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126-431: 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

252-457: A single converted radar antenna (broadside array) at 200 MHz near Sydney, Australia . This group used the principle of a sea-cliff interferometer in which the antenna (formerly a World War II radar) observed the Sun at sunrise with interference arising from the direct radiation from the Sun and the reflected radiation from the sea. With this baseline of almost 200 meters, the authors determined that

378-627: A 'One-Mile' and later a '5 km' effective aperture using the One-Mile and Ryle telescopes, respectively. They used the Cambridge Interferometer to map the radio sky, producing the Second (2C) and Third (3C) Cambridge Catalogues of Radio Sources. Radio astronomers use different techniques to observe objects in the radio spectrum. Instruments may simply be pointed at an energetic radio source to analyze its emission. To "image"

504-407: A 360 degree circle, east has azimuth 90°, south 180°, and west 270°. There are exceptions: some navigation systems use south as the reference vector. Any direction can be the reference vector, as long as it is clearly defined. Quite commonly, azimuths or compass bearings are stated in a system in which either north or south can be the zero, and the angle may be measured clockwise or anticlockwise from

630-504: A central point are preserved. Some navigation systems use south as the reference plane. However, any direction can serve as the plane of reference, as long as it is clearly defined for everyone using that system. If, instead of measuring from and along the horizon, the angles are measured from and along the celestial equator , the angles are called right ascension if referenced to the Vernal Equinox, or hour angle if referenced to

756-529: A conventional tracking radar on the single return from the warhead. 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

882-422: A day, and estimated that the telescope would soon collapse. 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

1008-471: 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

1134-419: A horizontal angle measured clockwise from a north base line or meridian . Azimuth has also been more generally defined as a horizontal angle measured clockwise from any fixed reference plane or easily established base direction line. Today, the reference plane for an azimuth is typically true north , measured as a 0° azimuth, though other angular units ( grad , mil ) can be used. Moving clockwise on

1260-478: 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. Furthermore, proposal measurements presented by George Doundoulakis and Helias Doundoulakis at

1386-768: A region of the sky in more detail, multiple overlapping scans can be recorded and pieced together in a mosaic image. The type of instrument used depends on the strength of the signal and the amount of detail needed. Observations from the Earth 's surface are limited to wavelengths that can pass through the atmosphere. At low frequencies or long wavelengths, transmission is limited by the ionosphere , which reflects waves with frequencies less than its characteristic plasma frequency . Water vapor interferes with radio astronomy at higher frequencies, which has led to building radio observatories that conduct observations at millimeter wavelengths at very high and dry sites, in order to minimize

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1512-440: A second Klystron tube and improving the design. 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. The Astronomical Sciences and Atmospheric Sciences divisions of

1638-518: 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." A team from the University of Texas at Austin was able to completely recover and back up the 3 petabytes of data that the telescope had captured since opening in the 1960s by May 2021 before further harm could come to

1764-640: 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 133 m (435 ft) tower centered in the 305 m (1,000 ft) reflector to support the feed. 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

1890-567: Is a subfield of astronomy that studies celestial objects at radio frequencies . The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation coming from the Milky Way . Subsequent observations have identified a number of different sources of radio emission. These include stars and galaxies , as well as entirely new classes of objects, such as radio galaxies , quasars , pulsars , and masers . The discovery of

2016-507: Is based on the distinctive layout of the Arecibo Telescope. 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

2142-405: Is because radio astronomy allows us to see things that are not detectable in optical astronomy. Such objects represent some of the most extreme and energetic physical processes in the universe. The cosmic microwave background radiation was also first detected using radio telescopes. However, radio telescopes have also been used to investigate objects much closer to home, including observations of

2268-399: Is called the azimuth. When used as a celestial coordinate , the azimuth is the horizontal direction of a star or other astronomical object in the sky . The star is the point of interest, the reference plane is the local area (e.g. a circular area with a 5 km radius at sea level ) around an observer on Earth's surface , and the reference vector points to true north . The azimuth

