How big is your dish? The world’s 6 largest radio telescopes

28 Nov 2015

China is building the world’s largest radio telescope that is the equivalent of 30 football pitches to listen to the stars

China is building the world’s largest radio telescope, which is the equivalent of 30 football pitches, to listen to the stars. This will eclipse what had been the world’s biggest telescope, in the Arecibo Observatory in Puerto Rico.

Hardly a week goes by without regaling you with some amazing discovery from outer space.

But apart from roving satellites in deep space or robots wandering the Mars landscape, a lot of the discovery actually takes place back here on the blue planet of Earth.

Gigantic radio telescopes are used to track and collect data from satellites and space probes and differ from optical telescopes because they operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on radio sources.

Usually located as far away as possible from urban populations and placed in valleys to avoid electromagnetic interference from TV, radio or radar, they are gigantic constructions that are beautiful to look at.

Below, we document the world’s largest radio telescopes.

FAST (China)


Construction of the 500 metre Aperture Spherical Telescope (FAST) in south-west China’s Guizhou province began in 2011 and will be completed in 2016. The gigantic radio telescope will cost £120m to build and will allow scientists to detect weaker radio signals from beyond our own solar system. Effectively, the dish will allow scientists to listen to the universe and will be the biggest in the world for at least the next 30 years. The telescope is made up of 4,450 reflective panels. The size of the dish will be about 30 football pitches. Cables are attached to every reflective panel to control its coordinates and astronomers will use lasers to pinpoint the exact coordinates, accurate to millimetres. It will be able to survey outer space 10 times better than the next biggest radio telescope, Arecibo in Puerto Rico.

Arecibo Observatory (Puerto Rico)


Built in 1963, the Arecibo Observatory in Puerto Rico will lose its title as the largest radio telescope on Earth when FAST becomes operational. Operated by SRI International, USRA and UMET under cooperation with the US National Science Foundation it had been managed by Cornell University until 2011. The telescope has a diameter of 1,000 ft and was built inside the depression left by a karst sinkhole. It currently contains the largest curved focusing dish on Earth and its surface is made of 38,778 perforated aluminium panels, each measuring 3ft x 6ft. The observatory has four  transmitters, with effective isotropic radiated powers of 20 TW at 2380MHz, 2.5TW (pulse peak) at 430MHz, 300MW at 47MHz, and 6MW at 8MHz.

RATAN-600 (Russia)


Russia’s RATAN-600 began operations in 1974 and consists of a 576m diameter circle of rectangular radio reflectors and sits near the village of Zelenchukskaya in the Caucasus Mountains in Russia, at an altitude of 970 metres. Unlike most radio telescopes, which utilise an array of dishes to focus electromagnetic radiation onto a receiver or receivers, RATAN-600 uses a ring of adjustable reflecting panels to direct the radiation from any point in the sky to a central conical receiver. The RATAN-600 is primarily operated as a transit telescope, in which the rotation of the earth is used to sweep the telescope focus across the subject of observation. Radio frequency observations can be made in the frequency band 610MHz to 30GHz, though primarily in the centimetric waveband, with an angular resolution of up to two arcseconds. Observation of the sun at radio wavelengths, in particular of the solar corona, has been a long-standing focus of the RATAN-600’s scientific programme.

Effelsberg 100-m (Germany)


Operational in 1972, the Effelsberg 100-m radio telescope is located in the north Rhine-Westphalia region of Germany and for 29 years was the world’s largest fully steerable radio telescope until it was surpassed by the Green Bank Telescope in West Virginia in the US. Located 1.3km north-east of the town of Bad Münstereifel, the Effelsberg is operated by the Max Planck Institute for Radio Astronomy in Bonn and has a diameter of 100 metres. It listens to the universe using the Finite element method (FEM), which tilts and moves mirrors in order to increase accuracy. About 45pc of the observing time of Effelsberg 100-m is available to external astronomers.

Green Bank Telescope (US)


Built between 1991 and 2002, not only is the Robert C. Byrd Green Bank Telescope the world’s largest fully steerable radio telescope, it is also the world’s largest moveable land object. It is part of the National Radio Astronomy Observatory (NRAO) site at Green Bank, West Virginia. The Green Bank Telescope operates at metre-to-millimetre wavelengths. Its 100-metre diameter collecting area, unblocked aperture, and good surface accuracy provide superb sensitivity across the telescope’s full 0.1–116GHz operating range. The GBT is fully steerable, and 85pc of the entire celestial sphere is accessible. It is used for astronomy about 6,500 hours every year, with 2000–3000 hours per year going to high-frequency science.

Lovell Telescope (UK)


When construction of the Lovell Telescope at Jodrell Bank Observatory in Chesire finished in 1957, the telescope was the largest steerable dish radio telescope in the world. It is now a part of British history and is a Grade I listed building. Built using the bearings from World War I battleships HMS Revenge and HMS Royal Sovereign, which were being broken up in 1950, construction began in 1952 and it became operational in 1957. The bowl has a diameter of 76.2 metres and became operational just in time for the launch of Sputnik 1, the world’s first artificial satellite, and the telescope took part in some of the early work of satellite communication. It was also used to track both Soviet and American probes aimed at the Moon in the late 1950s and early 1960s. In 1961, it detected signal from Venera 1, a Russian satellite en route to Venus. It also tracked Mars probes 1, 2 and 3 and in more recent years has searched for several lost Mars spacecraft, including Mars Observer in 1993.

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John Kennedy is a journalist who served as editor of Silicon Republic for 17 years