The Square Kilometre Array (SKA) is an intergovernmental international

radio telescope A radio telescope is a specialized antenna and radio receiver used to detect radio waves from astronomical radio sources in the sky. Radio telescopes are the main observing instrument used in radio astronomy, which studies the radio frequency ...

project being built in Australia (low-frequency) and South Africa (mid-frequency). The combining infrastructure, the Square Kilometre Array Observatory (SKAO), and headquarters, are located at the

Jodrell Bank Observatory Jodrell Bank Observatory () in Cheshire, England, hosts a number of radio telescopes as part of the Jodrell Bank Centre for Astrophysics at the University of Manchester. The observatory was established in 1945 by Bernard Lovell, a radio astro ...

in the United Kingdom. The SKA cores are being built in the southern hemisphere, where the view of the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

galaxy is the best and radio interference at its least. Conceived in the 1990s, and further developed and designed by the late-2010s, when completed a total collecting area of approximately one

square kilometre Square kilometre ( International spelling as used by the International Bureau of Weights and Measures) or square kilometer (American spelling), symbol km2, is a multiple of the square metre, the SI unit of area or surface area. 1 km2 is equ ...

. It will operate over a wide range of frequencies and its size will make it 50 times more sensitive than any other radio instrument. If built as planned, it should be able to survey the sky more than ten thousand times faster than before. With receiving stations extending out to a distance of at least from a concentrated central core, it will exploit

radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...

's ability to provide the highest-resolution images in all astronomy. The SKAO consortium was founded in Rome in March 2019 by seven initial member countries, with several others subsequently joining; there were 14 members of the consortium. This international organisation is tasked with building and operating the facility. The project has two phases of construction: the current SKA1, commonly just called SKA, and a possible later significantly enlarged phase sometimes called SKA2. The construction phase of the project began on 5 December 2022 in both South Africa and Australia.

History

The Square Kilometre Array (SKA) was originally conceived in 1991 with an international working group set up in 1993. This led to the signing of the first Memorandum of Agreement in 2000. In the early days of planning, China vied to host the SKA, proposing to build several large dishes in the natural limestone depressions (

karst Karst is a topography formed from the dissolution of soluble rocks such as limestone, Dolomite (rock), dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathe ...

) that dimple its southwestern provinces; China called their proposal Kilometer-square Area Radio Synthesis Telescope (KARST). Australia's first radio quiet zone was established by the

Australian Communications and Media Authority The Australian Communications and Media Authority (ACMA) is an Australian government statutory authority within the Communications portfolio. ACMA was formed on 1 July 2005 with the merger of the Australian Broadcasting Authority and the Aus ...

(ACMA) on 11 April 2005 specifically to protect and maintain the current "radio-quietness" of the main Australian SKA site at the

Murchison Radio-astronomy Observatory The Murchison Radio-astronomy Observatory (MRO) was established by CSIRO (Commonwealth Scientific and Industrial Research Organisation) in 2009. It lies in a designated radio quiet zone located near Boolardy Station in the Murchison Shire of ...

. The project has two phases of construction: the current SKA1, commonly just called SKA, and a possible later significantly enlarged phase sometimes called SKA2. PrepSKA commenced in 2008, leading to a full SKA design in 2012. Construction of Phase 1 providing an operational array, with Phase 2 At Jodrell Bank Observatory 2018 040

In April 2011,

of the

University of Manchester The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The university owns and operates majo ...

, in

Cheshire Cheshire ( ) is a ceremonial and historic county in North West England, bordered by Wales to the west, Merseyside and Greater Manchester to the north, Derbyshire to the east, and Staffordshire and Shropshire to the south. Cheshire's county tow ...

, England was announced as the location for the project headquarters. In November 2011, the SKA Organisation was formed as an

intergovernmental organisation An international organization or international organisation (see spelling differences), also known as an intergovernmental organization or an international institution, is a stable set of norms and rules meant to govern the behavior of states a ...

