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ENGINEERING the SQUARE KILOMETRE ARRAY  
Written by Dr. Martin Cole

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The benefits of Astronomy are usually seen in terms of Science – exploring the beauty of the Solar System, the Galaxy and the Universe – to understand our origins, evolution and fate, and to contemplate space travel, space colonisation, extra-terrestrial life and extra-terrestrial intelligence. 

Astronomy also requires the essential, enabling dimension of Engineering, which in turn benefits the broader economy.  Take for example the Australia Telescope National Facility (ATNF) at Narrabri NSW.  This “compact array” of six, 22m radio telescopes was built at a cost of $50M.  The great majority of this funding went to Australian industry, developing local expertise, generating employment, spin-off businesses and exports.  The ongoing business that was generated from this project, is estimated at between two and three times the initial investment.  Moreover, the continuing international exchange of technology has maintained Australia’s reputation at the forefront of advanced astronomical and communications equipment.  

The Square Kilometre Array (SKA) is the most exciting large-scale project that I have been associated with.  Designed for 100 times the sensitivity of current radio telescopes, it will have a collecting surface of I million square metres, or one square kilometre.  It involves not only leading-edge Science, but leading-edge Engineering in a firm partnership.  There are significant opportunities for research, design, construction, employment and export.

Science has provided the inspiration, the vision and the specification for this project.  It will serve many scientific purposes.  It will penetrate the "Dark Ages” of the universe – an epoch possibly more than 14 billion years ago – and explore a time before the first stars had formed.  No light was produced then.  Only radio waves can reveal the swirling gases leading to the formation of stars and the early structure of the universe.  This knowledge will test theories that extrapolate to predict the ultimate fate of us all.  Of more immediate interest, SKA will detect the presence of Earth-sized planets in distant star systems, and will be able to listen with unprecedented sensitivity, for any indication of remote intelligent life.  NASA will use SKA technology for communication and control of deep space probes.  And SKA has numerous other tasks in prospect.

Engineering will provide the research & development, construction and commissioning of this remarkable scientific tool.  One recent Australian design proposal is for 52,802 antenna flux concentrators, deployed in 300 sites that span the continent in a spiral pattern.  Each concentrator may be a “Luneburg lens”, being a fixed 7 metre diameter sphere weighing 7 tonnes, designed to focus radio waves in the range of 100MHz to 5GHz, arriving from all directions.  Antenna feeders placed at the focus generate a narrow reception beam in the sky (0.25 to 0.005 arcsec).  100 such beams are planned for each lens simultaneously, requiring 100 feeders per lens, or 5 million feeders for the project.  This requires mass production on a significant scale.

While there will be an international site selection process, many believe that Australia is the location of choice for this project because of the radio-quietness of our outback regions, our political stability, educated community and southern hemisphere exposure to the Milky Way.  If built here, with 300 remote sites each containing 176 lenses, there is significant opportunity in site works - excavation, foundations, drainage, access roads, fencing, landscaping, weather and bushfire resistance, and other works that also benefit local communities.

Power supplies to remote regions represent another opportunity.  Depending upon location, power will be derived from the grid or a renewable supply such as wind, tidal or solar.

Telecommunications will represent a major undertaking indeed.  The 300 sites will linked by fibreoptic cable, expanding our telecommunications infrastructure to the benefit of local communities and cities that lie within reach.  The challenge for engineers will be to develop a data speed capability that is more than 100 times greater than present technology permits, over a maximum reach of 3000km.

The necessary signal processing for correlation of the 5 million channels is not yet possible.  Leading supercomputers and astronomical signal processing engines today operate at speeds measured in Teraflops (1,000,000,000,000 floating-point operations per second).  For the SKA, data processing capability in the Petaflop range will be required.  SKA engineers are banking on the famous Moore’s Law to continue over the next 10-15 years, giving them the required processing capacity by the time the telescope is operational in 2015-2020.

In the mean time there is an exciting opportunity involving many schools.  Under the SEARFE (Students Exploring Australia’s Radio Frequency Environment) project, students monitor radio receiving scanners, logging the levels of radio interference in their region.  IEAust is donating a scanner to be shared by a number of groups.  This supports an active program by some State governments in locating the most ideal SKA sites.  

Arising from it’s innovation statement “Backing Australia’s Ability”, the Federal government is providing $23.5M additional funding to astronomy, half of which goes toward current R&D projects for the SKA.  Matching funding is coming from CSIRO, university, State government and industry participants, while enquiries from other interested parties are welcome.

Finally, as the world’s premier instrument for astronomical imaging, SKA will generate significant tourism to witness its enormity, power and precision.  It will be of great interest to astronomers, engineers and enthusiasts from around the world, bringing great prestige to Australia and the professions involved. 

Credits:  Dr Chris Fluke, Swinburne University of Technology (Luneburg lens illustrations) and Dr Peter Hall, CSIRO ATNF (lens design details).