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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). The observatory is the sole facility of the National Astronomy and Ionosphere Center (NAIC), which refers to 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 1000 foot radio telescope is the world's largest single-aperture telescope. 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 scientific board. The observatory has appeared in film 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 starting in 2008.〔〔 (72 pages, with many historic b&w photos and 18 color photos)〕 It was the featured listing in the National Park Service's weekly list of October 3, 2008. The Center was named in IEEE Milestone in 2001. It has a visitor center that is open part time.〔(Visitor Center )〕 == General information == The main collecting dish is in diameter, constructed inside the depression left by a karst sinkhole. It contains the largest curved focusing dish on Earth, giving Arecibo the largest electromagnetic-wave-gathering capacity. The dish surface is made of 38,778 perforated aluminum panels, each about , supported by a mesh of steel cables. The ground beneath is accessible and supports shade-tolerant vegetation. The observatory has four radar transmitters, with effective isotropic radiated powers of 20 TW 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. 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 above the dish by 18 cables running from three reinforced concrete towers, one 365 feet high and the other two 265 feet high, placing their tops at the same elevation. The platform has a rotating, bow-shaped track 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 Saturn is longer than the 2.6 hour time that the telescope can track a celestial position, preventing radar observations of more distant objects. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Arecibo Observatory」の詳細全文を読む スポンサード リンク
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