©1999 IEEE VESIT Student Branch Hits :
Webauthor : Saumitra M Das
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THE WORLD'S LARGEST RADIO TELESCOPE God made the sky and the stars and gave us a hobby-astronomy. Galileo used the telescope and made it into a passion! That just about describes what a telescope means to a stargazer (yeah! So what does it mean anyway?)It is evident that light radiation is given out by stars which reach us and make it visible. A telescope only makes us see more of their light and hence the planets appear bigger and the stars more visible. Now, a radio telescope detects radio waves (radiation other than light radiation) sent out by the stars and magnifies these waves. Also, since radio waves are not affected by any weather, it can be used in daytime or at night. Another advantage of the radio telescope that the ordinary telescope can never match, is that these telescopes can see beyond the giant clouds of dust and gases. So much for facts about radio telescopes: now to get down to the real thing. The largest radio telescope in the world is near completion and is a completely INDIAN venture!! Its true! You can take my word for it or check it out at Pune(literally!) Read on for more fascinating facts about one of India`s most proud creations to be….GMRT stands for Giant Metrewave Radio Telescope and will be the largest Metrewave Radio telescope in the World. It is to be fully commissioned early this year. It is being set up by National Centre for Radio Astrophysics(NCRA) which is a part of Tata Institute of Fundamental Research (TIFR) for research in Radio Astronomy and is a totally indigenous Indian Project. It will provide a large collecting area over a wide frequency range of about 30 MHz to 1500 MHz. The GMRT is located at Khodad, about 80 kms from Pune on the Pune-Nasik highway. ARRAY CONFIGURATION: The radio telescope which is the largest at present is the Very Large Array (VLA) telescope, in New Mexico with 27 widely spaced antennas. But, the GMRT consists of 30 fully settable parabolic dishes of 45 m diameter each. The dishes are configured such that 12 of them are located in a compact central array in a 1 km x 1 km region and the other 18 are placed along the three 14 km long arms of an approximate ‘Y’ configuration providing a maximum baseline of about 25 kms. GMRT operates as an "Earth Rotation Aperture Synthesis Radio Telescope". Its array configuration has been chosen so as to be sensitive to both compact and broad features of celestial radio sources. FEATURES: GMRT will operate in following 6 different frequency bands protected for Radio Astronomy in India: 37 MHz, 150 MHz, 233 MHz, 327 MHz, 610 MHz, 1,420 MHz. The GMRT will be a versatile instrument for investigating a variety of radio astrophysical problems concerning the sun, radio stars, pulsars, H(II) regions, supernova remnants, the Galactic centre, nearby galaxies, radio galaxies, quasars and cosmology. However, two of the important scientific objectives of the GMRT is to search for neutral hydrogen clouds prior to the formation of galaxies and clusters in the universe and to search for and study rapidly-rotating Pulsars in our galaxy. The dishes have been made light-weight and economical using a novel concept nicknamed SMART (Stretched Mesh Attached to Rope Trusses) . The total weight of a parabolic dish including the yoke is only about 85 tonnes. This is much lower than the typical weight of about 250 tonnes for the structural parts of a 25 m dish operating at centimetre and decimetre wavelengths. The GMRT will provide high sensitivity, good spectral and polarisation capability, excellent sky coverage and reasonably good angular resolution and will have a total effective collecting area of about 30,000 sq. metres, which will make it the largest and most powerful collecting area interferometric array in the world. -ALOK AGRAWAL |
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©1999 IEEE VESIT Student Branch Hits :
Webauthor : Saumitra M Das |