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Coordinates: 18°20′48″N 66°45′12″W / 18.3467°N 66.7533°W / 18.3467; -66.7533
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Splitting into an article on the observatory and the telescope, sorry for the disruption.
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{{short description|Radio observatory in the municipality of Arecibo, Puerto Rico}}
{{short description|Radio observatory in the municipality of Arecibo, Puerto Rico}}
{{Infobox telescope
{{Infobox
| image = File:Arecibo_radio_telescope_SJU_06_2019_6144.jpg
| caption = The Arecibo radio telescope in 2019
| first_light = {{Start date|1963|11|1}}
| decommissioned = Announced {{End date|2020|11|19}} <br>
Collapsed {{End date|2020|12|1}}
| nrhp = {{Infobox NRHP
| embed = yes
| name = National Astronomy and Ionosphere Center
| nrhp_type = hd
| nocat = yes
| nearest_city = Arecibo
| mapframe = yes
| mapframe-frame-coord = {{coord|18.34661|-66.75278}}
| mapframe-zoom = 7
| area = {{convert|118|acre|ha}}
| architect = Gordon, William E; [[Thomas Christian Kavanagh|Kavanaugh, T. C.]]
| engineer = von Seb, Inc., [[Thomas Christian Kavanagh|T. C. Kavanaugh]] of Praeger-Kavanagh, and [[Severud Associates|Severud-Elstad-Krueger Associates]]<ref>{{Cite journal |title=Radio-Radar Telescope Will Probe Solar System |journal=Electrical Engineering |volume=80 |issue=7 |pages=561 |date=July 1961 |doi=10.1109/EE.1961.6433355}}</ref>
| architecture =
| added = September 23, 2008<ref name=newlistings20081003>{{cite web |url=http://www.nps.gov/history/nr/listings/20081003.HTM |title=Weekly List Actions |author=National Park Service |date=October 3, 2008 |access-date=February 6, 2018| archive-date=March 29, 2013| archive-url=https://web.archive.org/web/20130329001745/http://www.nps.gov/history/nr/listings/20081003.HTM| url-status=live}}</ref>
| visitation_num =
| visitation_year =
| refnum = 07000525
| mpsub =
| governing_body = Federal
}}
}}
The '''Arecibo Observatory''' is<!-- the observatory still exists and will remain functional even without the telescope, do not change to "was"--> an [[observatory]] in [[Arecibo, Puerto Rico]], also known as the '''National Astronomy and Ionosphere Center''' ('''NAIC'''). It is owned by the US [[National Science Foundation]] (NSF).
The '''Arecibo Observatory''' is<!-- the observatory still exists and will remain functional even without the telescope, do not change to "was"--> an [[observatory]] in [[Arecibo, Puerto Rico]], also known as the '''National Astronomy and Ionosphere Center''' ('''NAIC'''). It is owned by the US [[National Science Foundation]] (NSF).


The main instrument of the observatory was the Arecibo Telescope, a {{cvt|305|m|ft|sigfig=2}} [[spherical reflector]] dish built into a natural [[sinkhole]], a cable-mount steerable receiver mounted {{convert|150|m|ft|abbr=on|sigfig=3}} above the dish, and several [[radar]] transmitters for emitting signals. For more than 50 years, the Arecibo Telescope was the world's largest single-aperture telescope, surpassed in July 2016 by the [[Five-hundred-meter Aperture Spherical Telescope]] (FAST) in China. The Observatory also includes a [[radio telescope]], a [[Lidar]] facility, and a visitor's center.
The main instrument of the observatory was the Arecibo Telescope, a {{cvt|305|m|ft|sigfig=2}} [[spherical reflector]] dish built into a natural [[sinkhole]], a cable-mount steerable receiver mounted {{convert|150|m|ft|abbr=on|sigfig=3}} above the dish, and several [[radar]] transmitters for emitting signals. For more than 50 years, the Arecibo Telescope was the world's largest single-aperture telescope, surpassed in July 2016 by the [[Five-hundred-meter Aperture Spherical Telescope]] (FAST) in China. The Observatory also includes a [[radio telescope]], a [[Lidar]] facility, and a visitor's center.


The Arecibo Telescope was primarily used for research in [[radio astronomy]], [[atmospheric science]], and [[radar astronomy]], as well as for programs that [[search for extraterrestrial intelligence]] (SETI). Scientists wanting to use the observatory submitted proposals that were evaluated by independent scientific referees. [[NASA]] also used the telescope for [[Near-Earth object|near-Earth object detection programs]]. The observatory, funded primarily by the [[National Science Foundation]] (NSF) with partial support from NASA, was managed by [[Cornell University]] from its completion in 1963 until 2011, after which it was transferred to a partnership led by [[SRI International]]. In 2018, a consortium led by the [[University of Central Florida]] assumed operation of the facility.


== Telescopes ==
The telescope's unique and futuristic design led to several appearances in film, gaming and television productions, such as for the climactic fight scene in the [[List of James Bond films|James Bond]] film ''[[GoldenEye]]'' (1995). It has been listed on the US [[National Register of Historic Places]] since 2008.<ref name="newlistings20081003"/><ref name="nrhpreg">{{cite web |title=National Register of Historic Places Registration: National Astronomy and Ionosphere Center / Arecibo Observatory |url=http://www.nps.gov/history/nr/feature/weekly_features/IonosphereCenter.pdf |date=March 20, 2007 |author=Juan Llanes Santos |publisher=[[National Park Service]] |access-date=October 21, 2009 |archive-date=May 30, 2009 |archive-url=https://web.archive.org/web/20090530091523/http://www.nps.gov/history/nr/feature/weekly_features/IonosphereCenter.pdf |url-status=live}} (72 pages, with many historic b&w photos and 18 color photos)</ref> The center was named an [[List of IEEE milestones|IEEE Milestone]] in 2001.<ref>{{cite web |url=http://www.ieeeghn.org/wiki/index.php/Milestones:NAIC/Arecibo_Radiotelescope,_1963 |title=Milestones:NAIC/Arecibo Radiotelescope, 1963 |work=IEEE Global History Network |publisher=[[IEEE]] |access-date=July 29, 2011 |archive-date=March 6, 2012 |archive-url=https://web.archive.org/web/20120306051000/http://www.ieeeghn.org/wiki/index.php/Milestones:NAIC/Arecibo_Radiotelescope,_1963 |url-status=live}}</ref> It has a visitor center that is open part-time.<ref>[http://www.naic.edu/general/index.php?option=com_content&view=article&id=162:vc-description&catid=107&Itemid=638 Visitor Center] {{webarchive|url=https://web.archive.org/web/20130106095641/http://www.naic.edu/general/index.php?option=com_content&view=article&id=162%3Avc-description&catid=107&Itemid=638 |date=January 6, 2013 }}</ref>
The main feature of the Arecibo Observatory was its large [[Arecibo Telescope|radio telescope]]. The telescope's main collecting dish had the shape of a [[spherical cap]] {{convert|305|m|ft|sigfig=3|order=flip}} in diameter with an {{convert|265|m|ft|sigfig=3|adj=on|order=flip}} [[radius of curvature]],<ref name="arecibo-multifeed">{{cite journal |last1=Goldsmith |first1=P. F. |last2=Baker |first2=L. A. |last3=Davis |first3=M. M. |last4=Giovanelli |first4=R. |title=Multi-feed Systems for the Arecibo Gregorian |journal=Astronomical Society of the Pacific Conference Series |date=1995 |volume=75 |bibcode=1995ASPC...75...90G |pages=90–98}}</ref> and was constructed inside a [[karst]] [[sinkhole]].<ref name="naic about"/> The dish surface was made of 38,778 perforated aluminum panels, each about {{convert|1|by|2|m|ft|0|order=flip}}, supported by a mesh of steel cables.<ref name="arecibo-multifeed"/> The ground beneath supported shade-tolerant vegetation.<ref>{{cite web |url=https://www.nsf.gov/mps/ast/env_impact_reviews/arecibo/eis/DEIS.pdf |website=nsf.gov |publisher=NSF |page=66 |title=Environmental Impact Statement for the Arecibo Observatory Arecibo, Puerto Rico (Draft) |quote=At the Arecibo Observatory, a mix of shade-tolerant species have colonized the area beneath the 305-meter radio telescope dish.}}</ref>

Since 2006, the NSF has reduced its funding commitment to the observatory, leading academics to push for additional funding support to continue its programs. The telescope was damaged by [[Hurricane Maria]] in 2017 and was affected by earthquakes in 2019 and 2020. Two cable breaks, one in August 2020 and a second in November 2020, threatened the structural integrity of the support structure for the suspended platform and damaged the dish. Due to uncertainty over the remaining strength of the other cables supporting the suspended structure, and the risk of collapse owing to further failures making repairs dangerous, the NSF announced on November 19, 2020, that it would decommission and dismantle the telescope, with the radio telescope and LIDAR facility remaining operational.<ref name="NSFrelease20-010">{{cite web |title=NSF begins planning for decommissioning of Arecibo Observatory's 305-meter telescope due to safety concerns [News Release 20-010]|url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674 |website=www.nsf.gov |access-date=November 19, 2020 |language=en |archive-date=November 19, 2020 |archive-url=https://web.archive.org/web/20201119163316/https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674 |url-status=live}}</ref><ref>{{Cite web |last=Clery |first=Daniel |date=November 19, 2020 |title=Famed Arecibo telescope, on the brink of collapse, will be dismantled |url=https://www.sciencemag.org/news/2020/11/famed-arecibo-telescope-brink-collapse-will-be-dismantled|url-status=live|archive-url=https://web.archive.org/web/20201119163508/https://www.sciencemag.org/news/2020/11/famed-arecibo-telescope-brink-collapse-will-be-dismantled|archive-date=November 19, 2020|access-date=November 19, 2020 |website=Science {{!}} AAAS|language=en}}</ref><ref name=pmid33214727>{{cite journal |last1=Witze |first1=A |title=Legendary Arecibo telescope will close forever - scientists are reeling. |journal=Nature |date=November 2020 |volume=587 |issue=7835 |pages=529–530 |doi=10.1038/d41586-020-03270-9 |pmid=33214727 |doi-access=free }}</ref> Before it could be decommissioned, however, one of the telescope's receiver's support towers broke in half, sending the entire receiver and its supported structure collapsing into the dish on December 1, 2020.<ref name="guardian collapsed">{{cite news |title=Giant Arecibo radio telescope collapses in Puerto Rico |url=https://www.theguardian.com/world/2020/dec/01/arecibo-radio-telescope-collapses-puerto-rico |access-date=1 December 2020 |work=[[The Guardian]] |agency=[[Associated Press]] |date=1 December 2020}}</ref><ref name="ap collapse">{{cite news | url = https://apnews.com/article/puerto-rico-0da6abb251f455977bf0c752348e712e | title = Huge Puerto Rico radio telescope, already damaged, collapses | first = DÁNICA | last = Coto | date = December 1, 2020 | accessdate = December 1, 2020 | publisher = [[Associated Press]] |via=[[Yahoo!]]}}</ref>

