Arecibo Observatory

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Arecibo Radio Telescope
Arecibo Observatory Aerial View.jpg
Aerial view of the Observatory
Organization SRI International
USRA
UMET
Location Arecibo, Puerto Rico
Wavelength electromagnetic spectrum: (3.00 cm to 1.00 meter)
Built completed in 1963
Telescope style spherical reflector
Diameter 1,000 ft (300 m)
Collecting area 73,000 square meters (790,000 sq ft)
Mounting semi-transit telescope: fixed primary with secondary (Gregorian reflector) and a delay-line feed, each of which moves on tracks to point to different parts of the sky.
Dome none
Website www.naic.edu
National Astronomy and Ionosphere Center
Arecibo Observatory is located in Puerto Rico
Arecibo Observatory
Coordinates 18°20′39″N 66°45′10″W / 18.34417°N 66.75278°W / 18.34417; -66.75278Coordinates: 18°20′39″N 66°45′10″W / 18.34417°N 66.75278°W / 18.34417; -66.75278
Area 118 acres (480,000 m2)
Architect Gordon, William E; Kavanaugh, T.C.
Governing body Federal
NRHP Reference # 07000525
Added to NRHP September 23, 2008[1]

The Arecibo Observatory is a radio telescope in the municipality of Arecibo, Puerto Rico. This observatory is operated by SRI International, USRA and UMET, under cooperative agreement with the National Science Foundation (NSF).[2][3] This observatory is also called the National Astronomy and Ionosphere Center, although "NAIC" refers to both the observatory and the staff that operates it.[4] From its construction in the 1960s until 2011, the observatory was managed by Cornell University.

The observatory's 1,000 ft (305 m) radio telescope is the world's largest single-aperture telescope. It is used in three major areas of research: radio astronomy, aeronomy, and radar astronomy. Scientists who want to use the telescope submit proposals that are evaluated by an independent scientific board.

The telescope has made appearances in motion picture and television productions and got more recognition in 1999 when it began to collect data for the SETI@home project. It has been listed on the American National Register of Historic Places beginning in 2008.[1][5] It was the featured listing in the National Park Service's weekly list of October 3, 2008.[6] The center was named an IEEE Milestone in 2001.[7]

Ángel Ramos Foundation Visitor Center[edit]

Opened in 1997, the Ángel Ramos Foundation Visitor Center [1] features interactive exhibits and displays about the operations of the radio telescope, astronomy, and atmospheric science. The center is named after the financial foundation that honors Ángel Ramos, the owner of the El Mundo newspaper and the founder of Telemundo. This foundation provided half of the money to build the visitors center, with the rest coming from private donations and from Cornell University. It is normally open Wednesday-Sunday, with additional opening hours on many holidays and school breaks. As of 2012, the admission fee is $10.00 for adults and $6.00 for seniors and children under 10.[8]

General information[edit]

The main collecting dish is 1,000 ft (305 m) in diameter, constructed inside the depression left by a karst sinkhole.[9] It contains the largest curved focusing dish on Earth, giving Arecibo the largest electromagnetic-wave-gathering capacity.[10] The dish surface is made of 38,778 perforated aluminum panels, each about 3 by 6 feet (1 by 2 m), supported by a mesh of steel cables. The ground underneath is accessible and supports shade-tolerant vegetation.[11]

The telescope has three radar transmitters, with effective isotropic radiated powers of 20 TW at 2380 MHz, 2.5 TW (pulse peak) at 430 MHz, and 300 MW at 47 MHz.

The telescope is a spherical reflector of radius 870 ft, not a parabolic reflector. To aim the telescope, the receiver is moved to intercept signals reflected from different directions by the spherical dish surface. A parabolic mirror would have varying astigmatism when the receiver is off the focal point, but the error of a spherical mirror is the same in every direction.

The receiver is on a 900-ton platform suspended 150 m (500 ft) above the dish by 18 cables running from three reinforced concrete towers, one 110 m (365 ft) high and the other two 80 m (265 ft) high, placing their tops at the same elevation. The platform has a 93-meter-long rotating bow-shaped track, called the azimuth arm, carrying the receiving antennas and secondary and tertiary reflectors. This allows 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 the Northern Tropic allows Arecibo 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 can track a celestial position, preventing radar observations of more distant objects.

