echoes were caused by some other effect. So he suggested that Lovell should go to see Stanley Hey, who had experience with using the V2 detection equipment during the war, as he must also have detected these short-lived signals.

In the mid 1960s the Smithsonian Astrophysical Observatory (SAO) decided to move their satellite tracking station from White Sands to a better observing site at higher altitude and to make this new site the location for an astronomical observatory.(1) Fred Whipple, the director of the SAO, began to investigate possible locations and settled on the Tucson area in southern Arizona as the most suitable. There he considered three possible sites, namely Kitt Peak, Mount Lemmon, and Mount Hopkins. He rejected Kitt Peak because of its relatively low altitude and potential light pollution. Mount Lemmon was the highest peak, and so should be the best for infrared observations. But Mount Lemmon was only 16 miles (25 km) from Tucson and was already suffering from light pollution. So Whipple chose Mount Hopkins in the Coronado National Forest, about 35 miles (55 km) from Tucson, as the site for the new SAO observatory.

The SAO began to build their new observatory in 1966 on a 7,600 to 7,800 ft (2,320 to 2,380 m) high ridge on Mount Hopkins, leaving the 8,590 ft (2,620 m) summit for the construction of a large optical telescope later.(2) The new observatory initially included a laser and f/1.0 Baker-Nunn camera for satellite range-finding and tracking, and a 10 m diameter optical reflector for gamma-ray astronomy. Then in 1969 the SAO built a 60 inch (1.5 m) telescope on the ridge, to be used for photoelectric spectrophotometry. It was named after Carlton W. Tillinghast, a Smithsonian administrator who died in 1969 at the age of 36.

Whilst the 60 inch was being constructed, Fred Whipple and colleagues investigated possible designs for the SAO's projected large optical telescope. At first they considered building a telescope with a fixed, large, spherical segmented primary mirror, similar to one proposed by Aden Meinel when he had been at Yerkes in 1953 as the optical equivalent of the Arecibo radio dish.(3) But they rejected this as the reflecting area would continuously change during an observation making the interpretation of infrared observations difficult.

At about the same time Frank Low of the University of Arizona's Lunar and Planetary Laboratory (LPL) had been developing observational techniques to detect faint objects in the infrared with a 1.5 m telescope.

Owens Valley Radio Observatory

Edward G. (Taffy) Bowen, head of the Radiophysics Laboratory in Australia, paid a visit to some old wartime friends during a visit to the United States in 1951. These included Lee DuBridge, the president of Caltech, Robert Bacher, head of the physics department at Caltech, Vannevar Bush, president of the Carnegie Institution in Washington, and Alfred Loomis, a trustee of both the Carnegie Corporation and the Rockefeller Foundation.(1) His discussions with these luminaries of America's scientific establishment tended to focus on the tremendous advances in radio astronomy in Australia and the relatively poor situation of radio astronomy in the United States. So in December 1951 Bacher asked Bowen if he would produce a draft specification for a suitable telescope to get the USA back in the game, whilst shortly afterwards DuBridge asked Bowen to outline the sort of instruments that would be required to build the radio equivalent of the superb optical observatories on Mount Wilson and Palomar Mountain. DuBridge wanted Bowen to be the director of the radio observatory with John Bolton as his deputy. But at this stage Bowen was non-committal about his future as he was also interested in building a large radio telescope in Australia.

In August 1952 Bowen wrote to Vannevar Bush to ask whether Carnegie would consider funding both the proposed Caltech radio telescope and a similar instrument in the southern hemisphere as a collaborative development. This eventually resulted in the trustees of the Carnegie Corporation approving funding in May 1954 for what was to become the Parkes Radio Telescope in Australia (see Section 16.2). In the meantime, as mentioned in the previous chapter, an interdisciplinary conference had been held in Washington, DC in January 1954, jointly sponsored by the NSF, Caltech and the Carnegie Institution, to discuss the state of radio astronomy in the USA and what to do about it. This eventually resulted in the NSF funding the National Radio Astronomy Observatory, whilst Caltech decided to go it alone and build their own observatory which was largely funded in the early years by the US Office of Naval Research.