== General information ==
The main feature of the Arecibo Observatory was its large radio telescope. The telescope's main collecting dish had the shape of a [[spherical cap]] {{convert|305|m|ft|sigfig=3|order=flip}} in diameter with an {{convert|265|m|ft|sigfig=3|adj=on|order=flip}} [[radius of curvature]],<ref name="arecibo-multifeed"/> and was constructed inside a [[karst]] [[sinkhole]].<ref name="naic about"/> The dish surface was made of 38,778 perforated aluminum panels, each about {{convert|1|by|2|m|ft|0|order=flip}}, supported by a mesh of steel cables.<ref name="arecibo-multifeed"/> The ground beneath supported shade-tolerant vegetation.<ref>{{cite web |url=https://www.nsf.gov/mps/ast/env_impact_reviews/arecibo/eis/DEIS.pdf |website=nsf.gov |publisher=NSF |page=66 |title=Environmental Impact Statement for the Arecibo Observatory Arecibo, Puerto Rico (Draft) |quote=At the Arecibo Observatory, a mix of shade-tolerant species have colonized the area beneath the 305-meter radio telescope dish.}}</ref>

The telescope had three [[radar]] transmitters, with [[effective isotropic radiated power]]s (EIRPs) of 25&nbsp;[[Watt#Terawatt|TW]] (continuous) at 2380&nbsp;MHz, 3.2&nbsp;[[Watt#Terawatt|TW]] (pulse peak) at 430&nbsp;MHz, and 200&nbsp;[[Watt#Megawatt|MW]] at 47&nbsp;MHz,<ref>{{cite web|url=https://www.naic.edu/~phil/hardware/xmiter430/430tx_manual_hagen.pdf|title=Areciebo 430 MHz Radar Operation and Maintenance Manual|pages=6–7|last=Hagen|first=Jon |date=2005|website=NAIC|access-date=November 21, 2020}}</ref> as well as an ionospheric modification facility operating at 5.1 and 8.175&nbsp;MHz.<ref>{{cite web|url=https://www.naic.edu/~enossa/HF-docs/HF-Call2018-official.pdf|title=Arecibo Call for Ionospheric Modification (HF facility) Proposals – 2018|date=December 8, 2017|author=Eliana Nossa|publisher=Arecibo Observatory}}</ref>

The dish remained stationary, while receivers and transmitters were moved to the proper focal point of the telescope to aim at the desired target.<ref name=Cohen2009>{{cite journal |last1=Cohen |first1=Marshall H. |date=2009 |title=Genesis of the 1000-foot Arecibo Dish |journal=Journal of Astronomical History and Heritage |volume=12 |issue=2 |pages=141–1526 |bibcode=2009JAHH...12..141C |s2cid=18990068 |url=http://resolver.caltech.edu/CaltechAUTHORS:20091231-11073077 }}</ref> As a spherical mirror, the reflector's focus is along a line rather than at one point. As a result, complex line feeds were implemented to carry out observations, with each line feed covering a narrow [[Frequency range|frequency band]] measuring 10–45 MHz. A limited number of line feeds could be used at any one time, limiting the telescope's flexibility.<ref name="arecibo-multifeed">{{cite journal |last1=Goldsmith |first1=P. F. |last2=Baker |first2=L. A. |last3=Davis |first3=M. M. |last4=Giovanelli |first4=R. |title=Multi-feed Systems for the Arecibo Gregorian |journal=Astronomical Society of the Pacific Conference Series |date=1995 |volume=75 |bibcode=1995ASPC...75...90G |pages=90–98}}</ref>

The receiver was on an {{convert|900|ST|t|adj=on|order=flip}} platform suspended {{convert|150|m|ft|abbr=on|sigfig=3}} above the dish by 18 cables running from three [[reinforced concrete]] towers, one {{convert|365|ft|m|abbr=on|order=flip}} high and the other two {{convert|265|ft|abbr=on|order=flip}} high, placing their tops at the same elevation. The platform had a rotating, bow-shaped track {{convert|93|m|ft|abbr=on|sigfig=3}} long, called the [[azimuth]] arm, carrying the receiving antennas and secondary and tertiary reflectors. This allowed the telescope to observe any region of the sky in a forty-degree cone of visibility about the local [[zenith]] (between &minus;1 and 38 degrees of [[declination]]). [[Puerto Rico]]'s location near the Northern [[Tropic of Cancer|Tropic]] allowed the Arecibo telescope to view the planets in the Solar System over the northern half of their orbit. The round trip light time to objects beyond [[Saturn]] is longer than the 2.6-hour time that the telescope could track a celestial position, preventing [[radar]] observations of more distant objects.<ref name="naic about">{{cite web |url=https://www.naic.edu/ao/telescope-description |title=Telescope Description |publisher=[[National Astronomy and Ionosphere Center]] |access-date=November 20, 2020 | archive-date = November 20, 2020 | archive-url = https://web.archive.org/web/20201120035144/https://www.naic.edu/ao/telescope-description | url-status = live}}</ref>{{failed verification|date=November 2020}}


The Arecibo Observatory also has other facilities beyond the main telescope, including a {{convert|12|m|ft}} radio telescope used for VLBI,<ref>{{cite journal |last1=Roshi |first1=D. Anish |last2=Anderson |first2=L. D. |last3=Araya |first3=E. |last4=Balser |first4=D. |last5=Brisken |first5=W. |last6=Brum |first6=C. |last7=Campbell |first7=D. |last8=Chatterjee |first8=S. |last9=Churchwell |first9=E. |last10=Condon |first10=J. |last11=Cordes |first11=J. |last12=Cordova |first12=F. |last13=Fernandez |first13=Y. |last14=Gago |first14=J. |last15=Ghosh |first15=T. |last16=Goldsmith |first16=P. F. |last17=Heiles |first17=C. |last18=Hickson |first18=D. |last19=Jeffs |first19=B. |last20=Jones |first20=K. M. |last21=Lautenbach |first21=J. |last22=Lewis |first22=B. M. |last23=Lynch |first23=R. S. |last24=Manoharan |first24=P. K. |last25=Marshall |first25=S. |last26=Minchin |first26=R. |last27=Palliyaguru |first27=N. T. |last28=Perera |first28=B. B. P. |last29=Perillat |first29=P. |last30=Pinilla-Alonso |first30=N. |last31=Pisano |first31=D. J. |last32=Quintero |first32=L. |last33=Raizada |first33=S. |last34=Ransom |first34=S. M. |last35=Fernandez-Rodriguez |first35=F. O. |last36=Salter |first36=C. J. |last37=Santos |first37=P. |last38=Sulzer |first38=M. |last39=Taylor |first39=P. A. |last40=Venditti |first40=F. C. F. |last41=Venkataraman |first41=A. |last42=Virkki |first42=A. K. |last43=Wolszczan |first43=A. |last44=Womack |first44=M. |last45=Zambrano-Marin |first45=L. F. |title=Astro2020 Activities and Projects White Paper: Arecibo Observatory in the Next Decade |journal=arXiv:1907.06052 [astro-ph] |date=13 July 2019 |arxiv=1907.06052 }}</ref> and a LIDAR facility.<ref name="NSFrelease20-010" />
The Arecibo Observatory also has other facilities beyond the main telescope, including a {{convert|12|m|ft}} radio telescope used for VLBI,<ref>{{cite journal |last1=Roshi |first1=D. Anish |last2=Anderson |first2=L. D. |last3=Araya |first3=E. |last4=Balser |first4=D. |last5=Brisken |first5=W. |last6=Brum |first6=C. |last7=Campbell |first7=D. |last8=Chatterjee |first8=S. |last9=Churchwell |first9=E. |last10=Condon |first10=J. |last11=Cordes |first11=J. |last12=Cordova |first12=F. |last13=Fernandez |first13=Y. |last14=Gago |first14=J. |last15=Ghosh |first15=T. |last16=Goldsmith |first16=P. F. |last17=Heiles |first17=C. |last18=Hickson |first18=D. |last19=Jeffs |first19=B. |last20=Jones |first20=K. M. |last21=Lautenbach |first21=J. |last22=Lewis |first22=B. M. |last23=Lynch |first23=R. S. |last24=Manoharan |first24=P. K. |last25=Marshall |first25=S. |last26=Minchin |first26=R. |last27=Palliyaguru |first27=N. T. |last28=Perera |first28=B. B. P. |last29=Perillat |first29=P. |last30=Pinilla-Alonso |first30=N. |last31=Pisano |first31=D. J. |last32=Quintero |first32=L. |last33=Raizada |first33=S. |last34=Ransom |first34=S. M. |last35=Fernandez-Rodriguez |first35=F. O. |last36=Salter |first36=C. J. |last37=Santos |first37=P. |last38=Sulzer |first38=M. |last39=Taylor |first39=P. A. |last40=Venditti |first40=F. C. F. |last41=Venkataraman |first41=A. |last42=Virkki |first42=A. K. |last43=Wolszczan |first43=A. |last44=Womack |first44=M. |last45=Zambrano-Marin |first45=L. F. |title=Astro2020 Activities and Projects White Paper: Arecibo Observatory in the Next Decade |journal=arXiv:1907.06052 [astro-ph] |date=13 July 2019 |arxiv=1907.06052 }}</ref> and a LIDAR facility.<ref name="NSFrelease20-010" />


{{Wide image|Panorama arecibo telescope from observation deck.jpg|800px|The Arecibo Radio Telescope as viewed from the observation deck, October 2013}}
{{Wide image|Panorama arecibo telescope from observation deck.jpg|800px|The Arecibo Radio Telescope as viewed from the observation deck, October 2013}}

== History ==
=== Design and construction ===
[[File:Arecibo Radiotelescopio SJU 06 2019 7428.jpg|thumb|300px|A detailed view of the beam-steering mechanism. The triangular platform at the top was fixed, and the [[azimuth]] arm rotated beneath it. To the right was the Gregorian sub-reflector, and to the left was the remains of the {{convert|96|ft|m|adj=mid|-long}} line feed tuned to 430 MHz (destroyed by Hurricane Maria). Also to the right was the catwalk and part of the rectangular [[waveguide]] that brought the 2.5 MW 430 MHz radar transmitter's signal up to the focal region.]]

