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Frequently Asked Questions about the SKA


Progress in the Square Kilometre Array (SKA) project over the last few years and months has been enormous, taking us ever closer to the start of construction, scheduled for the end of 2021.

This progress is generating a growing interest in the world’s largest radio telescope, from regional and national governments – both those already formally engaged and those considering joining the project – the science and engineering community worldwide, industry, local people in the host countries, the media, and the public at large.

SKA Organisation is committed to communicating the exciting developments in the project through a wide range of channels and resources, including announcements on this website, SKA social media platforms, the SKAO bi-monthly bulletin, and this list of Frequently Asked Questions (FAQ). The FAQ covers general aspects about the project, and aims to provide more explanation about recent developments in the design of the telescope and details on the way forward.

What does SKA mean?

SKA stands for Square Kilometre Array. This reflects the original desire to construct a telescope with up to one square kilometre in collecting surface through an array of antennas distributed over a much larger area. This dates back from the early 1990s, and although the original name remains, the concept has expanded still further. The collecting area of the first phase of the SKA telescope (SKA1), which represents just a fraction of the full SKA, is already almost half a square kilometre. The full SKA will largely exceed 1km2.

What is the SKA and what will it do?

The Square Kilometre Array (SKA) is an international project to build a radio telescope tens of times more sensitive and hundreds of times faster at mapping the sky than today’s best radio astronomy facilities. Simply put: the world’s largest radio telescope.

The SKA is not a single telescope, but a collection of various types of antennas, called an array, to be spread over long distances.

The SKA will be the world’s largest public science data project. Once completed it will generate unprecedented volumes of data.

The SKA telescope will be powerful enough to detect very faint radio signals emitted by cosmic sources billions of light years away from Earth, those signals emitted in the first billion years of the Universe (more than 13 billion years ago) when the first galaxies and stars started forming.

The SKA will be used to answer fundamental questions of science and about the laws of nature, such as: how did the Universe, and the stars and galaxies contained in it, form and evolve? Was Einstein’s theory of relativity correct? What is the nature of ‘dark matter’ and ‘dark energy’? What is the origin of cosmic magnetism? Is there life somewhere else in the Universe? But, perhaps, the most significant discoveries to be made by the SKA are those we cannot predict.

What will the SKA look like?

The SKA will use different antenna technologies: parabolic antennas (“dishes”, similar to, but much larger than a standard domestic satellite dish) and dipole antennas (which resemble domestic TV aerials) in phase 1 of construction, and possibly a third type in the second phase of construction.

Each antenna design is best suited to receive signals at different frequencies: the dipole antennas receive very low frequencies, similar to those on which you receive FM radio stations; and the dishes operate at higher frequencies, similar to those used for mobile phone signal transmission.

Dishes: SKA-mid – The full SKA will include several hundreds of dishes (up to two thousand, though the exact number is not yet fully defined), each 15m in diameter. The majority of these dishes will be located in South Africa, with a number being installed in SKA African partner countries. The SKA’s dishes will be capable of withstanding varying environmental conditions with low cost and low maintenance requirements.

Artist's impression of the low-frequency antennasDipoles: SKA-low – The full SKA will consist of up to a million dipole antennas. Thousands of stations spread across hundreds of kilometres will each host a few hundred antennas in what is called an aperture array. Aperture arrays consist of a large number of small dipole antennas arranged on the ground.

Details of the instruments are available in the table below:

  SKA1-low SKA1-mid
Location Australia South Africa
frequency range 50 MHz – 350 MHz 350 MHz – 14 GHz
collecting area 0.4km2 33,000m2
antenna type low frequency aperture array (dipole) dish
quantity (approximate) 130,000 200 (includes 64 MeerKAT dishes)
maximum baseline (km) 65 150
raw data output (TB/s) 157 2
resolution improvement (over LOFAR for LOW and JVLA for MID) 1.25 4
sensitivity improvement (over LOFAR for LOW and JVLA for MID) 8 5
survey speed improvement (over LOFAR for LOW and JVLA for MID) 135 60



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 hear on a car radio. 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 the Universe.

