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Brief History of
THE CERRO TOLOLO INTER-AMERICAN OBSERVATORY

Dr. Víctor Blanco
February 1993

In 1960, there were only 10 astronomical observatories in the southern hemisphere compared to the 88 that operated north of the equator. None of the southern observatories was located in a site chosen carefully for atmospheric excellence and their telescopes could only collect 10% of the light collected by the northern ones.

Most astronomers recognized that this imbalance in the world-wide distribution of optical telescopes was especially objectionable because of the location in the southern skies of many singular astronomical objects. Such astrophysically unique objects of the southern sky as the Magellanic Clouds, the brightest globular clusters, and the clusters and nebulae-rich Carina-Centaurus Milky Way region, to name but a few, were inaccessible to many astronomers unless they were lucky enough to be invited to a southern observatory. Astronomical problems requiring the study of such objects and also of all-sky observations were often neglected or were very difficult to carry out.

It is no wonder that more than a century ago the leading observatories of the world, which were located either in Europe or in the United States, started sending so called "astronomical expeditions" to the southern hemisphere. More often than not Chile was the preferred country for these expeditions, especially those from the United States. One such expedition established in 1849 a small observatory on Cerro Santa Lucia in Santiago. This facility was transferred in 1852 to the Chilean "lnstituto Nacional” and eventually became Chile's National Observatory. The chief aim of that expedition was to measure the distance to planet Mars and to the sun by a triangulation method which required simultaneous observations from the United States and Chile. Symbolic of the future important role of Chile in the development of astronomy is the fact that the earth-sun distance then determined was in error by only 3.5%.

Another expedition which came in 1903 from the Lick Observatory erected at 0.92 reflecting telescope on Cerro San Cristobal, and for 25 years photographed over 10,000 stellar spectra. Measurements of the Doppler-shifts shown by these spectra and by a similar set of spectra for northern stars photographed from the United States, resulted in the first reliable determination of how the sun and its family of planets move among the stars. The telescope on San Cristobal is still in use by the "Universidad Católica de Chile."

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During another expedition, the spectra of stars in the Magellanic Clouds were photographed from Chuquicamata during 1922 and 1923. The results obtained by this expedition as well as by the one to Cerro San Cristobal are still standard reference material.

The very first initiative towards establishing in Chile the observatory that eventually was erected on Cerro Tololo was undertaken by U. of Chile Prof. Federico Rutlant who suggested to Drs. G.P. Kuiper and W.A. Hiltner of the Yerkes Observatory, University of Chicago, establishment of a "cooperative" observatory in Chile.

The earliest published AURA reference to what eventually became the Cerro Tololo Inter-American Observatory is found in the Annual Report of the Peak National Observatory for the period July 1, 1960 -June 30, 1961. The report described how, following Prof.  Rutlant’s initiative, site surveys had been initiated by Dr. Gerard P. Kuiper and placed under the direction of Dr. Jurgen Stock of the University of Chicago and the U. of Texas with the sponsorship of the U.S. Air Force, and with the cooperation of the University of Chile. Dr. Kuiper moved from the University of Chicago to the University of Arizona in 1960. The University of Chicago then requested AURA to take over this project. On June 30, 1960, urged by the National Science Foundation, the AURA Board of Directors agreed to take over this project under the sponsorship, during the initial year, of the U.S. Air Force and later, of the National Science Foundation. This was followed by an agreement between AURA and the U. of Chile for cooperation in the establishment of the Observatory. The role of the U. of Chile in the establishment of CTIO can not be overemphasized. The original idea for the observatory came from the U. of Chile, the site surveys were mostly manned by U. of Chile personnel, and the U. of Chile sponsored CTIO in obtaining from the Chilean Government the various duty free importation, and taxation free benefits that the observatory now enjoys.