The origins of the observatory trace to late 1950s efforts to develop [[anti-ballistic missile]] (ABM) defenses as part of the newly formed [[Defense Advanced Research Projects Agency|ARPA's]] ABM umbrella-effort, Project Defender. Even at this early stage it was clear that the use of [[chaff (countermeasure)|radar decoys]] would be a serious problem at the long ranges needed to successfully attack a warhead, ranges on the order of {{convert|1000|mile|km|abbr=on|order=flip}}.<ref name=darpa>Barry Rosenberg, [http://www.darpa.mil/Docs/Missile_Defense_200807180930582.pdf "DARPA Paves the Way for U.S. Efforts in Ballistic Missile Defense"] {{webarchive|url=https://web.archive.org/web/20160305010418/http://www.darpa.mil/Docs/Missile_Defense_200807180930582.pdf |date=March 5, 2016 }}, 50 Years of Bridging the Gap, DARPA</ref><ref name=press>[http://www.alternatewars.com/WW3/WW3_Documents/DARPA/DARPA_II_PRESS.htm "Defender Anti-Ballistic Missile"] {{Webarchive|url=https://web.archive.org/web/20140531234413/http://www.alternatewars.com/WW3/WW3_Documents/DARPA/DARPA_II_PRESS.htm |date=May 31, 2014 }}, DARPA Technical Accomplishments Volume II: A Historical Review Of Selected DARPA Projects, April 1991, Section I: PRESS.</ref>

Among the many Defender projects were several studies based on the concept that a re-entering [[nuclear warhead]] would cause unique physical signatures while still in the upper atmosphere. It was known that hot, high-speed objects caused ionization of the atmosphere that reflects [[radar]] waves, and it appeared that a warhead's signature would be different enough from decoys that a detector could pick out the warhead directly, or alternately, provide added information that would allow operators to focus a conventional tracking radar on the single return from the warhead.<ref name=darpa/><ref name=press/>

Although the concept appeared to offer a solution to the tracking problem, there was almost no information on either the physics of re-entry or a strong understanding of the normal composition of the upper layers of the [[ionosphere]]. ARPA began to address both simultaneously. To better understand the radar returns from a warhead, several radars were built on [[Kwajalein Atoll]], while Arecibo started with the dual purpose of understanding the ionosphere's F-layer while also producing a general-purpose scientific radio observatory.<ref name=darpa/><ref name=press/>

The observatory was built between mid-1960 and November 1963. [[William E. Gordon]] of [[Cornell University]] oversaw its design for study of the Earth's [[ionosphere]].<ref name="Gold 119">{{Citation |last=Gold |first=Thomas| author-link =Thomas Gold |date=2013 |title=Taking the Back off the Watch: A Personal Memoir |volume=381 |chapter=7| chapter-url =https://books.google.com/books?id=vlaFA0zgmSoC&q=gordon |edition=1 |publisher=Springer Heidelberg |location=New York |language=en |page=119 |isbn=978-3-642-27587-6 |url=https://books.google.com/books?id=vlaFA0zgmSoC&q=Gordon+ |doi=10.1007/978-3-642-27588-3 |series=Astrophysics and Space Science Library| access-date =October 14, 2020| archive-date =November 20, 2020| archive-url =https://web.archive.org/web/20201120204556/https://books.google.com/books?id=vlaFA0zgmSoC&q=Gordon+| url-status =live}}</ref><ref name="Frè 276">{{Citation |last=Frè |first=Pietro |date=2013 |title=Gravity, a geometrical course |chapter=7| chapter-url =https://books.google.com/books?id=1klJvLbHEQYC&q=radio+telescope+suspension+system&pg=PA276 |edition=1 |volume=1:Development of the theory and basic physical applications |publisher=Springer |location=New York |language=en |page=276 |isbn=978-94-007-5360-0 |doi=10.1007/978-94-007-5361-7 |bibcode=2013ggc1.book.....F| access-date =October 14, 2020| archive-date =November 20, 2020| archive-url =https://web.archive.org/web/20201120204542/https://books.google.com/books?id=1klJvLbHEQYC&q=radio+telescope+suspension+system&pg=PA276| url-status =live}}</ref><ref name=Mathews2013>{{cite journal |last1=Mathews |first1=J. D. |title=A short history of geophysical radar at Arecibo Observatory |journal=History of Geo- and Space Sciences |date=13 March 2013 |volume=4 |issue=1 |pages=19–33 |doi=10.5194/hgss-4-19-2013 |bibcode=2013HGSS....4...19M }}</ref><ref name=Cohen2009/> He was attracted to the [[sinkholes]] in the [[karst]] regions of [[Puerto Rico]] that offered perfect cavities for a very large dish.<ref>{{cite web |url=http://www.ieee.org/web/aboutus/history_center/arecibo.html |title=IEEE History Center: NAIC/Arecibo Radiotelescope, 1963 |publisher=[[Institute of Electrical and Electronics Engineers]] |access-date=September 2, 2008| archive-date=July 6, 2008| archive-url=https://web.archive.org/web/20080706035625/http://www.ieee.org/web/aboutus/history_center/arecibo.html| url-status=live}}</ref><ref>{{cite web |publisher=National Astronomy and Ionosphere Center |url=http://www.naic.edu/history_gal/historicgal.html |title=Pictures of the construction of Arecibo Observatory (start to finish) |access-date=May 5, 2009 |archive-url=https://web.archive.org/web/20090505205805/http://www.naic.edu/history_gal/historicgal.html |archive-date=May 5, 2009 | url-status= live}}</ref><ref>{{cite web |work=Acevedo, Tony (June 2004) |url=http://www.naic.edu/public/descrip_eng.htm |title=Description of Engineering of Arecibo Observatory |access-date=May 5, 2009 |archive-url=https://web.archive.org/web/20090504055743/http://www.naic.edu/public/descrip_eng.htm |archive-date=May 4, 2009| url-status= dead |df=mdy-all}}</ref> Originally, a fixed parabolic reflector was envisioned, pointing in a fixed direction with a {{convert|150|m|ft|abbr=on|sigfig=3}} tower to hold equipment at the focus. This design would have limited its use in other research areas, such as [[radar astronomy]], [[radio astronomy]] and atmospheric science, which require the ability to point at different positions in the sky and track those positions for an extended time as the Earth rotates.

Ward Low of the [[Advanced Research Projects Agency]] (ARPA) pointed out this flaw and put Gordon in touch with the [[Air Force Cambridge Research Laboratories|Air Force Cambridge Research Laboratory]] (AFCRL) in [[Boston, Massachusetts]], where one group headed by Phil Blacksmith was working on spherical reflectors and another group was studying the propagation of [[radio wave]]s in and through the upper atmosphere. Cornell University proposed the project to ARPA in mid-1958 and a contract was signed between the AFCRL and the University in November 1959. Cornell University and Zachary Sears published a request for proposals (RFP) asking for a design to support a feed moving along a spherical surface {{convert|435|ft|m|0|order=flip}} above the stationary reflector. The RFP suggested a tripod or a tower in the center to support the feed. On the day the project for the design and construction of the antenna was announced at Cornell University, Gordon had also envisioned a {{convert|435|ft|m|abbr=on|order=flip}} tower centered in the {{convert|1000|ft|m|abbr=on|sigfig=3|order=flip}} reflector to support the feed.<ref>{{Citation |last=Gordon |first=William| author-link = William E. Gordon |title=Cornell will build a radar to observe the ionosphere |newspaper=New York Herald Tribune |location=New York City |type=Engineer's News Supplement |date=October 25, 1959 |page=1}}</ref><ref>{{Citation |first1=William E. |last1=Gordon | author-link =William E. Gordon |first2=Henry |last2=Booker | author2-link =Henry G. Booker |first3=Ben |last3=Nichols |title=Design Study of a Radar to Explore the Earth's Ionosphere and Surrounding Space | book-title=Research Report EE 395 |series=3 |year=1958 |pages=23 |place=Ithaca, New York |publisher=Cornell University, School of Electrical Engineering}}</ref><ref name=Mathews2013/>