2394-408: Is east or west. The directions are chosen so that the angle, stated between them, is positive, between zero and 90 degrees. If the bearing happens to be exactly in the direction of one of the cardinal points , a different notation, e.g. "due east", is used instead. We are standing at latitude φ 1 {\displaystyle \varphi _{1}} , longitude zero; we want to find

2520-413: Is the horizontal angle from a cardinal direction , most commonly north , in a local or observer-centric spherical coordinate system . Mathematically, the relative position vector from an observer ( origin ) to a point of interest is projected perpendicularly onto a reference plane (the horizontal plane ); the angle between the projected vector and a reference vector on the reference plane

2646-618: Is the angle between the north vector and the star's vector on the horizontal plane . Azimuth is usually measured in degrees (°), in the positive range 0° to 360° or in the signed range -180° to +180°. The concept is used in navigation , astronomy , engineering , mapping , mining , and ballistics . The word azimuth is used in all European languages today. It originates from medieval Arabic السموت ( al-sumūt , pronounced as-sumūt ), meaning "the directions" (plural of Arabic السمت al-samt = "the direction"). The Arabic word entered late medieval Latin in an astronomy context and in particular in

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2772-468: Is the angle measured at our viewpoint by a theodolite whose axis is perpendicular to the surface of the spheroid; geodetic azimuth (or geodesic azimuth ) is the angle between north and the ellipsoidal geodesic (the shortest path on the surface of the spheroid from our viewpoint to Point 2). The difference is usually negligible: less than 0.03 arc second for distances less than 100 km. Normal-section azimuth can be calculated as follows: where f

2898-399: Is the flattening and e the eccentricity for the chosen spheroid (e.g., 1 ⁄ 298.257 223 563 for WGS84 ). If φ 1 = 0 then To calculate the azimuth of the Sun or a star given its declination and hour angle at a specific location, modify the formula for a spherical Earth. Replace φ 2 with declination and longitude difference with hour angle, and change the sign (since

3024-420: Is the reason why the X and Y axis in the above formula are swapped. If the azimuth becomes negative, one can always add 360°. The formula in radians would be slightly easier: Note the swapped ( x , y ) {\displaystyle (x,y)} in contrast to the normal ( y , x ) {\displaystyle (y,x)} atan2 input order. The opposite problem occurs when

3150-557: Is the size of the antennas furthest apart in the array. In order to produce a high quality image, a large number of different separations between different telescopes are required (the projected separation between any two telescopes as seen from the radio source is called a "baseline") – as many different baselines as possible are required in order to get a good quality image. For example, the Very Large Array has 27 telescopes giving 351 independent baselines at once. Beginning in

3276-710: Is with-in the responsibility of the appropriate national administration. The allocation might be primary, secondary, exclusive, and shared. In line to the appropriate ITU Region the frequency bands are allocated (primary or secondary) to the radio astronomy service as follows. MOBILE-SATELLITE RADIO ASTRONOMY AERONAUTICAL MOBILE-SATELLITE RADIO ASTRONOMY AERONAUTICAL RADIODETERMINATION- MOBILE-SATELLITE RADIO ASTRONOMY AERONAUTICAL Radiodetermination- Azimuth An azimuth ( / ˈ æ z ə m ə θ / ; from Arabic : اَلسُّمُوت , romanized :  as-sumūt , lit.   'the directions')

3402-717: The Cavendish Astrophysics Group developed the technique of Earth-rotation aperture synthesis . The radio astronomy group in Cambridge went on to found the Mullard Radio Astronomy Observatory near Cambridge in the 1950s. During the late 1960s and early 1970s, as computers (such as the Titan ) became capable of handling the computationally intensive Fourier transform inversions required, they used aperture synthesis to create

3528-580: 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". On March 25, 2022,

3654-576: The Coqui 2 experiment, supported by NASA . The telescope also originally had military intelligence uses, including locating Soviet radar installations by detecting their signals bouncing off the Moon . 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

3780-482: The National Astronomy and Ionosphere Center (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 Universidad Metropolitana de Puerto Rico , with a number of other collaborators. NSF also decertified NAIC as a Federally Funded Research and Development Center (FFRDC) , which

