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SKA & Apertif Take Us To The Stars And Beyond

Cover image credit: © Chris Sciacca, IBM

Have you ever dreamed about becoming an astronaut when you were a little kid? If so this might be interesting for you. It might also be worth reading if you like great technology or are interested in the world behind our blue skies here on earth.

The project to build the “Square Kilometre Array” (SKA) and the technology created within the project “Aperitif” from ASTRON in the Netherlands promise important and exciting new astronomical research opportunities.

The SKA Organisation – How it started


Artist’s impression of the full Square Kilometre Array at night featuring all four elements. (image: SKA Organisation, July 2015 licensed under Creative Commons Attribution 3.0 Unported License)

Let’s start at the beginning and back-up in history real quick. The history of the SKA began in September 1993 when the International Union of Radio Science (URSI) established the Large Telescope Working Group to begin a worldwide effort to develop the scientific goals and technical specifications for a next generation radio observatory.
In 1997, eight institutions from six countries (Australia, Canada, China, India, the Netherlands, and the U.S.A.) signed a Memorandum of Agreement to cooperate in a technology study program leading to a future very large radio telescope.

Today’s SKA Organisation, a not-for-profit company established in December 2011, consists out of ten members, now including Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom and seeks to formalise relationships between the international partners and centralise the leadership of this grand endeavour.

Why SKA is one of the greatest astronomical projects ever

Why is the SKA so exciting? The project aims to build the world’s largest radio telescope, with eventually over a square kilometre (one million square metres) of collecting area. To do so the SKA will use thousands of dishes and up to a million antennas that will enable astronomers to monitor the sky in unprecedented detail and survey the entire sky much faster than any system currently in existence.


Infographic: How will SKA1 be better than today’s best radio telescopes? (image: SKA Organisation, March 2015 licensed under Creative Commons Attribution 3.0 Unported License)

The project will be set-up in two locations: Australia and South Africa. Whilst 10 member countries are the cornerstone of the SKA, around 100 organisations across about 20 countries are participating in the design and development of the SKA. World leading scientists and engineers designing and developing a system which will require supercomputers faster than any in existence in 2015, and network technology that will generate more data traffic than the entire Internet.

Revealing a Galaxy 5 billion light years away

Here is a teaser of what to expect from SKA in the future: The Australian SKA Pathfinder Telescope has revealed a galaxy 5 billion light years away this year. The galaxy was uncovered in radio emission travelling to Earth using CSIRO’s Australian SKA Pathfinder telescope (ASKAP), located at the Murchison Radio-astronomy Observatory (MRO) in Western Australia.
The five-billion-year-old radio emission was stamped with the ‘imprint’ of hydrogen gas it had travelled through on its way to Earth. The gas absorbs some of the emission, creating a tiny dip in the signal. “At many observatories, this dip would have been hidden by background radio noise, but our site is so radio quiet it stood out clearly,” Dr James Allison said.


CSIRO’s newest radio telescope, the Australian SKA Pathfinder (ASKAP)

Apertif is the next step in radio telescope evolution

Now let’s take a look at the Aperitif project which is exploring one of the technologies providing a larger field of view (i.e. the region of the sky that can be imaged in a single observation), while also trying to exploit it for doing science. The technology is one crucial part of the bigger SKA project which uses also low frequency antennas (this is an ASTRON implementation called Low Frequency Aperture Array or LFAA) and mid frequency antennas (MFAA) for the dishes.

Within the Apertif project the Westerbork Synthesis Radio Telescope (WSRT) is equipped with a receiver array in the focus of each parabolic dish of the WSRT, instead of the single receiver element that the current system employs. With this the field of view can be increased by a factor 25!


Apertif aims to increase the field of view of the Westerbork Synthesis Radio Telescope (WSRT) with a factor 25 (image: Apertif)

Transforming Telescopes into effective fast-transient search machines

And why do we want that? The new technology enables us to research the decreasing gas supplies in in and around galaxies which could be the reason for the decreasing number of new stars which are born for the last several billion years.

Further the array will transform the WSRT into a very effective fast-transient search machine. Arrays of radio telescopes generally have the problem of the limited field of view of the array beam. However, because the WSRT is a linear (i.e. purely east-west) array, combined with the fact that the spacings between the antennae of the array is regular (i.e. most of the dishes are 144 m apart), the WSRT equipped with Apertif does not have this limitation. Using a dedicated, high-power “beam former” and transient-search compute cluster, Apertif can exploit the full field of view to search for fast transients and pulsars.

This still sounds rather abstract but below is a visual example of how cool the array technology is: In early 2008 a prototype focal-plane array mounted in one of the WSRT dishes was used to make a spectroscopic observation of the nearby galaxy M31. The object on the left is the neutral hydrogen in M31 as seen with the Apertif prototype, while on the right is the image made with the full WSRT. Although the new image looks much worse compared to the old one, it still means an enormous improvement. The reason that the old image looks sharper is that  all 14 WSRT dishes were used to make it, while for the new one with the FPA only one dish was used. The big improvement is that to make the new image, only one telescope pointings has to be used, while for the old image 163 pointings were used.


On the left is an image taken with Aperitif, only one telescope pointing has to be used. On the right 163 pointings were used  (image: Apertif)

With these great achievements which are only representing a first possibility of what will be possible in the future being an astronaut might become an down-to-earth job!