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Everything you wanted to know about the SKA

What is the SKA?

The Square Kilometre Array (SKA) is a radio telescope to be built in South Africa and Australia which will have a total collecting area of approximately one square kilometre. It will operate over a wide range of frequencies and its size will make it 50 times more sensitive, and up to 10 000 faster (in terms of its survey speed) than the best radio telescopes of today. It will be powerful enough to detect radio waves from objects millions or even billions of light years away from Earth. (A light year is the distance light can travel in one year, at a velocity of 300 000 km/s.)

The SKA will focus on addressing questions that can only be answered using a radio telescope. Scientists will use it to help us understand how the Universe evolved, how stars and galaxies form and change, and what "dark matter" really is. Scientists expect that the SKA will make new discoveries that we can't even imagine now. They may even find life elsewhere in the Universe!

What makes the SKA so special?

The SKA is a mega-science project, which will push the limits of engineering and scientific endeavour over the coming decades. Building the SKA will require the development of cutting edge technology and innovation, including the design of the world's fastest supercomputers to process data at rates greater than the current global internet traffic. The SKA will use thousands of radio antennas, with different antenna technologies. This will enable astronomers to probe the universe in unprecedented detail. The SKA will also be able to survey the entire sky much faster than any radio astronomy facility currently in existence.

The SKA project is an international effort comprising organisations from ten countries. While 10 member countries form the core of the SKA, about 100 organisations from 20 countries have been participating in the design and development of the SKA.

How does a radio telescope work?

Radio signals are emitted by a large number of cosmic sources. They sound like the white noise you can see on a television which is not tuned to a channel. Radio telescopes are significantly more sensitive than conventional radios and detect the very weak radio signals from outer space which are processed by computers to form images of galaxies and other objects in the Universe.

A radio telescope is made up of an antenna, receiver and digital back-end (or data recorder). By building large antennas with sophisticated receivers incorporating very sensitive amplifiers, the weak cosmic signal is detected and amplified. If the antennas are spread over a large area, the array will have very good resolution, i.e. it will be able to distinguish very fine details in the objects it observes.

Who is building the SKA?

Many different countries are working together to build - and pay for - the SKA. 10 member countries are the cornerstone of the SKA and 100 organisations from 20 countries have participated in the design and development of the SKA. World leading scientists and engineers are designing and developing a system which will require supercomputers faster than any in existence in 2013 and network technology that will generate more data traffic than the entire Internet.

What is the latest news on the SKA?

The international SKA Organisation (SKAO) has taken crucial steps forward and is now well on track.

In March 2015, the board of directors and the members of the organisation agreed to the proposal for re-baselining the first phase of SKA, called SKA1. This was done to ensure that SKA1 could be built within the cost cap of €650 million but still have the capability to carry out the science that it will be expected to do.

The SKAO will incorporate the SKA precursor, MeerKAT (64 dishes) into SKA1_MID, which will include the addition of another 133 dishes in the Karoo – all of them 15m in diameter. SKA1_MID will therefore consist of 197 dishes in an array spread over baselines of up to 150km. 125 000 low-frequency antennas will be constructed in Western Australia.

Following the re-baselining decision the detailed design of the SKA1 system is proceeding through international consortia. SKA South Africa plays a leading role in most of these consortia. They have all completed their preliminary design reviews.

The SKA project has now entered its final pre-construction phase (or detailed design phase) before construction of SKA1 commences in 2018.

In parallel, we are working with the science community around the world to refine the Key Science Projects to be addressed in the first years of operation of the telescope, from 2020 onwards. These are the main science drivers for the SKA and the principal reason it is built.

On the policy front, work continues towards establishing the SKA Organisation as an international Treaty Organisation – similar to CERN or ESO – which will ensure a smooth procurement and strong governance over the lifetime of the project.

What will the SKA look like?

SKA's three main telescope types will include: Dishes, Low Frequency Antennas and Mid Frequency Antennas.