3906-533: 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

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4032-647: The Sun and solar activity, and radar mapping of the planets . Other sources include: Earth's radio signal is mostly natural and stronger than for example Jupiter's, but is produced by Earth's auroras and bounces at the ionosphere back into space. Radio astronomy service (also: radio astronomy radiocommunication service ) is, according to Article 1.58 of the International Telecommunication Union's (ITU) Radio Regulations (RR), defined as "A radiocommunication service involving

4158-594: The Telecommunications Research Establishment that had carried out wartime research into radar , created a radiophysics group at the university where radio wave emissions from the Sun were observed and studied. This early research soon branched out into the observation of other celestial radio sources and interferometry techniques were pioneered to isolate the angular source of the detected emissions. Martin Ryle and Antony Hewish at

4284-400: The U.S. Patent office . 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

4410-599: The United States Congress on the importance of the work of the observatory. led to additional US$ 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 planetary radar system and student training. Arecibo's budget from NSF continued to wane in

4536-633: 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

4662-661: The Very Long Baseline Array (with telescopes located across North America) and the European VLBI Network (telescopes in Europe, China, South Africa and Puerto Rico). Each array usually operates separately, but occasional projects are observed together producing increased sensitivity. This is referred to as Global VLBI. There are also a VLBI networks, operating in Australia and New Zealand called

4788-526: The celestial meridian . In mathematics, the azimuth angle of a point in cylindrical coordinates or spherical coordinates is the anticlockwise angle between the positive x -axis and the projection of the vector onto the xy - plane . A special case of an azimuth angle is the angle in polar coordinates of the component of the vector in the xy -plane, although this angle is normally measured in radians rather than degrees and denoted by θ rather than φ . For magnetic tape drives , azimuth refers to

4914-511: The cosmic microwave background radiation , regarded as evidence for the Big Bang theory , was made through radio astronomy. Radio astronomy is conducted using large radio antennas referred to as radio telescopes , that are either used singularly, or with multiple linked telescopes utilizing the techniques of radio interferometry and aperture synthesis . The use of interferometry allows radio astronomy to achieve high angular resolution , as

5040-426: 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. A metal mesh screen was also installed around the perimeter to block the ground's thermal radiation from reaching the feed antennas. As part of this upgrade the power of the 2380 MHz transmitter was doubled to 1 MW by adding

5166-411: The horizontal coordinate system , used in celestial navigation , azimuth is one of the two coordinates . The other is altitude , sometimes called elevation above the horizon. It is also used for satellite dish installation (see also: sat finder ). In modern astronomy azimuth is nearly always measured from the north. In land navigation, azimuth is usually denoted alpha , α , and defined as

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5292-574: The supermassive black hole at the center of the Milky Way as a prime target. 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. 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

5418-514: The 1860s, James Clerk Maxwell 's equations had shown that electromagnetic radiation is associated with electricity and magnetism , and could exist at any wavelength . Several attempts were made to detect radio emission from the Sun including an experiment by German astrophysicists Johannes Wilsing and Julius Scheiner in 1896 and a centimeter wave radiation apparatus set up by Oliver Lodge between 1897 and 1900. These attempts were unable to detect any emission due to technical limitations of

5544-490: The 1970s, improvements in the stability of radio telescope receivers permitted telescopes from all over the world (and even in Earth orbit) to be combined to perform very-long-baseline interferometry . Instead of physically connecting the antennas, data received at each antenna is paired with timing information, usually from a local atomic clock , and then stored for later analysis on magnetic tape or hard disk. At that later time,

5670-466: The 1997 installation of the Gregorian dome, the main support cables and support towers had been engineered with a safety factor of two, as to be able to sustain twice the weight of the platform. When the dome was added in 1997, the auxiliary cables were intended to retain the safety factor of two once all design factors were considered, but Kerr believed that that was never the case as evenly distributing

5796-399: The 2010s had raised the concerns of structural engineers over the stability of the observatory. 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