and the project moved from a collaboration to an independent, not for profit, company. In February 2012, a former Australian SKA Committee chairman raised concerns with South African media about risks at the Australian candidate site, particularly in terms of cost, mining interference and land agreements. SKA Australia stated that all points had been addressed in the site bid. In March 2012 it was reported that the SKA Site Advisory Committee had made a confidential report in February that the South African bid was stronger. However a scientific working group was set up to explore possible implementation options of the two candidate host regions, and on 25 May 2012 it was announced that it had been determined that the SKA would be split over the South African and African sites, and the Australia and New Zealand sites. While New Zealand remained a member of the SKA Organisation in 2014, it appeared that no SKA infrastructure was likely to be located in New Zealand. In April 2015, the headquarters of the SKA project were chosen to be located at the

in the UK,UK to be giant telescope's HQ
. Jonathan Amos, ''BBC News''. 29 April 2015. officially opened in July 2019. Initial construction contracts began in 2018. Scientific observations with the fully completed array On 12 March 2019, the Square Kilometre Array Observatory (SKAO) was founded in Rome by seven initial member countries: Australia, China, Italy, the Netherlands, Portugal, South Africa and the United Kingdom. India and Sweden are expected to follow shortly, and eight other countries have expressed interest to join in the future. This international organisation was tasked with building and operating the facility, with the first construction contracts By mid-2019, the start of scientific observations were expected to start no earlier than 2027. In July 2019, New Zealand withdrew from the project. , four precursor facilities were already operating:

MeerKAT MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Meerkat National Park, in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square Ki ...

and the

Hydrogen Epoch of Reionization Array The Hydrogen Epoch of Reionization Array (HERA) is a radio telescope dedicated to observing large scale structure during and prior to the epoch of reionization. HERA is a Square Kilometre Array (SKA) precursor instrument, intended to observe t ...

(HERA) in South Africa, and the

Australian SKA Pathfinder The Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Mid West region of Western Australia. The facility began as a technology demonstrator for the i ...

(ASKAP) and

Murchison Widefield Array The Murchison Widefield Array (MWA) is a joint project between an international consortium of organisations to construct and operate a low-frequency radio array. 'Widefield' refers to its very large field of view (on the order of 30 degrees ac ...

(MWA) in

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...

. The construction phase of the project began on 5 December 2022 in Australia and South Africa, with delegations from each of the eight countries leading the project attending ceremonies to celebrate the event. The Australian part of the project comprises 100,000 antennas built across , also in the

Murchison region The Murchison is an interim Australian bioregion located within the Mid West of Western Australia. The bioregion is loosely related to the catchment area of the Murchison River and has an area of . Traditionally the region is known as ''Th ...

, in the traditional lands of the

Wajarri The Wajarri people, also spelt Wadjari, Wadjarri, Watjarri, and other variations, are an Aboriginal Australian people whose traditional lands are in the Mid West region of Western Australia. Boolardy Station, along with the tiny settlement of ...

Aboriginal people.

Bulldozer A bulldozer or dozer (also called a crawler) is a large, motorized machine equipped with a metal blade to the front for pushing material: soil, sand, snow, rubble, or rock during construction work. It travels most commonly on continuous track ...

s The site has been named Inyarrimanha Ilgari Bundara, meaning "sharing sky and stars" in the

Wajarri language Wajarri is an endangered Australian Aboriginal language. It is one of the Kartu languages of the Pama–Nyungan family. Geographic distribution Wajarri country is inland from Geraldton, and extends as far south and west as Mullewa, north ...

Description

The SKA will combine the signals received from thousands of small antennas spread over a distance of several thousand kilometres to simulate a single giant radio telescope capable of extremely high sensitivity and angular resolution, using a technique called

aperture synthesis Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection. At each separation and ...

. Some of the sub-arrays of the SKA will also have a very large field-of-view (FOV), making it possible to survey very large areas of sky at once. One innovative development is the use of focal-plane arrays using phased-array technology to provide multiple FOVs. This will greatly increase the survey speed of the SKA and enable several users to observe different pieces of the sky simultaneously, which is useful for (e.g.) monitoring multiple pulsars. The combination of a very large FOV with high sensitivity means that the SKA will be able to compile extremely large surveys of the sky considerably faster than any other telescope. The combined SKA will provide a wide range of coverage, with Australia's Murchison Widefield Array providing low-frequency converage and South Africa's MeerKAT providing mid-frequency coverage. There will be continuous frequency coverage from 50 MHz to 14 GHz in the first two phases of its construction. * Phase 1: Providing ~10% of the total collecting area at low and mid frequencies by 2023 (SKA1). * Phase 2: Completion of the full array (SKA2) at low and mid frequencies by 2030. The frequency range from 50 MHz to 14 GHz, spanning more than two

decades A decade () is a period of ten years. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years. Usage Any period of ten years is a "decade". For example, the statement that "du ...