Dishes: Many aspects of the SKA dish-design challenge are without precedent, not only because of the large numbers of dishes required, and the engineering accuracy that entails, but also because of the huge sensitivity and the amounts of data that will result from this vast collecting area. The dishes for the SKA will probably be made from carbon fibre composites, with high accuracy in their shape. Capable of withstanding high winds, and all sorts of intense thermal and environmental stresses, the SKA's dishes will be unique in the world of radio astronomy.

Low and Medium Frequency Telescopes: Used in the low and medium frequency ranges, aperture arrays comprise a large number of small radio wave receptors arranged on the ground. Whereas with a traditional radio telescope radio signals bounce off the surface of a dish and are then captured at the focus, with aperture arrays the radio signals are captured when they first hit the receptor on the ground. The signals from all the elements are then added together electronically, in phase, to synthesise antenna arrays, and the result is a fast and flexible system. An aperture array is a large number of small, fixed antenna elements coupled to appropriate receiver systems which can be arranged in a regular or random pattern on the ground. A signal "beam" is formed and steered by combining all the received signals after appropriate time delays have been introduced to align the phases of the signals coming from a particular direction. Innovative, efficient and low cost, aperture array antennas provide a large field of view and are capable of observing more than one part of the sky at once. By simultaneously using different sets of timing delays, this "beam forming" can be repeated many times to create multiple independent beams, yielding an enormous total field of view. The ability to configure numerous beams will permit the system to look at multiple regions of the sky simultaneously, greatly increasing the telescope survey speed.

How will the SKA work?

Radio telescopes work in much the same way as your radio. As you tune your radio to different frequencies, the receiver in your radio picks up different music stations. The big difference is that radio telescopes collect radio waves from outer space. These radio signals are processed by computers that can interpret the signals to form images that give us snapshots of the Universe.

A basic radio telescope is made up of an antenna, a receiver and amplifier, and a recorder. The antenna is used to collect the incoming radio waves. The receiver and amplifier boost the very weak radio signal to a measurable level. On the MeerKAT and KAT-7 the amplifiers are extremely sensitive and are normally cooled to very low temperatures to minimise interference due to the noise generated by the movement of the atoms in the metal (called thermal noise). On the MeerKAT and KAT-7 dishes, the signal is also converted from analogue to digital using a digitiser before it is stored using a recorder.

What will the SKA be used for?

The SKA will partly be used to answer questions which have not yet been asked. Radio astronomers will use the SKA to understand how stars and galaxies are formed, and how they evolved over time, and perhaps to detect life elsewhere in the Universe. SKA will be used to obtain a better understanding of dark energy and dark matter.

Where will the SKA be built?

Thousands of SKA antenna dishes will be built in South Africa (in the Karoo, not far from the small town called Carnarvon), with outstations in other parts of South Africa, as well as in eight African partner countries, namely Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia. Another part of the telescope, the low-frequency array, will be built in Western Australia.

What makes the SKA so powerful?

The popular perception of a radio telescope is of a single large dish. However, there are structural and engineering limits on how big a single dish can be, so to build bigger telescopes, astronomers use a technique called interferometry, using large numbers of smaller antennas connected together by optical fibre networks and working as a single telescope, called an array. The more antennas, the larger the effective collecting area and the greater the sensitivity to detect the very weak cosmic radio signals. More antennas spread over longer distances also means that the images made have finer resolution than is possible with a single antenna.

A combination of unprecedented collecting area, versatility and sensitivity will make the SKA the world's premier imaging and survey telescope over a wide range of radio frequencies, producing the sharpest pictures of the sky of any current radio telescope.

Why is the SKA built in such remote locations?

Radio telescopes must be located as far away as possible from man-made electronics or machines that emit radio waves that will interfere with the faint radio signals coming from the distant Universe. The site should also be high and dry, because some radio waves are absorbed by the moisture in our atmosphere.

When will the SKA be built?

