First MeerKAT antenna and high-tech data centre launched in the Karoo
27 March 2014
Dignitaries from around the world, including the Director General of the SKA Organisation, representatives from SKA Organisation member countries and ministers from African SKA partner countries, will convene at the Radio Astronomy Reserve in the Karoo, about 90 km from Carnarvon, for the event.
"The launch of the first MeerKAT antenna signifies South Africa's ardent commitment to the MeerKAT project and the broader SKA project. It further typifies the excellent engineering and technical capabilities in South Africa that have enabled us to deliver a project of this magnitude within projected timeframes and budget allocations," says Minister Hanekom. He adds that the launch of the processor building and the associated design and development activities undertaken mark South Africa's readiness to embark on a big data programme at national level.
Standing 19.5 m tall and weighing 42 tons, the new MeerKAT antenna towers above the antennas of the nearby KAT-7 instrument. KAT-7 was completed in 2010 as an engineering prototype for MeerKAT, and is now routinely used for scientific research. MeerKAT is one of the precursors to the Square Kilometre Array (SKA) telescope, and will later be incorporated into the mid-frequency component of SKA Phase 1 when that instrument is being constructed. The SKA will be the world's largest radio telescope, located in Australia and Africa, but shared by astronomers around the globe.
Because of its so-called "Offset Gregorian" design, each MeerKAT antenna has two reflectors - a main reflector with a 13.5 m projected diameter and a smaller sub-reflector with a diameter of 3.8 m. "With this design there are no struts in the way to block or scatter incoming electromagnetic signals," MeerKAT project manager Willem Esterhuyse explains. "This means that the instrument will be more sensitive than a more conventional symmetric design, and will deliver excellent imaging quality."
The full MeerKAT array will consist of 64 identical receptors (antennas with receivers, digitizers and other electronics installed). Connected by 170 km of underground fibre optic cable, the 64 receptors will operate as a single, highly sensitive astronomical instrument, controlled and monitored remotely from the MeerKAT control room in Cape Town.
Data will flow via buried optical fibres from each receptor to the Karoo Array Processor Building (KAPB), which will house all the racks of digital data processing systems and the electrical power equipment. "The processed data is then sent to the MeerKAT archive in Cape Town, and on to science collaborators in South Africa and abroad," Esterhuyse explains.
"Once up and running, the MeerKAT will generate enough data from the antennas to fill about four and a half million standard 4.7 GB DVDs in a day," Dr Jasper Horrell, general manager for science computing and innovation at SKA SA explains. "However, much of this data is processed on-the-fly and the archive will initially be sized at the equivalent of about 2 million DVDs, retaining some of the larger volume, less processed data for shorter periods and only retaining the smaller volume, more processed science data products indefinitely."
The KAPB is 5 m below ground level in order to protect MeerKAT from radio frequency interference (RFI) generated by the electrical and electronic equipment housed in the data centre. Being underground also enhances the thermal efficiency of the building. The racks of data processing systems are housed in a huge shielded enclosure within the underground KAPB. This 'steel box' is constructed from special steel panels that make sure that no RFI generated by the fast digital electronics 'leaks out'. An extremely precise atomic clock, a hydrogen maser, will be located in a separately partitioned room to ensure thermal stability of this precision device.
The Dutch company COMTEST provided the shielding (steel panels and RFI-tight doors), while the installation was done by a local company, ITC Services. "This is a good example of maximizing local content, while also drawing on international expertise," Esterhuyse says.
"We have done many RF shielding projects over the past 30 years, but taking four sea containers with roughly 48 tons of shielding materials deep into the Karoo and have it built like this, was a challenge," says Jan Kappert, who is in charge of project support and international sales at Comtest Engineering bv. "With the terrific support of the ITC installation team in South Africa, we managed this successfully and are happy that we were able to support the SKA SA project in this way."
All of the on-site infrastructure (buildings, roads, electrical power conditioning and reticulation, aircraft landing strip, etc) has been constructed by South African companies, and the SKA SA infrastructure team based in Johannesburg manages the complex project.
SKA SA engineers and contracted manufacturing companies will now continue to produce the massive, high-precision components of the remaining MeerKAT antennas, and install the antennas in the Karoo, according to a tight timeline. By the end of 2014, the first four receptors will be standing in the Karoo. All 64 receptors will be installed by the end of 2016, with final commissioning being completed in 2017.
The making of MeerKAT's components
At least 75% of the components making up the MeerKAT antennas will be manufactured in South Africa, but several industries in SKA Organisation partner countries around the world are also making crucial contributions. The global technology collaborations bring cutting-edge know-how and many years of antenna experience to the MeerKAT project, and are designed to transfer expertise to the South African industry partners. For example, the first set of reflector panels, as well as the first receiver indexer and sub-reflector were manufactured abroad, but the remainder of these will be made locally.
Key local suppliers of major antenna components include Efficient Engineering (pedestal and yoke), Titanus Slew Rings (azimuth bearing) and Tricom Structures (back-up structure).
