Cerro Tololo Inter-American Observatory

In 1959, German astronomer Jürgen Stock arrived in Santiago to look for the optimum site for an observatory, working on behalf of the Yerkes Observatory by the University of Chicago under Gerard Kuiper. He went to the semi-arid region of Coquimbo, South of the Atacama Desert, and climbed numerous mountains, carrying a Danjon telescope and an interferometer to determine visibility and accurately measure the wavelength of light. He did not have a barometer to do meteorological forecasting and learnt from muleteers to observe animal behavior, like condor accumulations, for weather changes. The site for the Inter-American Observatory on Mt. Cerro Tololo was identified by a team of scientists from Chile and the United States in 1959, and it was selected in 1962. Construction began in 1963 with Stock as the first director, and regular astronomical observations commenced in 1965. In 1974, construction of large buildings on Cerro Tololo ended with the completion of the Víctor Blanco Telescope, but smaller facilities have been built since then. Cerro Pachón is still under development, with two large telescopes (Gemini South and SOAR) inaugurated since 2000, and one in the final stages of construction as of 2023 (the Vera C. Rubin Observatory) == Organization ==

CTIO is one of two observatories managed by NOIRLab, the other being Kitt Peak National Observatory (KPNO) near Tucson, Arizona. NOIRLab is operated by the Association of Universities for Research in Astronomy (AURA), which owns the property around the two peaks in Chile and at the headquarters in La Serena, Chile. AURA also operates the Space Telescope Science Institute and the Gemini Observatory. The Gemini South Telescope located on Cerro Pachón is managed by AURA separately from CTIO for an international consortium. The National Science Foundation (NSF) is the funding agency for NOIRLab. The Small and Medium Research Telescope System (SMARTS) is a consortium formed in 2001 after NOAO, the predecessor to NOIRLab, announced it would no longer support anything smaller than two meters at CTIO. The member institutions of SMARTS now fund and manage observing time on four telescopes that fit that definition. Access has also been purchased by individual scientists. SMARTS contracts with NOIRLab to maintain the telescopes it controls at CTIO, and NOIRLab retains the right to 25% of the observing time, and Chilean scientists retain 10%. SMARTS began managing telescopes in 2003. CTIOPI is the Cerro Tololo Interamerican Observatory Parallax Investigation. It began in 1999 and uses two telescopes at Cerro Tololo, the SMARTS 1.5 m reflector and the SMARTS 0.9 m reflector. The purpose of CTIOPI is to discover nearby red, white, and brown dwarfs that lurk unidentified in the solar neighborhood. The goal is to discover 300 new southern star systems within 25 parsecs by determining trigonometric parallaxes accurate to 3 milliarcseconds. == Telescopes ==

• The Víctor M. Blanco Telescope (Blanco 4m) was completed in 1974 and is very similar to the Nicholas U. Mayall Telescope that was completed at KPNO in 1973. • Las Cumbres Observatory Global Telescope Network operates three and two telescopes at Cerro Tololo. Construction of the domes began in 2010 and was completed in 2011. The telescopes were installed and commissioned in 2012. • The Korean Microlensing Telescope Network (KMTNet), led by the Korea Astronomy and Space Science Institute (KASI), operates a telescope as part network of three telescopes dedicated to detecting exoplanets. The large CCD camera was installed on the telescope in September 2014. • The Evryscope is a multiple-aperture (22x telescopes) wide-field survey telescope taking approximately 5000 images per night. • The T80S telescope is operated by the Southern Photometric Local Universe Survey (S-PLUS) collaboration. Former telescopes • The Millimeter-wave Telescope is a Cassegrain reflector with a primary mirror made of machined aluminum, remachined in USA by Phelps-Dodge to a surface accuracy of lambda/400. It was installed at CTIO in 1982, and an identical telescope is located at the Center for Astrophysics Harvard & Smithsonian. It was used for spectrometric mapping-surveys of the distribution of carbon monoxide at a rest-wavelength of 2.6 millimeters in molecular clouds in the third and fourth quadrants of the Milky Way, and in the Magellanic Clouds while at CTIO. In 2009, it was moved to the Chilean National Astronomical Observatory's campus on Cerro Calán near Santiago. • A telescope was transported to the summit on mules in 1961 to perform site testing. It was later installed in a dome at CTIO in 1965. Its dome was used by the Millimeter-wave Telescope beginning in 1982. • A second telescope was installed in 1965. It was removed at some point and the building was used for UCAC. • A astrograph was used by the USNO CCD Astrograph Catalog (UCAC) project from 1998 to 2001. It was located in one of the 16-inch telescope domes. After surveying the southern sky, it was moved to United States Naval Observatory Flagstaff Station to complete its mission. • The Southern H-Alpha Sky Survey Atlas (SHASSA) operated at CTIO from 1997 to 2006 in its own small dome, which was dubbed El Enano ('the Dwarf') by the local staff. It was removed at the end of the project and donated to a school in La Serena. Future telescopes • The Vera C. Rubin Observatory (LSST) is a reflecting telescope under construction on Cerro Pachón. Construction began in 2011 and first light is expected in late 2015. It will be used for an astronomical survey similar to the 2MASS survey performed at CTIO. As with Gemini, the LSST will be managed separately from CTIO.. A smaller 1.4-meter support telescope for LSST will be built on an adjacent peak. Other scientific projects • The Andes Lidar Observatory is a National Science Foundation project to measure the upper atmosphere above the Andes which uses several passive optical instruments. == Discoveries ==

On the morning of Saturday, December 7, 2013, Luis González, a research assistant at the University of Chile, discovered what would later be confirmed as a supernova by José Maza, an astronomer at University of Chile and a researcher for CATA (Centro de Astrofísica y Tecnologías Afines or “Centre for Astrophysics and Related Technologies”). The supernova is the first discovery to be made by the CATA 500, a robotic telescope designed and operated by a Chilean team located in Santiago, approximately 500 kilometres to the south. It is part of the GLORIA project, which provides open access to astronomers from around the world to a network of remotely operated robotic telescopes. The new supernova lies in the galaxy ESO 365-G16, located 370 million light years from Earth, and has a mass eight times that of the Sun. Gomez's Hamburger, believed to be a young star surrounded by a protoplanetary disk, was discovered in 1985 on sky photographs obtained by Arturo Gomez, support technical staff at the Observatory. == See also ==