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 Kilometre Array Radio Telescope in Africa, and the locally designed and built MeerKAT was incorporated into the first phase of the SKA. MeerKAT was launched in 2018. MeerKAT is located inside a radio quiet zone within the park.
Along with the Hydrogen Epoch of Reionization Array, also in South Africa, and two radio telescopes in Western Australia, the Australian SKA Pathfinder and the Murchison Widefield Array, the MeerKAT is one of four precursors to the final SKA.
History
MeerKAT was originally planned to contain 20 receptors, and was known as the Karoo Array Telescope. However, the South African government increased the budget to allow for 64 receptors, which prompted the rename to MeerKAT, meaning “more of KAT”.Construction of the 64-dish MeerKAT array took place from 2014 to 2018 and was one of the largest scientific projects in South Africa. The telescope was officially inaugurated by Deputy President David Mabuza on July 13, 2018. In 2023, the MeerKAT team were awarded the Royal Astronomical Society's 2023 Group Achievement Award because of breakthrough observations in just a short period of operation, including large-scale radio bubbles around Sagittarius A, and radio afterglow from a neutron star merger event.
The MeerKAT is a precursor for the Square Kilometer Array telescope, as are the Hydrogen Epoch of Reionization Array, the Australian SKA Pathfinder and the Murchison Widefield Array. MeerKAT will be incorporated into SKA-Mid, a 197-dish array.
Description
It is located on the SKA site in the Karoo, and is a pathfinder for SKA-mid technologies and science. It was designed by engineers within the South Africa Radio Astronomy Observatory and South African industries, and most of the hardware and software was sourced in South Africa. It comprises 64 antennas, each 13.5m in diameter, equipped with cryogenic receivers. The antennas have positions for four receivers, and one of the three vacant positions will be filled by S-band receivers provided by the Max Planck Institute for Radio Astronomy. The array configuration has 61% of the antennas located within a 1 km diameter circle, and the remaining 39% distributed out to a radius of 4 km.The receiver outputs are digitised immediately at the antenna, and the digital data streams are transported to the Karoo Array Processor Building via buried optical fibres. The antenna signals are processed by the Correlator/Beamformer digital signal processor. Data from the CBF is passed on to the Science Processor computer cluster and disk storage modules. The MeerKAT antenna data is also made available to a number of user-supplied digital backends via the CBF, including pulsar and fast radio burst search engines, a precision pulsar timing system, and a SETI signal processor. A time and frequency reference system provides clock and absolute time signals required by the digitisers and other telescope subsystems. This TFR system comprises two hydrogen maser clocks, two rubidium atomic clocks, a precise crystal oscillator, and a set of GNSS receiver systems for time transfer with UTC.
The massive computing and digital signal-processing systems located at the KAPB are housed in a large shielded chamber to prevent radio signals from the equipment interfering with the sensitive radio receivers. The KAPB itself is partially buried below ground level to provide additional radio frequency interference protection, and to provide temperature stability. The KAPB also houses a power conditioning facility for the entire site, including three diesel rotary UPS units that provide an uninterrupted power supply to the whole site.
A long-haul optical fibre transfers data from the KAPB to the Centre for High Performance Computing and SARAO office in Cape Town, and provides a control and monitoring link to the SARAO operations centre in Cape Town. Telescope data processing and reduction is executed on compute facilities provided by the MeerKAT SP systems, and on other high performance computer facilities provides by MeerKAT users.