, cannot be realised using one design of antenna and so the SKA will comprise separate sub-arrays of different types of antenna elements that will make up the SKA-low, SKA-mid and survey arrays: SKA sparse array big

# SKA-low array: a phased array of simple

dipole antenna In radio and telecommunications a dipole antenna or doublet is the simplest and most widely used class of antenna. The dipole is any one of a class of antennas producing a radiation pattern approximating that of an elementary electric dipole wi ...

s to cover the frequency range from 50 to 350 MHz. These will be grouped in 40 m diameter stations each containing 256 vertically oriented dual-polarisation dipole elements. Stations will be arranged with 75% located within a 2 km diameter core and the remaining stations situated on three spiral arms, extending out to a radius of 50 km. # SKA-mid array: an array of several thousand dish antennas (around 200 to be built in Phase 1) to cover the frequency range 350 MHz to 14 GHz. It is expected that the antenna design will follow that of the

Allen Telescope Array The Allen Telescope Array (ATA), formerly known as the One Hectare Telescope (1hT), is a radio telescope array dedicated to astronomical observations and a simultaneous search for extraterrestrial intelligence (SETI). The array is situated at th ...

using an offset Gregorian design having a height of 15 metres and a width of 12 metres. # SKA-survey array: a compact array of parabolic dishes of 12–15 meters diameter each for the medium-frequency range, each equipped with a multi-beam, phased array feed with a large field of view and several receiving systems covering about 350 MHz – 4 GHz. The survey sub-array was removed from the SKA1 specification following a "rebaselining" exercise in 2015. The area covered by the SKA – extending out to ~3000 km – will comprise three regions: # A central region containing about 5 km diameter cores of SKA-mid antennas (South Africa) and SKA-low dipoles (Western Australia). These central regions will contain approximately half of the total collecting area of the SKA arrays. # A mid region extending out to 180 km. This will contain dishes and pairs of SKA-mid and SKA-low stations. In each case they will be randomly placed within the area with the density of dishes and stations falling off towards the outer part of the region. # An outer region from 180 km to 3000 km. This will comprise five spiral arms, along which dishes of SKA-mid, grouped into stations of 20 dishes, will be located. The separation of the stations increases towards the outer ends of the spiral arms.

Costs

The SKA was estimated to cost €1.8 billion in 2014, including €650 million for Phase 1, which represented about 10% of the planned capability of the entire telescope array. There have been numerous delays and rising costs over the nearly 30-year history of the intergovernmental project. , the whole project was reported to be worth around A$3 billion.

Members

In February 2021, the members of the SKAO consortium were: * Australia:

Department of Industry and Science The Department of Industry and Science was a department of the Australian Government responsible for consolidating the Government’s efforts to drive economic growth, productivity and competitiveness by bringing together industry, energy, resour ...

* Canada: National Research Council * China:

National Astronomical Observatories The National Astronomical Observatories, Chinese Academy of Sciences (NAOC, ) is an astronomical research institute operated by Chinese Academy of Sciences, along with Shanghai Astronomical Observatory, Purple Mountain Observatory and National Tim ...

of the

Chinese Academy of Sciences The Chinese Academy of Sciences (CAS); ), known by Academia Sinica in English until the 1980s, is the national academy of the People's Republic of China for natural sciences. It has historical origins in the Academia Sinica during the Republi ...

* France:

French National Centre for Scientific Research The French National Centre for Scientific Research (french: link=no, Centre national de la recherche scientifique, CNRS) is the French state research organisation and is the largest fundamental science agency in Europe. In 2016, it employed 31,63 ...

* Germany: Max-Planck-Gesellschaft * India: National Centre for Radio Astrophysics * Italy:

National Institute for Astrophysics The National Institute for Astrophysics ( it, Istituto Nazionale di Astrofisica, or INAF) is an Italian research institute in astronomy and astrophysics, founded in 1999. INAF funds and operates twenty separate research facilities, which in turn e ...

* Portugal:

Portugal Space Portugal Space (Portuguese: ''Agência Espacial Portuguesa'') is the Portuguese Space Agency created by the Portuguese government in collaboration with the regional government of the Azores in 2019. It is headquartered at Santa Maria Island, i ...

* South Africa: National Research Foundation * Spain: Institute of Astrophysics of Andalusia * Sweden:

Onsala Space Observatory Onsala Space Observatory (OSO), the Swedish National Facility for Radio Astronomy, provides scientists with equipment to study the Earth and the rest of the Universe. The observatory operates two radio telescopes in Onsala, 45 km south of Got ...

