Radio Astronomy History in a Nutshell

Radio astronomy began with Karl Jansky's discovery, in 1932, of a strong source of radio static which originated from the central region of our galaxy, the Milky Way. Jansky was using a rotating antenna and a receiver operating at 20.7 Mhz. Jansky's work was largely ignored except by a young engineer in Wheaton, Illinois named Grote Reber.

Karl Jansky and his rotating 20.7 Mhz antenna.

Reber, using his own funds and enormous personal effort constructed a fully steerable parabolic dish antenna. He built and used numerous receivers operating at a number of wavelengths and slowly was able to construct a sky map based on the strength of the radio signals emanating from the regions of the sky covered by his antenna. Not much else happened in the field until after World War II, when many scientists found themselves free of military concerns and armed with a wealth of new technology which sprung from the conflict. Radar had pushed the ability to receive signals to shorter and shorter wavelengths where antennas of reasonable size could be built to examine smaller regions of the sky (narrow beam widths).

Groups of engineers and scientists in Great Britain and Australia took the lead in the years following the war. John Bolton and others in Australia discovered several strong discrete sources using yagi antennas and a technique where the sources were observed from high ocean side cliffs as they rose above the horizon.  Martin Ryle developed interfereometric techniques which utilized combined signals from widely separated antennas.  Interferometry allowed observers to pinpoint sources to a degree where they could be searched for by optical astronomers.

Radios astronomy was slow to catch on in the USA, however, the 1950s saw a boom of activity, especially in microwave astronomy.  John Kraus, at Ohio State University, built several telescopes of innovative design. The National Radio Astronomical Observatory was born in the beautiful West Virginia countryside, where dish antennas began sprouting like giant mushrooms between the green mountains.  The NRAO continues to develop new technologies including the GBT, a 300 foot offset focus dish with and active surface.