[[George Doundoulakis]], who directed research at General Bronze Corporation in [[Garden City, New York]], along with Zachary Sears, who directed Internal Design at Digital B & E Corporation, New York, received the RFP from [[Cornell University]] for the antenna design and studied the idea of suspending the [[antenna feed|feed]] with his brother, [[Helias Doundoulakis]], a [[civil engineer]]. George Doundoulakis identified the problem that a tower or tripod would have presented around the center, (the most important area of the reflector), and devised a better design by suspending the [[antenna feed|feed]].<ref name="Frè 276"/><ref name="Gold 119"/> He presented his proposal to [[Cornell University]] for a doughnut or [[torus]]-type [[truss]] suspended by four cables from four towers above the reflector, having along its edge a rail track for the [[azimuth]]al [[truss]] positioning. This second [[truss]], in the form of an arc, or [[arch]], was to be suspended below, which would rotate on the rails through 360 degrees. The arc also had rails on which the unit supporting the feed would move for the feed's elevational positioning. A [[counterweight]] would move symmetrically opposite to the feed for stability and, if a hurricane struck, the whole feed could be raised and lowered. Helias Doundoulakis designed the [[Wire rope|cable]] suspension system which was finally adopted. Although the present configuration is substantially the same as the original drawings by George and Helias Doundoulakis, (although with three towers, instead of the original four as drawn in the original patent), the [[United States Patent and Trademark Office|U.S. Patent office]] granted Helias Doundoulakis a patent,<ref>{{US patent reference| number = 3273156| y = 1966| m = 09| d = 13| inventor = Helias Doundoulakis| title = Radio Telescope having a scanning feed supported by a cable suspension over a stationary reflector}}</ref><ref>{{cite journal |first=W. |last=Cooke |title=Arecibo radio antenna |journal=IEEE Antennas and Propagation Society Newsletter |volume=18 |issue=5 |pages=6–8 |date=October 1976 |doi=10.1109/MAP.1976.27265 |s2cid=31708779}}</ref> The idea of a spherical reflecting mirror with a steerable secondary has since been used in optical telescopes, in particular, the [[Hobby–Eberly Telescope]]<ref>{{cite book |doi=10.1117/12.458223 |chapter=The Hobby-Eberly Telescope Completion Project |title=Large Ground-based Telescopes |year=2003 |editor1-last=Oschmann |editor1-first=Jacobus M |last1=Booth |first1=John A. |last2=Wolf |first2=Marsha J. |last3=Fowler |first3=James R. |last4=Adams |first4=Mark T. |last5=Good |first5=John M. |last6=Kelton |first6=Philip W. |last7=Barker |first7=Edwin S. |last8=Palunas |first8=Povilas |last9=Bash |first9=Frank N. |last10=Ramsey |first10=Lawrence W. |last11=Hill |first11=Gary J. |last12=MacQueen |first12=Phillip J. |last13=Cornell |first13=Mark E. |last14=Robinson |first14=Edward L. |volume=4837 |page=919 |s2cid=121019413 |editor2-first=Larry M |editor2-last=Stepp }}</ref>

Construction began in mid-1960, with the official opening on November 1, 1963.<ref>{{cite web |url=http://www.history.com/encyclopedia.do?vendorId=FWNE.fw..ar136000.a |title=Arecibo Observatory |publisher=History.com |access-date=September 2, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20090314225635/http://www.history.com/encyclopedia.do?vendorId=FWNE.fw..ar136000.a |archive-date=March 14, 2009}}</ref>

=== Upgrades ===
Since then, the telescope had been upgraded several times. Initially, when the maximum expected operating frequency was about 500&nbsp;MHz, the surface consisted of half-inch galvanized wire mesh laid directly on the support cables. In 1973, a high-precision surface consisting of 38,000 individually adjustable aluminum panels replaced the old wire mesh,<ref>{{cite book |last1=Butrica |first1=Andrew |title=To See the Unseen: A History of Planetary Radar Astronomy |date=1996 |publisher=NASA |page=103 |url=https://ntrs.nasa.gov/api/citations/19960045321/downloads/19960045321.pdf |access-date=November 19, 2020 |archive-date=November 20, 2020 |archive-url=https://web.archive.org/web/20201120204524/https://ntrs.nasa.gov/api/citations/19960045321/downloads/19960045321.pdf |url-status=live}}</ref> and the highest usable frequency rose to about 5000&nbsp;MHz. A [[Gregorian telescope|Gregorian reflector system]] was installed in 1997, incorporating secondary and tertiary reflectors to focus radio waves at one point. This allowed installing a suite of receivers, covering the full 1–10&nbsp;GHz range, that could be easily moved to the [[Focus (optics)|focal point]], giving Arecibo more flexibility. A metal mesh screen was also installed around the perimeter to block the ground's thermal radiation from reaching the feed antennas. Finally, a more powerful 2400&nbsp;MHz transmitter was added.<ref>{{cite web |url=https://news.cornell.edu/stories/1997/06/inauguration-upgrade-arecibo-observatory-june-14 |title=World's largest radio telescope is even more powerful, sensitive |first=Larry |last=Bernard |date=June 12, 1997 |access-date=November 20, 2020 |work=Cornell Chornicle | archive-date = November 20, 2020 | archive-url = https://web.archive.org/web/20201120204542/https://news.cornell.edu/stories/1997/06/inauguration-upgrade-arecibo-observatory-june-14 | url-status = live}}</ref>
{{wide image|Arecibo Radiotelescopio Panamorama SJU 06 2019 7446.jpg|1200px|Panoramic view of the Arecibo radio telescope primary dish}}

=== Funding reductions ===
The Astronomical Sciences and Atmospheric Sciences divisions of the NSF had financially supported Arecibo since its completion in the 1970s, with incremental support by NASA, for operating the planetary radar.<ref name="SP4218">{{cite web |last=Butrica |first=Andrew J. |url=https://history.nasa.gov/SP-4218/sp4218.htm |title=NASA SP-4218: To See the Unseen – A History of Planetary Radar Astronomy |publisher=NASA |date=1996 |access-date=August 6, 2014 |archive-url=https://web.archive.org/web/20071101060112/https://history.nasa.gov/SP-4218/sp4218.htm |archive-date=November 1, 2007}}</ref> Between 2001 and 2006, NASA decreased, then eliminated, its support of the planetary radar.<ref>{{cite web |url=http://www.space.com/scienceastronomy/astronomy/arecibo_cuts_011220.html |title=NASA Trims Arecibo Budget, Says Other Organizations Should Support Asteroid Watch |access-date=July 8, 2008 |author=Robert Roy Britt |date=December 20, 2001 |work=Space.com |publisher=Imaginova |url-status=dead |archive-url=https://web.archive.org/web/20081205190409/http://www.space.com/scienceastronomy/astronomy/arecibo_cuts_011220.html |archive-date=December 5, 2008}}</ref>

A November 2006 report by the Astronomical Sciences division recommended substantially decreased astronomy funding for the Arecibo Observatory, from {{USD|10.5 million}} in 2007 to {{USD|4.0 million}} in 2011. The report further stated that if other sources of funding could not be found, closure of the Observatory was recommended.<ref>{{cite journal |last=Blandford |first=Roger |title=From the Ground Up: Balancing the NSF Astronomy Program |publisher=National Science Foundation |date=October 22, 2006 |url=https://www.nsf.gov/mps/ast/seniorreview/sr_report_mpsac_updated_12-1-06.pdf |access-date=July 7, 2008 |archive-url=https://web.archive.org/web/20080626170308/https://www.nsf.gov/mps/ast/seniorreview/sr_report_mpsac_updated_12-1-06.pdf| archive-date=June 26, 2008 | url-status=live}}</ref><ref>{{cite news |last=Weiss |first=Rick Weiss |title=Radio Telescope And Its Budget Hang in the Balance |url=https://www.washingtonpost.com/wp-dyn/content/article/2007/09/08/AR2007090801654.html?hpid=moreheadlines |work=The Washington Post |publisher=The Washington Post Company |location=Arecibo, Puerto Rico |page=A01 |date=September 9, 2007 |access-date=July 8, 2008 |quote=The cash crunch stems from an NSF ''senior review'' completed last November. Its $200&nbsp;million astronomy division, increasingly committed to ambitious new projects, but long hobbled by flat Congressional budgets, was facing a deficit of at least $30&nbsp;million by 2010. |archive-date=November 6, 2012 |archive-url=https://web.archive.org/web/20121106141623/http://www.washingtonpost.com/wp-dyn/content/article/2007/09/08/AR2007090801654.html?hpid=moreheadlines |url-status=live}}</ref>

Academics and researchers responded by organizing to protect and advocate for the observatory. They established the Arecibo Science Advocacy Partnership (ASAP) in 2008, to advance the scientific excellence of Arecibo Observatory research and to publicize its accomplishments in astronomy, aeronomy and planetary radar as to seek additional funding support for the observatory.<ref name="areciboscience.org">{{cite web |url=http://areciboscience.org/index.html |title=Areciboscience.org |publisher=Areciboscience.org |access-date=May 11, 2012 |archive-date=May 14, 2011 |archive-url=https://web.archive.org/web/20110514213802/http://areciboscience.org/index.html |url-status=live}}</ref> An additional {{USD|3 million}} in bonds were secured from the government of Puerto Rico.<ref>{{cite news |url=http://www.primerahora.com/XStatic/primerahora/template/nota.aspx?n=128502 |title=Senado aprueba emisión de bonos de $450 millones |newspaper=Primera Hora |language=es |date=November 14, 2007 |access-date=September 4, 2008 |archive-url=https://web.archive.org/web/20081208135546/http://www.primerahora.com/XStatic/primerahora/template/nota.aspx?n=128502 |archive-date=December 8, 2008 |url-status=dead}}</ref><ref>{{cite book |last1=Gerardo |first1=E. |last2=Alvarado |first2=León |title=Gobernador firma emisión de bonos |work=[[El Nuevo Día]] |date=August 10, 2008}}</ref> Academics, media and influential politicians pressured the [[United States Congress]] on the importance of the work of the observatory.<ref>Chang, K., [https://www.nytimes.com/2007/11/20/science/space/20scop.html?scp=2 "A Hazy Future for a 'Jewel' of Space Instruments"] {{Webarchive|url=https://web.archive.org/web/20151016214548/http://www.nytimes.com/2007/11/20/science/space/20scop.html?scp=2 |date=October 16, 2015 }}, ''New York Times'', November 20, 2007</ref><ref>Jacqui Goddard, [https://www.telegraph.co.uk/news/worldnews/northamerica/usa/2291068/Threat-to-world%27s-most-powerful-radio-telescope-means-we-may-not-hear-ET.html "Threat to world's most powerful radio telescope means we may not hear ET"] {{Webarchive|url=https://web.archive.org/web/20081205104758/http://www.telegraph.co.uk/news/worldnews/northamerica/usa/2291068/Threat-to-world%27s-most-powerful-radio-telescope-means-we-may-not-hear-ET.html |date=December 5, 2008 }}, ''Daily Telegraph'', July 12, 2008</ref> led to additional {{USD|3.1 million}} in funding to support Arecibo in the [[American Recovery and Reinvestment Act of 2009]]. This was used for basic maintenance and for a second, much smaller, antenna to be used for [[very long baseline interferometry]], new [[Klystron]] amplifiers for the [[Radar astronomy|planetary radar]] system and student training.<ref>{{cite web |url=http://www.naic.edu/science/new12m_antenna_arecibo.html |title=12-m Phase Reference Antenna |publisher=Naic.edu |date=June 28, 2010 |access-date=May 11, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120315121910/http://www.naic.edu/science/new12m_antenna_arecibo.html |archive-date=March 15, 2012}}</ref>