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

Design and architecture[edit]

A detailed view of the beam-steering mechanism and some antennas. The triangular platform at the top is fixed, and the azimuth arm rotates beneath it. To the left is the Gregorian sub-reflector, and to the right is the 96-foot-long (29 m) line feed tuned to 430 MHz. Just visible at the upper right is part of the rectangular waveguide that brings the 2.5 MW 430 MHz radar transmitter's signal up to the focal region.

The Arecibo telescope was built between mid-1960 and November 1963, and designed by William E. Gordon of Cornell University, who intended to use it to study Earth's ionosphere.[12][13][14] Originally, a fixed parabolic reflector was envisioned, pointing in a fixed direction with a 150 m (500 ft) tower to hold equipment at the focus. This design would have limited its use in other areas of research, such as planetary science and radio astronomy, which require the ability to point at different positions in the sky and to track those positions for an extended period as 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 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 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 435 feet (133 m) above the stationary reflector. The RFP suggested a tripod or a tower in the center to support the feed. At Cornell University on the day the project for the design and construction of the antenna was announced, Gordon had also envisioned a 435 ft (133 m) tower centered in the 1,000 ft (300 m) reflector to support the feed.

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 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 approach by suspending the feed. He presented his proposal to Cornell for a doughnut truss suspended by four cables from four towers above the reflector, having along its edge a rail track for the azimuthal positioning of the feed. A 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 elevational positioning of the feed. A counter-weight would move symmetrically opposite to the feed for stability, and the entire feed could be lowered and raised if a hurricane were present. Helias Doundoulakis designed the cable suspension system which was finally adopted. Although the present configuration is substantially the same as the original drawings by George and Helias (though with three towers instead of the original four), the U.S. Patent office granted Helias a patent[15] for the brothers' innovative idea. William J. Casey, later to be the director of the Central Intelligence Agency under President Ronald Reagan, was also an assignee on the patent.

Construction began in mid-1960, with the official opening on November 1, 1963.[16] As the primary dish is spherical, its focus is along a line rather than at a single point (as would be the case for a parabolic reflector); therefore, complicated line feeds had to be used to carry out observations. Each line feed covered a narrow frequency band (2–5% of the center frequency of the band) and a limited number of line feeds could be used at any one time, limiting the flexibility of the telescope.

The telescope has been upgraded several times. 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 1974 a high-precision surface consisting of thousands of individually adjustable aluminum panels replaced the old wire mesh, and the highest usable frequency was raised to about 5,000 MHz. A Gregorian reflector system was installed in 1997, incorporating secondary and tertiary reflectors to focus radio waves at a single point. This allowed the installation of a suite of receivers, covering the whole 1–10 GHz range, that could be easily moved onto the focal point, giving Arecibo more flexibility. At the same time, a ground screen was installed around the perimeter to block the ground's thermal radiation from reaching the feed antennas, and a more powerful 2,400 MHz transmitter was installed.

The telescope was damaged in an earthquake on January 13, 2014.[17] The earthquake damaged one of the suspension cables at the location of a splice that was made during the original installation in the 1960s and repair took two months.

Research and discoveries[edit]

The Arecibo message with added color to highlight the separate parts. The actual binary transmission carried no color information.

Many scientific discoveries have been made using the Arecibo telescope. On April 7, 1964, shortly after it began operations, Gordon Pettengill's team used it to determine that the rotation rate of Mercury was not 88 days, as previously thought, but only 59 days.[18] In 1968, the discovery of the periodicity of the Crab Pulsar (33 milliseconds) by Lovelace and others provided the first solid evidence that neutron stars exist.[19] In 1974, Hulse and Taylor discovered the first binary pulsar PSR B1913+16,[20] 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.[21] This object spins 642 times per second, and until the discovery of PSR J1748-2446ad in 2005, it was the fastest-spinning pulsar known.