A radio telescope is made up of an antenna, receiver and processing back-end (or data recorder). By building large antennas with sophisticated receivers incorporating amplifiers, the weak cosmic signal is detected and amplified. If they 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.

What makes the SKA so special?

The SKA is a mega-science project, which will test 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 far 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.

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 virtual 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 are of 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.

SKA Telescope Infographic_OP

SKA 3 aspects Infographic V6



What are pathfinders and precursors?

SKA pathfinders and precursors are telescopes engaged in SKA related technology and science studies to pave the way for the SKA. The valuable experience learnt in building and operating them is fed back to help design the SKA. Precursors are located on the SKA sites in Australia and South Africa, and include MeerKAT and HERA in South Africa, and MWA and ASKAP in Australia. Pathfinders are dotted around the globe, and include such telescopes as the VLA in the USA, LOFAR in the Netherlands, GMRT in India, Parkes in Australia, e-MERLIN in the UK, NenuFAR in France, etc. More information is available here.

What’s SKA1 and SKA2?

The SKA is to be constructed in two phases: Phase 1 (SKA1) in South Africa and Australia representing a fraction of the full SKA; and Phase 2 (SKA2) expanding into other African countries, with the Australian component also being expanded.

Why is the construction of the SKA phased?

The decision to adopt a phased-approach for building the SKA telescope was mainly to manage risk and to permit technological evolution, building upon a decade of substantial investment in precursor telescopes, technologies, and design studies. SKA1 will deliver a major enhancement in capability over the current state-of-the-art and is due to begin construction around the end of 2021, with science verification results expected in the mid-2020s. Construction of the full SKA will require more than a decade; the full implementation of the SKA will rely on further refinement of some of the enabling technologies over the coming years.



What is the current status of the SKA project?

The SKA project in now in its final pre-construction phase (or detailed design phase) which consists of fine-tuning the design of the telescope before construction of SKA1 can start at the end of the decade. It is like making sure all of the pieces of this giant puzzle fit together in the best possible way before starting to build it.

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. These are the main science drivers for the SKA and the principal reason it is built.

On the policy front, the process of establishing the SKA Observatory as an intergovernmental organisation (similar to CERN or ESO) is well under way. In March 2019, seven countries signed the SKA Observatory Convention and it will come in to force when five of them – including the SKA host countries Australia, South Africa and the UK – have completed the ratification process.

This transition from the SKA Organisation – a private, non-profit company which has overseen the telescope design phase – into the SKA Observatory, will ensure a smooth procurement and strong governance over the lifetime of the project. You can read more about it here.

Is the design of the telescope fixed?

The design of the first phase of the project, SKA1, has been set, although it will be refined further by engineers before the end of the pre-construction phase and numbers can still vary slightly. Indeed, the SKA instruments are scalable machines and further incremental expansion may happen as new technological innovations take place and technology related costs are brought down over time, and of course as new members join the project.

SKA1 will represent a fraction of the full SKA in terms of its capability to observe the sky in unprecedented detail.

SKA1 will consist of two complementary instruments, providing a continous frequency coverage from 50 MHz to 14 GHz: a low-frequency instrument made of dipole antennas in Australia (50–350 MHz) and a mid-frequency instrument made of dishes in South Africa (350 MHz–14 GHz).

South Africa will host the mid-frequency instrument of the SKA telescope (SKA1-mid), a versatile array of hundreds of dishes that will address key science areas, such as observing pulsars and black holes to detect the gravitational waves predicted by Einstein, testing gravity, and looking for signatures of life in the galaxy.

Australia will host the low-frequency SKA instrument (SKA1-low), an array composed of over a hundred thousand antennas that will address one of the last unexplored times in the history of our Universe – the epoch of re-ionisation and Cosmic Dawn. We will be able to look back to the first billion years of the Universe at a time when the first stars and galaxies formed. Mapping the Universe over 13 billions years, the SKA will thus give great insights into dark matter and dark energy, and the future evolution of the Universe.

What was the original design and why will the actual telescope be different from that?

The SKA project started many years ago with a vision of what the next science questions to ask were and what major science mysteries needed solutions. An initial design of the SKA was developed to realise that vision, in a similar way that an architect will come with a concept or plans to build a house.

