Introduction

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 news announcements on this website, SKA social media platforms, the SKA magazine Contact, and this list of Frequently Asked Questions (FAQ) covering general aspects about the project.

What is the SKA and what will it do?

The SKA will be the world’s largest radio telescope, many times more powerful and faster at mapping the sky than today’s best radio telescopes. It 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 also be among the world’s largest public science data projects. Once completed it will generate enormous 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 does SKA mean?

SKA stands for Square Kilometre Array. This reflects the original desire to construct a telescope with a collecting surface of one square kilometre through an array of antennas distributed over large distances. The concept for the SKA dates back to the early 1990s, and although the original name remains, the science goals, concept and engineering behind the project have evolved over the years, resulting in the science requirements of today that call for 130,000 antennas and 200 dishes. After the first phase of construction, historically referred to as SKA1, the two arrays comprising the SKA will already have a combined collecting area of almost half a square kilometre. As antennas can be added to interferometers, a future expansion of the SKA would allow this collecting area to increase even further.

What will the SKA look like?

The SKA will use different technologies of antennas: parabolic antennas called “dishes” which are similar to satellite dishes used for TV, and dipole antennas which are like traditional TV aerials. Each antenna design is best suited to receive signals at different frequencies: the dipole antennas receive very low frequencies like those used for FM radio stations and the dishes receive higher frequencies like those used for wi-fi signals, 3G and 4G. Dishes: The SKA’s array of parabolic antennas will initially comprise 197 dishes, each 15m in diameter, spread across 150km in South Africa’s Karoo region. A future expansion in the K into other African countries is part of the vision for SKA. Dipoles: The SKA’s array of low-frequency antennas will initially include 131,000 dipole antennas contained within 512 stations and spread across 65km in the West Australian outback. Each station will hold 256 antennas. A future expansion of the array is envisioned as part of the full vision for the SKA. Details of the instruments are available in the table below: Dipoles Dishes 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 data output (Tb/s) 8 7

What is the difference between the two telescopes in terms of science?

The SKA’s dishes, to be located in South Africa, will address key science areas, such as observing pulsars and black holes to detect the gravitational waves predicted by Einstein, testing gravity, studying transient events like the enigmatic fast radio bursts and looking for signatures of life in the galaxy. In Australia, the SKA’s low-frequency antennas will study 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, 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. Overall however, more than 40% of the SKA’s science case will make use of both telescopes, showing the complementarity between the arrays. Read more about the SKA’s science goals here.

Where will it be built?

The first phase of the SKA 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 ultimate ambition is to expand the SKA further both in Australia and in Africa, extending into African partner countries across the continent: Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia.

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.

What is the current status of the SKA project?

Our teams have now concluded the detailed design phase of the SKA, closing out what is called the System Critical Design Review (CDR) in early 2020. Such a milestone marks the final stage of pre-construction, which consists of fine-tuning the design of the telescope before construction can begin in 2021. 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 being built. A new structure, the SKA Observatory, is being created to oversee construction and operation of the SKA as an intergovernmental organisation like CERN and ESO, the European Southern Observatory. You can read more about it here.

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.

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 is SKA2?

SKA2 has been used to refer to a future expansion of the SKA. For now, work is focused on delivering the first phase of the SKA as defined above (see: “What will the SKA look like?“), with the possibility of a later extension to deliver the full SKA vision.

Is the design of the telescope fixed?

Yes, it is now. In December 2019, the six-year detailed design work involving hundreds of experts at the SKA central office and around the world culminated with the completion of the overall System Critical Design Review, which was preceded by critical design reviews for each of the SKA’s elements. There may still be small changes as we move toward the industrialisation phase but we don’t expect major changes to the agreed design. You can read more about this work here.

Has the SKA’s design evolved over time?

Absolutely! 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 was developed to realise that vision, in a similar way that an architect will come with a concept or plans to build a house. This served as a working basis from which to refine the design of the telescope that would fit within a set budget while having the ability to achieve the game-changing science set out initially. The engineering process behind that refinement involved consultation with representatives from the science and engineering community worldwide and advice from experts from world-leading astronomical facilities. This has meant the look of the SKA dishes and antennas – and the design of the associated hardware and software that are also essential – has evolved over time. 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.

Can the SKA be considered a game-changer telescope?

Absolutely! The first phase of the SKA’s low-frequency array, to be built in Western Australia, will be eight times more sensitive and 135 times faster than LOFAR, the best radio telescope at these frequencies. The first phase of the mid-frequency array, to be built in South Africa, will be almost five 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, a future expansion of the SKA would vastly increase these capabilities.

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. The scale of the data to be generated is enormous: an average of 5 Terabits per second will flow from the central processing facilities at the telescope sites to the SKA’s supercomputers. This is approximately 1,000 times the equivalent data rate generated by the Atacama Large Millimeter Array (ALMA), a joint European/USA/East Asia facility in the Chilean Andes. To face this challenge, the SKA has worked with 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.

How much will the SKA cost?

In 2020, the cost of the SKA Phase 1 including construction of the two telescopes and the first 10 years of operations (2021-2030) is estimated to be around 1.9 billion Euros (in 2020 Euros).

Who is building the SKA?

The SKA is an international endeavour, and organisations from 15 countries are currently taking part at government or national-coordination level. The SKA Organisation is supervising and coordinating all SKA-related activities around the world from the Headquarters located at the historic Jodrell Bank Observatory in the UK. Read more on the countries involved here. Over 100 research institutions and companies from these member countries and other partner countries have been participating in an international effort to deliver the design for the SKA.

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

Beyond the transformational science it will carry out – advancing 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.

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?