5922-576: The Arecibo Amateur Radio Club KP4AO again conducted moon-bounce activity using the antenna. 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. Due to its unique shape and concept, the telescope had been featured in many contemporary works. It serves as one of

6048-659: The Arecibo Observatory, beginning with a cut to US$ 10.5 million in 2007 and continuing to decrease 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. 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

6174-428: 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. This would enable better study of

6300-458: The Earth's ionosphere . He was attracted to the sinkholes in the karst regions of Puerto Rico that offered perfect cavities for a very large dish. Originally, a fixed parabolic reflector was envisioned, pointing in a fixed direction with a 150 m (492 ft) 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

6426-619: The LBA (Long Baseline Array), and arrays in Japan, China and South Korea which observe together to form the East-Asian VLBI Network (EAVN). Since its inception, recording data onto hard media was the only way to bring the data recorded at each telescope together for later correlation. However, the availability today of worldwide, high-bandwidth networks makes it possible to do VLBI in real time. This technique (referred to as e-VLBI)

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6552-512: The NSF announced on November 19, 2020, that the telescope would be decommissioned and dismantled, with the LIDAR facility remaining operational. Before it could be decommissioned, several of the remaining support cables suffered a critical failure and the support structure, antenna, and dome assembly all fell into the dish at 7:55 a.m. local time on December 1, 2020, destroying the telescope. The NSF decided in October 2022 that it would not rebuild

6678-528: The NSF began committing to major projects. However, the funding increase never arrived and the NSF was left with the new commitments. In 2005 the Astronomical Sciences division commissioned a "Senior Review" of its facilities to deal with its increasingly constrained budget. The Senior Review report released in November 2006 "regretfully" recommended substantially decreased astronomy funding for

6804-463: The NSF had financially supported Arecibo since its completion in the 1970s, with incremental support by NASA, for operating the planetary radar. In 2001 NASA announced a rampdown and elimination of its support of the planetary radar by 2005. In 2002, after several years of discussion, the US Congress passed a bill to double the NSF budget, and instructed the NSF to begin new projects. As a result,

6930-473: 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, but which would also remove the FFRDC 's promise of stability intended to retain the very best technical staff. While the Observatory continued to operate under the reduced NSF budget and NASA funds, NSF signaled in 2015 and 2016 that it

7056-475: The NSF to reduce its contribution towards Arecibo's operating costs from $ 8 million to $ 2 million from the fiscal year 2022–2023, thus securing the observatory's future. With this, the UCF consortium were named the new operators of the observatory in 2018. 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

7182-575: The Northern 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. The origins of the observatory trace to late 1950s efforts to develop anti-ballistic missile (ABM) defenses as part of

7308-466: 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. He presented his proposal to Cornell University for

7434-477: The RFP meeting on December 10, 1959, were not referenced in Cooke's editorial response. 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

7560-489: The Sun. Both researchers were bound by wartime security surrounding radar, so Reber, who was not, published his 1944 findings first. Several other people independently discovered solar radio waves, including E. Schott in Denmark and Elizabeth Alexander working on Norfolk Island . At Cambridge University , where ionospheric research had taken place during World War II , J. A. Ratcliffe along with other members of

7686-500: 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

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7812-543: The Type ;I bursts. Two other groups had also detected circular polarization at about the same time ( David Martyn in Australia and Edward Appleton with James Stanley Hey in the UK). Modern radio interferometers consist of widely separated radio telescopes observing the same object that are connected together using coaxial cable , waveguide , optical fiber , or other type of transmission line . This not only increases

7938-635: 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 ARPA pointed out this flaw and put Gordon in touch with the 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 waves in and through

8064-588: The aforesaid U.S. Patent No. 3, 273, 156 to Cornell University.” The idea of a spherical reflecting mirror with a steerable secondary has since been used in optical telescopes, in particular, the Hobby–Eberly Telescope 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)

8190-467: The azimuth from our viewpoint to Point 2 at latitude φ 2 {\displaystyle \varphi _{2}} , longitude L (positive eastward). We can get a fair approximation by assuming the Earth is a sphere, in which case the azimuth α is given by A better approximation assumes the Earth is a slightly-squashed sphere (an oblate spheroid ); azimuth then has at least two very slightly different meanings. Normal-section azimuth

