Editing Square Kilometre Array (section)

== Description ==

[[File:SKA participants map.svg|thumb|320px|Countries that participated in the preparatory phase of SKA<ref name=SKAorghist>{{cite news | url= http://www.skatelescope.org/the-organisation/history-of-the-organisation/participating-countries/ |title=Participating countries |publisher=SKA Organisation}}</ref>]]
The SKA will combine the signals received from thousands of small [[antenna (radio)|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]].<ref name=skalayout>{{cite web|title=The SKA Layout|url=https://www.skatelescope.org/layout/|website=SKA Telescope|access-date=5 October 2015|archive-url=https://web.archive.org/web/20150921001143/https://www.skatelescope.org/layout/|archive-date=21 September 2015|url-status=live}}</ref> Some of the sub-arrays of the SKA will also have a very large [[field of view|field-of-view]] (FOV), making it possible to survey very large areas of sky at once.<ref>{{cite web|title=The World's Largest Radio Telescope Takes A Major Step Towards Construction|url=https://www.skatelescope.org/news/worlds-largest-radio-telescope-near-construction/|website=SKA Science|date=9 March 2015|access-date=5 October 2015|archive-url=https://web.archive.org/web/20160108044154/https://www.skatelescope.org/news/worlds-largest-radio-telescope-near-construction/|archive-date=8 January 2016|url-status=live}}</ref> One innovative development is the use of [[Focal-plane array (radio astronomy)|focal-plane arrays]] using [[phased-array]] technology to provide multiple FOVs.<ref>{{cite web|title=SKA Aperture Arrays|url=https://www.skatelescope.org/aperture-arrays/|website=SKA Telescope|access-date=5 October 2015|archive-url=https://web.archive.org/web/20150921022000/https://www.skatelescope.org/aperture-arrays/|archive-date=21 September 2015|url-status=live}}</ref> 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.<ref>{{cite web|title=How will SKA1 be better than today's best radio telescopes? [image]|url=https://www.skatelescope.org/wp-content/uploads/2015/03/SKA-3-aspects-Infographic_OP-rgb.jpg|website=SKA Telescope|access-date=5 October 2015|archive-url=https://web.archive.org/web/20160304085949/https://www.skatelescope.org/wp-content/uploads/2015/03/SKA-3-aspects-Infographic_OP-rgb.jpg|archive-date=4 March 2016|url-status=live}}</ref>

The combined SKA will provide a wide range of coverage, with Australia's Murchison Widefield Array providing low-frequency coverage and South Africa's MeerKAT providing mid-frequency coverage.<ref name=facts>{{cite web |url=http://www.skatelescope.org/about/facts-figures/ |title=Facts and figures |publisher=SKA Organisation |access-date=26 May 2012 |archive-url=https://web.archive.org/web/20120728191729/http://www.skatelescope.org/about/facts-figures/ |archive-date=28 July 2012 |url-status=dead }}</ref><ref>{{Cite journal | doi = 10.1117/2.3201407.12| title = Philip Diamond plenary: The Square Kilometre Array: A Physics Machine for the 21st Century| journal = SPIE Newsroom| year = 2014| last1 = Spie}}</ref><ref name="SKAO 2022"/> There will be continuous frequency coverage from 50&nbsp;MHz to 14&nbsp;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).<ref name=ska1>{{cite web|title=SKA1|url=http://astronomers.skatelescope.org/ska1/|website=SKA Science|date=21 February 2014 |access-date=5 October 2015|archive-url=https://web.archive.org/web/20160108044154/http://astronomers.skatelescope.org/ska1/|archive-date=8 January 2016|url-status=live}}</ref>
* Phase 2: Completion of the full array (SKA2) at low and mid frequencies by 2030.<ref>{{cite web|title=SKA2|url=http://astronomers.skatelescope.org/ska2/|website=SKA Science|date=21 February 2014 |access-date=5 October 2015|archive-url=https://web.archive.org/web/20160108044154/http://astronomers.skatelescope.org/ska2/|archive-date=8 January 2016|url-status=live}}</ref>

The frequency range from 50&nbsp;MHz to 14&nbsp;GHz, spanning more than two [[Decade (log scale)|decades]], 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:

[[File:SKA sparse array big.jpg|thumb|right|Artist's impression of a Low-Band SKA Sparse Aperture Array Station]]
[[File:SKA dense array big.jpg|thumb|right|Artist's impression of a SKA Dense Aperture Array Station]]

