36 results
Changes in the Bathymetry and Volume of Glacial Lake Agassiz between 9200 and 7700 14C yr B.P.
- David W. Leverington, Jason D. Mann, James T. Teller
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- Quaternary Research / Volume 57 / Issue 2 / March 2002
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- 20 January 2017, pp. 244-252
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Computer reconstructions of the bathymetry of the lake were used to quantify variations in the size and form of Lake Agassiz during its final two phases (the Nipigon and Ojibway phases), between about 9200 and 7700 14C yr B.P. (ca. 10,300–8400 cal yr B.P.). New bathymetric models for four Nipigon Phase stages (corresponding to the McCauleyville, Hillsboro, Burnside, and The Pas strandlines) indicate that Lake Agassiz ranged between about 19,200 and 4600 km3 in volume and 254,000 and 151,000 km2 in areal extent at those times. A bathymetric model of the last (Ponton) stage of the lake, corresponding to the period in which Lake Agassiz was combined with glacial Lake Ojbway to the east, shows that Lake Agassiz–Ojibway was about 163,000 km3 in volume and 841,000 km2 in areal extent prior to the final release of lake waters into the Tyrrell Sea. During the Nipigon Phase, a number of catastrophic releases of water from Lake Agassiz occurred as more northerly (lower) outlets were made available by the retreating southern margin of the Laurentide Ice Sheet; we estimate that each of the four newly investigated Nipigon Phase releases involved water volumes of between 1600 and 2300 km3. The final release of Lake Agassiz waters into the Tyrrell Sea at about 7700 14C yr B.P. is estimated to have been about 163,000 km3 in volume.
Changes in the Bathymetry and Volume of Glacial Lake Agassiz Between 11,000 and 9300 14C yr B.P.
- David W. Leverington, Jason D. Mann, James T. Teller
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- Quaternary Research / Volume 54 / Issue 2 / September 2000
- Published online by Cambridge University Press:
- 20 January 2017, pp. 174-181
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The volume and surface area of glacial Lake Agassiz varied considerably during its 4000-year history. Computer models for seven stages of Lake Agassiz were used to quantify these variations over the lake's early history, between about 11,000 and 9300 14C yr B.P. (ca. 13,000 to 10,300 cal yr B.P.). Just after formation of the Herman strandlines (ca. 11,000 14C yr B.P.), the volume of Lake Agassiz appears to have decreased by >85% as a consequence of the abrupt rerouting of overflow to its eastern outlet from its southward routing into the Mississippi River basin. This drainage released about 9500 km3 of water into the North Atlantic Ocean via the Great Lakes and Gulf of St. Lawrence. Following closure of this eastern routing of overflow, the lake reached its maximum size at about 9400 14C yr B.P. with an area of >260,000 km2 and a volume of >22,700 km3. A second major reduction in volume occurred shortly after that, when its volume decreased >10% following the opening of the Kaiashk outlet to the east into the Great Lakes, and 2500–7000 km3 of water was released into the North Atlantic Ocean. These discharges may have affected ocean circulation and North Atlantic Deep Water production.
19 - Early Radio Observatories Away from the Australian–British Axis
- from Part 2 - Radio Observatories
- David Leverington
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- Observatories and Telescopes of Modern Times
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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.
22 - Further North and Central American Observatories
- from Part 2 - Radio Observatories
- David Leverington
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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.
1 - Palomar Mountain Observatory
- from Part 1 - Optical Observatories
- David Leverington
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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.
7 - European Southern Observatory
- from Part 1 - Optical Observatories
- David Leverington
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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.
16 - Australian Radio Observatories
- from Part 2 - Radio Observatories
- David Leverington
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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)
2 - The United States Optical Observatory
- from Part 1 - Optical Observatories
- David Leverington
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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.
Radio Observatory and Telescope Index
- David Leverington
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18 - Jodrell Bank
- from Part 2 - Radio Observatories
- David Leverington
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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.
Observatories and Telescopes of Modern Times
- Ground-Based Optical and Radio Astronomy Facilities since 1945
- David Leverington
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This volume gives an historical overview of the development of professional optical and radio observatories from 1945 to today. It covers the environment in which these facilities were developed by organisations in the United States, Europe and elsewhere, often led by larger-than-life individuals, as well as exploring the financial and political factors that both constrained and encouraged progress. As ever more expensive optical facilities were built, they exploited new technologies to significantly improve their performance: CCDs, active and adaptive optics, and spun honeycomb and segmented mirrors. The second half of this volume turns to the parallel history of radio astronomy facilities throughout the world, finishing with the ALMA observatory in Chile. This is the ground-based companion to the author's previous work on space astronomy, New Cosmic Horizons (2001). It is written for both technical and non-technical readers interested in the modern history of astronomy and its observational facilities.
10 - Mount Hopkins' Whipple Observatory and the MMT
- from Part 1 - Optical Observatories
- David Leverington
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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.
21 - Owens Valley and Mauna Kea
- from Part 2 - Radio Observatories
- David Leverington
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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.