Vertex Antennentechnik (VA) in Germany is playing a key role on the contract to provide the MeerKAT antenna positioners. They have been responsible for a significant portion of the antenna design and analysis work, and will be providing the control system for the antennas as a sub-contractor to GDSatcom/Stratosat.
The extremely sensitive cryogenically cooled MeerKAT radio receivers were developed by South African company EMSS Antennas (Stellenbosch), and the UK company Oxford Cryosystems will provide the cryogenic cold-heads that are critical components of these receivers. These two companies have collaborated closely to develop a cold-head that is optimised for the MeerKAT application.
The National Research Council of Canada (NRC), through the Herzberg Programs in Astronomy and Astrophysics, developed the low-noise amplifiers (LNAs) that were chosen for MeerKAT's L-Band receivers (0.9-1.67 GHz). "The LNAs are critically important in achieving MeerKAT's sensitivity and the LNAs from NRC Herzberg were at least 5% more sensitive than any others we could source from leading suppliers around the world," Esterhuyse explains. The LNAs for the L-Band receivers are about to enter production through a sub-contract to industry, while NRC Herzberg completes development of the LNAs for the Ultra High Frequency (UHF) band (0.58 - 1.015 GHz). In challenging the orthodoxy of using metal panels for large dishes, the NRC has developed world-leading expertise in the application of composite structures to radio telescopes and will provide the complex 3.8-m sub-reflector for the first of the MeerKAT Antennas.
"NRC Herzberg congratulates the South African SKA team upon achieving this major milestone today. We are honoured to contribute to this marvelous instrument and very much look forward to the exciting science ahead with MeerKAT and the SKA," Dr Gregory Fahlman, General Manager, NRC Herzberg, Programs in Astronomy and Astrophysics, and SKA Canada Board member, says.
Astronomy teams from around the world have signed up to start using MeerKAT as soon as 16 of its receptors have been commissioned (around June 2015). The full array should be doing routine science observations by the end of 2017.
"MeerKAT's configuration - the way the antennas are placed on the ground - was determined by the science to be performed with the instrument," Dr Horrell explains. "Having dishes close together provides sensitivity for imaging large, extended radio structures in the sky. It's also good for searching for pulsars. Having dishes further apart provides for high resolution, i.e. being able to separate out very closely spaced celestial objects. In addition, one wants to create a 'well-behaved' imaging beam, by carefully designing the overall distribution of antennas to reduce imaging artifacts and ensuring sensitivity to a range of object sizes of potential interest. Other MeerKAT science, such as pulsar timing, does not depend on the configuration."
In the core of the MeerKAT array, 48 of the 64 antennas will be packed closely together in an area about 1 km in diameter. The rest of the antennas will extend up to 4 km from the core, with the largest spacing between antennas being about 8 km.
The MeerKAT science and engineering teams are currently focused on the L-Band (0.9 to 1.67 GHz) and UHF-Band (0.58 - 1.015 GHz) development and verification plans, since these receivers will be deployed first. Until the SKA Phase 1 is completed, MeerKAT will be the most sensitive L-Band radio interferometer in the world. The importance of the L- and UHF-Bands lies in being able to image neutral hydrogen throughout a large cosmic volume and to great distances in the Universe.
MeerKAT will also participate in global VLBI (very long baseline interferometry) operations with all major VLBI networks around the world operating at the MeerKAT frequencies, and add considerably to the sensitivity of the global VLBI networks.
Cool MeerKAT facts
The telescope was originally known as the Karoo Array Telescope (KAT) that would consist of 20 receptors. When the South African government increased the budget to allow the building of 64 receptors, the team re-named it "MeerKAT" - i.e. "more of KAT". The MeerKAT (scientific name Suricata suricatta) is also a much-beloved small mammal that lives in the Karoo region.
About the SKA
The SKA project is an international effort to build the world's largest radio telescope, with a square kilometre (one million square metres) of collecting area. The scale of the SKA represents a huge leap forward in both the engineering and research & development of radio telescopes, and will deliver a transformational increase in science capability when operational. Deploying thousands of radio telescopes, in three unique configurations, it will enable astronomers to monitor the sky in unprecedented detail and survey the entire sky thousands of times faster than any system currently in existence. The SKA telescope will be co-located in Africa and in Australia. It will have an unprecedented scope in observations, exceeding the image resolution quality of the Hubble Space Telescope by a factor of 50 times, whilst also having the ability to image huge areas of sky simultaneously. With a range of other large telescopes in the optical and infrared being built and launched into space over the coming decades, the SKA will perfectly augment, complement and lead the way in scientific discovery. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and to centralise the leadership of the project. Eleven countries are currently members of the SKA Organisation - Australia, Canada, China, Germany, India (associate member), Italy, New Zealand, South Africa, Sweden, the Netherlands and the United Kingdom. Find out more at www.ska.ac.za and www.skatelescope.org