* Switzerland:

École Polytechnique Fédérale de Lausanne École may refer to: * an elementary school in the French educational stages normally followed by secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing in région Île-de-France * École, Savoi ...

* The Netherlands:

Netherlands Organisation for Scientific Research The Dutch Research Council (NWO, Dutch: Nederlandse Organisatie voor Wetenschappelijk Onderzoek) is the national research council of the Netherlands. NWO funds thousands of top researchers at universities and institutes and steers the course o ...

* United Kingdom:

Science and Technology Facilities Council The Science and Technology Facilities Council (STFC) is a United Kingdom government agency that carries out research in science and engineering, and funds UK research in areas including particle physics, nuclear physics, space science and astro ...

, there were 16 countries involved in the project.

SKA locations

The headquarters of the SKA are located at the

, England, while the telescopes will be installed in Australia and South Africa. Suitable sites for the SKA telescope must be in unpopulated areas with guaranteed very low levels of man-made radio interference. Four sites were initially proposed in South Africa, Australia, Argentina and China. After considerable site evaluation surveys, Argentina and China were dropped and the other two sites were shortlisted (with New Zealand joining the Australian bid, and 8 other African countries joining the South African bid):

Australia

The core site is located at the

(MRO) at Mileura Station near

Boolardy Boolardy Station is a remote former sheep and cattle station in the Mid West (Murchison) region of Western Australia, about north-north-east of Pindar and west-south-west of Meekatharra. It is within the Shire of Murchison and situated on ...

in the state of

, north-east of

Geraldton Geraldton ( Wajarri: ''Jambinu'', Wilunyu: ''Jambinbirri'') is a coastal city in the Mid West region of the Australian state of Western Australia, north of the state capital, Perth. At June 2018, Geraldton had an urban population of 37,648. ...

Amos, J
Nations vie for giant telescope
,

BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broadc ...

, 28 September 2006.

South Africa

The core site is located at the

Meerkat National Park Meerkat National Park is a large National Park in the Northern Cape, South Africa, that encompasses the Square Kilometre Array, MeerKAT and HERA telescopes. To ensure long term viability of the Karoo site for the MeerKAT and the SKA, and for ...

, at an elevation of about 1000 metres, in the

Karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe !Orakobab or Khoemana word ''ǃ’Aukarob'' "Hardveld") is a semi-desert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its ex ...

area of the arid

Northern Cape The Northern Cape is the largest and most sparsely populated province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley. It includes the Kalahari Gemsbok National Park, part of the Kgalagadi ...

Province. There are also distant stations in

Botswana Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label= Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kal ...

Ghana Ghana (; tw, Gaana, ee, Gana), officially the Republic of Ghana, is a country in West Africa. It abuts the Gulf of Guinea and the Atlantic Ocean to the south, sharing borders with Ivory Coast in the west, Burkina Faso in the north, and Tog ...

Kenya ) , national_anthem = " Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi , ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Afric ...

Mauritius Mauritius ( ; french: Maurice, link=no ; mfe, label= Mauritian Creole, Moris ), officially the Republic of Mauritius, is an island nation in the Indian Ocean about off the southeast coast of the African continent, east of Madagascar. It ...

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

and

Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most central point. Its neighbours are t ...

Precursors, pathfinders and design studies

Many groups are working globally to develop the technology and techniques required for the SKA. Their contributions to the international SKA project are classified as either: Precursors, Pathfinders or Design Studies. * Precursor facility: A telescope on one of the two SKA candidate sites, carrying out SKA-related activity. * Pathfinder: A telescope or programme carrying out SKA-related technology, science and operations activity. * Design Study: A study of one or more major sub-systems of the SKA design, including the construction of prototypes

Precursor facilities

Australian SKA Pathfinder (ASKAP)

The Australian SKA Pathfinder, or ASKAP, is an A$100 million project which built a telescope array of thirty-six twelve-metre dishes. It employs advanced, innovative technologies such as phased array feeds to give a wide field of view (30 square degrees). ASKAP was built by

CSIRO The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government agency responsible for scientific research. CSIRO works with leading organisations around the world. From its headquarters in Canberra, CSIRO ...

at the Murchison Radio-astronomy Observatory site, located near

in the mid-west region of Western Australia. All 36 antennas and their technical systems were officially opened in October 2012.