The SKA “baseline” design served as a working basis from which to refine the design of the telescope that would fit within the available budget while having the ability to achieve the game-changing science set out initially.

The engineering process done to produce this refined design (called re-baselining) has taken place over many months, involving consultation with representatives from the science and engineering community worldwide and advice from experts from world-leading astronomical facilities. The result is SKA1, a telescope already several times better than any existing state-of-the-art facility and comprising two world-class instruments: one in Australia, one in South Africa. These instruments will then be scaled up to form the full SKA.

Such a process is common practice in projects of the scale of the SKA and other examples in astronomy in the recent past include the ALMA telescope, the Very Large Telescope (VLT), and the LOFAR telescope.

What is the current status of SKA1?

The SKAO is moving towards finalising the detailed design of the SKA1 radio telescope which will culminate in Critical Design Reviews (CDR) for all the telescope products and associated infrastructure and power during the course of 2018 and 2019.  The detailed design is being undertaken by 9 Design Consortia from across the world.

At the meeting of the SKA Board of Directors in July 2017, the SKA Board agreed to the following recommendations in relation to the budget, design and construction for SKA1:

1.The Design Baseline for all Design Consortia will be the basis for Critical Design Reviews and the long-term ambition of the SKA1 project.

  • For SKA1-mid in South Africa, the Design Baseline includes the following: 133 antennas and associated infrastructure and power which includes 21 antennas located in three spiral arms with a maximum baseline of 150km;
  • For SKA1-low in Australia, the Design Baseline includes the following: 512 stations in a large core and three spiral arms with a maximum baseline of 65km.

2. The SKA1 Deployment Baseline will be defined in the SKA Construction Proposal which is currently under development. It will include as much of the Design Baseline as can be afforded at that time. The current Deployment Baseline is formulated on the assumption that €674M (2016 Euros) will be available. Scientific assessment of the proposed deployment baseline demonstrates that the SKA Observatory will deliver transformational science capabilities. Re-instatement of the omitted capabilities, up to the full restoration of the Design Baseline, is planned, either during or after the construction phase, should additional funding become available. The Deployment Baseline will be regularly reviewed by the SKA Science and Engineering Advisory Committee (SEAC) under the direction of the SKA Board.

The implications to these SKA Board approvals are that the scaling options, as well as the steps taken to reduce the cost of the Design Baseline will be implemented to achieve the current calculated Deployment Baseline. The current Deployment Baseline includes the following:

  • For SKA1-mid in South Africa: 130 antennas and associated infrastructure and power which includes 18 antennas located in three spiral arms with a maximum baseline of 120km;
  • For SKA1-low in Australia, the Design Baseline includes the following: 476 stations with a maximum baseline of 40km.

The implication for the SKA Land Acquisition Programme currently underway in South Africa is that the international SKA Organisation, working with the South African Radio Astronomy Observatory (SARAO), will implement the Design Baseline (133 antennas which includes 21 antennas and associated infrastructure and power in the three spiral arms at a maximum baseline of 150km).

SARAO will therefore continue to secure Servitude Agreements with affected landowners on the Design Baseline to mitigate any uncertainty in the local communities with regards to servitudes and execute the land acquisition programme cost-effectively.  The principle of this approach is to ensure the availability of land in the event that additional funding is secured by the SKAO through member countries to achieve the Design Baseline.

The construction phase of SKA1 is expected to commence towards the end of 2020 when all the relevant construction licenses have been secured.

Can SKA1 be considered a game-changer telescope in its own right?

Absolutely! SKA1-low, to be built in Western Australia, will be 8 times more sensitive and 135 times faster than LOFAR, the best radio telescope at these frequencies.

SKA1-mid, to be built in South Africa, will be almost 5 times more sensitive and 60 times faster than the Karl G. Jansky Very Large Array (JVLA) in the USA, currently the state-of-the-art in the radio domain!

These figures set the scene for a number of fundamental discoveries which scientists are already discussing for when the telescope comes online. And remember, SKA1 is just the start of SKA, corresponding to a fraction of the full capabilities of the telescope…

The SKA is often called a Big Data project. What does it mean?

