Located 8 km (5 mi) southwest of Cambridge, England, the Mullard Radio Astronomy Observatory (opened in 1957) is one of the
foremost British research institutions. Led by 1974 Nobel Prize laureates Antony Hewish and Sir Martin Ryle, scientists at Mullard have constructed large dish antennas and extensive lines and fields of dipoles that are capable of great resolving power, extreme positional accuracy, and high sensitivity for detecting faint sources of radio emission. PulsarsÑhot neutron stars that rotate like beaconsÑwere detected at Mullard in 1967 by Jocelyn Bell-Burnell and explained by Hewish. Several catalogs of radio sources in space have become world standards for reference; they use "Cambridge" numbers because Mullard is part of Cambridge University. The Mullard instruments typically are designated by their sizes. The One-Mile Radio
Telescope (
operational in 1964) uses three dishes, all 60 ft (18 m) in diameter. Two of them are fixed and the other is movable along a railroad track. The 5-kilometer telescope (operational in 1972) consists of four fixed and four mobile dishes, all 42 ft (12.6 m) in diameter. Together they have a resolving power of 0.02 second of arc at a wavelength of 6 cm (2.4 in). Adjacent to these telescopes are arrays of antennas, such as the 4-acre array with which Bell-Burnell discovered pulsars.