Solar Radiation at Radio Frequencies and Its Relation to Sunspots

Some Highlights of Interferometry in early Radio Astronomy

“…The very fast variations and intense signals recorded at 0600 represent a solar outburst. (McCready, Pawsey and Payne-Scott 1947) In a seminal paper submitted to the Proceedings of the Royal Society in July 1946, McCready, Pawsey andPayne-Scott (1947) reported the above results and also explained many basics of the sea-cliff interferometer, considering effects such as refraction (the worst uncertainty), the earth's curvature, tides, and imperfect reflection from a choppy sea. As mentioned above, many of these effects had already been worked out before the war.…”

The history of innovation in radio astronomy

“…In 1947 Joe Pawsey, who had done his PhD with Jack Ratcliffe at Cambridge, joined the CSIRO Radiophysics Laboratory in Sydney and with his colleagues used sea interferometer fringes to co-locate solar emission with sunspots [12]. The first published suggestion that it would be possible to synthesise an image of the radio sky by measuring a range of Fourier components was made by Lindsay McCready, Joe Pawsey and Ruby Payne-Scott [13]. However, this technique was impractical with the cliff interferometers they were using, and was not suitable for imaging solar bursts which were strongly variable in both time and frequency.…”

The Development of High-Resolution Imaging in Radio Astronomy

“…During World War II, shipboard radar operators noticed that radar echoes from airplanes varied in amplitude because of the interference between the signal received directly from the aircraft and that reflected from the ocean. This radio analog of Lloyd's mirror led to the development of the sea interferometer by Pawsey et al (1946) and by McCready et al (1947), who were the first to use interferometric observations in radio astronomy. Their sea interferometers were located on cliffs a few hundred feet above the Pacific Ocean in Australia and had an angular resolution of about 30 arcmin.…”