In August 1989, the observatory directly imaged an asteroid for the first time in history: 4769 Castalia.[22] 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 and a possible comet.[23][24] These were the first extrasolar planets discovered. In 1994, John Harmon used the Arecibo radio telescope to map the distribution of ice in the poles of Mercury.[25]

In January 2008, detection of prebiotic molecules methanimine and hydrogen cyanide were reported from Arecibo Observatory radio spectroscopy measurements of the distant starburst galaxy Arp 220.[26]

SETI / METI[edit]

The Arecibo message[edit]

In 1974, the Arecibo message, an attempt to communicate with potential extraterrestrial life, was transmitted from the radio telescope toward the globular cluster M13, about 25,000 light-years away.[27] 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 itself.[28]

The RuBisCo Stars[edit]

On November 7, 2009, as part of the 35th anniversary of the Drake/Sagan transmission to M13 the RuBisCO gene sequence was transmitted to three “nearby” stars: GJ 83.1, Teagarden's star SO 025300.5+165258, and Kappa Ceti (G5B). The project was by artist Joe Davis with support from Paul Gilster, Arecibo Observatory, Cornell University, and various others.

SETI searches[edit]

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 observations.[29] The Einstein@Home distributed computing project has discovered more than 20 pulsars in Arecibo data.[30]

Other uses[edit]

Terrestrial aeronomy experiments at Arecibo have included the Coqui 2 experiment, which were supported by NASA. The telescope also has had military intelligence uses; among them, locating Soviet radar installations by detecting their signals bouncing off the Moon.[31]

Limited amateur radio operations have occurred, using "moon bounce" or Earth-Moon-Earth communication, in which the Moon is used to reflect radio signals aimed at it back to the Earth . The first of these operations was on April 13-14, 1964, using the call KP4BPZ. A dozen or so two-way contacts were made on 144 and 432 MHz. On July 3 and July 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 callsigns (though of course not two-way contacts). From April 16 to 18, 2010, the Arecibo Amateur Radio Club KP4AO again conducted moon-bounce activity using the antenna.[32] On 10 November 2013, the KP4AO Arecibo Amateur Radio Club conducted a 50 Year commemoration activation, lasting 7 hours on 14.250 MHz SSB, though not using the main dish antenna.

Funding issues[edit]

A report by the division of Astronomical Sciences of the National Science Foundation, made public on November 3, 2006, recommended substantially decreased astronomy funding for Arecibo Observatory, ramping down from $10.5 million in 2007 to $4.0 million in 2011.[33][34] If other sources of money could not be obtained, the observatory would have to close. The report also advised that 80 percent of the observation time be allocated to the surveys already in progress, reducing the time available for smaller programs. NASA gradually eliminated its share of the planetary radar funding at Arecibo from 2001 thorough 2006.[35]

Academics and researchers responded by organizing to protect and advocate for the observatory. They established the Arecibo Science Advocacy Partnership (ASAP), which was meant to advance the scientific excellence of Arecibo Observatory research and to publicize its accomplishments in astronomy, aeronomy and planetary radar.[36] ASAP's goals include mobilizing the existing broad base of support for Arecibo science within the fields it serves directly, the broad scientific community; provide a forum for the Arecibo research community and enhance communication within it; promote the potential of Arecibo for groundbreaking science; suggest the paths that will maximize it into the foreseeable future; showcase the broad impact and far-reaching implications of the science currently carried out with this unique instrument.[36]

Contributions by the government of Puerto Rico may be one way to help fill the funding gap, but are controversial and uncertain. At town hall meetings about the potential closure, Puerto Rican Senate President Kenneth McClintock announced an initial local appropriation of $3.0 million during fiscal year 2008 to fund a major maintenance project to restore the three pillars that hold up the antenna platform to their original condition, pending inclusion in the next bond issue.[37] The bond authorization, with the $3.0 million appropriation, was approved by the Senate of Puerto Rico on November 14, 2007, on the first day of a special session called by Aníbal Acevedo Vilá.[38] The Puerto Rico House of Representatives repeated this action on June 30, 2008. The Governor of Puerto Rico signed the measure into law in August 2008.[39] These funds were made available in the second half of 2009.

