Name of the Project
Square Kilometre Array (SKA) project.

Location
South Africa’s Karoo region and Western Australia’s Murchison Shire have been chosen as co-hosting locations.

South Africa’s Karoo will host the core of the high- and mid-frequency dishes, ultimately extending over the African continent. Australia’s Murchison Shire will host the low-frequency antennas.

Project Owner/s
SKA Observatory (SKAO), comprising Australia, China, Italy, the Netherlands, Portugal, South Africa and the UK, with others expected to join in due course.

Nine countries are currently observers in the SKAO Council, including those that took part in the design phase of the SKA telescopes (Canada, France, Germany, India, Spain, Sweden and Switzerland). Japan and South Korea have recently joined.

Project Description
The SKA will provide a collecting area of one-million square metres. This will make the SKA the biggest radio telescope array ever built.

The project will use three types of antennas (radio-wave receptors) – dishes, mid-frequency aperture arrays and low-frequency aperture arrays – to provide continuous frequency coverage from 70 MHz to 10 GHz. Combining the signals from the antennas will create a telescope with a collecting area equivalent to a dish with an area of about 1 km2.

The project will comprise two radio telescope arrays, currently designated SKA-Mid and SKA-Low.

The South African instrument, known as SKA–Mid, will comprise 197 dishes and operate in the 350 MHz to 14 GHz frequency range. The Australian instrument, known as SKA–Low, will comprise 131 072 dipole antennas and will operate in the 50 MHz to 350 MHz frequency range.

SKA–Mid will include the 64 dishes of the South African precursor to the SKA, the MeerKAT radio telescope array. Australia’s precursor, the Australian SKA Pathfinder (better known as Askap) will serve as surveying instrument for the SKA.

The central regions, in Australia and in South Africa, will contain cores, each 5 km in diameter – one for each antenna type. Fifty per cent of the collecting area will be within the central cores. The aperture array antennas will extend to about 200 km from the core regions. In Africa, the dishes will be positioned at distant stations that are 3 000 km from the core regions.

The construction of the SKA will be phased, which means that the SKA can start operating before construction is completed.

Potential Job Creation
Five-hundred engineers from 100 institutions across 20 countries are involved in the design of the SKA telescopes.

More than 1 000 scientists from 40 countries are involved in the development of the science case for the SKA telescopes.

Capital Expenditure
The overall design commitment for funding is €2-billion, under 2021 economic conditions. With every passing year, this number increases by the inflation rate.

Planned Start/End Date
The entire array is expected to start early operations by July 2028.

Latest Developments
SKA-Mid is currently in the AA 0.5 phase, with the SKA-Low, in Australia, progressing at the same pace. This involves the construction of four dishes.

The AA 0.5 dishes are really preproduction units; the final design will be signed off only after the testing and evaluation of the four initial dishes.

The first dish is being shipped to South Africa. It will arrive in the country this December and be shipped to the site. Its erection will start in January 2024.

The first SKA-Mid dish has already been set up in China. The dish antennas for the SKA-Mid are being produced in that country, as one of the “fair work return” work packages assigned to that country as a full member of the SKAO. All the member countries have been assigned SKA work packages. The dish in China will serve as a test and evaluation unit.

Every dish will be fully fitted with all its detection, operational and control systems as it is built. The idea is to test the dishes as much as possible, so it is in the SKAO’s interests to deploy as much functionality in every dish as it can.

The AA 0.5 dishes will be subject to individual testing and evaluation immediately after they are completed. The expectation is that there will be no need to adjust the design of the dishes or that only minor adjustments will be required.

The SKAO wants dishes that can be pointed as quickly as possible – to be able to respond to important but transient astronomical phenomena – while maintaining their observational stability and performance. The length of this test and evaluation period will be determined in 2024.

Once two dishes have been completed, it will be possible to start testing their pointing accuracy and the accuracy of their dish surfaces, or holography. These tests require the two dishes to be operated together as a single unit.

Distortions in the dish panels, imperceptible to the human eye, can degrade performance. Such distortions could result from manufacturing or shipping errors, but could also be the result of stresses imposed by design flaws in the dish support structures.

Once all four dishes are completed, it will be possible to undertake the signal processing tests.

Phase AA 0.5 will be completed, with all four dishes erected and fully equipped, by early 2025.

Work packages
South Africa has been assigned four work packages.

The main local work package is the construction of the infrastructure for the SKA-Mid array, including roads and power connections, as well as fibre and other signal networks.

The South African Radio Astronomy Observatory (SARAO) has been contracted to test the individual dishes and the different phases of the array as they are deployed. This is a services contract. SARAO is also contributing to different software design packages.