MeerKAT

MeerKAT is a South African project consisting of an array of sixty-four 13.5-metre diameter dishes as a world class science instrument, and was also built to help develop technology for the SKA.

KAT-7 KAT-7 is a radio telescope situated in the Meerkat National Park, in the Northern Cape of South Africa. Part of the Karoo Array Telescope project, it is the precursor engineering test bed to the larger MeerKAT telescope, but it has become a scie ...

, a seven-dish engineering and science testbed instrument for MeerKAT, near Carnarvon in the Northern Cape Province of South Africa was commissioned in 2012 and was up and running by May 2018 when all sixty-four 13.5-metre diameter (44.3 feet) dish antennae were completed, with verification tests then underway to ensure the instruments are functioning correctly. The dishes are equipped with a number of high performance single pixel feeds to cover frequencies from 580 MHz up to 14 GHz.

Murchison Widefield Array (MWA)

The Murchison Widefield Array is a low-frequency radio array operating in the frequency range 80–300 MHz that began upgraded operation in 2018 at the Murchison Radio-astronomy Observatory site in Western Australia.

Hydrogen Epoch of Reionization Array (HERA)

The HERA array is located in the South African Karoo Radio Astronomy Reserve. It is designed to study highly redshifted atomic hydrogen emission emitted prior to, and during the epoch of reionization.

Pathfinders

* APERture Tile in Focus (Apertif) *

Very Long Baseline Interferometry Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or in space. T ...

* Electronic MultiBeam Radio Astronomy ConcEpt *

e-MERLIN Merlin ( cy, Myrddin, kw, Marzhin, br, Merzhin) is a mythical figure prominently featured in the legend of King Arthur and best known as a mage, with several other main roles. His usual depiction, based on an amalgamation of historic and le ...

* Expanded Very Large Array *

Long Wavelength Array The Long Wavelength Array (LWA) is a radio telescope in central New Mexico. It began preliminary tests of the hardware in 2011, and began regular operations in late 2015. It is one of the few observatories to utilize relatively low frequencies (1 ...

* SKA Molonglo Prototype (SKAMP) * NenuFAR *

Giant Metrewave Radio Telescope The Giant Metrewave Radio Telescope (GMRT), located near Pune, Junnar, near Narayangaon at khodad in India, is an array of thirty fully steerable parabolic radio telescopes of 45 metre diameter, observing at metre wavelengths. It is operated by t ...

Allen Telescope Array

The Allen Telescope Array in California uses innovative 6.1m offset Gregorian dishes equipped with wide band single feeds covering frequencies from 500 MHz to 11 GHz. The 42-element array in operation by 2017 is to be extended to 350 elements. The dish design has explored methods of low-cost manufacture.

LOFAR

LOFAR —a €150 million Dutch-led project— a novel low-frequency phased aperture array spread over northern Europe. An all-electronic telescope covering low frequencies from 10 to 240 MHz, it came online from 2009 to 2011. LOFAR was in 2017 developing crucial processing techniques for the SKA.

Design studies

Aperture Array Verification Programme In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

* Canadian SKA Program * Preparatory Study for the SKA *

Square Kilometre Array Design Studies In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90- degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-lengt ...

(SKADS) ** Electronic MultiBeam Radio Astronomy ConcEpt (EMBRACE) **

BEST Best or The Best may refer to: People * Best (surname), people with the surname Best * Best (footballer, born 1968), retired Portuguese footballer Companies and organizations * Best & Co., an 1879–1971 clothing chain * Best Lock Corporation ...

Data challenges

The amount of sensory data collected poses a huge storage problem, and will require real-time

signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...

to reduce the raw data to relevant derived information. In mid 2011 it was estimated the array could generate an

exabyte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

a day of raw data, which could be compressed to around 10

petabyte The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable uni ...

s. China, a founding member of the project, has designed and constructed the first prototype of the regional data processing centre. An Tao, head of the SKA group of the

Shanghai Astronomical Observatory Shanghai Astronomical Observatory (SHAO), is an astronomical observatory in Shanghai. It has a long history of astrometry, and also operates the Sheshan radio telescope as part of the Chinese VLBI array and the European VLBI Network (EVN). ...

