Arecibo Telescope
Alternative names | Arecibo Telescope |
---|---|
Named after | Arecibo, William E. Gordon, James Gregory |
Part of | Arecibo Observatory |
Location(s) | Arecibo, Puerto Rico, Caribbean |
Coordinates | 18°20′39″N 66°45′10″W / 18.34417°N 66.75278°W |
Organization | University of Central Florida |
Altitude | 498 m (1,634 ft) |
Wavelength | 3 cm (10.0 GHz)–1 m (300 MHz) |
First light | November 1, 1963 |
Decommissioned | Announced November 19, 2020 Collapsed December 1, 2020 |
Telescope style | Gregorian telescope radio telescope |
Diameter | 304.8 m (1,000 ft 0 in) |
Secondary diameter | 27 m (88 ft 7 in) |
Illuminated diameter | 221 m (725 ft 1 in) |
Collecting area | 73,000 m2 (790,000 sq ft) |
Focal length | 132.6 m (435 ft 0 in) |
Website | www |
Related media on Commons | |
The Arecibo Telescope was a 305 m (1,000 ft)
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 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.
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
The NSF reduced its funding commitment to the observatory from 2006, leading academics to push for additional funding support to continue its programs. The telescope was damaged by
General information
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,[9] and was constructed inside a karst sinkhole.[10] 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.[9] The ground beneath supported shade-tolerant vegetation.[11]
The telescope had three
The dish remained stationary, while receivers and transmitters were moved to the proper focal point of the telescope to aim at the desired target.
History
Design and construction
The origins of the observatory trace to late 1950s efforts to develop
Among the many Defender projects were several studies based on the concept that a re-entering
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.[18][19]
The observatory was built between mid-1960 and November 1963.
Ward Low of the ARPA pointed out this flaw and put Gordon in touch with the
George Doundoulakis, who directed research at the 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 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 feed.[21][20] 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 azimuthal 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 cable suspension system which was finally adopted. The final configuration was substantially the same as in the original drawings by George and Helias Doundoulakis, although with three towers, instead of the four drawn in the patent, which was granted to Helias Doundoulakis by the U.S. Patent office.[28][29]
The suspended structure was designed by Dr. Thomas C. Kavanagh, Fred Severud, and Dr. Hans Bandel, who were selected after the 1959 RFP issued by Cornell University. A proposal by the General Bronze Corporation was not selected as it did not meet specifications, according to an editorial response by Donald Cooke (Cornell's spokesperson) to Helias Doundoulakis in a newsletter of the Institute of Electrical and Electronics Engineers (IEEE). Cooke stated that Doundoulakis used an incorrect feed/paraxial surface measurement. However, the measurement Cooke used was from Doundoulakis’ patent issued in 1966, and not from the 1959 RFP meetings which predated the patent by seven years.[29][28] Furthermore, proposal measurements presented by George Doundoulakis and Helias Doundoulakis at the RFP meeting on December 10, 1959, were not referenced in Cooke's editorial response.[29] The originators of this proposal subsequently filed a dispute, originally for $1.2 million but was settled for $10,000 because "the defense in a court trial would cost far more than the $10,000 for which the case was settled," and accordingly, on April 11, 1975, Doundoulakis v. U.S. (Case 412-72) had been ruled in plaintiff's favor by the United States Court of Federal Claims, that “(a) a judgment has been entered in favor of the plaintiffs (Helias Doundoulakis, William J. Casey, and Constantine Michalos) against the United States and (b) in consideration of the sum of $10,000 to be paid by the United States Government to the plaintiff, the plaintiffs grants to the United States Government an irrevocable, fully-paid, non-exclusive license under the aforesaid U.S. Patent No. 3, 273, 156 to Cornell University.”[29]
The idea of a spherical reflecting mirror with a steerable secondary has since been used in optical telescopes, in particular, the Hobby–Eberly Telescope[30]
Construction began in mid-1960, with the telescope operational about three years later. The telescope's and the supporting observatory's official opening as the Arecibo Ionospheric Observatory (AIO) was held on November 1, 1963.[31][32]
Upgrades
Since its construction, the telescope was upgraded several times, following the facility's oversight from the DoD to the National Science Foundation on October 1, 1969, and subsequent renaming of the AIO to the National Astronomy and Ionosphere Center (NAIC) in September 1971.[16][32] Initially, when the maximum expected operating frequency was about 500 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,[33] and the highest usable frequency rose to about 5000 MHz. A 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 GHz range, that could be easily moved to the focal point, giving Arecibo more flexibility. The additional instrumentation added 270-tonne (300-short-ton) to the platform, so six additional support cables were added, two for each tower.[16] A metal mesh screen was also installed around the perimeter to block the ground's thermal radiation from reaching the feed antennas. In 1997, a more powerful 2400 MHz transmitter was added.[34] Finally, in 2013 with a grant of US$2.5 million, work for adding the ionospheric modification HF facility began which was completed in 2015. The HF facility consisted on the sender side of six foldable 100 kW crossed dipoles inside the main dish and a hanging 100m wide subreflector mesh between the dish and platform.[35][36]
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.[33] Between 2001 and 2006, NASA decreased, then eliminated, its support of the planetary radar.[37]
A November 2006 report by the Astronomical Sciences division recommended substantially decreased astronomy funding for the Arecibo Observatory, from US$10.5 million in 2007 to US$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.[38][39]
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.