General Index
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23 - Further European and Asian Radio Observatories
- from Part 2 - Radio Observatories
- David Leverington
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Stockert Observatory and the Effelsberg Radio Telescope
Germany was excluded from the development of radio astronomy in the crucial years immediately after the end of the Second World War as restrictions on radio research were not lifted until 1950. But even then there were still many more important calls on state funding to rebuild the country after the war. So there was no sudden explosion of radio astronomy research in Germany in the early 1950s to match that already underway in Australia, the UK and elsewhere.
But starting in 1952 Friedrich Becker and H. Strahl gave a number of lectures about radio astronomy in local government ministries in Düsseldorf, the state capital of Nordrhein-Westfalen.(1) This resulted in the idea of building a 25 m diameter fully steerable radio telescope which could also be used for radar research. Design studies were carried out by Metallwerk Friedrichshafen and Telefunken who had built the German Würzburg radar antennae during the war. Enthusiastic backing for the proposed project came from Telefunken's former chief engineer Leo Brandt who was then Secretary of State in the Ministry of Economics and Traffic in Nordrhein-Westfalen. With his support 1.2 million DM (about $300,000) was raised to pay for the project which was undertaken by a consortium of companies headed by Telefunken.
The basic requirement of this 25 m radio telescope was that it should be able to detect radio emissions at the 21 cm wavelength (1.4 GHz) of neutral hydrogen and shorter if possible. This meant that its dish should have a surface accurate to about ±5 mm. It was also expected that the dish, which would be supported by an altazimuth mount, would be pointed to an accuracy of 1 arcminute. Naturally, considering the pedigree of the main contractors involved, the actual design was based on that of the Second World War 7.5 m diameter Würzburg radar antennae. The surface panels were of 2 mm thick sheet aluminium with 10 mm square perforations to reduce wind resistence. As far as location of the telescope was concerned, its use for radar research required it to be built with a good view of the horizon.
6 - European Northern Observatory and Calar Alto
- from Part 1 - Optical Observatories
- David Leverington
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European Northern Observatory, Canary Islands
Night-time Telescopes on Tenerife
The Astronomer Royal for Scotland, Charles Piazzi Smyth, set up two small astronomical stations at high altitude on Tenerife in the Spanish Canary Islands in 1856. Although they were not there for very long, these observatories were the first to show the great advantage of observing at high altitude.(1) No one took much notice, however, and it was not until over fifty years later that Jean Mascart of the Paris Observatory suggested that an international astronomical observatory should be established on Mount Guajara on Tenerife. Discussions then started between the Spanish, French and German governments, but they were abandoned at the start of the First World War.
There was no progress with the idea of setting up an observatory at high altitude in the Canaries for a number of years. But astronomers observed a total solar eclipse from the Canaries in 1959. In the same year Spain founded the Observatorio del Teide at Izana, on Tenerife, at an altitude of 2,380 m (7,250 ft). A 30 cm (12 inch) French photopolarimeter was installed there in 1964 to study the zodiacal light, followed by a Spanish 25 cm heliographic telescope in 1969. The largest telescope at El Teide (now part of the European Northern Observatory) is the UK's 1.5 m Infrared Flux Collector (IRFC) that was built in 1971 as the prototype for the 3.8 m United Kingdom Infrared Telescope that was completed on Mauna Kea eight years later.
Site surveys carried out by JOSO (Joint Organization for Solar Observations) in the 1970s indicated that although El Teide on Tenerife was the better Canary Islands site for solar observations (see Solar telescopes later), the Roque de los Muchachos on La Palma was better for night-time observations. So although night-time telescopes continued to be built at El Teide (see Table 6.1), the largest such telescopes were built on La Palma (see Table 6.2).
15 - Solar Observatories
- from Part 1 - Optical Observatories
- David Leverington
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Climax Observatory and the Sacramento Peak Solar Observatory
Donald Menzel of Harvard College Observatory had been instrumental in establishing the solar observatory at Climax, Colorado, or more properly the Climax observing station of Harvard College Observatory, in 1940. Unfortunately it soon became clear to Menzel and Walter Roberts, a former student of Menzel and the station's superintendent, that this Climax station suffered from long periods of cloudiness, especially during the winter. Consequently they concluded that a second solar observatory should be built as soon as possible after the Second World War had ended.(1)
At about the same time H. H. (Hap) Arnold, the commanding general of the U S Army Air Forces (AAF), had asked his scientific advisor Theodore Von Karman to draw up a long-range research and development plan for the AAF after the war. Arnold had been particularly interested for some time in meteorology, especially as it affected the air force. So it was no great surprise to find that Von Karman included, in his proposed long-range plan, research into the influence of the Sun on the Earth's ionosphere and atmosphere. Arnold and the AAF were not only interested in the effect of the Sun on the ionosphere and radio communications, but also its effect on the upper atmosphere through which guided missiles and supersonic aircraft would travel.
