Why a dual-site SKA is a win for everyone

Why a dual-site SKA is a win for everyone

Summary: The Square Kilometre Array (SKA) is a concept that's been slowly growing and evolving since 1991. But on Friday night, this ambitious project took a giant leap towards reality, with the announcement of a SKA site decision.

TOPICS: Emerging Tech

commentary The Square Kilometre Array (SKA) is a concept that's been slowly growing and evolving since 1991. But on Friday night, this ambitious project took a giant leap towards reality, with the announcement of a SKA site decision.

The decision was a complex one, and one that recognised the enormous amount of international investment 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 on each continent. Each site will get 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 70MHz to more than 10,000MHz. 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 board 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, such as the one at Parkes, New South Wales, will be built in Africa. This naturally extends the MeerKAT array of dishes already under construction in the Karoo desert region of South Africa.

The remaining pieces of the puzzle are "phased array feeds", the fish-eye lens technology being developed by CSIRO for its Australian SKA Pathfinder (ASKAP) in Western Australia.

This technology will be further developed and expanded in Australia and New Zealand, and then possibly later installed on dishes in Africa. Australian and New Zealand technology on an African telescope truly is a win-win scenario.

Going forward, what this all means is that the money committed to construction by all of the SKA's international partners can now begin to flow. The hard-working engineers and scientists in Australia and New Zealand and in Africa can go back to collaborating, rather than competing.

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 New Zealand, special mention must go to the extraordinary CSIRO team, led by Brian Boyle, Michelle Storey, Phil Diamond and Lisa Harvey-Smith, who made a superb case for Australia and New Zealand 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 amid 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!

This article appears courtesy of the Australian Science Media Centre.

Bryan Gaensler is Director of the ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), and was formerly the International Project Scientist for the Square Kilometre Array.

This article was originally published at The Conversation. Read the original article.

Topic: Emerging Tech

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  • I'm finding it frustrating that there are so many articles on the subject of the choice of site for the SKA, but nowhere can I find one that cites actual physics.

    Earlier on there was talk about South Africa getting the SKA, but the only point actually raised in the media was that the South African site had higher altitude, thus a clearer view at high frequencies. But I've been able to find absolutely no details as to how much of an effect this is.

    Recently some articles have talked about South Africa being the preferred choice on purely scientific grounds. But again, no details as to why. Lately the South African press has talked this up, but again, no detail at all.

    Can I assume that there are other aspects of siting that make a difference in terms of pure physics? Who has the best site in terms of radio quietness, and on what frequencies? Again, nothing that cites real numbers. My take on this is that the Australian site has the edge. What do the experts think?

    What about issues to do with topography of the arrays? My take on this was that the Australia-NZ array is better in this regard. But maybe that doesn't matter at high frequencies? I wish someone would write about this.

    Is there anything else we're missing here - talking purely about doing the best science?

    Are there scientific benefits in spreading the whole thing over an even wider baseline?

    Has there been any talk about the necessary optic cable needed to link the two sites?

    Will the designers of the Australian site now go ahead and design a pure low frequency array, or will they in their plans, leave physical room in case they later want to add steerable dishes too?

    I hope someone can answer these questions :-)
  • Hi Russel,

    You'd likely find the report interesting. It says: There is no identified scientific advantage of a dual-site implementation over a single site implementation for the SKA observatory. Furthermore there are cost and programmatic risks which we discuss in more detail that are associated with adopting a dual-site implementation.

    For reference: http://www.skatelescope.org/uploaded/19942_120520_SOWG.Report.pdf