SKASquare Kilometre Array (SKA)


Michiel van Haarlem
Oude Hoogeveensedijk 4, 7991 PD Dwingeloo
Global Collaboration: many organisations involved

The Square Kilometre Array (SKA) is a large, distributed and highly innovative radio observatory 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 has been a key partner from the very start of the project. The design of Phase 1 is to be completed in early 2020, with construction starting in 2021. The SKA will consist of two independent radio telescopes: 1) an array of 130,000 low frequency antennas in West-Australia - modelled on the LOFAR radio telescope built by ASTRON and partners. And 2) an array of 197, 15m, dishes in the North-West of South Africa. The SKA's headquarters are at Jodrell Bank Observatory in the UK. The considerable amounts of data produced by the SKA (up to 700 Petabytes per year) will be distributed to a network of SKA regional centres in the SKA member countries.

The Square Kilometre Array (SKA), to be built in Australia and South Africa, will be the world’s most powerful radio telescope. The project will be realised in phases. The design of the first phase, SKA1 is nearing completion - the final reviews take place in December 2019. A construction proposal will be submitted to the Council of the new SKA Observatory, an intergovernmental treaty organisation, set up specifically for the build and operations of the SKA. Approval is expected late-2020/early-2021 and construction is to start in 2021.

SKA1 will comprise two telescopes in two locations, together with a distributed science and operations network and a headquarters that will co-ordinate development, construction and operations. SKA1_low in Australia will consist of 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 197 dishes (incorporating the 64 dishes of the MeerKAT Precursor). An initial suite of receivers will cover the 350 MHz – 25 GHz parts 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 SKA Regional Centres (SRCs) capable of handling the massive 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 ASTRON's own telescopes, LOFAR and WSRT/Apertif, but data from these facilities will also be a vital resource in preparing for the SKA.

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. The following large projects play a major role informing the design of SKA1:
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.

After the initial build, ongoing investment in the SKA telescopes will be managed and directed by the SKA Intergovernmental Organisation (IGO) in a similar mode to other major international telescope facilities (e.g. ESO).

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