Arecibo's budget from NSF continued to wane in the following years.<ref>[https://www.nsf.gov/about/budget/fy2010/toc.jsp "FY2010 Budget Request to Congress"] {{Webarchive|url=https://web.archive.org/web/20180303050446/https://www.nsf.gov/about/budget/fy2010/toc.jsp |date=March 3, 2018 }}. Retrieved May 26, 2009</ref><ref name="2011budget">[https://www.nsf.gov/about/budget/fy2011/pdf/22-Facilities_fy2011.pdf "Major multi-user research facilities"] {{Webarchive|url=https://web.archive.org/web/20170718123127/https://www.nsf.gov/about/budget/fy2011/pdf/22-Facilities_fy2011.pdf |date=July 18, 2017 }} p.&nbsp;35–38. Retrieved February 10, 2010</ref> Starting in FY2010, NASA restored its historical support by contributing $2.0&nbsp;million per year for [[planetary science]], particularly the study of [[near-Earth object]]s, at Arecibo. NASA implemented this funding through its Near Earth Object Observations program.<ref>[https://web.archive.org/web/20121006232826/http://science.nasa.gov/media/medialibrary/2010/04/27/NASAsupport_to_Planetary_Radar.pdf "NASA Support to Planetary Radar"] Retrieved July 7, 2011</ref> NASA increased its support to $3.5&nbsp;million per year in 2012.

In 2011, NSF removed [[Cornell University]], which had managed NAIC since the 1970s, as the operator and transferred these responsibilities to [[SRI International]], along with two other managing partners, [[Universities Space Research Association]] and [[Metropolitan University (Puerto Rico)|Universidad Metropolitana de Puerto Rico]], with a number of other collaborators.<ref name="sri">{{cite pressrelease |url=http://www.sri.com/newsroom/press-releases/sri-international-selected-national-science-foundation-manage-arecibo-observ |title=SRI International to Manage Arecibo Observatory |publisher=[[SRI International]] |date=July 10, 2013 |access-date=July 10, 2013|archive-date=July 3, 2013|archive-url=https://web.archive.org/web/20130703073001/http://www.sri.com/newsroom/press-releases/sri-international-selected-national-science-foundation-manage-arecibo-observ|url-status=live}}</ref><ref>{{cite news |url=http://www.news.cornell.edu/stories/June11/AreciboStmt.html |title=SRI International to manage Arecibo Observatory |work=[[Cornell Chronicle]] |date=June 3, 2011 |access-date=January 11, 2012 |archive-date=January 3, 2012 |archive-url=https://web.archive.org/web/20120103082345/http://www.news.cornell.edu/stories/June11/AreciboStmt.html |url-status=live}}</ref> NSF also decertified NAIC as a [[Federally Funded Research and Development Center|Federally Funded Research and Development Center (FFRDC)]], which the NSF said would give NAIC greater freedom to establish broader scientific partnerships and pursue funding opportunities for activities beyond the scope of those supported by NSF.<ref name="2011budget"/><ref>[https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=5652 "Management and Operation of the NAIC"] {{Webarchive|url=https://web.archive.org/web/20180303050341/https://www.nsf.gov/funding/pgm_summ.jsp?pims_id=5652 |date=March 3, 2018 }} Retrieved April 6, 2013</ref>

While the Observatory continued to operate under the reduced NSF budget and NASA funds, NSF signaled in 2015 and 2016 that it was looking towards potential decommissioning of the Observatory by initiating [[environmental impact statement]]s on the effect of deconstructing the unit.<ref name="natgeo 2016">{{cite web |url=https://www.nationalgeographic.com/science/phenomena/2016/06/10/with-earths-largest-telescope-threatened-its-homeland-rallies/ |title=With Earth's Largest Telescope Threatened, Its Homeland Rallies |first=Nadia |last=Drake |date=June 10, 2016 |access-date=November 20, 2020 |work=[[National Geographic]] | archive-date = November 17, 2020 | archive-url = https://web.archive.org/web/20201117193113/https://www.nationalgeographic.com/science/phenomena/2016/06/10/with-earths-largest-telescope-threatened-its-homeland-rallies/ | url-status = live}}</ref> The NSF continued to indicate it would like to reduce funding to the Observatory in the near future.<ref name="DCL2015">{{cite web |url=https://www.nsf.gov/pubs/2016/nsf16005/nsf16005.jsp |title=Dear Colleague Letter: Concepts for Future Operation of the Arecibo Observatory |date=October 26, 2015 |access-date=November 11, 2015 |archive-date=October 29, 2015 |archive-url=https://web.archive.org/web/20151029235529/http://www.nsf.gov/pubs/2016/nsf16005/nsf16005.jsp |url-status=live}}</ref><ref name="DCL2016">{{cite web |url=https://www.nsf.gov/pubs/2016/nsf16144/nsf16144.jsp |title=Dear Colleague Letter: Intent to Release a Solicitation Regarding Future Continued Operations of the Arecibo Observatory |date=September 30, 2016 |access-date=October 2, 2016 |archive-date=October 5, 2016 |archive-url=https://web.archive.org/web/20161005081900/https://www.nsf.gov/pubs/2016/nsf16144/nsf16144.jsp |url-status=live}}</ref> As in 2008, academics expressed their concern over the loss of scientific discoveries that could occur should the Observatory be shut down.<ref name="natgeo 2016"/>

=== 2020 damage, decommissioning plans, and collapse ===
[[File:Arecibo_observatory_damage_map.svg|thumb|Map of Arecibo Observatory after November 2020 cable damage<ref name=pmid33214727/>]]
Several hurricanes and storms over the 2010s had raised the concerns of structural engineers over the stability of the observatory.<ref name="verge decommission"/> On September 21, 2017, high winds associated with [[Hurricane Maria]] caused the 430&nbsp;MHz line feed to break and fall onto the primary dish, damaging roughly 30 of the 38,000 aluminum panels. Most Arecibo observations do not use the line feed but instead rely on the feeds and receivers located in the dome. Overall, the damage inflicted by Maria was minimal,<ref>{{cite web |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2017/09/20/arecibo-observatory-puerto-ricos-famous-radio-telescope-is-battered-by-hurricane-maria/ |title=Arecibo Observatory, Puerto Rico's famous telescope, is battered by Hurricane Maria |last=Kaplan |first=Sarah |work=[[The Washington Post]] |date=September 22, 2017|access-date=September 24, 2017|archive-date=September 21, 2017|archive-url=https://web.archive.org/web/20170921090157/https://www.washingtonpost.com/news/speaking-of-science/wp/2017/09/20/arecibo-observatory-puerto-ricos-famous-radio-telescope-is-battered-by-hurricane-maria/|url-status=live}}</ref><ref>{{cite web |url=http://news.nationalgeographic.com/2017/09/arecibo-radio-telescope-damaged-puerto-rico-hurricane-maria-science/ |title=Hurricane Damages Giant Radio Telescope—Why It Matters |last=Drake |first=Nadia |work=[[National Geographic (magazine)|National Geographic]] |date=September 22, 2017|access-date=September 23, 2017|archive-date=September 24, 2017|archive-url=https://web.archive.org/web/20170924010319/http://news.nationalgeographic.com/2017/09/arecibo-radio-telescope-damaged-puerto-rico-hurricane-maria-science/|url-status=live}}</ref><ref name="auto">{{cite news |title=Damage to Arecibo less than feared |url=http://spacenews.com/damage-to-arecibo-less-than-feared/ |work=[[SpaceNews]] |first=Jeff |last=Foust |date=September 27, 2017 |access-date=February 5, 2018 |archive-date=November 20, 2020 |archive-url=https://web.archive.org/web/20201120204515/https://spacenews.com/damage-to-arecibo-less-than-feared/ |url-status=live}}</ref><ref name="auto1">{{cite news |title=Good news, earthlings! Puerto Rico telescope still guarding the galaxy despite Maria |url=http://www.miamiherald.com/news/nation-world/world/americas/article180486971.html |work=[[Miami Herald]] |date=October 23, 2017 |language=en|access-date=October 24, 2017|archive-date=October 24, 2017|archive-url=https://web.archive.org/web/20171024011837/http://www.miamiherald.com/news/nation-world/world/americas/article180486971.html|url-status=live}}</ref> but it further clouded the observatory's future. Restoring all the previous capabilities required more than the observatory's already-threatened operating budget, and users feared the decision would be made to decommission it instead.<ref>{{cite journal |title=Hurricane damage threatens Arecibo Observatory's future |first=Daniel |last=Clery |date=September 26, 2017 |journal=Science |doi=10.1126/science.aaq0598 |doi-access=free}}</ref>