José Enrique Serrano, a member of the U.S. House of Representatives Appropriations Committee, asked the National Science Foundation to keep Arecibo in operation in a letter published on September 19, 2007.[40]

Language similar to that in the letter of September 19 was included in the FY-2008 omnibus spending bill. In October 2007, Puerto Rico's then-Resident Commissioner, Luis Fortuño, along with Dana Rohrabacher, filed legislation to assure the continued operation of the observatory.[41] A similar bill was filed in the U.S. Senate in April 2008 by the junior Senator from New York, Hillary Clinton.[42]

Since the Arecibo observatory is owned by the Government of the United States, direct donations by private or corporate donors cannot be made. However, as non-profit (501(c)(3)) "public charities" under US law, Cornell University and subsequently SRI International can accept contributions on behalf of the Arecibo Observatory.[43]

In September 2007, in an open letter to researchers, the NSF clarified the status of the budget for NAIC, stating that the present plan could hit the targeted budgetary revision.[44] No mention of private funding was made. However, it need be noted that the NSF is undertaking studies to mothball or demolish the observatory to return it to its natural setting in the event that its budget target is not reached.

In November 2007, The Planetary Society urged the U.S. Congress to prevent the Arecibo Observatory from closing because of insufficient funding since its radar contributes greatly to the accuracy of predictions of asteroid impacts on the Earth.[45] The Planetary Society believes that continued operation of the observatory will reduce the cost of mitigation (that is, deflection of a near-Earth asteroid on collision to Earth), should that be necessary.

Also in November of that year The New York Times described the consequences of the budget cuts at the site.[46] In July 2008, the British newspaper The Daily Telegraph reported that the funding crisis, due to federal budget cuts, was still very much alive.[47]

The SETI@home program is using the telescope as a primary source for the research. The program is urging people to send a letter to their political representatives, in support of full federal funding of the observatory.[48]

The NAIC received $3.1 million from the American Recovery and Reinvestment Act of 2009, and 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 for student training.[49] This allotment was an increase of around 30 percent over the FY-2009 budget. However, the FY-2010 funding request by NSF was cut by $1.2 million (−12.5 percent) over the FY-2009 budget) in light of their continued plans to reduce funding.[50]

The 2011 NSF budget was reduced by a further $1.6 million, −15 percent compared to 2010, with a further $1.0 million reduction projected by FY-2014.[51] Beginning in FY-2010, NASA began 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.[52]

Also in 2010, the NSF issued a call for new proposals for the management of NAIC beginning in FY-2012.[4] On May 12, 2011, the agency informed Cornell University that it would no longer be the operator of the NAIC, and thus of the Arecibo Observatory, as of October 1, 2011. At that time, Cornell transferred its operations 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.[3][53] Upon the award of the new cooperative agreement for NAIC management and operation, NSF also decertified NAIC as a Federally Funded Research and Development Center (FFRDC),[51] with the stated goal of providing the NAIC with greater freedom to establish broader scientific partnerships and pursue funding opportunities for activities beyond the scope of those supported by the NSF.[54]

In popular culture[edit]

Arecibo Observatory Directors[edit]

See also[edit]

References[edit]

