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Arecibo Observatory

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Jennie McGrath
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« on: August 16, 2007, 11:21:31 pm »

Arecibo Observatory



Organization: Cornell, NSF, NASA
Location: Arecibo, Puerto Rico
Wavelength: radio (3 cm-1 m)
Built: 1963
Telescope style: spherical reflector
Diameter: 305 m, 1000ft
Collecting area: ~73 000 m², ~790 000 ft², ~18 acres
Focal length: 132.5 m, 434.7ft
Mounting: transit instrument: fixed primary with secondary (Gregorian reflectors) on tracks for pointing
Dome: none
Website: www.naic.edu
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Jennie McGrath
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« Reply #1 on: August 16, 2007, 11:22:09 pm »

The Arecibo Observatory is located approximately 9 miles south-southwest from Arecibo, Puerto Rico (near the extreme southwestern corner of Arecibo pueblo). It is operated by Cornell University under cooperative agreement with the National Science Foundation. The observatory works as the National Astronomy and Ionosphere Center (NAIC) although both names are officially used to refer to it. NAIC more properly refers to the organization that runs both the observatory and associated offices at Cornell University.

The observatory's 305-m radio telescope is the largest single-aperture telescope (cf. multiple aperture telescope) ever constructed. It carries out three major areas of research: radio astronomy, aeronomy (using both the 305-m telescope and the observatory's lidar facility), and radar astronomy observations of solar system objects. Usage of the telescope is gained by submitting proposals to the observatory, which are evaluated by an independent board of referees.

The telescope is visually distinctive and has been used in the filming of two notable motion pictures: as the villain's antenna in the James Bond movie GoldenEye and as itself in the film Contact. The telescope received additional international recognition in 1999 when it began to collect data for the SETI@home project.
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Jennie McGrath
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« Reply #2 on: August 16, 2007, 11:22:41 pm »

General information

The Arecibo telescope is distinguished by its enormous size: the main collecting dish is 305 m in diameter, constructed inside the depression left by a karst sinkhole. The dish is the largest curved focusing dish on Earth, giving Arecibo the largest electromagnetic-wave gathering capacity. The Arecibo telescope's dish surface is made of 38,778 perforated aluminum panels, each measuring about 1 m by 2 m (3 ft by 6 ft), supported by a mesh of steel cables.

It is a spherical reflector (as opposed to a parabolic reflector). This form is due to the method used to aim the telescope: the telescope's dish is fixed in place, but the receiver at its focal point is repositioned to intercept signals reflected from different directions by the spherical dish surface. The receiver is located on a 900-ton platform which is suspended 150 m (450 ft) in the air above the dish by 18 cables running from three reinforced concrete towers, one of which is 110 m (365 ft) high and the other two of which are 80 m (265 ft) high (the tops of the three towers are at the same elevation). The platform has a 93 m long rotating bow-shaped track called the azimuth arm on which receiving antennae, secondary and tertiary reflectors are mounted. This allows the telescope to observe any region of the sky within a forty degree cone of visibility about the local zenith (between -1 and 38 degrees of declination). Puerto Rico's location near the equator allows Arecibo to view all of the planets in the solar system, though the round trip light time to objects beyond Saturn is longer than the time the telescope can track it, preventing radar observations of more distant objects.
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Jennie McGrath
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« Reply #3 on: August 16, 2007, 11:23:42 pm »



A detailed view of the receiver array
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« Reply #4 on: August 16, 2007, 11:24:25 pm »

Design and architecture

The construction of the Arecibo telescope was initiated by Professor William E. Gordon of Cornell University, who originally intended to use it for the study of Earth's ionosphere. 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 had a very limited use for other potential 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 a 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 the summer of 1958 and a contract was signed between the AFCRL and the University in November of 1959. Cornell University published a request for proposals (RFP) asking for a design to support a feed moving along a spherical surface 435 feet above the stationary reflector. The RFP suggested a tripod or a tower in the center to support the feed. George Doundoulakis, director of research for the antenna design company General Bronze Corp in Garden City, N.Y. received the RFP from Cornell and studied it with his brother, Helias Doundoulakis, a civil engineer.

The two brothers thought of a more efficient way to suspend the feed, and finally designed the cable suspension system that was used in final construction. U.S. Patent office granted Helias Doundoulakis patent No. 3,273,156 on Sept. 13, 1966 with the title “Radio Telescope having a scanning feed supported by a cable suspension over a stationary reflector”.

Construction began in the summer of 1960, with the official opening taking place on November 1, 1963. 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), thus 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 undergone several significant upgrades over its lifespan. The first major upgrade was in 1974 when a high precision surface was added for the current reflector. In 1997 a Gregorian reflector system was installed, incorporating secondary and tertiary reflectors to focus the 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 a flexibility it had not previously possessed. At the same time a ground screen was installed around the perimeter to prevent receivers from sensing the ground (which, due to its temperature, would make observations less sensitive) and a more powerful transmitter was installed.