8316-469: The cable car. In 2024 the National Academies of Sciences, Engineering and Medicine issued a report on the collapse. 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 was not 88 days, as formerly thought, but only 59 days. In 1968, the discovery of

8442-624: 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), and in The X-Files television episode " Little Green Men ". One map in the 2013 video game Battlefield 4 , while set in China,

8568-646: The climactic fight scene in the James Bond film GoldenEye (1995). It is one of the 116 pictures included in the Voyager Golden Record . It has been listed on the US National Register of Historic Places since 2008. The telescope was named an IEEE Milestone in 2001. 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

8694-443: 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

8820-408: The coordinates ( X 1 , Y 1 ) of one point, the distance D , and the azimuth α to another point ( X 2 , Y 2 ) are known, one can calculate its coordinates: This is typically used in triangulation and azimuth identification (AzID), especially in radar applications. There is a wide variety of azimuthal map projections . They all have the property that directions (the azimuths) from

8946-499: The data is correlated with data from other antennas similarly recorded, to produce the resulting image. Using this method it is possible to synthesise an antenna that is effectively the size of the Earth. The large distances between the telescopes enable very high angular resolutions to be achieved, much greater in fact than in any other field of astronomy. At the highest frequencies, synthesised beams less than 1 milliarcsecond are possible. The pre-eminent VLBI arrays operating today are

9072-495: The discovery of PSR J1748-2446ad in 2005, was identified as the fastest-spinning pulsar. In 1980, Arecibo made the first radar observation of a comet when it successfully detected Comet Encke . In August 1989, the observatory directly imaged an asteroid for the first time in history: 4769 Castalia . The following year, Polish astronomer Aleksander Wolszczan made the discovery of pulsar PSR B1257+12 (Lich), which later led him to discover its three orbiting planets. These were

9198-412: The dish itself as it fell. The UCF engineering staff, which had been monitoring the cables with support from the U.S. Army Corps of Engineers , and the engineering firms they had hired previously evaluated the remaining cables from Tower 4. One engineering firm proposed stabilization efforts, while another suggested that they try to sever parts of the instrument platform such as the Gregorian dome to reduce

9324-510: The dome. Overall, the damage inflicted by Maria was minimal, 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. A consortium consisting of the University of Central Florida (UCF), Yang Enterprises and UMET , came forward to supply funding in February 2018 to allow

9450-534: The dual purpose of understanding the ionosphere's F-layer while also producing a general-purpose scientific radio observatory. On November 6, 1959, Cornell University entered into a contract with ARPA to carry out development studies for a large-scale ionospheric radar probe, exploring how this instrument could also be utilized in radio astronomy and other scientific areas. The observatory was built between mid-1960 and November 1963. William E. Gordon and George Peter of Cornell University oversaw its design for study of

9576-409: 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

9702-481: The field of radio astronomy was born. In October 1933, his discovery was published in a journal article entitled "Electrical disturbances apparently of extraterrestrial origin" in the Proceedings of the Institute of Radio Engineers . Jansky concluded that since the Sun (and therefore other stars) were not large emitters of radio noise, the strange radio interference may be generated by interstellar gas and dust in

9828-569: The first extrasolar planets discovered. In 1994, John Harmon used the Arecibo Radio Telescope to map the distribution of ice in the polar regions of Mercury . 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 . From January 2010 to February 2011, astronomers Matthew Route and Aleksander Wolszczan detected bursts of radio emission from

9954-413: The following few weeks after determining the safest route to do so with a safety exclusion zone immediately put in place. 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. While waiting for NSF to make the decommissioning plans, steps had been taken to try to reduce the load that each of

10080-469: The following years. 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. NASA increased its support to $ 3.5 million per year in 2012. In 2011, NSF removed Cornell University , which had managed