A consortium consisting of the [[University of Central Florida]] (UCF), Yang Enterprises and [[Metropolitan University (Puerto Rico)|UMET]], came forward to supply funding in February 2018 to allow the NSF to reduce its contribution towards Arecibo's operating costs from $8&nbsp;million to $2&nbsp;million from the fiscal year 2022–2023, thus securing the observatory's future.<ref>{{cite journal |last=Clery |first=Daniel |title=Arecibo telescope saved by university consortium |journal=Science |date=March 2, 2018 |volume=359 |issue=6379 |pages=965–966 |bibcode=2018Sci...359..965C |doi=10.1126/science.359.6379.965 |pmid=29496850}}</ref> With this, the UCF consortium were named the new operators of the observatory in 2018.<ref>{{cite news |url=http://www.sciencemag.org/news/2018/02/iconic-arecibo-radio-telescope-saved-university-consortium |title=Iconic Arecibo radio telescope saved by university consortium |work=[[Science (journal)|Science]] |date=February 22, 2018 |url-status=dead |access-date=March 3, 2018 |archive-url=https://web.archive.org/web/20180304172439/http://www.sciencemag.org/news/2018/02/iconic-arecibo-radio-telescope-saved-university-consortium |archive-date=March 4, 2018}}</ref><ref name="ucf">{{cite pressrelease |url=https://today.ucf.edu/ucf-led-consortium-manage-arecibo-observatory-puerto-rico/ |title=UCF-led Consortium to Manage Arecibo Observatory in Puerto Rico |publisher=[[UCF Today]] |date=February 22, 2018|access-date=April 18, 2018|archive-date=April 19, 2018|archive-url=https://web.archive.org/web/20180419120618/https://today.ucf.edu/ucf-led-consortium-manage-arecibo-observatory-puerto-rico/|url-status=live}}</ref>

[[File:Arecibo_dish_remains_after_collapse.jpg|thumb|right|The remains of the dish after the collapse on December 1, 2020. The receiver platform can be seen at the bottom left, and one of the sheared towers in the bottom right.]]
On August 10, 2020, a platform support cable broke, causing damage to the telescope, including a {{cvt|100|ft}} gash in the reflector dish.<ref name="UCFtodayBroken">{{Cite web |last=Gonzalez Kotala |first=Zenaida |title=Broken Cable Damages Arecibo Observatory |url=https://www.ucf.edu/news/broken-cable-damages-arecibo-observatory/ |work=[[UCF Today]] |publisher=[[University of Central Florida]] |date=August 11, 2020 |language=en |access-date=August 12, 2020 |archive-date=August 11, 2020 |archive-url=https://web.archive.org/web/20200811230030/https://www.ucf.edu/news/broken-cable-damages-arecibo-observatory/ |url-status=live}}</ref><ref>{{Cite web |title=Cable roto causa daños al Observatorio de Arecibo |url=https://www.notiuno.com/noticias/cable-roto-causa-da-os-al-observatorio-de-arecibo/article_3287f3bc-dc04-11ea-b705-63a6ba353c61.html |date=August 11, 2020|access-date=August 11, 2020 |work=[[WUNO]] |publisher=UNO Radio Group |location=[[San Juan, Puerto Rico]] |language=es|archive-date=September 16, 2020|archive-url=https://web.archive.org/web/20200916021326/https://www.notiuno.com/noticias/cable-roto-causa-da-os-al-observatorio-de-arecibo/article_3287f3bc-dc04-11ea-b705-63a6ba353c61.html|url-status=live}}</ref> No one was reported to have been hurt by the partial collapse. The facility had recently reopened following the passing of [[Tropical Storm Isaias]]. It was unclear if the cable failure was caused by Isaias. Damage included six to eight panels in the Gregorian Dome, and to the platform used to access the dome. The facility was closed as damage assessments were made.<ref name="bi_2020">{{cite web |url=https://www.businessinsider.com/broken-cable-tears-100-foot-hole-in-arecibo-observatory-2020-8 |title=A broken cable smashed a hole 100 feet wide in the Arecibo Observatory, which searches for aliens and tracks dangerous asteroids |publisher=Insider Inc. |work=Business Insider |date=August 11, 2020 |access-date=August 24, 2020 |last=McFall-Johnsen |first=Morgan |quote=One of the world's most prominent astronomical observatories has a hole. On Monday, a 3-inch-thick cable at the Arecibo Observatory broke, tearing a gash 100 feet long in the reflector dish of the 20-acre radio telescope in Puerto Rico. | archive-date=August 14, 2020 | archive-url=https://web.archive.org/web/20200814234421/https://www.businessinsider.com/broken-cable-tears-100-foot-hole-in-arecibo-observatory-2020-8 | url-status=live}}</ref>

The management team had ordered a replacement cable to replace the broken one, but on November 7, 2020, before the new cable could be installed, a second cable broke, shattering part of the dish itself as it fell.<ref>{{cite web |url=https://spaceref.com/news/viewpr.html?pid=56545 |title=A Second Cable Fails at NSF's Arecibo Observatory in Puerto Rico |publisher=University of Central Florida |website=spaceref.com |date=November 8, 2020 |access-date=November 8, 2020| archive-date=November 20, 2020| archive-url=https://web.archive.org/web/20201120204527/http://spaceref.com/news/viewpr.html?pid=56545| url-status=live}}</ref> The engineering staff, which had been monitoring the cables with support from the [[U.S. Army Corps of Engineers]], evaluated the remaining cables and made the determination that there was no way to safely repair the damage at this point, as the remaining cables could be suspect,<ref>{{Cite web|date=2020-11-12|title=Letter Thornton Thomasetti|url=https://www.nsf.gov/news/ramonlugo.pdf|url-status=live|archive-url=https://web.archive.org/web/20201120231018/https://www.nsf.gov/news/ramonlugo.pdf|archive-date=2020-11-21}}</ref><ref>{{Cite web|date=2020-11-11|title=Letter WSP|url=https://www.nsf.gov/news/areciboletter.pdf|url-status=live|archive-url=https://web.archive.org/web/20201120231258/https://www.nsf.gov/news/areciboletter.pdf|archive-date=2020-11-21}}</ref> and furthermore that a controlled decommissioning of the telescope was the only effective means to avoid catastrophic failure which would threaten the other buildings on campus.<ref>{{cite web |url=https://www.nationalgeographic.com/science/2020/11/arecibo-observatory-in-puerto-rico-at-risk-of-collapsing/ |title=Iconic radio telescope in Puerto Rico is at risk of collapsing |author=Nadia Drake |website=nationalgeographic.com |date=November 12, 2020 |access-date=November 12, 2020 |archive-date=November 12, 2020 |archive-url=https://web.archive.org/web/20201112203029/https://www.nationalgeographic.com/science/2020/11/arecibo-observatory-in-puerto-rico-at-risk-of-collapsing/ |url-status=live}}</ref> One engineering firm proposed stabilization efforts.<ref>{{Cite web|date=2020-11-12|title=Letter WJE|url=https://www.nsf.gov/news/stabilizationefforts.pdf|url-status=live|archive-url=https://web.archive.org/web/20201120231440/https://www.nsf.gov/news/stabilizationefforts.pdf|archive-date=2020-11-21}}</ref> The NSF made the announcement on November 19, 2020 that they would decommission Arecibo over the following few weeks after determining the safest route to do so with a safety exclusion zone immediately put in place.<ref> https://www.nsf.gov/news/news_summ.jsp?cntn_id=301674</ref> NSF's Sean Jones stated, "This decision is not an easy one for NSF to make, but safety of people is our number one priority." The [[lidar]] facility will remain operational.<ref name="verge decommission">{{cite web |url=https://www.theverge.com/2020/11/19/21575025/arecibo-observatory-puerto-rico-decommission-structural-collapse-cable-break |title=Facing collapse, the famed Arecibo Observatory will be demolished |first=Loren |last=Grush |date=November 19, 2020 |access-date=November 19, 2020 |work=[[The Verge]] | archive-date = November 19, 2020 | archive-url = https://web.archive.org/web/20201119165655/https://www.theverge.com/2020/11/19/21575025/arecibo-observatory-puerto-rico-decommission-structural-collapse-cable-break | url-status = live}}</ref><ref name="NSFrelease20-010"/>

While waiting for NSF to make the decommissioning plans, engineers from UCF had been monitoring the telescope and observed that the support wires for the support towers had been breaking at a rate of one or two a day, and estimated that the telescope would soon collapse.<ref>{{cite web | url =https://www.sciencemag.org/news/2020/12/arecibo-telescope-collapses-ending-57-year-run | title = Arecibo telescope collapses, ending 57-year run | first= Eric | last = Hand | date = December 1, 2020 | accessdate = December 1, 2020 | work = [[Science Magazine]] }}</ref> Before the decommission plan could be set in place, at around 6:55 a.m. EST on December 1, 2020, one of the towers supporting the cables sheared in half, resulting in the full collapse of the receiving platform. The collapse caused extensive additional damage to the dish.<ref name="guardian collapsed"/><ref name="ap collapse"/><ref name="upi collapse">{{cite web | url = https://www.upi.com/Science_News/2020/12/01/Iconic-dome-at-Arecibo-Observatory-collapses/3861606831206/ | title = Iconic dome at Arecibo Observatory collapses | first = Paul | last = Brinkman | date = December 1, 2020 | accessdate = December 1, 2020 | publisher = [[UPI]] }}</ref> As the receiver fell, it also sheared the tips of the other two towers which the other support cables ran through, causing some small amount of structure damage to the other buildings on the observatory. No injuries from the collapse were reported.<ref>{{cite web | url = https://www.nationalgeographic.com/science/2020/12/arecibo-radio-telescope-in-puerto-rico-collapses/ | title = Iconic radio telescope in Puerto Rico collapses | first = Nadia | last =Drake | date = December 1, 2020 | accessdate = December 1, 2020 | work = [[National Geographic]] }}</ref>