Projected milestones for SKA South Africa

  • 2014 - 2017: Building the 64-dish MeerKAT array (while design and planning for SKA is under way)
  • 2018 - 2023: Construction of SKA Phase 1 (scientists can already do research with MeerKAT)
  • 2023 - 2030: Construction of SKA Phase 2 (Including outstations in African partner countries)

How will it benefit the country and the world at large?

Africa's share of the iconic SKA project means that the continent is set to become a sought-after science destination. Over the next decades, many top scientists and research students will come here to do cutting-edge science.

The SKA will collect and process vast amounts of data and will stimulate cutting-edge advances in high-performance computing. Producing the thousands of dishes required for the SKA within the project's time scales will also demand an entirely new way of building highly sophisticated and sensitive scientific instruments - which should lead to innovations in manufacturing and construction. This mega-project is therefore an ideal platform to excite young people about a career in science, engineering and technology, and to deliver skills that will be in demand in the global knowledge economy of the future.

For the next ten to twelve years, job opportunities will be created by the building of and support services to MeerKAT and the SKA itself. Following that, the running and maintenance of the SKA will create jobs for the next 50 years.

Another important impact of South Africa's SKA Project (and our successful bid to host the SKA) is that it is causing a surge of interest in studying mathematics, engineering and astrophysics at local universities, and attracting top students and academics from around the world to South Africa.

The SKA SA Project invests in developing skills for MeerKAT and the SKA through its dedicated Human Capacity Development Programme. More than 700 people, ranging from artisans to postgraduate students and postdoctoral fellows, have already received bursaries and grants.

How does the MeerKAT telescope fit into all of this?

South Africa's MeerKAT telescope is an SKA precursor or 'pathfinder' telescope. It will consist of 64 dish-shaped antennas, each 13.5 metres in diameter, so that each antenna stands about four stories high. It will be the most powerful radio telescope in the southern hemisphere. MeerKAT will become part of SKA Phase 1. MeerKAT will form 25% of the Phase 1 dish array in South Africa. A team of South African scientists and engineers in the SKA South Africa Project Office has designed and is building the world-leading MeerKAT telescope on the site.

The MeerKAt antennas will be distributed over 8 km and are connected by buried power lines and optical fibre connections to very fast computers in the underground Karoo Array Processor Building (KAPB) on the Losberg site. There is intense interest from the international astronomy community in the MeerKAT and 300 international scientists, including South African scientists, have been allocated observing time. Other countries are already investing in the MeerKAT, which will be the most sensitive radio telescope in the world until the SKA is built. The Max Planck Institute in Germany is investing €11 million in more radio receivers for the MeerKAT.

What is KAT-7?

South Africa has already built seven dishes (KAT-7), as an engineering prototype for the MeerKAT and this seven-dish array has already produced its first scientific images. Radio astronomers are using the instrument to do research and have started publishing research articles based on data from KAT-7. Although it was intended as an engineering test bed, it has worked so well that it is in demand by scientists for their observations and is producing good science.

What is the relation between SKA and MeerKAT?

The MeerKAT telescope, currently under construction in the Karoo, will be a 64-dish radio telescope. MeerKAT will eventually be fully integrated as part of SKA Phase One. Scientists from around the world are already lined up to use it for research.

South Africa has already completed a smaller (seven-dish) prototype telescope to test all the systems for MeerKAT. This instrument, KAT-7, is now in regular use by scientists and is yielding scientific information.

South Africa's SKA site in the Karoo has seen teams of contractors preparing the infrastructure for MeerKAT. They have built roads, dish manufacturing sheds, antenna foundations, and the electrical and fibre ducting reticulation network. A new on-site landing strip has been built.

Plans are on track to erect the 64 MeerKAT antennas by 2017.

What spin-offs can be expected from the SKA?

The technologies and systems required for the SKA will require engineers to work at the cutting edge of design and innovation, such as better high-performance computing and new manufacturing and construction techniques. The most important spin-off, however, will be the generation of new knowledge and knowledge workers - young scientists and engineers with cutting edge skills and expertise in a wide range of scarce and innovative fields.

Updated November 2015