Joseph Lade Pawsey (14 May 1908 – 30 November 1962) was an Australian engineer, radiophysicist, and radio astronomer.
He was born in Ararat, Victoria to a family of farmers. At the age of 14 he was awarded a government scholarship to study at Wesley College, Melbourne, followed by a scholarship to study at the University of Melbourne. In 1929 he earned his B.Sc. from the university, followed by a M.Sc. in Natural Philosophy in 1931. He was then awarded an Exhibition Research Scholarship to study at Cambridge University, where he worked under the direction of J.A. Ratcliffe. He studied the effects of the ionosphere on radio propagation and his discovery of the presence of irregularities in the Kennelly-Heaviside Layer proved vital to the later development of this branch of ionospheric physics[1]. In 1935 he was awarded a Ph.D. from Cambridge and in September of that year he married Greta Lenore Nicoll, a 32-year-old Canadian[2]. He then became a research physicist at EMI. until 1939.
In February 1940 he returned to Australia to work at the recently formed Radiophysics Division of the CSIR/CSIRO. One group he led developed a microwave set for the Royal Australian Navy, while another group under his direction investigated the 'super-refraction' of radio waves in the earth's atmosphere[2]. Pawsey continued as a research physicist at the CSIR/CSIRO Division of Radiophysics until 1962, becoming assistant chief in 1952.
At the end of World War II he became a pioneer of the new science of Radio Astronomy, his interest being stirred by the discovery of radio waves from the Galaxy and by reports of intense interference in metre-wave radar receivers caused by disturbances on the Sun[1]. To investigate the latter Pawsey, along with Ruby Payne-Scott and Lindsay McCready used an existing RAAF antenna at Collaroy, a northern Sydney suburb[3]. As well as confirming that the Sun was a source of radio noise their data also showed that the temperature in some regions of the Sun were as high as one million degrees. This temperature was far higher than was thought possible at the time. Work by the physicist David Forbes Martyn showed that temperatures peak in the Sun's corona at one million degrees. The observations with the Collaroy antenna not only marked the beginning of radio astronomy in Australia, but also the first time radio astronomy had provided important information on a problem in traditional optical astronomy[3]
In early 1946 Pawsey turned his attention to sunspots as a source of strong fluctuating radio noise. To overcome the limitations of the available antennas Pawsey used sea interferometry and began observations at Dover Heights which provided a better vantage point than Collaroy. The observations confirmed beyond doubt that sunspots were the source of the strong increase in radio noise. This work was confirmed four months later by radio astronomers at Cambridge University led by Martin Ryle[3]
Members of Pawsey's group invented techniques that were subsequently incorporated into general use in radio astronomy as well as making important discoveries about the discrete sources of radio emission in the Milky Way and external galaxies[1]. Pawsey did some work on his own, but his main focus was on guiding and administering his research group[1].
In 1952 he became president of the Radio Astronomy Commission of the IAU, serving until 1958. From 1960 until 1961 he was president of the Australian Branch for the Institute of Physics. He was appointed as director of the U.S. National Radio Astronomy Observatory in 1962, but he died in Sydney of a brain tumour before he took office[2]. He was survived by his wife, two sons and a daughter[4]
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