== Research and discoveries ==
[[File:Arecibo message.svg|145px|right|thumb|The [[Arecibo message]] with added color to highlight the separate parts. The actual binary transmission carried no color information.]]
Many scientific discoveries were made with the observatory. On April 7, 1964, soon after it began operating, [[Gordon Pettengill]]'s team used it to determine that the [[rotation]] period of [[Mercury (planet)|Mercury]] was not 88 days, as formerly thought, but only 59 days.<ref>{{cite journal |last1=Dyce |first1=R. B. |first2=G. H. |last2=Pettengill |author-link2=Gordon_Pettengill |first3=I. I. |last3=Shapiro |author-link3=Irwin_I._Shapiro |title=Radar determination of the rotations of Venus and Mercury |journal=[[The Astronomical Journal|Astron. J.]] |volume=72 |issue=3 |pages=351–359 |doi=10.1086/110231 |date=April 1967 |bibcode=1967AJ.....72..351D}}</ref> In 1968, the discovery of the periodicity of the [[Crab Pulsar]] (33 milliseconds) by Lovelace and others provided the first solid evidence that [[neutron star]]s exist.<ref>{{cite web |url=http://www.aep.cornell.edu/pdf/CrabPeriodDiscovery.pdf |title=Discovery of the Period of the Crab Nebula Pulsar |author=Richard V.E. Lovelace |publisher=Cornell University |access-date=September 2, 2008 |archive-url=https://web.archive.org/web/20080912173347/http://www.aep.cornell.edu/pdf/CrabPeriodDiscovery.pdf |archive-date=September 12, 2008|url-status=dead}}</ref> In 1974, [[Russell Alan Hulse|Hulse]] and [[Joseph Hooton Taylor, Jr.|Taylor]] discovered the first binary pulsar [[PSR B1913+16]],<ref>{{cite journal |last1=Hulse |first1=R. A. |last2=Taylor |first2=J. H. |title=Discovery of a pulsar in a binary system |journal=The Astrophysical Journal |date=January 1975 |volume=195 |pages=L51 |doi=10.1086/181708 |bibcode=1975ApJ...195L..51H }}</ref> an accomplishment for which they later received the Nobel Prize in Physics. In 1982, the first [[millisecond pulsar]], [[PSR B1937+21]], was discovered by [[Donald C. Backer]], [[Shrinivas Kulkarni]], [[Carl Heiles]], Michael Davis, and Miller Goss.<ref>{{cite journal |last1=Backer |first1=D. C. |last2=Kulkarni |first2=Shrinivas R. |last3=Heiles |first3=Carl |last4=Davis |first4=M. M. |last5=Goss |first5=W. M. |title=A millisecond pulsar |journal=Nature |date=December 1982 |volume=300 |issue=5893 |pages=615–618 |doi=10.1038/300615a0 |bibcode=1982Natur.300..615B |s2cid=4247734 }}</ref> This object spins 642 times per second and, until the discovery of [[PSR J1748-2446ad]] in 2005, was identified as the fastest-spinning pulsar.

In August 1989, the observatory directly imaged an [[asteroid]] for the first time in history: [[4769 Castalia]].<ref>{{cite web |url=http://echo.jpl.nasa.gov/asteroids/4769_Castalia/cast01.html |title=Asteroid 4769 Castalia (1989 PB) |publisher=NASA |access-date=September 2, 2008 |archive-url=https://web.archive.org/web/20080916092150/http://echo.jpl.nasa.gov/asteroids/4769_Castalia/cast01.html |archive-date=September 16, 2008|url-status=live}}</ref> The following year, Polish astronomer [[Aleksander Wolszczan]] made the discovery of [[pulsar]] [[PSR B1257+12]], which later led him to discover its three orbiting planets.<ref>{{cite journal |last1=Wolszczan |first1=A. |title=Confirmation of Earth-Mass Planets Orbiting the Millisecond Pulsar PSR B1257 + 12 |journal=Science |date=22 April 1994 |volume=264 |issue=5158 |pages=538–542 |doi=10.1126/science.264.5158.538 |pmid=17732735 |bibcode=1994Sci...264..538W |s2cid=19621191 }}</ref> These were the first [[extrasolar planet]]s discovered. In 1994, John Harmon used the Arecibo Radio Telescope to map the distribution of ice in the polar regions of [[Mercury (planet)|Mercury]].<ref>{{cite journal |last1=Harmon |first1=J. K. |last2=Slade |first2=M. A. |last3=Vélez |first3=R. A. |last4=Crespo |first4=A. |last5=Dryer |first5=M. J. |last6=Johnson |first6=J. M. |title=Radar mapping of Mercury's polar anomalies |journal=Nature |date=May 1994 |volume=369 |issue=6477 |pages=213–215 |doi=10.1038/369213a0 |bibcode=1994Natur.369..213H |s2cid=4320356 }}</ref>

In January 2008, detection of prebiotic molecules [[methylene imine|methanimine]] and [[hydrogen cyanide]] were reported from the observatory's radio spectroscopy measurements of the distant starburst galaxy [[Arp 220]].<ref name=ScienceDaily2008>{{cite news |author=Staff |title=Life's Ingredients Detected in Far Off Galaxy |url=https://www.sciencedaily.com/releases/2008/01/080114110715.htm |work=[[ScienceDaily]] |publisher=ScienceDaily LLC |date=January 15, 2008 |access-date=March 29, 2008 |quote=[Article] Adapted from materials provided by [[Cornell University]]. |archive-url=https://web.archive.org/web/20080421095946/https://www.sciencedaily.com/releases/2008/01/080114110715.htm |archive-date=April 21, 2008|url-status= live}}</ref>

From January 2010 to February 2011, American astronomers Matthew Route and [[Aleksander Wolszczan]] detected bursts of radio emission from the T6.5 brown dwarf 2MASS J10475385+2124234. This was the first time that radio emission had been detected from a T dwarf, which has methane absorption lines in its atmosphere. It is also the coolest brown dwarf (at a temperature of ~900K) from which radio emission has been observed. The highly polarized and highly energetic radio bursts indicated that the object has a >1.7&nbsp;[[Gauss (unit)|kG]]-strength magnetic field and magnetic activity similar to both the planet [[Jupiter]] and the [[Sun]].<ref>{{cite journal |last1=Route |first1=M. |last2=Wolszczan |first2=A. |title=The Arecibo Detection of the Coolest Radio-flaring Brown Dwarf |journal=The Astrophysical Journal |date=10 March 2012 |volume=747 |issue=2 |pages=L22 |doi=10.1088/2041-8205/747/2/L22 |arxiv=1202.1287 |bibcode=2012ApJ...747L..22R |s2cid=119290950 }}</ref>

=== The Arecibo message ===
{{main|Arecibo message}}
In 1974, the [[Arecibo message]], an attempt to communicate with potential [[extraterrestrial life]], was transmitted from the radio telescope toward the globular cluster [[Messier 13]], about 25,000 light-years away.<ref>{{cite web |url=http://www.zwire.com/site/news.cfm?newsid=15663534&BRD=1395&PAG=461&dept_id=216620&rfi=6 |title=Making Contact |author=Larry Klaes |work=Ithaca Times |date=November 30, 2005 |access-date=September 2, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081205064953/http://www.zwire.com/site/news.cfm?newsid=15663534&BRD=1395&PAG=461&dept_id=216620&rfi=6 |archive-date=December 5, 2008}}</ref> The 1,679 [[bit]] pattern of 1s and 0s defined a 23 by 73 pixel [[bitmap]] image that included numbers, stick figures, chemical formulas and a crude image of the telescope.<ref>{{cite web |url=http://www.physics.utah.edu/~cassiday/p1080/lec06.html |title=The Arecibo Message |author=Geaorge Cassiday |publisher=The University of Utah: Department of Physics |access-date=July 27, 2007 |archive-url=https://archive.today/20070717133904/http://www.physics.utah.edu/~cassiday/p1080/lec06.html |archive-date=July 17, 2007 |url-status=live}}</ref>

=== SETI and METI projects ===
{{main|SETI|Active SETI}}
[[Search for extraterrestrial intelligence]] (SETI)<ref>{{cite journal |last1=Tarter |first1=Jill |title=The Search for Extraterrestrial Intelligence (SETI) |journal=Annual Review of Astronomy and Astrophysics |date=September 2001 |volume=39 |issue=1 |pages=511–548 |doi=10.1146/annurev.astro.39.1.511 |bibcode=2001ARA&A..39..511T |s2cid=53122223 }}</ref> is the search for extraterrestrial life or advanced technologies. SETI aims to answer the question "Are we alone in the Universe?" by scanning the skies for transmissions from intelligent civilizations elsewhere in our galaxy.

In comparison, METI (messaging to extraterrestrial intelligence) refers to the [[active SETI|active search]] by transmitting messages.

Arecibo is the source of data for the [[SETI@home]] and [[Astropulse]] [[distributed computing]] projects put forward by the Space Sciences Laboratory at the [[University of California, Berkeley]], and was used for the [[SETI Institute]]'s [[Project Phoenix (SETI)|Project Phoenix]] observations.<ref>{{cite news |url=https://www.space.com/searchforlife/seti_arecibo_prep_030414.html |title=Project Phoenix: SETI Prepares to Observe at Arecibo |author=Peter Backus |work=[[Space.com]] |date=April 14, 2003 |access-date=September 2, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081204130953/http://www.space.com/searchforlife/seti_arecibo_prep_030414.html |archive-date=December 4, 2008}}</ref> The [[Einstein@Home]] distributed computing project has found more than 20 [[pulsar]]s in Arecibo data.<ref>{{cite web |url=http://einstein.phys.uwm.edu/radiopulsar/html/BRP4_discoveries/ |title=Einstein@Home new discoveries and detections of known pulsars in the BRP4 search |date=August 27, 2012 |publisher=Einstein@Home |access-date=August 28, 2012|archive-date=June 18, 2016|archive-url=https://web.archive.org/web/20160618054737/https://einstein.phys.uwm.edu/radiopulsar/html/BRP4_discoveries/|url-status=live}}</ref>

=== Other uses ===
Terrestrial aeronomy experiments at Arecibo have included the [[NASA Coqui|Coqui 2]] experiment, supported by [[NASA]]. The telescope also originally had [[military intelligence]] uses, including locating [[Soviet Union|Soviet]] [[radar]] installations by detecting their signals [[EME (communications)|bouncing]] off the [[Moon]].<ref>Steve Blank "Secret history of Silicon Valley" talk</ref>

