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28th of February 2020
Vale John Murray
John Murray, a leading receiver engineer from the early days of Australian radio astronomy, passed away recently at the age of 95. Murray joined CSIRO’s Division of Radiophysics in 1947, initially working with Paul Wild’s solar noise group. In 1951 the predicted spectral line emitted by hydrogen gas at 21 cm had been detected at Harvard University and was confirmed shortly afterwards by CSIRO, beginning an area of research which continues to this day. Initially this work was done with a primitive four-channel hydrogen line receiver at CSIRO’s Potts Hill field station but, in 1953, Radiophysics’ Assistant Chief, Joe Pawsey, tired of the ongoing problems with this receiver, asked Murray to fix it. After detailed analysis, Murray successfully argued that a 48-channel receiver be developed instead.

This receiver became the prototype for the future Parkes radio telescope, with the engineering group building a 6 m antenna fitted the new receiver and installing it at the Murraybank field station (a corner of Murray’s 2.5 hectare block in Pennant Hills!). Using the prototype system, the team conducted effectively a pilot survey, making the first hydrogen line maps of the whole southern sky, including the now famous images of our nearest galaxies, the Magellanic Clouds.

In the mid 1960s, Murray worked with Venkatraman Radhakrishnan and Miller Goss to make the first HI absorption measurements using Parkes and the nearby 18-m Kennedy dish (which was mounted on railway tracks) as a variable baseline spectral line interferometer. In 1973 he and Don Mathewson used a modified version of his original receiver on the Kennedy dish to discover the Magellanic stream – a trail of gas extending from those galaxies and halfway around our own. John Murray, pictured at right with Dick McGee at left in the image above, retired from CSIRO in 1989 after a career spanning some 39 years. (Image credit: CSIRO Radio Astronomy Image Archive. Text credit: Nic Svenson, Ron Ekers, Mal Sinclair and John Reynolds)

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