  1. ^ a b National Park Service (3 October 2008). "Weekly List Actions". Retrieved 2008-10-03. 
  2. ^ Bhattacharjee, Yudhijit (20 May 2011). "New Consortium to Run Arecibo Observatory". Science. Retrieved 2012-01-11. 
  3. ^ a b "SRI International to Manage Arecibo Observatory" (Press release). SRI International. 2013-07-10. Retrieved 2013-07-10. 
  4. ^ a b "NSF request for proposals issued in 2010". Retrieved 2011-09-02. 
  5. ^ Juan Llanes Santos (March 20, 2007). "National Register of Historic Places Registration: National Astronomy and Ionosphere Center / Arecibo Observatory" (PDF). National Park Service. Retrieved October 21, 2009.  (72 pages, with many historic b&w photos and 18 color photos)
  6. ^ "Milestones:NAIC/Arecibo Radiotelescope, 1963". IEEE Global History Network. IEEE. Retrieved July 29, 2011. 
  7. ^ "Ángel Ramos Foundation Visitor's Center Schedule and Hours". Retrieved April 21, 2012. 
  8. ^ David Brand (21 January 2003). "Astrophysicist Robert Brown, leader in telescope development, named to head NAIC and its main facility, Arecibo Observatory". Cornell University. Retrieved 2008-09-02. 
  9. ^ Frederic Castel (8 May 2000). "Arecibo: Celestial Eavesdropper". Space.com. Retrieved 2008-09-02. 
  10. ^ "General Views of the Arecibo Observatory". Image Gallery. Arecibo Observatory. Retrieved 25 August 2013. 
  11. ^ "IEEE History Center: NAIC/Arecibo Radiotelescope, 1963". Institute of Electrical and Electronics Engineers. Retrieved 2008-09-02. 
  12. ^ "Pictures of the construction of Arecibo Observatory (start to finish)". National Astronomy and Ionosphere Center. Archived from the original on May 5, 2009. Retrieved 2009-05-05. 
  13. ^ "Description of Engineering of Arecibo Observatory". Acevedo, Tony (June 2004). Archived from the original on May 4, 2009. Retrieved 2009-05-05. 
  14. ^ US patent 3273156, Helias Doundoulakis, "Radio Telescope having a scanning feed supported by a cable suspension over a stationary reflector", issued 1966-09-13 
  15. ^ "Arecibo Observatory". History.com. Retrieved 2008-09-02. [dead link]
  16. ^ "M6.4 - 61km N of Hatillo, Puerto Rico". Retrieved February 26, 2014. 
  17. ^ Dyce, R. B.; Pettengill, G. H.; Shapiro, I. I. (1967). "Radar determination of the rotations of Venus and Mercury". Astron. J. 72 (3): 351–359. doi:10.1086/110231. 
  18. ^ Richard V.E. Lovelace. "Discovery of the Period of the Crab Nebula Pulsar". Cornell University. Archived from the original on September 12, 2008. Retrieved 2008-09-02. 
  19. ^ Hulse, R.A., and Taylor, J.H. (1975). "Discovery of a pulsar in a binary system". Astrophys. pp. 195, L51–L53. 
  20. ^ D. Backer et al. (1982). "A millisecond pulsar". Nature 300 (5893): 315–318. Bibcode:1982Natur.300..615B. doi:10.1038/300615a0. 
  21. ^ "Asteroid 4769 Castalia (1989 PB)". NASA. Archived from the original on September 16, 2008. Retrieved 2008-09-02. 
  22. ^ Wolszczan, A. (1994). "Confirmation of Earth Mass Planests Orbiting the Milliesecond Pulsar PSR: B1257+12". Science. p. 538. 
  23. ^ Daniel Fischer (2002). "A comet orbiting a pulsar?". The Cosmic Mirror (244). 
  24. ^ Harmon, J.K., M.A. Slade, R.A. Velez, A. Crespo, M.J. Dryer, and J.M. Johnson (1994). "Radar Mapping of Mercury's Polar Anomalies". Nature. p. 369. 
  25. ^ Staff (15 January 2008). "Life's Ingredients Detected In Far Off Galaxy". ScienceDaily (ScienceDaily LLC). Archived from the original on April 21, 2008. Retrieved 2008-03-29. "[Article] Adapted from materials provided by Cornell University." 
  26. ^ Larry Klaes (30 November 2005). "Making Contact". Ithaca Times. Retrieved 2008-09-02. 
  27. ^ Geaorge Cassiday. "The Arecibo Message". The University of Utah: Department of Physics. Archived from the original on July 17, 2007. Retrieved 2007-07-27. 
  28. ^ Peter Backus (14 April 2003). "Project Phoenix: SETI Prepares to Observe at Arecibo". Space.com. Retrieved 2008-09-02. 
