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
National Science Foundation (NSF). The observatory is the sole
facility of the National
Ionosphere Center (NAIC), which
is the formal name of the observatory. From its construction in the
1960s until 2011, the observatory was managed by Cornell University.
For more than 50 years, the observatory's 1,000-foot (305-meter) radio
telescope was the world's largest single-aperture telescope, from its
completion in 1963 until July 2016 when the Five hundred meter
Spherical Telescope (FAST) in China was completed. It is used
in three major areas of research: radio astronomy, atmospheric
science, and radar astronomy. Scientists who want to use the
observatory submit proposals that are evaluated by an independent
The observatory has appeared in film, gaming and television
productions, gaining 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
National Register of Historic Places starting in 2008. It was
the featured listing in the National Park Service's weekly list of
October 3, 2008. The center was named an
IEEE Milestone in 2001.
It has a visitor center that is open part-time.
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 about 30 out of 38,000 aluminum panels. Most Arecibo
observations do not use the line feed but instead rely on the feeds
and receivers located in the dome. Overall, the damage inflicted by
Maria was minimal.
1 General information
2 Design and architecture
3 Research and discoveries
4 SETI, METI
4.1 The Arecibo Message
4.2 The RuBisCo Stars
SETI and METI projects
5 Other uses
6 Funding concerns
7 Ángel Ramos Foundation Visitor Center
8 List of directors
9 In popular culture
10 See also
12 Further reading
13 External links
The main collecting dish is 305 m (1,000 ft) in diameter,
constructed inside the depression left by a karst sinkhole. 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 beneath is accessible and supports shade-tolerant
The observatory has four radar transmitters, with effective isotropic
radiated powers of 20 TW (continuous) at 2380 MHz,
2.5 TW (pulse peak) at 430 MHz, 300 MW at 47 MHz,
and 6 MW at 8 MHz.
The reflector is a spherical reflector, not a parabolic reflector. To
aim the device, the receiver is moved to intercept signals reflected
from different directions by the spherical dish surface of 270 m
(870 ft) radius. A parabolic mirror would have varying
astigmatism when the receiver is off the focal point, but the error of
a spherical mirror is uniform in every direction.
The receiver is on a 900-ton platform suspended 150 m
(492 ft) above the dish by 18 cables running from three
reinforced concrete towers, one 111 m (365 ft) high and the
other two 81 m (265 ft) high, placing their tops at the same
elevation. The platform has a rotating, bow-shaped track 93 m
(305 ft) long, 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
longer than the 2.6 hour time that the telescope can track a celestial
position, preventing radar observations of more distant objects.
The Arecibo Radio Telescope as viewed from the observation deck,
Design and architecture
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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
The origins of the observatory trace to late 1950s efforts to develop
anti-ballistic missile (ABM) defences as part of the newly formed
ARPA's 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 1,000 miles (1,600 km).
Among the many Defender projects were several studies based on the
concept that a re-entering nuclear warhead would cause unique physical
signatures while still in the upper atmosphere. It was known that hot,
high-speed objects caused ionization of the atmosphere that reflects
radar waves, and it appeared that a warhead's signature would be
different enough from decoys that a detector could pick out the
warhead directly, or alternately, provide added information that would
allow operators to focus a conventional tracking radar on the single
return from the warhead.
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.
The observatory was built between mid-1960 and November 1963 and
William E. Gordon
William E. Gordon of Cornell University, who intended to
use it to study 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 the ability to
point at different positions in the sky and track those positions for
an extended time 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. On
the day the project for the design and construction of the antenna was
announced at Cornell University, Gordon had also envisioned a
435 ft (133 m) tower centered in the 1,000 ft
(305 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
design by suspending the feed. He presented his proposal to Cornell
University for a doughnut truss suspended by four cables from four
towers above the reflector, having along its edge a rail track for the
azimuth 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
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
Doundoulakis, (although with three towers, instead of the original
four as drawn in the original patent), the U.S. Patent office granted
Helias Doundoulakis a patent, for the brothers' innovative idea.
Two other assignees on the patent were friends William J. Casey, who
later became director of the
Central Intelligence Agency
Central Intelligence Agency under
President Ronald Reagan, and Constantine Michalos, an attorney.
The idea of a spherical reflecting mirror with a steerable secondary
has since been used in optical telescopes, in particular the
Hobby–Eberly Telescope and the Southern African Large Telescope.
Construction began in mid-1960, with the official opening on November
1, 1963. As the primary dish is spherical, its focus is along a
line rather than at one point, as would be the case for a parabolic
reflector. As a result, complex line feeds were implemented to carry
out observations. Each line feed covered a narrow frequency band:
2–5% of the center frequency of the band. A limited number of line
feeds could be used at any one time, limiting the telescope's
Since then, 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
40,000 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 the focal point,
giving Arecibo more flexibility. A metal mesh screen was also
installed around the perimeter to block the ground's thermal radiation
from reaching the feed antennas. Finally, a more powerful
2400 MHz transmitter was added.
Research and discoveries
Arecibo message with added color to highlight the separate parts.
The actual binary transmission carried no color information.
