Grote Reber (December 22, 1911 – December 20, 2002) was an American pioneer of radio astronomy, which combined his interests in amateur radio and amateur astronomy. He was instrumental in investigating and extending Karl Jansky's pioneering work and conducted the first sky survey in the radio frequencies.
His 1937 radio antenna was the second ever to be used for astronomical purposes and the first parabolic reflecting antenna to be used as a radio telescope. For nearly a decade he was the world's only radio astronomer.
Life
Reber was born and raised in Wheaton, Illinois, a suburb of Chicago, and graduated from Armour Institute of Technology (now Illinois Institute of Technology) in 1933 with a degree in electrical engineering. He was an amateur radio operator, and worked for various radio manufacturers in Chicago from 1933 to 1947.
When he learned of Karl Jansky's work in 1933, he decided this was the field he wanted to work in, and applied to Bell Labs, where Jansky was working.
Early experimentation
In the summer of 1937, Reber decided to build his own radio telescope in his back yard in Wheaton, IL. Reber's radio telescope was considerably more advanced than Jansky's, and consisted of a parabolic sheet metal dish 9 meters in diameter, focusing to a radio receiver 8 meters above the dish. The entire assembly was mounted on a tilting stand, allowing it to be pointed in various directions, though not turned. The telescope was completed in September 1937.
Reber's first receiver operated at 3300 MHz and failed to detect signals from outer space, as did his second, operating at 900 MHz. Finally, his third attempt, at 160 MHz, was successful in 1938, confirming Jansky's discovery. In 1940, he achieved his first professional publication, in the Astrophysical Journal, but Reber refused a research appointment with Yerkes Observatory. He turned his attention to making a radiofrequency sky map, which he completed in 1941 and extended in 1943. He published a considerable body of work during this era, and was the initiator of the "explosion" of radio astronomy in the immediate post-Second World War era. His data, published as contour maps showing the brightness of the sky in radio wavelengths, revealed the existence of radio sources such as Cygnus A and Cassiopeia A for the first time. For nearly a decade from 1937 on he was the world's only radio astronomer, a field that only expanded after World War Two when scientists, who had gained a great deal of knowledge during the wartime expansion of RADAR, entered the field, starting with Project Diana.
During this time he uncovered a mystery that was not explained until the 1950s. The standard theory of radio emissions from space was that they were due to black-body radiation, light (of which radio is a non-visible form) that is given off by all hot bodies. Using this theory one would expect that there would be considerably more high-energy light than low-energy, due to the presence of stars and other hot bodies. However Reber demonstrated that the reverse was true, and that there was a considerable amount of low-energy radio signal. It was not until the 1950s that synchrotron radiation was offered as an explanation for these measurements.
Reber sold his telescope to the National Bureau of Standards, and it was erected on a turntable at their field station in Sterling, Virginia. Eventually the telescope made its way to the National Radio Astronomy Observatory in Green Bank, West Virginia, and Reber supervised its reconstruction at that site. Reber also helped with a reconstruction of Jansky's original telescope.
Medium frequency research
Starting in 1951, he received generous support from the Research Corporation in New York, and moved to Hawaii. In the 1950s, he wanted to return to active studies but much of the field was already filled with very large and expensive instruments. Instead he turned to a field that was being largely ignored, that of medium frequency (hectometre) radio signals in the 0.5–3 MHz range, around the AM broadcast bands. However, signals with frequencies below 30 MHz are reflected by an ionized layer in the Earth's atmosphere called the ionosphere. In 1954, Reber moved to Tasmania, the southernmost state of Australia, where he worked with Bill Ellis at the University of Tasmania. There, on very cold, long, winter nights the ionosphere would, after many hours shielded from the sun's radiation by the bulk of the Earth, 'quieten' and de-ionize, allowing the longer radio waves into his antenna array. Reber described this as being a "fortuitous situation". Tasmania also offered low levels of man-made radio noise, which permitted reception of the faint signals from outer space.