The SKA project requires substantial technology development particularly in Big Data and ultra-fast computing. It could well be the world’s largest public data project.

Just in its first phase, the telescope will produce some 160 terabytes of raw data per second that the supercomputers will need to handle. That’s the equivalent of more than 35,000 DVDs every second.

To face this challenge, the SKA project is teaming up with companies like IBM, Intel, Nvidia, Amazon Web Services and others to look at innovative solutions such as cloud computing, graphic processing and energy-efficient chips.

What is the funding situation and how much will the SKA cost?

The current design phase of the telescope is fully funded, at a cost of over 150 million euros.

The total cost expenditure for the construction of SKA1 was capped by the SKA Board of Directors at 650 million euros in 2013, adjusted to 674 millions euros for inflation in 2016.

Formal negotiations with governments are currently ongoing, the first step to approving national contributions before construction. Already several countries have expressed their solid commitments, including the host countries, which corresponds to a significant portion of the total funding.

SKA1 represents a fraction of the full SKA, currently estimated to be 10% in terms of capability. However this does not mean the cost of the full SKA will also be 10 times greater. There are important economies of scale to be realised when building a large facility like the SKA, and technological progress in particular in terms of computing power and energy efficiency mean that the cost of building and operating these facilities will go down as time goes by. The precise construction cost of the full SKA will be estimated once further engineering work has been performed.

In order to ensure the delivery of SKA1 against the defined cost cap, the SKA Office undertook a review of the existing design in end 2016-early 2017 to explore and capitalise on a range of cost-saving measures. This work was meant to ensure the telescope is built with the best possible value for money. Such review included drawing on cost reduction options already identified and further exploiting potential cost-saving and risk-reduction technology developments and solutions provided by existing SKA precursor and pathfinder facilities. This work was done under the guidance of a Board Subcommittee comprising all SKA Board Science Directors, with the objectives of preserving the transformational science capabilities of SKA1, minimising impact on the project schedule, and allowing expansion of the telescopes as additional funding becomes available. It concluded in July 2017, when the SKA Board confirmed the Baseline Design set in March 2015 as the long-term ambition of the SKA1 project and approved the definition of a ‘Deployment Baseline’, corresponding to the telescopes currently deliverable at that funding level. Formal resolution is available in the Notes from the Chair of the July 2017 SKA Board meeting.

Who is building the SKA?

The SKA project is a international enterprise with currently 13 member countries forming the international SKA Organisation. SKA Organisation is supervising and coordinating all SKA-related activities around the world from the Headquarters located at the University of Manchester’s Jodrell Bank Observatory in the UK.

Over 100 research institutions and companies from these member countries and also other partner countries are currently participating in an international effort to deliver the detailed design for SKA1.

Where will it be built?

SKA1 will be built in South Africa and in Australia, the two best locations that were identified to host the SKA after extensive site-testing around the world. In South Africa, the SKA site is located in the Karoo near Carnarvon in the Northern Cape province. In Australia, the SKA site is located in the Murchison, inland from Geraldton, in remote Western Australia.

The full SKA, an order of magnitude larger than SKA1, will see a massive increase in terms of the low-frequency antennas in Australia and the dishes in South Africa compared to SKA1. Eight African partner countries, namely Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia, plan to host further dishes (about 10% of the totality). During that phase, a technology called mid-frequency aperture arrays, currently under development, may also be installed in the Karoo in South Africa.

Why is the SKA built in such remote locations?

Radio telescopes must be located as far away as possible from human-made electronics or machines that emit radio waves, which could interfere with the ability of the telescopes to detect faint radio signals from the rest of the Universe. The observatory site should also be in a dry environment at altitude, especially for the higher frequency radio waves which are more absorbed by moisture in our atmosphere.

Are other countries interested in joining SKA Organisation?

SKA Organisation certainly welcomes any new partners. Several countries have been engaged in the project for a long time and have expressed interest in taking part in what is considered one of the most ambitious science adventures of the 21st century. Japan, Portugal, South Korea, Switzerland to name but a few have expressed their interest in the project and have an Observer status in the SKA Board of Directors.

What is the funding contribution of each SKA member country?