Arecibo's budget from NSF continued to wane in the following years.[46][47] Starting in FY2010, NASA restored its historical support by contributing $2.0 million per year for planetary science, particularly the study of near-Earth objects, at Arecibo. NASA implemented this funding through its Near Earth Object Observations program.[48] NASA increased its support to $3.5 million per year in 2012.
In 2011, NSF removed
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 statements on the effect of disassembling the unit.[52] The NSF continued to indicate it would like to reduce funding to the Observatory in the short term.[53][54] As in 2008, academics expressed their concern over the loss of scientific discoveries that could occur should the Observatory be shut down.[52]
2020 damage, decommissioning plans, and collapse
Several hurricanes and storms over the 2010s had raised the concerns of structural engineers over the stability of the observatory.[55] On September 21, 2017, high winds associated with Hurricane Maria caused the 430 MHz line feed to break and fall onto the primary dish, damaging roughly 30 of the 38,000 aluminum panels. Most Arecibo observations did not use the line feed but instead relied on the feeds and receivers located in the dome. Overall, the damage inflicted by Maria was minimal,[56][57][58][59] 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.[60]
A consortium consisting of the
On August 10, 2020, an auxiliary platform support cable separated from Tower 4, causing damage to the telescope, including a 100 ft (30 m) gash in the reflector dish.[64][65] Damage included six to eight panels in the Gregorian dome, and to the platform used to access the dome. No one was reported to have been hurt by the partial collapse. The facility was closed as damage assessments were made.[66]
The facility had recently reopened following the passing of
Before repairs could be started, on November 7, 2020, one of the two main support cables from Tower 4 snapped, shattering part of the dish itself as it fell.
While waiting for NSF to make the decommissioning plans, steps had been taken to try to reduce the load that each of the towers were carrying, including reducing the strain on the backstay support cables for the individual towers. Other plans, such as having helicopters hoisting part of the load while hovering above the telescope, were proposed but deemed too risky.[70] Engineers from UCF had been monitoring the telescope and observed that wires in the backstay cables for the support towers had been breaking at a rate of one or two a day, and estimated that the telescope would soon collapse.[71] In the weekend prior to December 1, 2020, wire strands in the receiver's supporting cables had also been snapping apart at a rapid rate, according to Ángel Vázquez, the director of operations. This culminated in the collapse of the receiver platform at around 6:55 a.m. AST (10:55 UTC) on December 1, 2020, as the second main cable from Tower 4 failed with the other two remaining support cables failing moments later. The collapse of the receiver structure and cables onto the dish caused extensive additional damage.[7][8][72] As the receiver fell, it also sheared the tips of the towers which the support cables ran through. Once the main cables from Tower 4 released, the backstay cables, which normally balanced the horizontal component of force from the main cables, pulled the tower outwards and broke off the top. The other two towers, once the force of supporting the platform was released, also had their tips sheared off due to the backstay cable tension.[70] The top of Tower 12 caused some structural damage to other buildings on the observatory as it fell. No injuries from the collapse were reported.[73][70][74]
Post-collapse
In the weeks following Arecibo's collapse, the administration of the
In late December 2020, Wanda Vázquez Garced, then governor of Puerto Rico signed an executive order for $8 million for the removal of debris and for the design of a new observatory to be built in its place. The governor stated reconstruction of the observatory is a "matter of public policy". The executive order also designated the area as a history site.[76]
As required by the Consolidated Appropriations Act, 2021, the NSF sent a report to Congress in March 2022 "on the causes and extent of the damage, the plan to remove debris in a safe and environmentally sound way, the preservation of the associated [Arecibo Observatory] facilities and surrounding areas, and the process for determining whether to establish comparable technology at the site, along with any associated cost estimates".[77][78] On March 25, 2022, a survey salvage committee formed by UCF and the NSF issued a final report, identifying materials from the site that may be salvaged for their "historic importance or scientific utility."[79]
A team from the