Specifications
MeerKAT inaugurated in July 2018 consists of 64 dishes of 13.5 metres in diameter each with an offset Gregorian configuration. An offset dish configuration has been chosen because its unblocked aperture provides uncompromised optical performance and sensitivity, excellent imaging quality and good rejection of unwanted radio frequency interference from satellites and terrestrial transmitters. It also facilitates the installation of multiple receiver systems in the primary and secondary focal areas and is the reference design for the mid-band SKA concept.MeerKAT supports a wide range of observing modes, including deep continuum, polarisation and spectral line imaging, pulsar timing and transient searches. A range of standard data products are provided, including an imaging pipeline. A number of "data spigots" are also available to support user-provided instrumentation. Significant design and qualification efforts are planned to ensure high reliability to achieve low operational cost and high availability.
| Number of antennae | 64 |
| Dish diameter | 13.5 m |
| Minimum baseline | 29 m |
| Maximum baseline | 8 km |
| Frequency bands | 0.58 – 1.015 GHz 0.9 - 1.67 GHz 8 – 14.5 GHz |
| Continuum imaging dynamic range at 1.4 GHz | 60 dB |
| Line-to-line dynamic range at 1.4 GHz | 40 dB |
| Mosaicing imaging dynamic range at 1.4 GHz | 27 dB |
| Linear polarisation cross coupling across −3 dB beam | −30 dB |
MeerKAT's 64 dishes are distributed over two components:
- A dense inner component containing 70% of the dishes. These are distributed in a two-dimensional fashion with a Gaussian distribution with a mean dispersion of 300 m, a shortest baseline of 29 m and a longest baseline of 1 km.
- An outer component containing 30% of the dishes. These are also distributed in a two-dimensional Gaussian distribution with a mean dispersion of 2,500 m and a longest baseline of 8 km.
Construction schedule
During 2007, the eXperimental Development Model Telescope was built at the Hartebeesthoek Radio Astronomy Observatory to serve as a testbed for MeerKAT.
Construction of the MeerKAT Precursor Array, on the site started in August 2009. In April 2010 four of the seven first dishes were linked together as an integrated system to produce its first interferometric image of an astronomical object. In Dec 2010, there was a successful detection of very long baseline interferometry fringes between the Hartebeesthoek Radio Astronomy Observatory 26 m dish and one of the KAT-7 dishes.
Despite original plans to complete MeerKAT by 2012, construction was suspended in late 2010 due to budget restructure. Science Minister Naledi Pandor denied the suspension marked any setback to the SKA project or 'external considerations'. MeerKAT construction received no funding in 2010/11 and 2011/12. The 2012 South African National Budget projected that just 15 MeerKAT antennas would be completed by 2015.
The last of the reinforced concrete foundations for the MeerKAT antennas was completed on 11 February 2014. Almost 5000 m3 of concrete and over 570 tonnes of steel were used to build the 64 bases over a 9-month period.
MeerKAT is planned to be completed in three phases. The first phase will include all the antennas but only the first receiver will be fitted. A processing bandwidth of 750 MHz is available. For the second and third phases, the remaining two receivers will be fitted and the processing bandwidth will be increased to at least 2 GHz, with a goal of 4 GHz. With construction of all sixty-four MeerKAT antennas complete, verification tests have begun to ensure the instruments are functioning correctly. Following this, MeerKAT will be commissioned in the second half of 2018 with the array then coming online for science operations.
Inauguration
On 13 July 2018, the Deputy President of South Africa, David Mabuza, inaugurated the MeerKAT Telescope, and unveiled an image produced by MeerKAT that revealed unprecedented detail of the region surrounding the supermassive black hole at the centre of our Milky Way Galaxy.The 64 MeerKAT antennas will be incorporated into Phase 1 of the SKA Mid Frequency Array once the 133 SKA dishes have been built and commissioned on the Karoo site, resulting in a total of 197 antennas for the SKA array. All of the infrastructure currently associated with MeerKAT will be transferred to the SKA array. The KAPB has the capacity to house the additional equipment required by SKA Mid.
| 2011 Precursor | 2016 MeerKAT Phase 1 | 2018 MeerKAT Phase 2 and 3 | |
| Number of dishes | 7 | 64 | 64 |
| Receiver bands | 0.9 – 1.6 | 1.00 – 1.75 | 0.58 – 1.015 0.9 - 1.67 8 – 14.5 |
| Max processed BW | 0.256 | 0.75 | 2 |
| Max baseline | 0.2 | 8 | 20 |
| Min baseline | 20 | 29 | 29 |