By mid 1960, the site surveys were concentrating on various mountains in the southern fringes of the Atacama desert near the town of Vicuña in Chile. Their purpose was to locate a modern telescope in the southern hemisphere. During 1961, Cerro Tololo was found to be the best site in the Vicuña vicinity. In order to explore other possibilities the site survey had been, however, extended 240 kilometers northward into the desert and conditions on Cerro La Peineta near the town of Copiapó were also being investigated.

On November 23, 1962, the decision was made to locate the new observatory on Cerro Tololo and to call it the "Cerro Tololo Inter-American Observatory." Prior to that, CTIO was usually referred to by AURA officials as the "Chile Project." Before the selection of Tololo, in August 1961, a 0.41 m telescope had been hauled to the mountain top, on mule back, for the final site testing and was used part of the time for serious astronomical research by Dr. J. Stock, and by University of Chile astronomers, especially Prof. Hugo Moreno.

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The first construction efforts at CTIO were thus spent on building a primitive shelter for the 0.41 m telescope, laying a rudimentary road to a place called "El Zapallo” (i.e., "Squash") halfway to a watering hole named "Los Placeres" (i.e., "Pleasures") found on the way up to the mountain, and on improving the mule-trail to the mountain top. It is worth noting here that before these improvements, a typical trip from La Serena to Tololo started with a 3 hour taxi ride to Vicuña over a very narrow and winding road, followed by a 5 or 6 hour mule or horseback ride to Los Placeres with an overnight stay to recuperate from the long ride, and a final 2 to 4 hours ride - depending on one's riding ability - to the mountain top.

On November 25, 1962 AURA bought the property called "El Totoral” which includes close to 30,000 hectares with Cerro Tololo near its center. "El Totoral” means a place where Totora grass, a reed-like plant used for roofing, grows.  This grass is, however, rare in AURAS’s Totoral.   After deciding to purchase of El Totoral, AURA officials wanted to conclude the deal as soon as possible.  In order to locate the owner, Sr. Juan Orrego, the officials asked the help of the lntendente of the Province of Coquimbo within which La Serena, Vicuña, and El Totoral were located. The Intendente, in turn, solicited the help of the Vicuña chief of police. The request must have been a forceful one because the chief proceeded to send two policemen after Sr. Orrego and bring him to headquarters where he was later met by the AURA executives who flew in from Santiago.

The early years in the development of CTIO were recorded in diary form by Dr. Jurgen Stock. One may still savor those adventure-filled days by quoting Dr. Stock's picturesque description of the work that led to a flag raising in Los Placeres to commemorate AURA’s acquisition of El Totoral.

I quote:

"The lntendente of the Coquimbo Province had suggested an official flag hoisting on Tololo.  This was planned for Sunday, December 2nd, 1962 with the Governor of the Elqui Department and the Captain of the Police present. The only difficulty with this was the flag poles. The flags needed poles of at least 6m length. Arturo (Garrote, who worked at CTIO until 1980) told me that we had a special mula for that. So we cut two 7 m eucalyptus poles. I took the poles to El Zapallo in the truck while Arturo brought up the animals”.

"The poles were the only cargo we had, and it did not take long to put them on our  pole-mula, one on each side. One has to consider that a mule with the tail stretched out horizontally at one end and the tongue out at the other end is not much over two meters long, about one third the length of the cargo. However, there was no problem. In sharp curves the animal would walk back and forth a few times until the poles had made the turn. When it got stuck, usually by running the front end of the poles into a bush, it just waited for Arturo to help out. The trip to Los Placeres was without mishaps but of course rather slow."

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Dr. Stock was named CTIO’s first director in 1963, and served as such until early in 1966, he was succeeded by the writer in July, 1967, by Dr. Osmer in 1981 and Dr. Williams in 1986. During 1966 and early 1967 CTIO had several Acting Directors including Drs. Hoag, Edmonson, and Hiltner.

The conceptual design for the “modern southern hemisphere telescope” of the “Chile Project” was initiated at KPNO in 1963 and a 1.5m telescope was then envisioned. The telescope would have a special advanced optical design that would yield a large coma-free field on flat plates. The telescope would also be versatile, and have several foci.