An early plan developed by NSF scientists suggest one possible replacement called the Next Generation Arecibo Telescope, using 1000 closely-packed 9-meter (30 ft) telescopes mounted on one or more flat plate(s) that would cover the 300-meter (980 ft) width of the Arecibo sinkhole. While the telescopes themselves would be fixed, the plate(s) would be able to be rotated more than 45° off the horizontal in any direction. This would allow the new instrument to have 500 times the field of view of the original Arecibo Telescope, and be twice as sensitive with four times the radar power. It was expected this would cost roughly US$450 million to build.[81] This would enable better study of the supermassive black hole at the center of the Milky Way as a prime target.[16]
NSF decided in October 2022 that the Arecibo site would not be used for a new telescope, instead converting the site to be a STEM educational center.[82]
The Arecibo Salvage Survey committee preserved some parts of the telescope, including parts of the zenith and azimuth tracks, a corner of the platform, the rotary joint, and the cable car.[83]
Research and discoveries
Many scientific discoveries were made with the observatory. On April 7, 1964, soon after it began operating,
In 1980, Arecibo made the first radar observation of a comet when it successfully detected
In January 2008, detection of prebiotic molecules methanimine and hydrogen cyanide were reported from the observatory's radio spectroscopy measurements of the distant starburst galaxy Arp 220.[92]
From January 2010 to February 2011, 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 kG-strength magnetic field and magnetic activity similar to both the planet Jupiter and the Sun.[93]
The 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.[94] 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.[95]
SETI and METI projects
Search for extraterrestrial intelligence (SETI)[96] 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 search by transmitting messages.
Arecibo was 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 observations.[97] The Einstein@Home distributed computing project has found more than 20 pulsars in Arecibo data.[98]
Other uses
Terrestrial aeronomy experiments at Arecibo included the
Limited amateur radio operations were carried out, 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 sign KP4BPZ. A dozen or so two-way contacts were made on 144 and 432 MHz. On July 3 and 24, 1965, KP4BPZ was again activated on 432 MHz, making approximately 30 contacts on 432 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 call signs. These were not two-way contacts. From April 16–18, 2010, the Arecibo Amateur Radio Club KP4AO again conducted moon-bounce activity using the antenna.[100] On November 10, 2013, the KP4AO Arecibo Amateur Radio Club conducted a Fifty-Year Commemoration Activation, lasting seven hours on 14.250 MHz SSB, without using the main dish antenna.[101]
Cultural significance
Due to its unique shape and concept, the telescope had been featured in many contemporary works. It serves as one of the central locations in The Sparrow, a science fiction novel written by Mary Doria Russell. 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), The Losers (2010),[102][69] and in The X-Files television episode "Little Green Men".[103] One map in the 2013 video game Battlefield 4, while set in China, is based on the distinctive layout of the Arecibo Telescope.[104] 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 next year, Chiang published a novelette also called The Great Silence. 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.[105]
The asteroid 4337 Arecibo is named after the observatory by Steven J. Ostro, in recognition of the observatory's contributions to the characterization of Solar System bodies.[106]
See also
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Further reading
- Friedlander, Blaine (November 14, 1997). "Research rockets, including an experiment from Cornell, are scheduled for launch into the ionosphere next year from Puerto Rico". Cornell University.
- Ruiz, Carmelo (March 3, 1998). "Activists protest US Navy radar project". Global Network Against Weapons and Nuclear Power in Space. Archived from the original on May 1, 2001.
- Amir Alexander (July 3, 2008). "Budget Cuts Threaten Arecibo Observatory". The Planetary Society. Archived from the original on July 21, 2008.
- Blaine Friedlander (June 10, 2008). "Arecibo joins global network to create 6,000-mile (9,700 km) telescope". EurekAlert.
- Lauren Gold (June 5, 2008). "Clintons (minus Hillary) visit Arecibo; former president urges more federal funding for basic sciences". Cornell university.
- Henry Fountain (December 25, 2007). "Arecibo Radio Telescope Is Back in Business After 6-Month Spruce-Up". New York Times.
- Entry into the National Register of Historic Places
- Cohen, Marshall H. (2009). "Genesis of the 1000-foot Arecibo Dish". Journal of Astronomical History and Heritage. 12 (2): 141–152.
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