10206-443: The galaxy, in particular, by "thermal agitation of charged particles." (Jansky's peak radio source, one of the brightest in the sky, was designated Sagittarius A in the 1950s and was later hypothesized to be emitted by electrons in a strong magnetic field. Current thinking is that these are ions in orbit around a massive black hole at the center of the galaxy at a point now designated as Sagittarius A*. The asterisk indicates that

10332-414: The hour angle is positive westward instead of east). The cartographical azimuth or grid azimuth (in decimal degrees) can be calculated when the coordinates of 2 points are known in a flat plane ( cartographical coordinates ): Remark that the reference axes are swapped relative to the (counterclockwise) mathematical polar coordinate system and that the azimuth is clockwise relative to the north. This

10458-402: The humid tropic climate. The platform had a rotating, bow-shaped track 93 m (305 ft) 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 −1 and 38 degrees of declination ). Puerto Rico 's location near

10584-407: The instruments. The discovery of the radio reflecting ionosphere in 1902, led physicists to conclude that the layer would bounce any astronomical radio transmission back into space, making them undetectable. Karl Jansky made the discovery of the first astronomical radio source serendipitously in the early 1930s. As a newly hired radio engineer with Bell Telephone Laboratories , he was assigned

10710-446: The load. The third firm made the determination that there was no way to safely repair the damage at this point, as the remaining cables could be suspect, 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. The NSF took this advice and made the announcement on November 19, 2020 that they would decommission Arecibo over

10836-405: The loads following that install would be difficult to do. Kerr also stated that there had been periods of neglect at the Observatory, during which the fans that were used to blow dry air along the wire bundles were not operating. The earlier storms would have brought seawater to the cables which could accelerate the rate of corrosion as well, according to Kerr. Engineering firms hired by UCF inspected

10962-415: The newly formed United States Department of Defense (DoD) Advanced Research Projects Agency (ARPA) ABM umbrella-effort, Project Defender. Even at this early stage it was clear that the use of radar decoys would be a serious problem at the long ranges needed to successfully attack a warhead, ranges on the order of 1,600 km (1,000 miles). Among the many Defender projects were several studies based on

11088-412: The other two remaining support cables failing moments later. The collapse of the receiver structure and cables onto the dish caused extensive additional damage. 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

11214-426: The particles at Sagittarius A are ionized.) After 1935, Jansky wanted to investigate the radio waves from the Milky Way in further detail, but Bell Labs reassigned him to another project, so he did no further work in the field of astronomy. His pioneering efforts in the field of radio astronomy have been recognized by the naming of the fundamental unit of flux density , the jansky (Jy), after him. Grote Reber

11340-700: The periodicity of the Crab Pulsar (33 milliseconds) by Richard V. E. Lovelace and others provided the first solid evidence that neutron stars exist. In 1974, Hulse and Taylor discovered the first binary pulsar PSR B1913+16 , 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. This object spins 642 times per second and, until

11466-457: The planet Jupiter and the Sun . 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. 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

11592-427: The proper focal point of the telescope to aim at the desired target. As a spherical mirror, the reflector's focus was 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 band measuring 10–45 MHz. A limited number of line feeds could be used at any one time, limiting the telescope's flexibility. The receiver

11718-411: The reflected signal from the sea) from incoming aircraft. The Cambridge group of Ryle and Vonberg observed the Sun at 175 MHz for the first time in mid July 1946 with a Michelson interferometer consisting of two radio antennas with spacings of some tens of meters up to 240 meters. They showed that the radio radiation was smaller than 10 arc minutes in size and also detected circular polarization in

11844-457: The reflector dish. 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. The facility had recently reopened following the passing of Tropical Storm Isaias . It was unclear if the cable failure was caused by Isaias. Former Arecibo Observatory director Robert Kerr stated that prior to

11970-444: The resolving power of an interferometer is set by the distance between its components, rather than the size of its components. Radio astronomy differs from radar astronomy in that the former is a passive observation (i.e., receiving only) and the latter an active one (transmitting and receiving). Before Jansky observed the Milky Way in the 1930s, physicists speculated that radio waves could be observed from astronomical sources. In