  29. ^ "Einstein@Home new discoveries and detections of known pulsars in the BRP4 search". Einstein@Home. August 27, 2012. Retrieved August 28, 2012. 
  30. ^ Steve Blank "Secret history of Silicon Valley" talk
  31. ^ "ARRL; Moonbounce for everyone". Retrieved January 10, 2013. 
  32. ^ Roger Blandford; Senior Review Committee, Division of Astronomical Sciences, National Science Foundation (22 October 2006). From the Ground Up: Balancing the NSF Astronomy Program (PDF). National Science Foundation. Archived from the original on June 26, 2008. Retrieved 2008-07-08. 
  33. ^ Rick Weiss (9 September 2007). "Radio Telescope And Its Budget Hang in the Balance". The Washington Post (Arecibo, Puerto Rico: The Washington Post Company). p. A01. Retrieved 2008-07-08. "The cash crunch stems from a "senior review" completed last November at NSF. Its $200 million astronomy division – increasingly committed to ambitious, new projects but long hobbled by flat Congressional budgets – was facing a deficit of at least $30 million by 2010." 
  34. ^ Robert Roy Britt (20 December 2001). "NASA Trims Arecibo Budget, Says Other Organizations Should Support Asteroid Watch". Space.com. Imaginova. Retrieved 2008-07-08. 
  35. ^ a b "Areciboscience.org". Areciboscience.org. Retrieved 2012-05-11. 
  36. ^ Liz Arelis Cruz Maisonave. "Buscan frenar cierre de Radiotelescopio en Arecibo". El Vocero (in Spanish). Retrieved 2008-09-04. 
  37. ^ "Senado aprueba emisión de bonos de $450 millones". Primera Hora (in Spanish). 14 November 2007. Retrieved 2008-09-04. 
  38. ^ Gerardo E, Alvarado León (10 August 2008). "Gobernador firma emisión de bonos". El Nuevo Día. 
  39. ^ José E. Serrano (19 September 2007). "Serrano concerned about potential Arecibo closure". serrano.house.gov. Archived from the original on 30 July 2008. Retrieved 2008-09-04. 
  40. ^ "Congress gets bill to save Arecibo Observatory". Cornell University. 3 October 2007. Archived from the original on August 21, 2008. Retrieved 2008-09-04. 
  41. ^ Jeannette Rivera-lyles (25 April 2008). "Clinton turns attention to observatory in Puerto Rico". Orlando Sentinel. Archived from the original on September 30, 2008. Retrieved 2008-09-04. 
  42. ^ "Arecibo-observatory.org". Cornell and NAIC. 22 June 2008. Archived from the original on July 7, 2008. Retrieved 2008-07-08. "Our mission is to establish a new funding model to supplement NSF support and maintain operations of the observatory now and into the future." 
  43. ^ "Dear Colleague Letter: Providing Progress Update on Senior Review Recommendations" (Press release). The National Science Foundation. 20 September 2007. Archived from the original on June 28, 2008. Retrieved 2008-07-09. 
  44. ^ Arecibo participated in 90 of the 111 asteroid radar observations in 2005–2007. See JPL's list of all asteroid radar observations.
  45. ^ Chang, K., "A Hazy Future for a 'Jewel' of Space Instruments.", New York Times, November 20, 2007
  46. ^ Jacqui Goddard, "Threat to world's most powerful radio telescope means we may not hear ET", Daily Telegraph, July 12, 2008
  47. ^ "Save Arecibo: Write to Congress". Retrieved July 19, 2008
  48. ^ "12-m Phase Reference Antenna". Naic.edu. 28 June 2010. Retrieved 2012-05-11. 
  49. ^ "FY2010 Budget Request to Congress". Retrieved May 26, 2009
  50. ^ a b "Major multi-user research facilities" p. 35–38. Retrieved 2010 Feb. 10
  51. ^ "NASA Support to Planetary Radar" retrieved 2011 July 7
  52. ^ "SRI International to manage Arecibo Observatory". Cornell Chronicle. 3 June 2011. Retrieved 2012-01-11. 
  53. ^ "Management and Operation of the NAIC" retrieved 2013 Apr 6
  54. ^ http://areciboradio.com
  55. ^ "Dinosaur Comics number 2554". 
  56. ^ "3,273,156 (1966-09-13) Helias Doundoulakis, Radio Telescope having a scanning feed supported by a cable suspension over a stationary reflector". U.S. Patent Office. 

Further reading[edit]

External links[edit]