CTIO’s first administrative office started operating in December 1961 at the Chilean National Observatory in Cerro Calán, Santiago. Soon after the selection of Tololo in 1962, an 8-hectare lot was acquired in La Serena next to the University and construction work was started on three houses and a headquarters building. The houses were completed in March 1965 and were occupied by an administrator, a scientific staff member, and a grounds-keeper. In the headquarters building one office was reserved for the scientists and 10 for the administrative staff.

When the first CTIO facilities in La Serena were to be built, AURA did not find it possible to interest any qualified construction company in tendering a reasonable bid. The decision was then made to do the construction with AURA-employed workers and AURA-owned machinery. Thus AURA in Chile became in effect something of a construction company. The successful completion of the early building program in La Serena led to the eventual construction by AURA of all of its infrastructure, including the monumental building that eventually housed the 4-meter telescope.

A first priority after AURA bought El Totoral property was the construction of a suitable road that would connect the mountain top with the road joining La Serena and Vicuña.  Some 38 kilometers of a primitive but passable road were laid out and on September, 1963 the first vehicle was driven to Tololo.  Road-opening ceremonies followed on December, 1963.  As time passed, however, it became obvious that this road was very inadequate and it had to be improved repeatedly during the next twelve years. As one drives up to Tololo today, many abandoned sections of the old road can still be seen, and if one looks closely one may also see, here and there, portions of the old mule-trail.

The topography of the Tololo summit was too irregular for the building programs that were envisioned in 1963 and it was decided to flatten the mountain top to a level 14 meters below the top. Between January and June, 1964, by blasting and bulldozing, Cerro Tololo was given what some AURA Board members referred to as a "crew cut."

In March, 1964 the AURA Board approved a 5-year master plan for the development of CTIO. In the contour maps then developed, one may notice a sharp drop-off on the north side of the mountain. This is believed by some to have led to the naming of mountain by the ancient Diaguitas Indians. Supposedly, “Tololo” means "in front of the abyss." Implementation of AURA’s master plan for CTIO was initiated with much activity. Since the planners were at KPNO headquarters in Tucson, Arizona and the builders were in Chile, rapid communications were essential. By February, 1964, the first radio messages were exchanged between KPNO and CTIO. To make this possible, the University of Chile let AURA use the wavelengths and call-letters assigned to it.

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Meanwhile, books for the CTIO library were being collected under the guidance of Dr. Helmut Abt of KPNO. By May 1964 the first 800 books were acquired for what eventually became a first-rate astronomical library with over 15,000 bound volumes. Among these are the Astrophysical Journals from Volume 1, 1895, to Volume 109, 1949, formerly owned by Otto Struve, and many others books and journals that had belonged to other illustrious astronomers.

Simultaneously, the first (64 KVA) electricity generator was purchased and sent to Chile. Eventually, CTIO would be connected to the Chilean commercial electric network but would have as standby backups a 625 KVA and two 187 KVA generators. The original generator acquired in 1964 was later installed in La Serena to be used in case of commercial power failure.

A reliable water source also had to be developed. At about 1 km below the summit, two natural springs in Los Placeres provided a convenient source. At the time AURA bought El Totoral, 15 families lived on the grounds and subsisted by raising goats. Principal among these was the Ramos family and they had their house in Los Placeres. The head of the family, Don Rogelio, was very gracious and helpful in all the pioneering site-surveys. In order to keep the water source clean, Don Rogelio's family and his animals had to be moved downstream a considerable distance. Moving Don Rogelio and family created a difficult human-relations problem for AURA. This was resolved by Dr. Stock by hiring Don Rogelio as manager of the El Totoral excluding the Tololo summit facilities. Our relations with Don Rolegio were later strained when he converted his house into a bar-discotheque. This resulted in an unusual amount of night-time traffic on the Tololo road, a development that was promptly terminated. In regard to the goat-herding families within the AURA holdings, nominal yearly rental charges were imposed. This measure prevented the families from becoming owners of the land they occupied through squatters' rights. Thus, among AURA's diversified activities in Chile one should include those of a landlord.