12096-429: The safety factor for Tower 4 had dropped to 1.67, believing that the structure was still safe while repairs could be effected, even if another cable collapsed. Plans were made to replace all six auxiliary cables since their socket welds were all considered suspect at a cost of US$ 10.5 million . Before repairs could be started, on November 7, 2020, one of the two main support cables from Tower 4 snapped, shattering part of

12222-445: 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. An additional US$ 3 million in bonds were issued by the government of Puerto Rico to fund the Observatory, which were used to modernize power generation and improve other aging infrastructure. Academics, media and influential politicians pressured

12348-479: The size of the full moon (30 minutes of arc). The difficulty in achieving high resolutions with single radio telescopes led to radio interferometry , developed by British radio astronomer Martin Ryle and Australian engineer, radiophysicist, and radio astronomer Joseph Lade Pawsey and Ruby Payne-Scott in 1946. The first use of a radio interferometer for an astronomical observation was carried out by Payne-Scott, Pawsey and Lindsay McCready on 26 January 1946 using

12474-427: The socket area where the cable had failed, and found a similar problem that had been observed in the 1980s during a routine cable replacement, in which the use of molten zinc to affix the cable to the socket mount at the tower was not complete, allowing moisture to get into the wire bundle and cause corrosion and leading to the cable slipping from its socket. The firms had developed models of the telescope that showed that

12600-515: The solar radiation during the burst phase was much smaller than the solar disk and arose from a region associated with a large sunspot group. The Australia group laid out the principles of aperture synthesis in a ground-breaking paper published in 1947. The use of a sea-cliff interferometer had been demonstrated by numerous groups in Australia, Iran and the UK during World War II, who had observed interference fringes (the direct radar return radiation and

12726-602: The storage equipment. The data was relocated to the school's servers at the Texas Advanced Computing Center to be made available for continued research. 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

12852-456: The support cables. In 1973, a high-precision surface consisting of 38,000 individually adjustable aluminum panels replaced the old wire mesh, 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

12978-402: The task to investigate static that might interfere with short wave transatlantic voice transmissions. Using a large directional antenna , Jansky noticed that his analog pen-and-paper recording system kept recording a persistent repeating signal or "hiss" of unknown origin. Since the signal peaked about every 24 hours, Jansky first suspected the source of the interference was the Sun crossing

13104-854: The telescope or build a similar observatory at the site. 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 , and was constructed inside a karst sinkhole . 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. The ground beneath supported shade-tolerant vegetation. The telescope had three radar transmitters, with effective isotropic radiated powers (EIRPs) of 22  TW (continuous) at 2380 MHz, 3.2  TW (pulse peak) at 430 MHz, and 200  MW at 47 MHz, as well as an ionospheric modification facility operating at 5.1 and 8.175 MHz. The dish remained stationary, while receivers and transmitters were moved to

13230-409: The telescope starting in 2021. 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. As required by

13356-482: The telescope. Search for extraterrestrial intelligence (SETI) 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

13482-557: The time it took for "fixed" astronomical objects, such as a star, to pass in front of the antenna every time the Earth rotated. By comparing his observations with optical astronomical maps, Jansky eventually concluded that the radiation source peaked when his antenna was aimed at the densest part of the Milky Way in the constellation of Sagittarius . Jansky announced his discovery at a meeting in Washington, D.C., in April 1933 and

13608-420: The total signal collected, it can also be used in a process called aperture synthesis to vastly increase resolution. This technique works by superposing (" interfering ") the signal waves from the different telescopes on the principle that waves that coincide with the same phase will add to each other while two waves that have opposite phases will cancel each other out. This creates a combined telescope that

13734-715: 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. 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. In the weeks following Arecibo's collapse, the administration of the Five-hundred-metre Aperture Spherical Telescope (FAST) in China, which had drawn some design principles from Arecibo, stated that they would start taking applications for international researchers to use

13860-416: 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. 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

13986-510: 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 133 metres (435 ft) above the stationary reflector. The RFP suggested a tripod or