, stated, "It will generate data streams far beyond the total Internet traffic worldwide." The

Tianhe-2 Tianhe-2 or TH-2 (, i.e. ' Milky Way 2') is a 33.86-petaflops supercomputer located in the National Supercomputer Center in Guangzhou, China. It was developed by a team of 1,300 scientists and engineers. It was the world's fastest supercompute ...

supercomputer was used in 2016 to train the software. The processing of the project will be performed on Chinese designed and manufactured Virtex-7 processors by

Xilinx Xilinx, Inc. ( ) was an American technology and semiconductor company that primarily supplied programmable logic devices. The company was known for inventing the first commercially viable field-programmable gate array (FPGA) and creating the fi ...

, integrated into platforms by the

. China has pushed for a unified beam forming design that has led other major countries to drop out of the project. Canada continues to use Altera Stratix-10 processors (by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...

). It is illegal for any US company to export high end Intel FPGAs or any related CSP design details or firmware to China amid the US-embargo which will severely limit cooperation.

Technology Development Project (TDP)

The Technology Development Project, or TDP, is a project to specifically develop dish and feed technology for the SKA. It is operated by a consortium of universities led by

Cornell University Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to tea ...

and was completed in 2012.

Project risks and opposition

Potential risks for priority astronomical sites in South Africa are protected by the

Astronomy Geographic Advantage Act Astronomy () is a natural science that studies celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and evolution. Objects of interest include planets, moons, stars, nebulae, galax ...

of 2007. Put in place to specifically support the South African SKA bid, it outlaws all activities that could endanger scientific operation of core astronomical instruments. In 2010, concerns were raised over the will to enforce this law when

Royal Dutch Shell Shell plc is a British multinational oil and gas company headquartered in London, England. Shell is a public limited company with a primary listing on the London Stock Exchange (LSE) and secondary listings on Euronext Amsterdam and the New ...

applied to explore the

for

shale gas Shale gas is an unconventional natural gas that is found trapped within shale formations. Since the 1990s a combination of horizontal drilling and hydraulic fracturing has made large volumes of shale gas more economical to produce, and some ...

using

hydraulic fracturing Fracking (also known as hydraulic fracturing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "fra ...

, an activity that would have the potential to increase radio interference at the site. An identified remote station location for the southern African array in

was subject to flooding and excluded from the project, despite the SKA Site Selection Committee technical analysis reporting that all African remote stations could implement flood mitigation solutions. During 2014, South Africa experienced a month-long strike action by the National Union of Metalworkers (NUMSA), which added to the delays of the installation of dishes. The plan was to have six dishes operational by November, but only one

dish stands on the

site in the Northern Cape. The largest risk to the overall project is probably its budget, which up until 2014 had not been committed. There has been opposition to the project from farmers, businesses, and individuals in South Africa since the project's inception. The advocacy group called Save the Karoo has stated that the radio quiet zone would create further unemployment in the South African region where unemployment is already above 32%. Farmers had stated that the agriculture-based economy in the Karoo would collapse if they were forced to sell their land.

Key projects

The capabilities of the SKA will be designed to address a wide range of questions in

astrophysics Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline said, Astrophysics "seeks to ascertain the nature of the h ...

, fundamental physics,

cosmology Cosmology () is a branch of physics and metaphysics dealing with the nature of the universe. The term ''cosmology'' was first used in English in 1656 in Thomas Blount's ''Glossographia'', and in 1731 taken up in Latin by German philosopher ...

and

particle astrophysics Astroparticle physics, also called particle astrophysics, is a branch of particle physics that studies elementary particles of astronomical origin and their relation to astrophysics and cosmology. It is a relatively new field of research emerging ...

as well as extending the range of the

observable universe The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these ob ...

. A number of key science projects that have been selected for implementation via the SKA are listed below.

Extreme tests of general relativity

For almost one hundred years,

Albert Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theor ...

general theory of relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the differential geometry, geometric scientific theory, theory of gravitation published by Albert Einstein in 1915 and is the current descr ...

has precisely predicted the outcome of every experiment made to test it. Most of these tests, including the most stringent ones, have been carried out using radio astronomical measurements. By using

pulsars A pulsar (from ''pulsating radio source'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward E ...

as cosmic

gravitational wave Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1 ...

detectors, or timing pulsars found orbiting

black holes A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...