By June, 1964, water was being pumped from Los Placeres to Cerro Tololo.  The water delivery system was later improved, and by December 1965 a 50,000 gallon storage tank had been built near the mountain summit and the pumping station had automatic filtering and chlorinating facilities. Unfortunately, the springs at Los Placeres dried up and CTIO had to develop another water source in 1975.  At that time two more 50,000 gallon tanks were added for storage at the summit. Meanwhile, we had to truck water from the Elqui River up to the Placeres springs.

Besides serving as landlord and builder, another sideline that AURA entered into with the purchase of El Totoral was mining. In Chile, the land owner does not have mining rights unless special mining claims are made and certain fees paid to the Government. In order to protect the observatory from such claims and possible active mining of iron, manganese, copper, or gold -- all of which are rumored to be found in El Totoral -- AURA staked its own mining claims and thus became, at least in name, a mining company. As the years went by the mining fees, which originally were nominal, increased so much that AURA sought special legislation to free itself from them. In 1977 at the request of CTlO and the gracious backing of Srta. Malena Saavedra, legal counsel at the U.S. Embassy (and later Chilean Cultural Attache at the United Nations), Chilean President Pinochet signed a decree declaring the CTlO lands a "Privileged Scientific Sanctuary," where mining is prohibited without the express consent of the Chilean President.

Prior evidence of the support by the Chilean Government of AURA's activities in Chile was related to importation and to freedom from taxation for AURA's non-Chilean employees. AURA's importation into Chile of the instruments and building materials required in developing CTlO were initially handled by the University of Chile which generously made it possible for AURA to use its duty-free franchises. In January 1963, with University of Chile sponsorship, the Chilean Congress passed, and President Alessandri signed into law, a decree that permitted direct duty-free importations by AURA. Furthermore, in 1968 the Chilean Government, then headed by President Frei, extended to AURA the rights and privileges enjoyed by foreign employees of the United Nations branch office in Santiago. These included freedom from Chilean income taxes. Even in the convulsed years of 1972 and 1973 CTlO received, by order of President Allende, preferred treatment in the distribution of food.

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In 1963, the National Science Foundation approved funding a 0.92m telescope for CTIO. Excavations for the buildings to house this and the 1.5m telescope, which had been funded by the U.S. Air Force, were started within weeks of the leveling of the summit in 1964. Also started then was the permanent housing for the 0.41m telescope that had been temporarily mounted during the site survey of Tololo in 1961 and for a second site-survey telescope, of similar size and design, that was received from KPNO.   The old site-survey instruments turned out to be worn out and costly to maintain and, in a few years had to be replaced by new ones of the same size.

The master plan for the Tololo summit, prepared in March 1964, showed what CTlO was expected eventually to look like. Buildings for telescopes with the following apertures are shown: 0.41m, 0.92m, a0.81/1.2m Schmidt, and even a 4m telescope!  Thus it was clear as early as 1964 that, if funds became available, CTlO -- under AURA's guidance -- would become the largest observatory in the southern hemisphere. The ancillary buildings envisioned at the time for Tololo included an administrative office building, a 6-bedroom dormitory with dining hall, a director's residence, a mountain superintendent residence, 8 smaller houses for service personnel, an instrument shop, a power house, a warehouse, and a vehicle maintenance shop. It is not clear where the staff engineers and scientists were going to have office space or even reside, except for the director. As it turned out the residences of the director and mountain superintendent as well as 3 of the 8 houses for the service personnel were eliminated from future planning in 1967. Five of these houses had been completed in 1966 but no "service personnel" were found willing to bring families to live on the mountain. In order to make work space available for the engineers and scientists, the Tololo administrative office building, by the time it was finished in October 1967, was converted into a so-called "scientific office building". Eventually, when scientific and engineering offices were made available elsewhere, this building would be assigned to the CTlO logistics-support group.

