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LOFAR is the Low-Frequency Array for Radio astronomy, built by ASTRON, the Netherlands Institute for Radio Astronomy and operated by ASTRON's radio observatory, of the Netherlands Organisation for Scientific Research. LOFAR is a large interconnected radio telescope using a new concept based on a vast array of omnidirectional antennas. The electronic signals from the antennas are digitised, transported to a central digital processor, and combined in software to emulate a conventional antenna. The project is based on an interferometric array of radio telescopes using about 20,000 small antennas concentrated in at least 48 stations. Forty of these stations are distributed across the Netherlands, five stations in Germany, and one each in Great Britain, France and Sweden. Further stations may also be built in other European countries. The total effective collecting area is approximately 300,000 square meters, depending on frequency and antenna configuration.〔http://www.astron.nl/radio-observatory/astronomers/technical-information/lofar-technical-information〕 The data processing is performed by a Blue Gene/P supercomputer situated in the Netherlands at the University of Groningen. LOFAR is also a technology precursor for the Square Kilometre Array. == Technical information == LOFAR was conceived as an innovative effort to force a breakthrough in sensitivity for astronomical observations at radio-frequencies below 250 MHz. Astronomical radio interferometers usually consist either of arrays of parabolic dishes (e.g. the One-Mile Telescope or the Very Large Array), arrays of one-dimensional antennas (e.g. the Molonglo Observatory Synthesis Telescope) or two-dimensional arrays of omnidirectional antennas (e.g. Antony Hewish' Interplanetary Scintillation Array). LOFAR combines aspects of many of these earlier telescopes; in particular, it uses omnidirectional dipole antennas as a phased array using the aperture synthesis technique developed in the 1950s. Like the earlier Cambridge Low Frequency Synthesis Telescope (CLFST) low-frequency radio telescope, the design of LOFAR has concentrated on the use of large numbers of relatively cheap antennas without any moving parts, concentrated in stations, with the mapping performed using aperture synthesis software. The direction of observation ("beam") is chosen electronically by phase delays between the antennas. LOFAR can observe in several directions simultaneously which allows a multi-user operation. LOFAR makes observations in the 10 MHz to 240 MHz frequency range with two types of antennas: Low Band Antenna (LBA) and High Band Antenna (HBA), optimized for 0-80 MHz and 120-240 MHz respectively.〔(【引用サイトリンク】 title=Antenna Description )〕 The electric signals from the LOFAR antennas are digitised, transported to a central digital processor, and combined in software in order to map the sky. Therefore, LOFAR is a "software telescope". The cost is dominated by the cost of electronics and will follow Moore's law, becoming cheaper with time and allowing increasingly large telescopes to be built. The antennas are simple enough, but there are about 20,000 in the LOFAR array. 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「LOFAR」の詳細全文を読む スポンサード リンク
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