Jacqueline Hochheiser, Corporate Communications


  • The first attempt at a radio telescope was by an amateur physicist named Karl Jansky, who was conducting an experiment for his employer, Bell Telephone Laboratories.
  • Grote Reber, an American radio astronomer, improved Jansky’s radio telescope model six years later and built the first fully operational radio telescope as we know it today.
  • Presently, radio telescopes are still reminiscent of Reber’s design, consisting of parabolic plates with antennas suspended above them. These modern-day telescopes have further enhanced human knowledge of the universe.

Radio astronomy and the complex technology known as radio telescopes, have enhanced human knowledge of the universe and the phenomena that happen within it. The radio telescope has come a long way from its humble origins back in 1931. The first attempt was designed by an amateur physicist named Karl Jansky, who all but stumbled upon the discovery of a radio antenna as something to be used for space research.

In fact, Jansky’s device was hardly a telescope at all, but a single antenna mounted on a rickety turntable to allow 360° of rotation. A motor and Ford Model T tires allowed the massive antenna to spin. The device was so cumbersome and large (roughly 100ft in diameter and 20ft tall), that it earned the nickname “Jansky merry-go-round.”

Figure 1: Jansky’s Telescope. Photo courtesy of https://www.aps.org/publications/apsnews/201505/physicshistory.cfm
Figure 2: Reber’s Telescope.

Jansky, who worked for Bell Telephone Laboratories, used this antenna to discover the sources for interference in telephone signals. Subsequently, although the antenna only operated at 20.5 MHz, his search uncovered a mysterious “hiss” of radiation that he determined was originating from outer space.

It wasn’t until 1937 that an American radio astronomer named Grote Reber created the first fully functional radio telescope as we know it today. The telescope consisted of a parabolic dish, about 29.5 ft in diameter, and an antenna mounted 26.2 ft above the dish. The antenna and dish were then installed on a tilting base, allowing the device to scan in multiple directions.

The addition of a parabolic dish gave Reber’s antenna a major advantage over Jansky’s device. Acting as a reflector, the dish would channel a narrow, symmetrical beam to the antenna, allowing a much more concentrated and accurate reading of radio data. In addition, Reber’s telescope could be adjusted to read three different frequencies: 3300 MHz, 900 MHz and 160 MHz. This gave the astronomer a wider range of data to study.

Having heard of Jansky’s discovery, Reber investigated with his more sophisticated technology and confirmed that Jansky’s suspicions were correct. Reber’s telescope detected low frequency radiation emitted from celestial bodies in space such as the sun and other stars in the Milky Way galaxy. Reber’s telescope even went a step further and documented new constellations, complete with maps of each. These constellations include Cygnus A and Cassiopeia A.

Today, radio telescopes are still reminiscent of Reber’s design, consisting of parabolic plates with antennas suspended above them. As technology advanced, telescopes adopted the use of multiple antennas to get a wider variety of radio data readings, as well as larger parabolic plates for high sensitivity. The Parkes Radio telescope in Australia, run by the Commonwealth Scientific and Industrial Research Organization (CSIRO), is the largest single-dish telescope in the southern hemisphere, with a diameter of 210 ft. Its multibeam receiver is ideal for large scale surveys of the sky.

Figure 3: Parkes Radio Telescope. Photo courtesy of https://www.ipl.nasa.gov/spaceimages/details.php?id=PIA17248