14112-555: The use of radio astronomy". Subject of this radiocommunication service is to receive radio waves transmitted by astronomical or celestial objects. The allocation of radio frequencies is provided according to Article 5 of the ITU Radio Regulations (edition 2012). In order to improve harmonisation in spectrum utilisation, the majority of service-allocations stipulated in this document were incorporated in national Tables of Frequency Allocations and Utilisations which

14238-743: The use of the Arabic version of the astrolabe astronomy instrument. Its first recorded use in English is in the 1390s in Geoffrey Chaucer 's Treatise on the Astrolabe . The first known record in any Western language is in Spanish in the 1270s in an astronomy book that was largely derived from Arabic sources, the Libros del saber de astronomía commissioned by King Alfonso X of Castile. In

14364-469: The view of his directional antenna. Continued analysis, however, showed that the source was not following the 24-hour daily cycle of the Sun exactly, but instead repeating on a cycle of 23 hours and 56 minutes. Jansky discussed the puzzling phenomena with his friend, astrophysicist Albert Melvin Skellett, who pointed out that the observed time between the signal peaks was the exact length of a sidereal day ;

14490-408: The water vapor content in the line of sight. Finally, transmitting devices on Earth may cause radio-frequency interference . Because of this, many radio observatories are built at remote places. Radio telescopes may need to be extremely large in order to receive signals with low signal-to-noise ratio . Also since angular resolution is a function of the diameter of the " objective " in proportion to

14616-454: The wavelength of the electromagnetic radiation being observed, radio telescopes have to be much larger in comparison to their optical counterparts. For example, a 1-meter diameter optical telescope is two million times bigger than the wavelength of light observed giving it a resolution of roughly 0.3 arc seconds , whereas a radio telescope "dish" many times that size may, depending on the wavelength observed, only be able to resolve an object

14742-402: The zero. For example, a bearing might be described as "(from) south, (turn) thirty degrees (toward the) east" (the words in brackets are usually omitted), abbreviated "S30°E", which is the bearing 30 degrees in the eastward direction from south, i.e. the bearing 150 degrees clockwise from north. The reference direction, stated first, is always north or south, and the turning direction, stated last,

14868-501: 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,

14994-689: Was held on November 1, 1963. 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. Initially, when the maximum expected operating frequency was about 500 MHz, the surface consisted of half-inch galvanized wire mesh laid directly on

15120-461: Was inspired by Jansky's work, and built a parabolic radio telescope 9m in diameter in his backyard in 1937. He began by repeating Jansky's observations, and then conducted the first sky survey in the radio frequencies. On February 27, 1942, James Stanley Hey , a British Army research officer, made the first detection of radio waves emitted by the Sun. Later that year George Clark Southworth , at Bell Labs like Jansky, also detected radiowaves from

15246-428: 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. 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. Radio astronomy Radio astronomy

15372-430: Was looking towards potential decommissioning of the Observatory by initiating environmental impact statements on the effect of disassembling the unit. The NSF continued to indicate it would like to reduce funding to the Observatory in the short term. As in 2008, academics expressed their concern over the loss of scientific discoveries that could occur should the Observatory be shut down. Several hurricanes and storms over

15498-510: 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,

15624-488: Was on an 820-tonne (900-short-ton) platform suspended 150 m (492 ft) above the dish by 18 main cables running from three reinforced concrete towers (six cables per tower), one 111 m (365 ft) high and the other two 81 m (265 ft) high, placing their tops at the same elevation. Each main cable was a 8 cm (3.1 in) diameter bundle containing 160 wires, with the bundle painted over and dry air continuously blown through to prevent corrosion due to

15750-449: Was originally pioneered in Japan, and more recently adopted in Australia and in Europe by the EVN (European VLBI Network) who perform an increasing number of scientific e-VLBI projects per year. Radio astronomy has led to substantial increases in astronomical knowledge, particularly with the discovery of several classes of new objects, including pulsars , quasars and radio galaxies . This

15876-607: 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. The Einstein@Home distributed computing project has found more than 20 pulsars in Arecibo data. Terrestrial aeronomy experiments at Arecibo included

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