# SKA-low array: a phased array of simple [[dipole antenna]]s to cover the frequency range from 50 to 350&nbsp;MHz. These will be grouped in 40&nbsp;m diameter stations each containing 256 vertically oriented dual-polarisation dipole elements.<ref>{{cite web |url=https://research.csiro.au/ska/technology/ |title=Developing technologies for SKA-Low |access-date=2022-10-22}}</ref> Stations will be arranged with 75% located within a 2&nbsp;km diameter core and the remaining stations situated on three spiral arms, extending out to a radius of 50&nbsp;km.<ref>{{cite web |url=https://www.skatelescope.org/lfaa/ |title=Low-Frequency Aperture Array |access-date=2022-10-22}}</ref>
# SKA-mid array: an array of several thousand [[Parabolic antenna|dish antennas]] (around 200 to be built in Phase 1) to cover the frequency range 350&nbsp;MHz to 14&nbsp;GHz. It is expected that the antenna design will follow that of the [[Allen Telescope Array]] using an offset Gregorian design having a height of 15 metres and a width of 12 metres.<ref name=ska1 /><ref>{{Cite web |date=2024-01-03 |title=Square Kilometre Array Project - Rau's IAS |url=https://compass.rauias.com/current-affairs/square-kilometre-array-project/ |access-date=2024-01-04 |website=compass.rauias.com |language=en-US}}</ref>
# 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&nbsp;MHz – 4&nbsp;GHz. The survey sub-array was removed from the SKA1 specification following a "rebaselining" exercise in 2015.<ref>{{cite web|last1=McPherson|first1=A.|title=REPORT AND OPTIONS FOR RE-BASELINING OF SKA-1|url=https://www.skatelescope.org/wp-content/uploads/2014/03/SKA-TEL-SKO-0000229_Report-and-Options-for-Re-Baselining-of-SKA-1-Word_Amm-signed.pdf|website=SKA Telescope|publisher=SKAO|access-date=5 October 2015|archive-url=https://web.archive.org/web/20151006071718/https://www.skatelescope.org/wp-content/uploads/2014/03/SKA-TEL-SKO-0000229_Report-and-Options-for-Re-Baselining-of-SKA-1-Word_Amm-signed.pdf|archive-date=6 October 2015|url-status=live}}</ref>

The area covered by the SKA – extending out to ~3000&nbsp;km – will comprise three regions:<ref name=skalayout /><ref>{{cite web|last1=Dewdney|first1=P. E.|title=SKA Baseline Design|url=https://www.skatelescope.org/wp-content/uploads/2012/07/SKA-TEL-SKO-DD-001-1_BaselineDesign1.pdf|website=SKA Telescope|access-date=5 October 2015|archive-url=https://web.archive.org/web/20160602160221/http://www.skatelescope.org/wp-content/uploads/2012/07/SKA-TEL-SKO-DD-001-1_BaselineDesign1.pdf|archive-date=2 June 2016|url-status=live}}</ref>
# A central region containing about 5&nbsp;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&nbsp;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&nbsp;km to 3000&nbsp;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.<ref>{{cite web |url=http://www.skatelescope.org/about/project/ |title=The project timeline |publisher=SKA Organisation |access-date=28 October 2014 |url-status=dead |archive-url=https://web.archive.org/web/20120805230658/http://www.skatelescope.org/about/project/ |archive-date=5 August 2012  }}</ref><ref>{{cite web |url=http://www.ska.ac.za/about/bid.php |title=SKA site bid outcome |publisher=SKA Africa |access-date=28 October 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140626022118/http://ska.ac.za/about/bid.php |archive-date=26 June 2014  }}</ref> There have been numerous delays and rising costs over the nearly 30-year history of the intergovernmental project.<ref name=physicsworld201907/>

{{as of|2022|12}}, the whole project was reported to be worth around A$3 billion.<ref name=firstoz2022/>
[[File:Square Kilometre Array Organisation members.svg|thumb|Square Kilometre Array Organisation (SKAO) membership map]]

===Members===

As per March 2025, the members of the SKAO consortium were:<ref name=SKAorg/><ref>https://www.skao.int/en/about-us/governance/100/skao-council</ref><ref>https://www.skao.int/en/partners/skao-members</ref>

