The Square Kilometre Array (SKA) is a large, distributed and highly
innovative radio-telescope that will allow astronomers to probe the early
phases of the universe, and to gain a deeper understanding of the fundamental
laws of physics. It will be the most powerful radio telescope operating at
cm-m wavelengths. The Netherlands is one of the initiators of the SKA and has been leading the R&D in aperture array technology, which uses many small antennas and smart computers instead of large traditional dishes.
The SKA Science case is broad and contains a number of key projects in which radio astronomy can make a unique contribution to our understanding of the Universe. They play a major role informing the design:
1) Probing the Dark Ages: Cosmic dawn and the Epoch of Reionisation
2) Challenging Einstein: Detecting gravitational waves, understanding their origin and testing theories of gravity using pulsars
3) Cosmic Magnetism: To understand the origin of magnetic fields
4) Cradle of Life: How do you make planets? Are we alone in the Universe?
5) Galaxy Evolution: Tracing atomic hydrogen using ~10 million galaxies, unraveling the life-cycle of a galaxy
6) The Bursting Sky: what is the source of the bursts of radio waves.
7) Forming Stars Through Cosmic Time: how were the first stars formed.
8) Cosmology and Dark Energy: understanding the nature of dark energy.
The SKA is to be built in Australia and South Africa and will be the world’s most powerful radio telescope. The project will be realised in phases. The first phase, SKA1, is in the detailed design stage, making good progress and looking to start construction by the end of 2018. A future extension, called SKA2, is under study, but construction will start no sooner than the second half of the next decade, after SKA1 has been successfully completed.
SKA1 will comprise two types of telescopes, together with a distributed science and operations network and a headquarters that will co-ordinate development, construction and operations. Following a science driven re-baselining process, completed in March 2015, the scope of SKA1 has been scaled to fit within the 650M€ (2013 value) cost cap for capital investments approved by the project's Board of Directors. SKA1_low in Australia will consist of nearly 130,000 antennas, distributed over 500 stations. Signals from the antennas in each station will be combined to form one or more ‘beams’ on the sky. The operating frequency will be between 50 MHz and 350 MHz. SKA1_mid will be located in South Africa and consist of 200 dishes (including the 64 dishes of the MeerKAT Precursor which will be incorporated). An initial suite of three receivers will cover the 350 MHz – 14 GHz range of the spectrum.
Signals from the telescopes and stations will be transported to a central processing facility on-site in each country, with a dedicated high bandwidth connection to initial science processing and archiving centres in Perth (AU) and Cape Town (SA). Further processing by science teams will take place in a federated and globally distributed network of Science Data Centres (SDC) capable of handling the big data streams coming from SKA.
ASTRON is leading the way in defining the scope and function of these SKA SDCs. In part this initiative is motivated by the immediate needs to deal with the data from LOFAR and WSRT/Apertif, but these facilities will also be a test-bed for such centres in the era of the SKA.