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Jennie McGrath
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« Reply #5 on: August 16, 2007, 11:25:12 pm »

Discoveries

The Arecibo telescope has made many significant scientific discoveries. On 7 April 1964, shortly after its inauguration, Gordon H. Pettengill's team used it to determine that the rotation rate of Mercury was not 88 days, as previously thought, but only 59 days. In 1968, the discovery of the periodicity of the Crab Pulsar (33 ms) by Lovelace and others provided the first solid evidence that neutron stars exist in the Universe. In 1974 Hulse and Taylor discovered the first binary pulsar PSR B1913+16, for which they were later awarded the Nobel Prize in Physics. In 1982, the first millisecond pulsar, PSR J1937+21, was discovered by Don Backer, Shri Kulkarni and others. This object spins 642 times per second, and it was until 2005 the fastest-spinning pulsar known.

In August 1989, the observatory directly imaged an asteroid for the first time in history: asteroid 4769 Castalia. 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). These were the first extra-solar planets ever discovered. In 1994, John Harmon used the Arecibo radio telescope to map the distribution of ice in the poles of Mercury.

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Jennie McGrath
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« Reply #6 on: August 16, 2007, 11:25:55 pm »

Other usage

The telescope also had military intelligence uses, for example locating Soviet radar installations by detecting their signals bouncing back off of the Moon. Arecibo is also the source of data for the SETI@home distributed computing project put forward by the Space Sciences Laboratory at the University of California, Berkeley and was used for the SETI Institute's Project Phoenix observations.

In 1974, the Arecibo message, an attempt to communicate with extraterrestrial life, was transmitted from the radio telescope toward the globular cluster M13, 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 itself.

Terrestrial aeronomy experiments include the controversial (Ruiz 1998) Coqui 2 experiment (Friedlander 1997).

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« Reply #7 on: August 16, 2007, 11:26:40 pm »

Arecibo in popular culture

Arecibo Observatory was used as a filming location in the final scene of the James Bond movie GoldenEye. In the film, the villain Alec Trevelyan used a similar dish in Cuba to communicate with a Russian satellite to fire an electromagnetic pulse at London. The dish and the ground below it could be covered with water to conceal it as a lake. Additionally, the use of Arecibo to communicate with an earth-orbiting satellite is nonsensical from a technical standpoint.

The observatory was also featured in a segment of a Reading Rainbow episode.

In the X-Files episode "Little Green Men", Fox Mulder was sent to the Arecibo Observatory by a U.S. Senator because contact had been made with extraterrestrial life. As was often the case in the series, Mulder was forced to escape as U.S. government military forces arrived, without taking definitive proof of alien contact with him.

The film Contact features Arecibo in a more life-like way, as main character Ellie Arroway uses the facility as part of a SETI project.

The Arecibo Observatory was also featured in the film Species, as the main setting for the James Gunn novel The Listeners (1972), and as a prominent element in the Mary Doria Russell novel The Sparrow (1996).

The aliens in the BBC radio serial Space Force (1984) contact Earth after receiving the Arecibo message. One of the characters in the episode "The Voice from Nowhere" says that the Arecibo Observatory was closed down and dismantled.

Songwriter and author Jimmy Buffett mentions the "giant telescope" in his book Where Is Joe Merchant?, and in the lyrics to the song "Desdemona's Building A Rocket Ship". In both, a talented baker and former backup singer named Desdemona has a tryst with one of the workers "under the giant telescope", and begins receiving telepathic messages from the Pleiades, telling her to build a spaceship and "come home".

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Jennie McGrath
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« Reply #8 on: August 16, 2007, 11:27:26 pm »

Funding issues

A report by the division of Astronomical Sciences of the National Science Foundation, made public on 2006-11-03, recommended substantially decreased astronomy funding for Arecibo Observatory, ramping down from USD 10.5M in 2007 to USD 4M in 2011. If other sources of funding cannot be obtained, the telescope will be shut down in 2011. The report also advised that 80% of the observation time be allocated to the surveys already in progress, reducing the time available for other scientific work. If the additional funding is not available, Arecibo's radar astronomy program will cease October 1 2008. Subsequent discussions during town hall meetings in Arecibo and San Juan held in late June, 2007 revealed that the decision about closure will occur in 2009. At the meetings, Puerto Rico Senate President Kenneth McClintock announced an initial local appropriation of $3 million during fiscal year 2008 to fund a major maintenance project to restore the three pillars from which the antenna platform is suspended to their original condition, pending inclusion in the territorial government's next bond issue. The appropriation would be the first time that the islands' government contributes financially to the operation of a federal installation.
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« Reply #9 on: August 16, 2007, 11:32:19 pm »

Arecibo message



This is the message with color added to highlight its separate parts. The actual binary transmission carried no color information.
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Jennie McGrath
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« Reply #10 on: August 16, 2007, 11:34:24 pm »