* Founding members:
** Australia: [[Department of Industry and Science]]<ref>https://www.skao.int/en/partners/skao-members/133/australia</ref>
** China: National Remote Sensing Centre of the [[Ministry of Science and Technology (China)|Ministry of Science and Technology of the People's Republic of China]] ''(中华人民共和国科学技术部 - Zhōnghuá Rénmín Gònghéguó Kēxué Jìshùbù)''<ref>https://www.skao.int/en/partners/skao-members/372/china</ref>
** Italy: [[Istituto Nazionale di Astrofisica|National Institute for Astrophysics]] ''(Istituto Nazionale di Astrofisica)''<ref>https://www.skao.int/en/partners/skao-members/292/italy</ref>
** Portugal: [[Portugal Space|Portugal Space Agency]] ''(Agência Espacial Portuguesa)''<ref>https://www.skao.int/en/partners/skao-members/389/portugal</ref>
** South Africa: South African Radio Astronomy Observatory of the [[National Research Foundation of South Africa|National Research Foundation]]<ref>https://www.skao.int/en/partners/skao-members/397/south-africa</ref>
** The Netherlands: [[ASTRON|ASTRON - Netherlands Institute for Radio Astronomy]] ( ''(ASTRON - Astronomisch Onderzoek in Nederland'')<ref>https://www.skao.int/en/partners/skao-members/163/netherlands</ref>
** United Kingdom: [[Science and Technology Facilities Council]]<ref>https://www.skao.int/en/partners/skao-members/396/united-kingdom</ref>

* Joined in 2022:
** Switzerland: SKACH Consortium<ref>https://www.skao.int/en/partners/skao-members/302/switzerland</ref>

* Joined in 2023:
** Spain: [[Institute of Astrophysics of Andalusia]] ''(Instituto de Astrofísica de Andalucía)''<ref>{{cite web |title=Spain joins the SKA Organisation - SKA Telescope |url=https://www.skatelescope.org/news/spain-joins-skao/ |website=SKA Telescope |access-date=19 June 2018 |date=19 June 2018 |archive-url=https://web.archive.org/web/20180619213907/https://www.skatelescope.org/news/spain-joins-skao/ |archive-date=19 June 2018 |url-status=live }}</ref><ref>https://www.skao.int/en/partners/skao-members/398/spain</ref>

* Joined in 2024:
** Canada: Radio Astronomy Directorate of the [[National Research Council (Canada)|National Research Council]]<ref>https://www.skao.int/en/partners/skao-members/388/canada</ref>
** Germany: Association for Data-Intensive Radio Astronomy ''(Verein für datenintensive Radioastronomie e.V.)''<ref>https://www.skao.int/en/partners/skao-members/399/germany</ref>
** India: [[National Centre for Radio Astrophysics]] ''(राष्ट्रीय रेडियो खगोल भौतिकी केन्द्र - Raashtreey Rediyo Khagol Bhautikee Kendr)''<ref>{{cite web |url=https://www.skatelescope.org/news/indias-ncra-becomes-11th-full-skao-member/ |title=India's National Centre for Radio Astrophysics becomes the 11th full SKA Organisation member |date=11 August 2014 |publisher=SKA Organisation |access-date=11 August 2014 |archive-url=https://web.archive.org/web/20160108044154/https://www.skatelescope.org/news/indias-ncra-becomes-11th-full-skao-member/ |archive-date=8 January 2016 |url-status=live }}</ref><ref>{{Cite web |title=Explained {{!}} Square Kilometre Array project, world's largest radio telescope, and India's role in it |url=https://www.deccanherald.com/science/space/explained-square-kilometre-array-project-worlds-largest-radio-telescope-and-indias-role-in-it-2833808 |access-date=2024-01-04 |website=Deccan Herald |language=en}}</ref><ref>https://www.skao.int/en/partners/skao-members/393/india</ref>

* Observers:
** France: [[French National Centre for Scientific Research|National Centre for Scientific Research]] ''(Centre National de la Recherche Scientifique)''<ref>https://www.skao.int/en/partners/prospective-members/188/france</ref>
** Japan: [[National Astronomical Observatory of Japan|National Astronomical Observatory]] ''(国立天文台 - Kokuritsu Tenmondai)''<ref>xhttps://www.skao.int/en/partners/prospective-members/191/japan</ref>
** Korea: [[Korea Astronomy and Space Science Institute]] ''(한국천문연구원 - Hangugcheonmun-Yeonguwon)''<ref>https://www.skao.int/en/partners/prospective-members/193/south-korea</ref>
** Sweden: [[Onsala Space Observatory]] - [[Chalmers University of Technology]] ''(Onsala rymdobservatorium - Chalmers tekniska högskola)''<ref>https://www.skao.int/en/partners/prospective-members/186/sweden</ref>

* African Patners, involved in coordinated action to support the future expansion of the SKA project in Africa:
** Botswana
** Ghana
** Kenya
** Madagascar
** Mauritius
** Mozambique
** Namibia
** Zambia