Limited amateur radio operations have occurred, using ''moon bounce'' or [[Earth–Moon–Earth communication]], in which radio signals aimed at the Moon are reflected back to Earth. The first of these operations was on June 13–14, 1964, using the call KP4BPZ. A dozen or so two-way contacts were made on 144 and 432&nbsp;MHz. On July 3 and 24, 1965, KP4BPZ was again activated on 432&nbsp;MHz, making approximately 30 contacts on 432&nbsp;MHz during the limited time slots available. For these tests, a very wide-band instrumentation recorder captured a large segment of the receiving bandwidth, enabling later verification of other amateur station callsigns. These were not two-way contacts. From April 16–18, 2010, again, the Arecibo Amateur Radio Club KP4AO conducted moon-bounce activity using the antenna.<ref>{{cite web |url=http://www.arrl.org/news/moonbounce-for-everyone-courtesy-of-the-arecibo-radio-telescope |title=ARRL; Moonbounce for everyone |access-date=January 10, 2013|archive-date=September 18, 2012|archive-url=https://web.archive.org/web/20120918045432/http://www.arrl.org/news/moonbounce-for-everyone-courtesy-of-the-arecibo-radio-telescope|url-status=live}}</ref><!--There's a QST article, but I can't find a good reference to it.--> On November 10, 2013, the KP4AO Arecibo Amateur Radio Club conducted a Fifty-Year Commemoration Activation, lasting seven hours on 14.250&nbsp;MHz SSB, without using the main dish antenna.<ref>{{Cite web |url=http://www.arrl.org/news/arecibo-observatory-50th-anniversary-special-event-set |title=Arecibo Observatory 50th Anniversary Special Event Set |access-date=November 20, 2020 |archive-date=May 31, 2020 |archive-url=https://web.archive.org/web/20200531221237/http://www.arrl.org/news/arecibo-observatory-50th-anniversary-special-event-set |url-status=live }}</ref>


== Ángel Ramos Foundation Visitor Center ==
== Ángel Ramos Foundation Visitor Center ==

Revision as of 20:44, 1 December 2020

Arecibo Observatory
The Arecibo Telescope in 2019
Alternative namesNational Astronomy and Ionosphere Center Edit this at Wikidata
Named afterArecibo Edit this on Wikidata
Organization
Observatory code 251 Edit this on Wikidata
LocationArecibo, Puerto Rico, Caribbean
Coordinates18°20′48″N 66°45′12″W / 18.3467°N 66.7533°W / 18.3467; -66.7533
Altitude498 m (1,634 ft) Edit this at Wikidata
Websitewww.naic.edu Edit this at Wikidata
Telescopes
  Related media on Commons
[edit on Wikidata]

The Arecibo Observatory is an observatory in Arecibo, Puerto Rico, also known as the National Astronomy and Ionosphere Center (NAIC). It is owned by the US National Science Foundation (NSF).

The main instrument of the observatory was the Arecibo Telescope, a 305 m (1,000 ft) spherical reflector dish built into a natural sinkhole, a cable-mount steerable receiver mounted 150 m (492 ft) above the dish, and several radar transmitters for emitting signals. For more than 50 years, the Arecibo Telescope was the world's largest single-aperture telescope, surpassed in July 2016 by the Five-hundred-meter Aperture Spherical Telescope (FAST) in China. The Observatory also includes a radio telescope, a Lidar facility, and a visitor's center.


Telescopes

The main feature of the Arecibo Observatory was its large radio telescope. The telescope's main collecting dish had the shape of a spherical cap 1,000 feet (305 m) in diameter with an 869-foot (265 m) radius of curvature,[1] and was constructed inside a karst sinkhole.[2] The dish surface was made of 38,778 perforated aluminum panels, each about 3 by 7 feet (1 by 2 m), supported by a mesh of steel cables.[1] The ground beneath supported shade-tolerant vegetation.[3]

The Arecibo Observatory also has other facilities beyond the main telescope, including a 12 metres (39 ft) radio telescope used for VLBI,[4] and a LIDAR facility.[5]

The Arecibo Radio Telescope as viewed from the observation deck, October 2013

Ángel Ramos Foundation Visitor Center

Logo of the observatory at the entrance gate

Opened in 1997, the Ángel Ramos Foundation Visitor Center features interactive exhibits and displays about the operations of the radio telescope, astronomy and atmospheric sciences.[6] The center is named after the financial foundation that honors Ángel Ramos, owner of the El Mundo newspaper and founder of Telemundo. The Foundation provided half of the funds to build the Visitor Center, with the remainder received from private donations and Cornell University.

The center, in collaboration with the Caribbean Astronomical Society,[7] host a series of Astronomical Nights throughout the year, which feature diverse discussions regarding exoplanets, and astronomical phenomena and discoveries (such as Comet ISON). The main purpose of the center is to increase public interest in astronomy, the observatory's research successes, and space endeavors.

List of directors

Source(s):[8][additional citation(s) needed]

Due to its unique shape and concept, the observatory is featured in many contemporary works. It was used as a filming location in the films GoldenEye (1995), Species (1995), and Contact (1997) (based on Carl Sagan's novel of the same name which also featured the observatory),[12][13] and in The X-Files television episode "Little Green Men".[14] In 2014, a video art installation piece titled The Great Silence by artists Jennifer Allora and Guillermo Calzadilla in collaboration with science fiction writer Ted Chiang featured the radio telescope at Arecibo Observatory to represent the search for extraterrestrial life. The juxtaposed text was later published as a short story with the same title in a special issue of the art journal e-flux in 2015 and was included in the author's short story collection Exhalation: Stories in 2019.[15]

See also

References

  1. ^ a b Goldsmith, P. F.; Baker, L. A.; Davis, M. M.; Giovanelli, R. (1995). "Multi-feed Systems for the Arecibo Gregorian". Astronomical Society of the Pacific Conference Series. 75: 90–98. Bibcode:1995ASPC...75...90G.
  2. ^ Cite error: The named reference naic about was invoked but never defined (see the help page).
  3. ^ "Environmental Impact Statement for the Arecibo Observatory Arecibo, Puerto Rico (Draft)" (PDF). nsf.gov. NSF. p. 66. At the Arecibo Observatory, a mix of shade-tolerant species have colonized the area beneath the 305-meter radio telescope dish.
  4. ^ Roshi, D. Anish; Anderson, L. D.; Araya, E.; Balser, D.; Brisken, W.; Brum, C.; Campbell, D.; Chatterjee, S.; Churchwell, E.; Condon, J.; Cordes, J.; Cordova, F.; Fernandez, Y.; Gago, J.; Ghosh, T.; Goldsmith, P. F.; Heiles, C.; Hickson, D.; Jeffs, B.; Jones, K. M.; Lautenbach, J.; Lewis, B. M.; Lynch, R. S.; Manoharan, P. K.; Marshall, S.; Minchin, R.; Palliyaguru, N. T.; Perera, B. B. P.; Perillat, P.; Pinilla-Alonso, N.; Pisano, D. J.; Quintero, L.; Raizada, S.; Ransom, S. M.; Fernandez-Rodriguez, F. O.; Salter, C. J.; Santos, P.; Sulzer, M.; Taylor, P. A.; Venditti, F. C. F.; Venkataraman, A.; Virkki, A. K.; Wolszczan, A.; Womack, M.; Zambrano-Marin, L. F. (13 July 2019). "Astro2020 Activities and Projects White Paper: Arecibo Observatory in the Next Decade". arXiv:1907.06052 [astro-ph]. arXiv:1907.06052.
  5. ^ Cite error: The named reference NSFrelease20-010 was invoked but never defined (see the help page).
  6. ^ Visitor Center information Archived November 4, 2013, at the Wayback Machine
  7. ^ "Sociedad de Astronomia del Caribe". www.sociedadastronomia.com. Archived from the original on May 5, 2014. Retrieved May 5, 2014.
  8. ^ Altschuler, Daniel; Salter, Chris (June 2014). "Early history of Arecibo Observatory". Physics Today. 67 (6): 12. Bibcode:2014PhT....67f..12A. doi:10.1063/PT.3.2402.
  9. ^ January 24; 2007. "Tor Hagfors, astronomy professor and Arecibo pioneer, dies at age 76". Cornell Chronicle. Archived from the original on November 20, 2020. Retrieved November 20, 2020. {{cite web}}: |last2= has numeric name (help)CS1 maint: numeric names: authors list (link)
  10. ^ Christiansen, Jen. "Pop Culture Pulsar: The Science Behind Joy Division's Unknown Pleasures Album Cover". Scientific American Blog Network. Archived from the original on November 12, 2020. Retrieved November 20, 2020.
  11. ^ a b Watson, Traci (November 2015). "Arecibo Observatory director quits after funding row". Nature. 527 (7577): 142–143. Bibcode:2015Natur.527..142W. doi:10.1038/nature.2015.18745. PMID 26560275.
  12. ^ Brinkman, Paul (November 29, 2019). "Iconic space observatory in Puerto Rico recovers after Hurricane Maria". UPI. Archived from the original on November 18, 2020. Retrieved November 19, 2020.
  13. ^ Drake, Nadia (November 12, 2020). "Iconic radio telescope in Puerto Rico is at risk of collapsing". National Geographic. Archived from the original on November 19, 2020. Retrieved November 19, 2020.
  14. ^ Overbye, Dennis (November 19, 2020). "Arecibo Observatory, a Great Eye on the Cosmos, Is Going Dark". The New York Times. Archived from the original on November 19, 2020. Retrieved November 19, 2020.
  15. ^ Morgan, Adam (May 6, 2019). "Ted Chiang, the mind behind Arrival, returns with another awe-inducing sci-fi collection". The A.V. Club. Archived from the original on November 7, 2020. Retrieved November 19, 2020.

Further reading

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