Telescopic eye looks to the sky

A satellite receiver that works like a giant eyeball has arrived in Sydney for testing by the CSIRO.

Its arrival brings a step closer one idea that has been proposed for the world’s next ‘mega-telescope’ – an army of giant spheres dotted in patches across the landscape that could collect radio waves from the cosmos.

The 1-m white sphere has the same function as a satellite dish – collecting and concentrating radio waves. Essentially, it’s just a lens that focuses radio waves to a point, just as the lens in an eyeball focuses light to a point on the retina. And like the eye, but unlike today’s radio telescopes or communications antennas, the lens can ‘see’ many radio sources in the sky at once.

The Lunenberg lens system is just one of the ideas that has been proposed for the development of the Square Kilometre Array or SKA telescope, an international project that has the aim of designing and ultimately manufacturing a telescope with an effective collecting area of one square kilometre.

Australia is just one of 11 countries developing ideas for the telescope, and the CSIRO is a member of the Australian SKA consortium, which is coordinating Australia’s participation in the project. Construction of the final design will not start until around 2010.

Although several other concepts for the telescope have been put forward, ranging from large collectors set into the ground to a swarm of satellite dishes, the Australians are favouring the Lunenberg approach. But there are several technical hurdles to be surmounted.

‘The SKA would need tens of thousands of Luneburg lenses, each about five metres in diameter,’ says Dr Peter Hall, CSIRO SKA Program Leader. And at the moment, the Russian-based designs are just too expensive.

The Russian lens, for example, is made of high-density polystyrene, so CSIRO is developing lighter, cheaper materials that absorb less of the precious radio signal.

‘We aim to build a ‘demonstrator system’ of lenses or flat collectors to show that the ideas will work,’ says Dr Hall. ‘They’d be built alongside CSIRO’s existing Australia Telescope at Narrabri and integrated with it.’ This would both test the viability of the technology and make the Australia Telescope uniquely able to see many different parts of the sky at once.

As well as undertaking technical work, Australia has also begun to test possible SKA sites – the first country to do so.

‘The site has to meet various technical requirements. One of the most important is being in an area relatively free of man-made radio signals, which can swamp the extremely weak cosmic signals,’ Dr Hall explains.

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