Many scientific discoveries have been 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 the periodicity of the
Crab Pulsar (33 milliseconds) by
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 the discovery of PSR
J1748-2446ad in 2005, was identified as the fastest-spinning pulsar.
In August 1989, the observatory directly imaged an asteroid for the
first time in history: 4769 Castalia. The following year, Polish
Aleksander Wolszczan made the discovery of pulsar PSR
B1257+12, which later led him to discover its three orbiting
planets. These were 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.
2010 to February 2011, American astronomers Matthew Route
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.
The Arecibo Message
Main article: 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.
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.
The RuBisCo Stars
Main article: RuBisCo Stars
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, the Arecibo Observatory, Cornell
University and others.
SETI and METI projects
SETI and Active SETI
Search for Extra-Terrestrial Intelligence
Search for Extra-Terrestrial 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 Extra-Terrestrial Intelligence)
refers to the active search by transmitting messages.
Arecibo is the source of data for the
SETI@home and Astropulse
distributed computing projects put forward by the Space Sciences
Laboratory at the
University of California, Berkeley
University of California, Berkeley and was used for
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 have included the Coqui 2
experiment, supported by NASA. The telescope also has military
intelligence uses, some of which include locating Soviet radar
installations by detecting their signals bouncing off the Moon.
Limited amateur radio operations have occurred, using moon bounce or
Earth–Moon–Earth communication, in which radio signals aimed at
Moon are reflected back to Earth. The first of these operations
was on June 13–14, 1964, using the call KP4BPZ. A dozen or so
two-way contacts were made on 144 and 432 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. These were not
two-way contacts. From April 16–18, 2010, again, the Arecibo Amateur
Radio Club KP4AO conducted moon-bounce activity using the antenna.
On November 10, 2013, the KP4AO Arecibo Amateur Radio Club conducted a
Fifty-Year Commemoration Activation, lasting 7 hours on
14.250 MHz SSB, without using the main dish antenna.
Since the early 1970s, the Arecibo
Observatory has been supported by
the NSF (
National Science Foundation
National Science Foundation divisions of Astronomical
Sciences and of Atmospheric Sciences) with incremental support by
NASA, for operating the planetary radar. Between 2001 and 2006,
NASA decreased, then eliminated, its support of the planetary
radar, but restored and increased the funding in FY-2010.
A report by the NSF division of Astronomical Sciences, made public on
November 3, 2006, recommended substantially decreased astronomy
funding for the Arecibo Observatory, from $10.5 million in 2007 to
$4.0 million in 2011. If other sources of money could not be
obtained, the observatory would be forced to close. The report also
advised that 80 percent of observing time be allocated to the surveys
already in progress, reducing available time for smaller programs.
Academics and researchers responded by organizing to protect and
advocate for the observatory. They established the Arecibo Science
Advocacy Partnership (ASAP), to advance the scientific excellence of
Observatory research and to publicize its accomplishments in
astronomy, aeronomy and planetary radar. ASAP's goals included
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 paths that will maximize it into the
foreseeable future, and showcase the broad impact and far-reaching
implications of the science currently carried out with this unique
Contributions by the government of
Puerto Rico may be one way to help
fill the funding gap, but remain controversial and uncertain. At town
hall meetings about the potential closure, Puerto Rican Senate
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 support the antenna platform
to their original condition, pending inclusion in the next bond
issue. The bond authorization, with a $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.
Puerto Rico House of Representatives repeated this action on June
30, 2008. Puerto Rico's governor signed the measure into law in August
2008. These funds were made available during the second half of
In a letter published on September 19, 2007, José Enrique Serrano, a
member of the
U.S. House of Representatives
U.S. House of Representatives Appropriations Committee,
National Science Foundation
National Science Foundation to keep Arecibo operating.
Language similar to that of 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 famed observatory. A similar bill was filed in the U.S. Senate
in April 2008 by the Junior Senator from New York, Hillary
Since the Arecibo observatory is owned by the Government of the United
States, donations by private or corporate donors cannot be made.
However, as non-profit (501(c)(3)) "public charities" under US law,
SRI International and Universidad Metropolitana, can
accept contributions on behalf of the Arecibo Observatory.
In September 2007, in an open letter to researchers, the NSF clarified
the status of the budget for NAIC, stating the present plan could hit
the targeted budgetary revision. No mention of private funding was
made. However, in the event that its budget target is not reached, it
must be noted that the NSF is undertaking studies to mothball or
demolish the observatory to return it to its natural setting.
In November 2007,
The Planetary Society
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. 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
The New York Times described the
consequences of the budget cuts at the site. In July 2008, the
The Daily Telegraph
The Daily Telegraph reported that the funding
crisis, due to federal budget cuts, was still very much alive.
SETI@home program is using the telescope as a primary source for
ET research. The program urges people to send a letter to their
political representatives in support of full federal funding of the
The NAIC received $3.1 million from 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
Klystron amplifiers for the planetary radar system
and student training. This allotment was an increase of about 30
percent over the FY-2009 budget. However, the FY-
2010 funding request
by NSF was cut by $1.2 million (−12.5%) over the FY-2009 budget, in
light of their continued plans to reduce funding.