The fourth major South African work package relates to the dish receivers. Every dish has several of these radio receivers, and South African company EMSS Antennas has been contracted to build one receiver for every SKA-Mid dish. The company will also provide the associated receiver systems services.

The SKA-Mid team has established a policy of involving as many local stakeholders as possible in the region around the telescope site.

The team has established a priority hierarchy of four ‘tiers’. Tier 1 is the four towns surrounding the array site – Carnarvon, Brandvlei, Vanwyksvlei and Williston; whenever possible, contractors should source as much as they can from Tier 1. Should they be unable to do so, they should then try Tier 2, which covers the districts in which the four towns are located; then Tier 3, which is the Northern Cape province; and the Tier 4, which comprises is the whole of South Africa.

AA 0.5 will be followed, from the start of 2025, by AA 1.0. This phase will result in the erection of a further four dishes to the production standard to take the total number of dishes to eight. The completion of AA 1.0, expected by early 2026, will take the SKA-Mid instrument to the point where its scientific performance can be validated. This will mark the start of scientific testing.

Testing will involve pointing the dishes at ‘test’ parts of the sky, where the scientists expect to get certain results, and see if the array delivers those results. Once AA 1.0 is formally completed, more dishes will be added.

Every new dish will first be plugged into a test array to validate it, and only after that will it be integrated into the operational array. The main constraint to dish deployment will be the development of the ‘back-end’ signal processing systems.

At the beginning of 2026, AA 2.0 will start. The main focus of this phase will be on the transfer of the array computing system from the Karoo Array Telescope site to Cape Town.

This process will be undertaken throughout 2026 to avoid disrupting the telescope’s operations. The AA 2.0 system will be configured to work with 64 dishes and should be operational by early 2027. At that point, the first data will be released to the science community for science verification.

The design baseline is for the SKA-Mid to have 197 dishes, including the MeerKAT dishes. This achievement will mark the completion of AA 4; however, the funding for AA 4.0 has not yet been secured.

So, an interim array design, in-between AA 3.0 (an early defined milestone with 133 dishes) and AA 4.0, has been developed, and should be complete by early 2028. This interim design is designated AA *, and corresponds with what can be built using the funding that should then be available.

In the interim, the SKAO director-general and the SKAO leadership are actively seeking additional funding, as the ambition remains to build the full design baseline for both telescopes.

The plan is to integrate MeerKAT into SKA-Mid. Originally a 64-dish array, a joint project between SARAO and Germany’s Max Planck Institute for Radio Astronomy.

Max Planck is adding up to 20 dishes to bring MeerKAT’s total up to 84. A highly successful and much regarded instrument, it is intended to be integrated into the SKA at some point after the completion of SKA-Mid’s AA 2.0.

Meanwhile, work on SKA-Low, or AA Verification System (AAVS) 3, is progressing in parallel with that on SKA-Mid. The Australian team is, like their South African colleagues, constructing and deploying the support infrastructure for their antennas.

The AA Verification System AAVS 3 is complete. The SKA-Low instrument will comprise a series of “stations”, each with 256 antennas. AAVS 3 is a complete station and is being tested.

The AA 0.5 deployment of the SKA-Low will start early in 2024 and the subsequent phases will be rolled out in parallel with those of the SKA-Mid telescope.

In the UK, the SKAO head office is on its way to being fully operational. It is responsible for programme delivery, science operations and engineering operations. Programme delivery includes overseeing the manufacture of the telescopes, ensuring the correctness of the designs and that the contracting is done correctly.

A science operations team is needed when the instrument is being built, as this is how they will learn to operate it.

Key Contracts, Suppliers and Consultants
About 70 contracts will be placed by the SKAO within its member States, with competitive bidding taking place in the countries.

Contracts awarded to date: Astron – Netherlands Institute for Radio Astronomy, CGI Netherlands, TriOpSys, S[&]T – Science and Technology Corporation, Vivo Technical, Interaction Design Solutions, International Centre for Radio Astronomy Research, Guangzhou University, Commonwealth Scientific and Industrial Research Organisation, Fourier Space, Observatory Sciences, CGI IT UK, The Numerical Algorithms Group, Persistent Systems, Covnetics, The National Institute for Astrophysics, ALTAR Innovation, Faculdade de Ciências da Universidade do Porto, Critical Software (software development); Zutari (MID infra professional services); SARAO (professional services); AVNET Silica (SPS FPGAs); Sanitas EG (SPS iTPM & Subracks); EMSS Antennas  (receivers for SKA-Mid dishes); Power Adenco Joint Venture (construction of the major civil infrastructure for the SKA-Mid); South African Radio Astronomy Observatory (softwate); and EMCOM, VIVO and Zutari.

Contact Details for Project Information
SKA South Africa, email enquiries@ska.ac.za.