The exact contribution from each of the SKA member countries is at the core of the on-going negotiations to establish the SKA Observatory as the governing body overseeing the construction and operations of the SKA telescopes. As a starting point for negotiations, a funding framework based on the relative size of national astronomical communities has been developed. The framework is designed to ensure that non-hosting countries gain an equitable science return from the telescope.

Larger astronomy nations would invest more than small astronomy countries, with the telescope sites and HQ hosts each contributing at a higher level.

What will be the actual cost of the SKA, including operations cost?

As per preliminary estimates, the construction of SKA1, the operational costs of the SKA HQ and the funding required for commissioning and early operations totals 1.8 billion euros over the period 2018-2027. Exact figure will be refined as the project gets closer to Critical Design Review and construction readiness.


How will it benefit the countries involved and the world at large?

Beyond the transformational science it will carry out – advancing’s humanity’s knowledge – the SKA will collect and process vast amounts of data and will stimulate cutting-edge advances in high-performance computing and Big Data science – especially the processing, analysis and visualisation of very large data sets. Computer hardware and processing algorithms are being developed in many of the SKA countries, and there is a great deal of technology development and transfer, as well as the creation of very high-level skills. This mega-project is therefore an ideal platform to excite young people about careers in science, engineering and technology, and to deliver skills that will be in demand in the global knowledge economy of the future.

During construction of the SKA over the next decade, companies from SKA member countries will get commercial contracts for the design and construction of the SKA – not only delivering infrastructure, but also high-technology components with innovative intellectual property. Following construction, the operations and maintenance of the SKA will result in further job opportunities over the life of the telescope in the host countries.

The South African partners have also been investing in developing skills for MeerKAT and the SKA through their dedicated Human Capacity Development Programme. Around 700 people, ranging from artisans to postgraduate students and postdoctoral fellows, have already received bursaries and grants from the project. This 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. Many of these students will use the SKA to conduct cutting edge research in South Africa.

Mega-science projects such as the SKA have the potential to seed or boost significant technological development, enhance capabilities and efficiencies across myriad industrial and educational sectors, as well as generate economic and social benefits to society.

Benefits of the SKA beyond the science case could include:

  • the use of sustainable energy sources;
  • the development of energy-efficient processing;
  • new data processing techniques on the cloud;
  • new data communication strategies and technologies to distribute large packets of data quickly around the world;
  • the development of human capacities and capabilities;
  • inspiring the future generations that will work on and with the SKA;
  • the enhancement of global and transcultural collaboration in the advancement of knowledge for the benefit of mankind.

Who will get commercial contracts with the SKA?

Funding will primarily be spent in the SKA member countries through commercial contracts with industries and the innovation sectors, ranging from major players through to SMEs. The benefit gained by industry is not merely in the contract value, but in the intellectual property and enhanced innovation gained by working to design and build one of the world’s most technically challenging programs.

Procurement of construction will be handled through an open, competitive, transparent and centrally controlled process within the membership. A combination of both cash and in-kind contributions are envisaged. Appropriate steps will be taken to ensure that member countries receive a level of return proportional to their investment. The details of the procurement mechanism are being discussed at present within the Organisation membership.

What spin-offs can be expected from the SKA?

The technologies and systems needed for the SKA will require engineers to work at the front line of design and innovation, such as high-performance computing, Big Data, and new manufacturing and construction techniques.

Many of our everyday products come from inventions pioneered by astronomy and radio astronomy research, including Wi-Fi technology, digital cameras and medical imagery devices. The GPS, used every day by millions of people around the world, would not work without the corrections predicted by Einstein’s Theory of Relativity.

The most important spin-off, however, will be the creation of new knowledge and knowledge workers – young scientists and engineers with skills and expertise in a wide range of innovative fields in a large number of countries around the world.

How long will the SKA be operating?

Once completed we intend the telescope to be operational for over 50 years. This is the typical lifetime for such facilities. It includes new instrumentation, software development programmes and other upgrades to maintain the world-class aspect of the telescope during its lifetime. It is hard to predict what the SKA will be in 50 years, but one thing is for sure: it will have transformed our understanding of the Universe and will be an integral part of humanity’s popular culture!