Llano de Chajnantor Observatory is the name for a group of
astronomicalobservatories located at an altitude of over 4,800 m (15,700 ft) in the
Atacama Desert of northern
Chile. The site is in the
Antofagasta Region approximately 50 kilometres (31 mi) east of the town of
San Pedro de Atacama. The exceptionally
arid climate of the area is inhospitable to humans, but creates an excellent location for millimeter,
submillimeter, and mid-infrared astronomy.[1] This is because
water vapour absorbs and
attenuates submillimetre radiation. Llano de Chajnantor is home to the largest and most expensive astronomical
telescope project in the world, the
Atacama Large Millimeter Array (ALMA). Llano de Chajnantor and the surrounding area has been designated as the Chajnantor Science Reserve (Spanish: Reserva Científica de Chajnantor) by the government of Chile.[2]
Site description
The Llano de Chajnantor is located on the western side of the
Puna de Atacama, which is another name for the southern part of the
Altiplano. The main ridge of the
Andes is over 200 kilometres (120 mi) to the east, well into
Argentina. The
Salar de Atacama basin borders the Puna de Atacama to the west, which in turn is bordered by the
Cordillera Domeyko. The western side of the Puna de Atacama is dotted with the volcanoes of the Central Volcanic Zone of the
Andean Volcanic Belt. The Llano de Chajnantor site itself is bounded by volcanic peaks of the
Purico Complex, which have been active in the
Holocene but have not erupted in historic times.[3] Cerro Chajnantor is to the north, Cerro El Chascón to the east, and smaller peaks to the south and west. The Pampa la Bola lies to the northeast, north of Cerro El Chascón and east of Cerro Chajnantor. Llano de Chajnantor has an average elevation of 5,000 m (16,000 ft), while Pampa la Bola averages 4,800 m (15,700 ft). The thin atmosphere makes work difficult for humans, so much of the activity for ALMA will be conducted at a
base camp in the Salar de Atacama basin at approximately 2,900 m (9,500 ft) in elevation.
The
University of Tokyo Atacama Observatory (TAO) is a 6.5 m (21 ft) optical and infrared telescope under construction (as of 2019) on Cerro Chajnantor, which is immediately north of Llano de Chajnantor. A test facility, the miniTAO, with a 1.0 m (3.3 ft) telescope was completed in 2009. It is currently the
highest permanent astronomical observatory in the world.[12]
The
Cerro Chajnantor Atacama Telescope (CCAT) is a proposed 25 m (82 ft)
submillimetre radio telescope which will be located on Cerro Chajnantor near the TAO. Originally called the Cornell Caltech Atacama Telescope earlier in the development process, it is now referred to on the project's website by the CCAT acronym. Completion was at one time expected in 2020.[13] The CCAT project has had trouble finding funding, and construction has not began as of 2019. The scientific collaboration has decided to build a pathfinder facility, CCAT-prime (CCAT-p), before pursuing the full CCAT. CCAT-p will be a similar type of telescope at CCAT, but much smaller, with 6 metre diameter. CCAT-p started construction in 2017 (fabrication started in late 2018) and first light is expected 2021.
The
QU Imaging Experiment (QUIET) telescope was a three-element radio telescope array designed to measure the
polarization of the
cosmic microwave background radiation. The telescopes were custom-designed of an unusual Mizuguchi-Dragone design fitted with highly sensitive
bolometers. The project, led by the
University of Chicago, was installed in 2009 in the facility that previously housed the CBI array. It operated until 2010 and was dismantled in 2011.[17]
The
Cosmic Background Imager (CBI) was a radio telescope interferometer designed to measure the intensity and polarization of the
cosmic microwave background radiation. It operated with thirteen 0.9 m (3.0 ft) antennas between 1999 and 2006, and from 2006 until 2008 with 1.4 m (4.6 ft) antennas. The CBI facility was later reused by the QUIET experiment.[18]
The Millimeter-wave Interferometer (MINT) was a heterogenous four-element array that operated on the slopes of Cerro Toco in late 2001. The prototype instrument contained two 0.3 m (12 in) and two 0.45 m (18 in)
Cassegrain reflectors. It was designed to measure the cosmic microwave background radiation.[19]
^Bustos, R.; Rubio, M.; Otárola, A.; Nagar, N. (2014). "Parque Astronómico de Atacama: An Ideal Site for Millimeter, Submillimeter, and Mid-Infrared Astronomy". Publications of the Astronomical Society of the Pacific. 126 (946): 1126.
arXiv:1410.2451.
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2014PASP..126.1126B.
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^Kohno, K. (2005). "The Atacama Submillimeter Telescope Experiment". The Cool Universe: Observing Cosmic Dawn. 344: 242.
Bibcode:
2005ASPC..344..242K.
^Kawamura, A.; Mizuno, N.; Yonekura, Y.; Onishi, T.; Mizuno, A.; Fukui, Y. (2005). "NANTEN2: A Submillimeter Telescope for Large Scale Surveys at Atacama". Astrochemistry: Recent Successes and Current Challenges. 235: 275P.
Bibcode:
2005IAUS..231P.275K.
^Fowler, J. W.; Niemack, M. D.; Dicker, S. R.; Aboobaker, A. M.; Ade, P. A. R.; Battistelli, E. S.; Devlin, M. J.; Fisher, R. P.; et al. (2007). "Optical design of the Atacama Cosmology Telescope and the Millimeter Bolometric Array Camera". Applied Optics. 46 (17): 3444–54.
arXiv:astro-ph/0701020.
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2007ApOpt..46.3444F.
doi:
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PMID17514303.
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^Minezaki, Takeo; Kato, Daisuke; Sako, Shigeyuki; Konishi, Masahiro; Koshida, Shintaro; Mitani, Natsuko; Aoki, Tsutomu; Doi, Mamoru; Handa, Toshihiro (2010). "The University of Tokyo Atacama 1.0-m Telescope". In Stepp, Larry M; Gilmozzi, Roberto; Hall, Helen J (eds.). Ground-based and Airborne Telescopes III. Proceedings of SPIE. Vol. 7733. p. 773356.
doi:
10.1117/12.856694.
S2CID173187679.
^Radford, S. J. E.; Giovanelli, R.; Sebring, T. A.; Zmuidzinas, J. (2009). "Ccat". Submillimeter Astrophysics and Technology: A Symposium Honoring Thomas G. Phillips ASP Conference Series. 417: 113.
Bibcode:
2009ASPC..417..113R.
^Fowler, J. W.; Doriese, W. B.; Marriage, T. A.; Tran, H. T.; Aboobaker, A. M.; Dumont, C.; Halpern, M.; Kermish, Z. D.; Loh, Y.‐S.; Page, L. A.; Staggs, S. T.; Wesley, D. H. (2005). "Cosmic Microwave Background Observations with a Compact Heterogeneous 150 GHz Interferometer in Chile". The Astrophysical Journal Supplement Series. 156 (1): 1–11.
arXiv:astro-ph/0403137.
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^Miller, A.; Beach, J.; Bradley, S.; Caldwell, R.; Chapman, H.; Devlin, M. J.; Dorwart, W. B.; Herbig, T.; et al. (2002). "The QMAP and MAT/TOCO Experiments for Measuring Anisotropy in the Cosmic Microwave Background". The Astrophysical Journal Supplement Series. 140 (2): 115–142.
arXiv:astro-ph/0108030.
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