Radio telescope being built in Australia and South Africa
The Square Kilometre Array (SKA) is an intergovernmental international radio telescope 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 in the United Kingdom. The SKA cores are being built in the southern hemisphere, where the view of the Milky Way galaxy is the best and radio interference is 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. 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'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; as of 2021[ [update]] 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) 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 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 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 
In April 2011, Jodrell Bank Observatory of the University of Manchester, in Cheshire, England was announced as the location for the project headquarters. In November 2011, the SKA Organisation was formed as an intergovernmental organisation 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 Jodrell Bank Observatory in the UK, 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.
As of November 2020[ [update]], five precursor facilities were already operating: MeerKAT and the Hydrogen Epoch of Reionization Array (HERA) in South Africa, the Australian SKA Pathfinder (ASKAP) and Murchison Widefield Array (MWA) in Western Australia and the International LOFAR Telescope, spread across Europe with a core in the Netherlands.
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, in the traditional lands of the Wajarri Aboriginal people. Bulldozers The site has been named , which means 'sharing sky and stars' in the Wajarri language.
The Department of Atomic Energy (DAE) in India and UK Research and Innovation (UKRI) are investigating the possibility of establishing supercomputing facilities to handle data from the Square Kilometre Array radio telescope. The UK and India are part of the team developing the computational processing for the SKA radio telescope. On 3 January 2024, Indian government approved joining the SKA project accompanied by a financial commitment of ₹1,250 crore which marks the initial step towards ratification as a member state.
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. 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 coverage 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.
The frequency range from 50 MHz to 14 GHz, spanning more than two 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:
The area covered by the SKA – extending out to ~3000 km – will comprise three regions:
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.
As of  2022[ [update]], the whole project was reported to be worth around A$3 billion.
Members.
In February 2021, the members of the SKAO consortium were:
As of  2022[ [update]], there were 16 countries involved in the project.
SKA locations.
The headquarters of the SKA are located at the University of Manchester's Jodrell Bank Observatory in Cheshire, 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 Murchison Radio-astronomy Observatory (MRO) at Mileura Station near Boolardy in the state of Western Australia, north-east of Geraldton
South Africa.
The core site is located at the Meerkat National Park, at an elevation of about 1000 metres, in the Karoo area of the arid Northern Cape Province. There are also distant stations in Botswana, Ghana, Kenya, Madagascar, Mauritius, Mozambique, Namibia and Zambia.
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 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 at the Murchison Radio-astronomy Observatory site, located near Boolardy 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, a seven-dish engineering and science testbed instrument for MeerKAT, in the Meerkat National Park 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 South Africa's Meerkat National Park. It is designed to study highly redshifted atomic hydrogen emission emitted prior to, and during the epoch of reionization.
Pathfinders.
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.
The International LOFAR Telescope —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.. Because of its baselines of up to 2000 km, it can make images with sub-arcsecond angular resolution over a wide field of view. Such high-resolution imaging at low frequencies is unique and will be a factor of more than an order of magnitude better than SKA1-LOW.
Design studies.
Data challenges.
The amount of sensory data collected poses a huge storage problem, and will require real-time signal processing to reduce the raw data to relevant derived information. In mid 2011 it was estimated the array could generate an exabyte a day of raw data, which could be compressed to around 10 petabytes. 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, stated, "It will generate data streams far beyond the total Internet traffic worldwide." The Tianhe-2 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, integrated into platforms by the CSIRO. China has pushed for a unified beamforming design that has led other major countries to drop out of the project. Canada continues to use Altera Stratix-10 processors (by Intel). 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 US$