English radioastronomer who with his colleague Martin Ryle mapped the radio sources in the sky in the 1950s. Smith discovered the strongly polarized nature of radiation from pulsars 1968, and estimated the strength of the magnetic field in interstellar space. He was Astronomer Royal from 1982 to 1990.
Smith was born in Roehampton, Surrey, and studied at Cambridge. During World War II he was assigned to the Telecommunications Research Establishment, and when he returned to Cambridge, he joined the radio research department at the Cavendish Laboratory. He was appointed professor of astronomy at Manchester 1964 and worked at Jodrell Bank until 1974. He was director of the Royal Greenwich Observatory 1976-81. In 1981, he moved back to Jodrell Bank to become director there.
In 1948, Smith and Ryle, investigating a source of radio waves in the constellation of Cygnus, detected a second source in the constellation Cassiopeia. Smith spent the following years trying to determine the precise location of both sources. Finally, astronomers at Mount Palomar, California, were able to pinpoint optical counterparts. Cassiopeia A was shown to derive from a supernova explosion within our Galaxy; Cygnus A is a double radio galaxy.
Smith and Ryle were the first to publish (in 1957) a paper on the possibility of devising an accurate navigational system that depended on the use of radio signals from an orbiting satellite.
In 1962 Smith installed a radio receiver in Aeriel II, one of a series of joint US-UK satellites, enabling it to make the first investigation of radio noise above the ionosphere.