, astronomers will be able to examine the limits of general relativity such as the behaviour of

spacetime In physics, spacetime is a mathematical model that combines the three dimensions of space and one dimension of time into a single four-dimensional manifold. Spacetime diagrams can be used to visualize relativistic effects, such as why differ ...

in regions of extremely curved space. The goal is to reveal whether Einstein was correct in his description of space, time and gravity, or whether

alternatives to general relativity Founded in 1994, Alternatives, Action and Communication Network for International Development, is a non-governmental, international solidarity organization based in Montreal, Quebec, Canada. Alternatives works to promote justice and equality ...

are needed to account for these phenomena.

Galaxies, cosmology, dark matter and dark energy

The sensitivity of the SKA in the 21 cm hydrogen line will map a billion galaxies out to the edge of the observable Universe. The

large-scale structure of the cosmos The observable universe is a ball-shaped region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because the electromagnetic radiation from these obj ...

thus revealed will give constraints to determine the processes resulting in

galaxy formation and evolution The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have gen ...

. Imaging

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-to ...

throughout the Universe will provide a

three-dimensional Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called '' parameters'') are required to determine the position of an element (i.e., point). This is the inform ...

picture of the first ripples of structure that formed individual galaxies and clusters. This may also allow the measurement of effects hypothetically caused by

dark energy In physical cosmology and astronomy, dark energy is an unknown form of energy that affects the universe on the largest scales. The first observational evidence for its existence came from measurements of supernovas, which showed that the univ ...

and causing the increasing rate of expansion of the universe. The cosmological measurements enabled by SKA galaxy surveys include testing models of dark energy, gravity, the primordial universe, and fundamental cosmology, and they are summarised in a series of papers available online.

Epoch of re-ionization

The SKA is intended to provide observational data from the so-called Dark Ages (between 300,000 years after the

Big Bang The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the ...

when the universe became cool enough for hydrogen to become neutral and decouple from radiation) and the time of First Light (a billion years later when young galaxies are seen to form for the first time and hydrogen becomes ionized again). By observing the primordial distribution of gas, the SKA should be able to see how the Universe gradually lit up as its stars and galaxies formed and then evolved. This period of the Dark Ages, culminating in First Light, is considered the first chapter in the cosmic story of creation, and the resolving power required to see this event is the reason for the Square Kilometre Array's design. To see back to First Light requires a telescope 100 times more powerful than the biggest radio telescopes currently in the world, taking up 1 million square metres of collecting area, or one square kilometre.

Cosmic magnetism

It is still not possible to answer basic questions about the origin and evolution of cosmic magnetic fields, but it is clear that they are an important component of interstellar and intergalactic space. By mapping the effects of magnetism on the radiation from very distant galaxies, the SKA will investigate the form of cosmic magnetism and the role it has played in the evolving Universe.

Search for extraterrestrial life

This key science program, called "Cradle of Life", will focus on three objectives: observing

protoplanetary disc A protoplanetary disk is a rotating circumstellar disc of dense gas and dust surrounding a stellar evolution, young newly formed star, a T Tauri star, or Herbig Ae/Be star. The protoplanetary disk may also be considered an accretion disk for th ...

s in habitable zones, searching for prebiotic chemistry, and contributing to the search for extraterrestrial intelligence (

SETI The search for extraterrestrial intelligence (SETI) is a collective term for scientific searches for intelligent extraterrestrial life, for example, monitoring electromagnetic radiation for signs of transmissions from civilizations on other pl ...

). *The SKA will be able to probe the

habitable zone In astronomy and astrobiology, the circumstellar habitable zone (CHZ), or simply the habitable zone, is the range of orbits around a star within which a planetary surface can support liquid water given sufficient atmospheric pressure.J. F. Kast ...

of Sun-like

protostar A protostar is a very young star that is still gathering mass from its parent molecular cloud. The protostellar phase is the earliest one in the process of stellar evolution. For a low-mass star (i.e. that of the Sun or lower), it lasts about 50 ...

s, where Earth-like planets or moons are most likely to have environments favourable for the development of life.SKA - Cradle Of Life
. T.J.W. Lazio, J.C. Tarter, D.J. Wilner. 2004. The signatures of forming Earth-like planets imprinted on circumstellar dust may be the most conspicuous evidence of their presence and evolution, and may even detect planets capable of supporting life.Curtin Institute of Radio Astronomy
- Cradle of Life. April 2015. * Astrobiologists will also use the SKA to search for complex

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

s (carbon-containing chemicals) in outer space, including

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha ...

s, by identifying spectral lines at specific frequencies. *The SKA will be capable of detecting extremely weak radio emission "leakage" from nearby extraterrestrial civilizations, if they exist.