The "instrument shop" in the 1964 master plan was completed in 1967 and immediately converted into an electronic shop. In 1974 this building was converted into a visitors center, and more recently, again, into an electronic shop. The 6-bedroom dormitory and dining hall was expanded into a 12 bedroom one, and was first occupied in October 1967. The permanent powerhouse, warehouse, and vehicle maintenance shops envisioned in the 1964 master-plan were never built; the temporary structures erected for these facilities in 1963 to satisfy early CTlO needs are still in service.

In regard to the telescopes, the need for a Schmidt-type telescope at CTlO was satisfied by an agreement concluded in 1966 by AURA and the University of Michigan to transfer the Curtis telescope to CTlO on a 10-year loan basis. Ironically, Dr. Curtis had visited the area interior to La Serena early in the century and decided the entire region not to be suitable for astronomical observations. The loan of the Curtis telescope was extended by 25 years in 1975. A building for this telescope was completed early in 1967 and the telescope was installed and first used in April of that year. Meanwhile, permanent buildings for the two previously mentioned 0.41m telescopes were completed in 1965 and soon thereafter these telescopes began regular operations. The buildings for the 0.92m and 1.5m  telescopes were completed early in 1967. A 0.92m telescope acquired from the Boller and Chivens Co. was installed outdoors in March 1967 and used by Dr. W.A. Hiltner, who was then Acting CTlO Director; it was then moved to its permanent building in May. The 1.5m telescope, whose mounting was built by the Westinghouse Co., was installed in October 1967 and first light was seen through it on the night of November 6, 1967.

The 1.5m telescope had to be ready on that date since the official inauguration of CTlO was scheduled for the next day. The inauguration ceremony was attended by NSF and AURA officials, by a delegation of U.S. Congressmen, by the President of Chile, Sr. Eduardo Frei Montalva, and by some 100 guests. Even though the timely completion of the telescope proved to be a very difficult task, the inauguration took place on schedule. One may add here that late in 1966, at the suggestion of Dr. Leo Goldberg, then at Harvard University, the Ford Foundation decided to donate 5-million dollars on a matching-fund basis for the fabrication of a southern hemisphere 4-meter telescope similar in design to the one then being planned for KPNO.

The U.S. Congress provided an equal amount of money to the National Science Foundation and agreed to provide funds for long-range operations. On April 14, 1967,

U.S. President Johnson and Chilean President Frei jointly announced that the telescope would be installed on Tololo.  Thus the future of CTlO as a truly major observatory was assured. This gave much importance to the November 7, 1967 inauguration as the guests could be shown the site of the future big telescope and told what could be expected from it.

Soon after the inauguration the decision was made to locate in the La Serena holdings all of the CTlO facilities that were not needed on the mountain top. Therefore, plans were initiated to relocate the observatory's instrument shop, the main electronic and mechanical engineering facilities, the library, the receiving warehouse, the vehicle maintenance shop, and a computing center. At this planning stage, adequate offices were at last envisioned for the engineering and scientific staff. On Tololo were to be kept the relatively small electronic, instrument, and machine shop facilities required for quick maintenance of telescopes and vehicles, and also a storage warehouse.

A word should be said here about the precautions taken by AURA to make all its buildings as safe as possible from earthquake damage. The so-called "California building code" was adopted very early.  This code calls for substantially more rigid construction than was then required by Chilean law. In the case of the 4m telescope building that would eventually be raised, AURA went even further. Computer-modelling of this building made it possible to strengthen the building beyond the requirements of the California code. In theory, this building is supposed to stand even a force 9 earthquake.

