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). This observatory is also called the National Astronomy and Ionosphere Center, although "NAIC" refers to both the observatory and the staff that operates it. 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. 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. Opened in 1997, the Ángel Ramos Foundation Visitor Center 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. 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. 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, it was the fastest-spinning pulsar known. 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, which later led him to discover its three orbiting planets and a possible comet. 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. 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. 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. 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. 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. 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. The Einstein@Home distributed computing project has discovered more than 20 pulsars in Arecibo data. 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.

• published: 25 Jan 2014
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