Radio astronomy

CSIRO’S PARKES RADIO TELESCOPE. CREDIT: DAVID MCCLENAGHAN/CSIRO.
CSIRO’S PARKES RADIO TELESCOPE. CREDIT: DAVID MCCLENAGHAN/CSIRO.

Radio waves were detected from the Sun and our galaxy before World War II. But radio astronomy—the use of radio waves as a tool for studying the cosmos—developed rapidly only after the war, powered by the new expertise in radio techniques, and in radar particularly, to which the conflict had given birth. Australia was one of the pioneers, led by CSIRO’s forerunner, the CSIR (Council for Scientific and Industrial Research). At the end of war, CSIR’s radio group stayed together to continue research in peace time uses of radio waves.

CSIRO’s research grew rapidly with the creation of the Parkes radio telescope, known locally simply as ‘The Dish’, and later the Australia Telescope Compact Array built for Australia’s Bicentenary.

Today, Australia is poised to take the lead in radio astronomy again, competing to host the international Square Kilometre Array (SKA), a vast radio telescope consisting of several thousand small antennas, which will be 10,000 times more powerful than any existing instrument. In the meantime, CSIRO is already building the Australian SKA Pathfinder, and a consortium of US, Australian and Indian universities and institutes have begun collecting data from the Murchison Widefield Array. Both are demonstrator projects for the SKA, but are also cutting-edge radio telescopes in their own right.

Radio astronomy’s rapid growth down under

The CSIRO Radiophysics Laboratory in Sydney houses an impressive concentration of radio experts. Perhaps it should not come as a surprise, then, that much of the sophisticated radio-based technology needed for astronomy has been developed in Australia.

“Radio is a very complicated field of electronics, still very much a black art,” says Terry Percival, a pioneer of radio telescope arrays. “But [the Radiophysics] laboratory has radio in its genes. It’s a collection of more than 100 people including 60 or 70 PhDs in radio.”

Radar—the radio equivalent of echo-location in bats—was developed in the 1930s. It allowed remote location and tracking of moving military targets, such as aircraft and ships. In Australia, the Radiophysics Laboratory was created in 1939 within CSIRO’s forerunner, the CSIR, to develop the technology for use during the Second World War.

The lab had a highly talented group of researchers, and after the war, the CSIR decided to keep them together to explore peaceful uses for radio. Many of the researchers started working on radio techniques for aircraft navigation and range-finding. Some began to study the physics of clouds and rain. But one group, led by Joe Pawsey, decided to investigate cosmic radio waves. “This was the beginning of Australian radio astronomy, a remarkable period of excitement and discovery,” says CSIRO Fellow and former director of CSIRO’s Australia Telescope National Facility, Ron Ekers.

Radio waves from a distant galaxy

CSIRO scientists and engineers turned surplus wartime radar equipment at Dover Heights in Sydney into a radio telescope, and with this discovered two radio sources that turned out to be galaxies millions of light-years away. Until then, people had thought that such radio sources were simply stars. “The finding was shocking,” says Ron. “These were the first extragalactic radio sources.” Using the same telescope, the researchers also detected radio emissions from the pulsar in the Crab Nebula, the remains of an exploded star. In another project, Pawsey’s group built a dish-type telescope at Dover Heights, and with this pinpointed the centre of our galaxy. These discoveries put Australian radio astronomy on the world map.

Pawsey’s group was also the first to describe the concept of aperture synthesis, a technique for combining signals from many receivers in a way that mimics the output of instruments with a much larger aperture. A number of radio telescopes have since been built on this principle, including the Molonglo Cross, built near Canberra by the University of Sydney in 1967. It still flourishes today under the name of SKAMP, and is now serving as a demonstrator of technology for the international Square Kilometre Array telescope (see Australia’s SKA demonstrator already booked out).

The Dish

During the 1950s, CSIRO also began pursuing a different option for radio astronomy—a large single-dish telescope. The resulting 64-metre parabolic reflector, built near Parkes in New South Wales, was opened in 1961, and is still going strong. Repeatedly enhanced with new equipment, today ‘the Dish’ is 10,000 times more sensitive than when it was first built. The Parkes telescope is well known for its role in receiving TV signals from the 1969 Moon landing, but its scientific record is even more notable: it is the second most highly cited radio telescope in the world (in terms of citations per paper).

By the 1970s, other new telescopes had sprung up around the world. Australia had fallen behind, and remained so until the advent in 1988 of the CSIRO Australia Telescope Compact Array near Narrabri in northwestern New South Wales, built as a project for the Bicentennial celebrations of the European settlement of Australia. An imaging radio telescope based on aperture synthesis concepts, it is an array of six 22-metre dishes on rails, spread over six kilometres. The vast majority of the technology was designed and manufactured in Australia. This served to stimulate an antenna export industry that recouped much more than the original $50 million the government put into constructing the telescope.

Hosting the next generation

The next goal is the Square Kilometre Array (SKA)—an international project involving about 20 countries to build a telescope consisting of several thousand small antennas over a baseline of 5,000 kilometres. It will be 10,000 times more powerful than any existing instrument. A team from Australia and New Zealand is competing with a group of Southern African countries to host the telescope. The core site of the Australia–New Zealand bid is at the Murchison Radio-astronomy Observatory (MRO), 315 kilometres northeast of Geraldton in Western Australia.

The Australian Government has already committed nearly $230 million on preparatory projects for the SKA bid. These include CSIRO’s Australian SKA Pathfinder (ASKAP) radio telescope (see Australia’s SKA demonstrator already booked out), being built now at the MRO, which will test some of the technologies for the SKA. It will be fully operational by 2013. Also at MRO, part of the Murchison Widefield Array (see Telescope of tiles), a powerful telescope for studying low-frequency radio sources and composed of flat tiles, is already operational. The first stage of the iVEC Pawsey Centre, which will process the data produced by the new telescopes, opened in Perth in 2010 (see Managing a data mountain).

The legacy of Australian radio astronomy has been vast, with many indirect benefits. For instance, CSIRO’s invention of technology that made possible fast, practical, wireless local-area ­networking—now known as Wi-Fi—was built on two strands of radio astronomy research: looking for radio signals from black holes, and techniques developed for cleaning up signals from space that had been distorted by the Earth’s atmosphere. Wi-Fi technology is now used in homes and offices around the world.

PHOTO: CSIRO’S PARKES RADIO TELESCOPE. CREDIT: DAVID MCCLENAGHAN / CSIRO.

CSIRO Astronomy and Space Science
Professor Ron Ekers, Tel: +61 (2) 9372 4600, Ron.Ekers@csiro.au

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