A radio telescope is a type of directional radio antenna, which is usually large and parabolic. It may be used singularly or in an array. It is used in radio astronomy for tracking and collecting of data from satellites and space probes. It functions in the radio frequency portion of the electromagnetic spectrum. Here, it can detect and gather data on radio sources. Radio observatories are set up far away from major centers of population to avoid electromagnetic interference from radar, TV, radio and other EMI emitting devices. Types The types of antennas used as radio telescopes vary in design, configuration and size. For wavelengths of 30 meters to 3 meters, these are usually directional antenna arrays. As the wavelengths related to these antennas are long, their reflector surfaces are made from coarse wire mesh. For short wavelengths, dish type radio telescopes are used. The angular resolution of a dish style antenna changes as per the diameter of the dish and is proportional to the wavelength of the electromagnetic radiation being observed. Telescopes operating at wavelengths of 3 meters to 30 cm are more than 100 meters in diameter. Those operating at wavelengths more than 30 cm vary from 3 to 90 meters in diameter. The biggest individual radio telescope is the RATAN-600 with an antenna having a diameter of 576 meters. Russia too has a large telescope for low-frequency observations. The largest radio antenna in Europe is one with a diameter of 100m in Effelsber, Germany. Examples Submillimeter-wave telescopes:

• Mt. Fuji 1.2 m submillimeter-wave telescope
• Antarctic Submillimeter Telescope and Remote Observatory 1.7 m submillimeter telescope
• Koln Observatory for Submillimeter astronomy 3 m submillimeter telescope
• Submillimeter telescope observatory 10 m submillimeter telescope
• Caltech submillimeter observatory 10.4 submillimeter telescope
• James Clerk Maxwell telescope 15 m submillimeter telescope

Millimeter-wave telescopes:

• Very small telescope University of Tokyo - NRO 60 cm
• NANTEN, Nagoya University 4 m
• National Radio astronomy observatory 12 m
• Five college radio astronomy observatory 14 m
• Delingha observatory 14 m, Purple mountain observatory
• Taeduk radio astronomy observatory 14 m
• Yebes 14 m, Calar Alto observatory, National astronomical observatory of Spain
• Swedish-ESO submillimeter telescope 15 m
• Onsala 20 m, Onsala space observatory at Chalmers University of Technology
• Institute of radio astronomy in millimeter 30 m
• Nobeyama radio astronomy 45 m

Centimeter and Meter-wave telescopes:

• Mopra 22 m, CSIRO
• Dwingeloo 25 m, NFRA
• Dominion radio astrophysical observatory 26 m
• MIT Haystack radio observatory 37 m
• Green bank 43 m (140 foot telescope) NRAO
• Parkes observatory 64 m CSIRO
• Jodrell bank 76 m
• Effelsberg 100 m
• Arecibo 305 m

Cylindrical Palaboloyds telescopes:

• Ooty radio telescope, 530 m X 30 m aperture, NCRA
• Molonglo observatory synthesis telescope MOST, 778 m X 12 m aperture X 2 elements
• Northern cross, 600 m X 600 m aperture, IRA
• RATAN 600, a 576 m circle of 595 elements

Radio Telescope and Astronomy A new concept radio telescope dedicated to galactic astronomy, and searching extraterrestrial intelligence is located close to the town of Hat Creek. The first 42 of the planned 350 radio dishes of the Allen Telescope Array have begun gathering data from the far reaches of the universe. This telescope can provide a better understanding of intelligent civilizations beyond Earth, exploding stars, massive black holes at the core of distant galaxies, and the many astronomical objects in space. Haystack Radio Telescope This is a fully steerable and remotely accessible radio telescope that operates at millimeter wavelengths. It is mainly used for astronomical research and educational purposes. It is a 37 meter telescope. It is now being upgraded at MIT Lincoln Laboratory to work as a radar at 95 Ghz, tremendously increases the capabilities of radio astronomy, and opening the 85-115 Ghz frequency range for users. Westford Radio Telescope Built in 1961 to support Project West Ford, this radome-enclosed type telescope has a diameter 18.3 meter (60 feet). It was initially used as an x-band radar to test the limits of communication technologies. Since 1981, it is used as for supporting geodetic VLBI operations. The Westford Antenna acts as a test bed for NASA for the development of new equipment and techniques to support the worldwide geodetic VLBI program.