The need to expand the La Serena facilities led to the acquisition of additional grounds contiguous to the 8 hectares acquired in 1963. A 1965 acquisition was a hectare lot with a residence that was later refurbished and occupied by several Acting CTIO Directors during 1966. Eventually this house was to be used until 1987 as a school to serve the growing number of children of the U.S. engineers and scientists as well as of ESO staff members and various Chilean families. This should eventually become the International School and now has its own campus and over 500 students. Another land purchase in La Serena was made in 1968 when 8 additional hectares were added. Eventually, 19 prefabricated houses and apartments and also a 9-bedroom motel-type building with lounge were imported from the U.S. and erected on the newly acquired acreage. Also two additional houses were built on previously purchased grounds. For recreational purposes, a tennis court, an indoor swimming pool and a squash court were eventually added. These recreational facilities were built with AURA corporation funds.

The main construction effort at CTlO in the year following the November 1967 inauguration was related to the 4m telescope. In the early long-range planning, space on the southern part of the Tololo summit was reserved for such a telescope. This particular location would put any large building located there under the south celestial pole as seen from the other telescopes. The limited area on the Tololo summit called for this kind of careful location of telescopes in order to minimize obstructions in the fields of view. The excavation for the 4m telescope building started in December 1967. The "AURA Construction Company" supervised by Srs. Stuart Hurdle and José Guarini tackled this job and successfully completed it in late 1972. The "topping" of the arch girders that would support the rotating 475-ton dome took place on September 4, 1969. According to Chilean tradition the last section of the arch-guiders, located 43 meters above ground level, had national flags attached. The occasion was followed by a memorable barbecue for the 175 workers then employed in the construction.

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Meanwhile, a 4m Cervit mirror blank had been cast in June, 1969 by the Illinois Co. of Toledo, Ohio and was being polished in the KPNO Optical shop. Although a 150-inch blank had been ordered, expansion of the Cervit-casting moulds resulted in the delivery of a 158-inch blank, i.e., exactly 4.013m.   In order to take advantage of the additional inches, the telescope tube was enlarged during its design stage. The CTIO 4m telescope mounting and a similar one for KPNO were constructed by Western Gear Corp. near Seattle, Washington. Engineer Lawrence Randall from KPNO, served as the in­house coordinator of the development work for the CTlO and KPNO 4m telescopes. Most of the telescope components arrived in the port of Coquimbo on June 1, 1973 in 86 boxes weighing a total of about 500 tons. Their transport to the Tololo summit was a memorable undertaking since parts of the shipment were very large. An underpass near Coquimbo had to be by-passed by an AURA-built road for the largest boxes in the shipment.

Erection of the telescope mounting was started on June 24, 1973. This was accomplished by a team of fewer than 10 individuals headed by Alan Bird a mechanic who had observed the erection of the KPNO 4m telescope.  Bird’s work was supervised from KPNO by Engineer Anthony Abrahams. The mirror arrived on Tololo in September 1974, and in November 8 of that year an informal prime focus "first-light" ceremony was held. Fine tuning of the telescope and the addition of the Cassegrain secondary were completed by November 1975 and the first visiting astronomers started observing with this telescope in January 1976.

Meanwhile, in 1969, AURA built the housing for a 0.6m telescope that the Lowell Observatory acquired for planetary observations from Tololo.  This telescope became AURA property five years later. In 1974 Yale University agreed to lend CTIO its 1m telescope and this was also put into operation in an AURA-built dome within a year.

By the end of 1975, after 13 years had passed since the decision to develop CTIO, AURA had put into operation eight telescopes including the one that still is the southern hemisphere's largest. This telescope alone took only 7 years from the time its funding became available until it first saw light on the night of September 25, 1974. These were indeed proud achievements especially if one considers the complex supporting infrastructure that the telescopes require in order to operate effectively at a remote location. Seventeen years have passed since the CTIO 4m telescope started operations. No major additional observing facilities have been built since then. Now that the possibility of building much larger telescopes is under consideration, it is hoped that AURA can offer the U.S.-astronomical community such a telescope in the southern hemisphere in the near future.

Victor M. Blanco
February 1993

N.B.: The CTIO 4m telescope was dedicated to Víctor M. Blanco on Septyember 8, 1995, and is now known as "the Blanco 4m"

 



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