After the war Menzel happened to meet Marcus O'Day of the AAF's Cambridge Field Station who had been given responsibility for upper atmospheric research using captured V2 rockets. During discussions O'Day told Menzel that he also had access to funding to set up a ground-based solar observatory. As a result O'Day mentioned that there was a possibility that the Air Force might be able to support his proposed solar observatory. This case for support would be significantly strengthened if a suitable location could be found on the Sacramento Mountain Range close to the White Sands Proving Grounds from which O'Day was planning to launch his V2s.
In the meantime, following a proposal from Menzel and Roberts, in 1946 the Climax observatory became an independent research institution in its own right.(2) Called the High Altitude Observatory (HAO) it was affiliated with Harvard University and the University of Colorado with Roberts as its first director.(3) Its headquarters were at Colorado's Boulder campus.
24 - ALMA and the South Pole
- from Part 2 - Radio Observatories
- David Leverington
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Summary
ALMA
As mentioned previously (see Section 20.8) the NRAO had been trying in the late 1970s to get funding for a new 25 m (82 ft) millimeter-wave radio telescope to be built on Mauna Kea, but this had been killed off in 1982 by the Astronomy Advisory Committee. However, in the same year, an internal NRAO proposal was made to build a VLA-type millimetre array of fifteen 10 m diameter dishes on 1 km long arms. The plan was to build it near the VLA(1) at an altitude of about 2,100 m (6,900 ft) on the Plains of San Augustin, New Mexico. A little later, higher sites were considered in Arizona and New Mexico to enable the telescope to operate down to a wavelength of at least 0.85 mm (frequency 350 GHz). Then in 1990 the NRAO proposed what was called the Millimeter Array (MMA) which was to consist of forty 8 m diameter dishes, with a total area of 2,000 m2, at a cost of at least $120 million.(2) It would operate in the wavelength range from 10 mm to 0.35 mm (frequencies 30 GHz to 850 GHz)(3) and be built on a site about 3 km in diameter at an altitude of about 2,500 m (8,200 ft) in Arizona. At this stage the NSF, the potential funding source, let it be known that they expected that any large project of this nature should involve a number of international partners. By the mid 1990s, the NRAO were considering much higher sites on Mauna Kea or on Llano de Chajnantor at an altitude of about 5,000 m (16,400 ft) in the Atacama Desert to enable the array to operate well into the submillimetre range.
In Japan, meanwhile, the Tokyo Astronomical Observatory had built the Nobeyama Millimeter Array in the 1980s (see Section 23.5) which consisted of a number of 10 m dishes operating down to 0.8 mm. They followed this with plans to build an array in northern Chile consisting of fifty 8 m or 10 m diameter dishes called the Large Millimeter and Submillimeter Array (LMSA) to operate down to 0.35 mm.
Part 2 - Radio Observatories
- David Leverington
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- Book:
- Observatories and Telescopes of Modern Times
- Published online:
- 15 December 2016
- Print publication:
- 24 November 2016, pp 261-262
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13 - Mount Graham International Optical Observatory
- from Part 1 - Optical Observatories
- David Leverington
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- Book:
- Observatories and Telescopes of Modern Times
- Published online:
- 15 December 2016
- Print publication:
- 24 November 2016, pp 238-243
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- Chapter
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Summary
Astronomers at the University of Arizona started planning in the early 1980s for an international observatory on the 10,700 ft (3,250 m) Mount Graham, the highest peak in the Pinaleno range, about 75 miles (120 km) from Tucson, Arizona. Mount Graham was chosen because of its low light pollution, low atmospheric water vapour, ease of access, and excellent seeing which was only a little worse than that on Mauna Kea. The planned telescopes included the 1.8 m Vatican Advanced Technology Telescope (VATT) of the Vatican Observatory, a submillimetre telescope (later called the Heinrich Hertz Submillimeter Telescope – see Section 23.6), and an optical-infrared binocular telescope, then called the Columbus Project, which consisted of two 8 m primary mirrors on a common mount.
For a time Mount Graham was also considered as a possible site for the National New Technology Telescope (NNTT, see Section 3.2). This was strongly advocated by the University of Arizona as they were hoping to supply its mirror. But Mauna Kea was eventually chosen in 1987 as its location after three years of site surveys, with Mount Graham as a backup.
Vatican Advanced Technology Telescope (VATT)
In the meantime the University of Arizona's Mirror Laboratory had spun-cast the 1.8 m, f/1.0 primary mirror blank for the VATT in 1985. In the same year construction work was also expected to begin on the VATT's new observatory building on Mount Graham, but environmental concerns over the mountain's red squirrels and its other sensitive habitats led to a series of delays.
The prospect of being able to build an astronomical observatory on Mount Graham received a major setback in June 1987 when the Mount Graham red squirrel was declared an endangered species. But it appeared as though the environmental impasse had been broken in October 1988 when university-sponsored legislation was passed by the United States Congress to allow the three planned telescopes to be built on the mountain without Forest Service approval. This legislation allowed the university to build four more telescopes, if the first three were found to have had a minimal impact on the red squirrel. But in March 1990, a Federal judge ordered a temporary halt to the observatory construction. Although this temporary injunction was overturned by the US Court of Appeals two months later, other potential legal problems had also arisen.