The Arecibo message is a radio message that was beamed into space at a ceremony to mark the remodeling of the Arecibo radio telescope on 16 November 1974. It was aimed at the globular star cluster M13 some 25,000 light years away because it was a large and close collection of stars that was available in the sky at the time and place of the ceremony.[1] The message consisted of 1679 binary digits (equivalent to nearly 205 bytes) transmitted at a frequency of 2380 MHz and modulated by shifting the frequency by 10 Hz, with a power of 1000 kWatt. The beam was extremely narrow (giving a power equivalent to 20 trillion Watts if it were omnidirectional) making it the strongest man-made signal ever sent. The entire transmission lasted 169 seconds and was not repeated.[2] The number 1679 was chosen because it is a semiprime (the product of two prime numbers) and therefore can only be broken down into 23 rows and 73 columns, or 73 rows and 23 columns. This assumes that those who read it will choose to arrange it as a rectangle. The information arranged the first way (23 rows, 73 columns) produces jumbled nonsense, but if arranged the second way (73 rows, 23 columns) it forms the image shown on the right (assuming the bits are arranged from left to right and the rows are arranged from top to bottom; otherwise a flipped image is formed), which is assumed to be recognizable as data.[3]
Reading the image from top to bottom and left to right, it can be divided into 7 parts that state (or show) the following:
1.   the numbers one (1) through ten (10);
2.   the atomic numbers of the elements hydrogen, carbon, nitrogen, oxygen, and phosphorus, which make up deoxyribonucleic acid (DNA);
3.   the formulas for the sugars and bases in the nucleotides of DNA;
4.   the number of nucleotides in DNA, and a graphic of the double helix structure of DNA;
5.   a graphic figure of a man, the dimension (physical height) of an average man, and the human population of Earth;
6.   a graphic of Earth's solar system; and
7.   a graphic of the Arecibo radio telescope and the dimension (the physical diameter) of the transmitting antenna dish.
Because it will take 25,000 years for the message to reach its intended destination of stars (and an additional 25,000 for any reply), the Arecibo message was more a demonstration of human technological achievement than a real attempt to enter into a conversation with extraterrestrials.
Dr. Frank Drake, then at Cornell University and creator of the famous Drake equation, wrote the message, with help from Carl Sagan, among others. Whether or not this message has any ostensible effects, it has nevertheless forced humanity to consider how it might communicate with extrasolar beings, and what the contents of any such communications might be.
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« Reply #11 on: August 16, 2007, 11:37:36 pm »

Numbers

  1 2 3 4 5 6 7 8 9 10
----------------------
0 0 0 1 1 1 1 00 00 00
0 1 1 0 0 1 1 00 00 10
1 0 1 0 1 0 1 01 11 01
X X X X X X X X  X  X <-least-significant-digit marker



The numbers from 1 to 10 appear in binary format (the bottom row marks the beginning of each number).

Even knowing binary, the encoding of the numbers may not be immediately obvious due to the way they have been written. To read the first seven digits, ignore the bottom row, and read them as three binary digits from top to bottom, with the top digit being the most significant.

The readings for 8, 9 and 10 are a little different, as they have been given an additional column next to the first (to the right in the image). This is probably intended to show that numbers too large to fit in a column can be written in several contiguous ones, where the contiguous columns do not have the base marker.

« Last Edit: August 16, 2007, 11:43:07 pm by Jennie McGrath » Report Spam   Logged
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« Reply #12 on: August 16, 2007, 11:39:13 pm »

DNA elements

1 6 7 8 15
----------
0 0 0 1 1
0 1 1 0 1
0 1 1 0 1
1 0 1 0 1
X X X X X



The numbers 1, 6, 7, 8 and 15 appear. These are the atomic numbers of hydrogen (H), carbon (C), nitrogen (N), oxygen (O) and phosphorus (P), the components of DNA.

The numbers 8 and 15 are written in a logical extension of binary encoding, rather than with the contiguous-columns method shown in the message's number figures at the top:

« Last Edit: August 16, 2007, 11:42:36 pm by Jennie McGrath » Report Spam   Logged
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« Reply #13 on: August 16, 2007, 11:40:48 pm »

Nucleotides

  Deoxyribose Adenine Thymine Deoxyribose
(C5OH7) (C5H4N5) (C5H5N2O2) (C5OH7)
Phosphate Phosphate
(PO4) (PO4)
Deoxyribose Cytosine Guanine Deoxyribose
(C5OH7) (C4H4N3O) (C5H4N5O) (C5OH7)
Phosphate Phosphate
(PO4) (PO4)



The nucleotides are described as sequences of the five atoms that appear on the preceding line. Each sequence represents the molecular formula of the nucleotide as incorporated into DNA (as opposed to the free form of the nucleotide).

For example, deoxyribose (C5OH7 in DNA, C5O4H10 when free), the nucleotide in the top left in the image, is read as:

11000
10000
11010
XXXXX
-----
75010
i.e. 7 atoms of hydrogen, 5 atoms of carbon, 0 atoms of nitrogen, 1 atom of oxygen, and 0 atoms of phosphorus.

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« Reply #14 on: August 16, 2007, 11:44:11 pm »

Double helix

11
11
11
11
11
01
11
11
1111 1111 1111 0111 1111 1011 0101 1110 (binary)
01 = 4,294,441,822 (decimal)
11
01
11
10
11
11
01
X



DNA double helix (the vertical bar represents the number of nucleotides, but the value depicted is around 4.3 billion when in fact there are about 3.2 billion base pairs in the human genome).

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