The 2011 NSF budget was reduced by a further $1.6 million, −15%
compared to 2010, with a further $1.0 million reduction projected by
FY-2014. Starting in FY-2010,
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
NASA increased its support to $3.5 million per year in
2010 the NSF issued a call for new proposals for the
management of NAIC starting in FY-2012. On May 12, 2011, the agency
Cornell University that, as of October 1, 2011, it would no
longer be the operator of the NAIC and the Arecibo Observatory. 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. 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), 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 NSF.
In October 2015, the NSF released a "Dear Colleague Letter"
reiterating its desire for a "substantially reduced funding commitment
On September 30, 2016, the NSF released a followup to the October 2015
"Dear Colleague Letter" announcing a solicitation for future operation
Observatory stating "The subject Solicitation will request the
submission of formal proposals involving the continued operation of
Observatory under conditions of a substantially reduced
funding commitment from NSF."
The damage sustained from
Hurricane Maria in September 2017 further
clouded the observatory's future. Although the damage was
minimal, 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.
However, it was announced in February 2018 that a consortium led by
University of Central Florida
University of Central Florida will allow the NSF to reduce its
contribution towards Arecibo's operating costs from $8 million to $2
million from the fiscal year 2022–2023, with the shortfall made up
by the consortium partners, thus securing the observatory's
Ángel Ramos Foundation Visitor Center
Logo of the observatory at the entrance gate
Opened in 1997, the Ángel Ramos Foundation Visitor Center features
interactive exhibits and displays about the operations of the radio
telescope, astronomy and atmospheric sciences. The center is named
after the financial foundation that honors Ángel Ramos, owner of the
El Mundo newspaper and founder of Telemundo. The Foundation provided
half of the funds to build the Visitor Center, with the remainder
received from private donations and Cornell University.
The center, in collaboration with the Caribbean Astronomical
Society, host a series of Astronomical Nights throughout the year,
which feature diverse discussions regarding exoplanets, and
astronomical phenomena and discoveries (such as Comet ISON). The main
purpose of the center is to increase public interest in astronomy, the
observatory's research successes, and space endeavors.
List of directors
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1960–1965, William E. Gordon
1965–1966, John W. Findlay
1966–1968, Frank Drake
1968–1971, Gordon Pettengill
1971–1973, Tor Hagfors
1973–1982, Harold D. Craft Jr.
1982–1987, Donald B. Campbell
1987–1988, Riccardo Giovanelli
1988–1992, Michael M. Davis
1992–2003, Daniel R. Altschuler (es)
2003–2006, Sixto A. González
2006–2007, Timothy L. Hankins
2007–2008, Robert B. Kerr
2008–2011, Michael C. Nolan
2011–2015, Robert B. Kerr
2016–present Francisco Córdova
In popular culture
Due to its unique shape and concept the observatory is featured in
many movies, video games and novels.
The observatory was featured on Cosmos: A Personal Voyage in part 12,
The observatory was used as a filming location in the climax of the
James Bond movie
GoldenEye (1995), and as a level in the accompanying
Nintendo 64 video game
The film Contact (1997), based on the
Carl Sagan 1985 novel of the
same name, features the main character using the observatory as part
The 1998 film The Survivor features the observatory as an
interplanetary gateway that the protagonist Tharkin is sent to when he
is condemned to life imprisonment on Earth
Fox Mulder went to the observatory in
The X-Files episode, "Little
The observatory is featured in the film Species (1995), the James Gunn
novel The Listeners (1972), the
Robert J. Sawyer
Robert J. Sawyer novel Rollback, the
Mary Doria Russell
Mary Doria Russell novel The Sparrow (1996) and the film The Losers
A radio telescope based on the observatory is featured in the
videogame Just Cause 2.
Although never specifically named, the first lines of the Arthur C.
Clarke novel 2010: Odyssey Two strongly imply that the opening scene
takes place at the observatory. However, for the 1984 film adaptation,
this scene was filmed at the
Very Large Array
Very Large Array in New Mexico.
Battlefield 4 multiplayer map, Rogue Transmission, is inspired by
The movie of The Losers has one scene filmed in the observatory.
Jimmy Buffett's novel
Where Is Joe Merchant? includes a character
named Desdemona who once worked at the observatory, where she began
receiving telepathic messages from outer space. Buffett also wrote a
song about her, called "Desdemona's Building A Rocket Ship".
In the game
Supertuxkart there is a level called Alien Signal
featuring a giant telescope in a natural sinkhole inspired by the
Puerto Rico portal
Air Force Research Laboratory
Atacama Large Millimeter Array
Atacama Large Millimeter Array (Chile)
Five hundred meter Aperture Spherical Telescope
Five hundred meter Aperture Spherical Telescope (China)
List of radio telescopes
Sixto González, former director of the observatory (2003–2006)
Tor Hagfors, former director of the observatory (1971–1973) and also
of NAIC (October 1982 to September 1992).
William E. Gordon, founder and first director of the observatory (AIO
Radar Telescope Will Probe Solar System". IEEE. July 1961.
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