Opinion- 26 May 2012

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The SKA - click for larger image

Bryan Gaensler* Comments on the
Decision to Place the Square Kilometre Array on Two Continents

Professor Bryan Gaensler

Director Centre for All-sky

Astrophysics, Sydney University


pdf file-available from Australasian Science


The Square Kilometre Array is a concept that's been slowly growing and evolving since 1991. But today this ambitious project took a sudden giant leap towards reality with the announcement of the SKA site decision. The decision is a complex one, which recognises the enormous amount of international investment that will be needed to make the SKA happen: the array will be split between Africa and Australia/New Zealand.


What this does not mean is that half the telescope will be built in each continent. Each site gets a full square kilometre of collecting area, with the full scientific functionality originally envisaged. However, the SKA's science goals require a facility that can tune into radio waves ranging from 70 MHz up to above 10,000 MHz. It's impossible for any single technology to cover this vast range, so the plan has always been to build two or even three different types of antennas, which together can span the full range needed.


What the SKA project has decided is to put different technologies in different places, playing to the strengths of each site.


The lowest frequency component, consisting of antennas that do not move or steer and that can collect signals from the whole sky at once, will be built in Australia and New Zealand. This capitalises on the superb radio quietness of the SKA core planned for Murchison in outback Western Australia - one of the few places on the planet that isn't polluted by FM radio and other artificial signals in this low frequency band.


The higher frequency technology, consisting of more traditional steerable dishes like the one at Parkes, will be built in Africa. This naturally extends on the MeerKAT array of dishes already under construction at the SKA core site in the Karoo desert region of South Africa.


The remaining piece of the puzzle are "phased array feeds", the fish-eye lens technology being developed by CSIRO for their Australian SKA Pathfinder (ASKAP) in Western Australia. These will be further developed and expanded in Australia and NZ, and then possibly later installed on dishes in Africa. Aus/NZ technology on an African telescope is truly a win-win scenario.


Going forward, what this all means is that the money committed to construction by all the SKA's international partners can now begin to flow. The hard-working engineers and scientists in Aus/NZ and in Africa can go back to collaborating rather than competing. And the SKA will attract brilliant young researchers from around the world to help solve the daunting technological challenges ahead of us.


Few people will appreciate the small teams at the heart of the two site bids who have sunk years of their lives into this project. For Australia and NZ, special mention must go to the extraordinary CSIRO team lead by Brian Boyle, Michelle Storey, Phil Diamond and Lisa Harvey-Smith, who made a superb case for Aus/NZ to host the SKA. Africa, led by Justin Jonas and Bernie Fanaroff, must also be congratulated, for creating a thriving African radio astronomy community and a stellar SKA site bid from scratch in barely 10 years. The governments involved have also all been extremely supportive: a positive sign that amidst all the other pressures and challenges, basic research and cosmic discovery still have a place in our nations' priorities.


I am excited that the SKA now looks like it's really going to happen. I can't wait to point it at my favourite stars and galaxies, and to get the data in my hands!


Credit Science: The Square Kilometre Array timeline and split.


*Professor Gaensler's webesite is  http://www.physics.usyd.edu.au/~bmg/