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COMPANY PROFILE

2014

SKA

27 11 442 2434 | www.ska.ac.za

company profile

SKA and MeerKAT the RFI and

other challenges Editorial: Christian Jordan Production: Emily Woodhall

With the inauguration of MeerKAT in March this year, the installation of the first MeerKAT dish and the official opening of the specialised MeerKAT Karoo Array Processor Building was celebrated. The building is a cutting edge data centre for the MeerKAT telescope that has been built in an underground bunker at the Karoo observatory site. MeerKAT Project Manager, Willem Esterhuyse tells IndustrySA that the building is vital for containing the radio frequency interference (RFI) generated by all of the electronic equipment required for the data processing and control of the telescope.

Radio frequency interference (RFI) is a common phenomenon in modern life. It is all around us; it comes from electrical devices and has an effect on the radio frequencies that we monitor. It has been a problem for many organisations in the past; the military, the telecommunications industry and of course, the scientific community, but over the years ways to manage RFI have been developed. At the site of the MeerKAT telescope in the Northern Cape, an innovative idea is helping to deal with the problem of RFI, a problem which can obviously have a serious impact on the science produced by MeerKAT. The MeerKAT radio telescope is a precursor to the Square Kilometre Array (SKA) telescope and will be integrated into the mid-frequency component of SKA Phase 1. The SKA Project is an international enterprise to build the largest and most sensitive radio telescope in the world, and will be located in Africa and Australia. So clearly, RFI is a problem that has to be addressed

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early and MeerKAT Project Manager, Willem Esterhuyse tells us that the new MeerKAT Karoo Array Processor Building is providing a perfect solution.

SEALED IN “An important milestone was the site selection,” he says. “The main reason for our successful SKA site bid was not just because we have been doing a good job on MeerKAT, KAT7 and the site bid proposal – but because we had an inherent good site. It is one of the last low RFI sites and that is really key because as I always say; having RFI on a site is like shining a torch into an optical telescope – it just wipes out what you want to observe. With all the effort around SKA and the site, scientists have definitely started to realise that the future of radio astronomy is in Africa and Australia. “We have a very good radio quiet site. Your problem in many instances is not just existing RFI but also RFI that you create during construction and operation - so called

SKA SA

self-generated RFI. All of the electronic equipment and computer equipment generates RFI so, to an extent, you can become your own worst enemy and this is why we have a very stringent procedure with any equipment that goes to site. All components and subsystems such as motors used to drive the antennas have to go through rigorous RFI testing. Obviously we have gained a lot of experience on solutions that will work. For example, your antenna drive motor has to be a brushless DC motor, which does not cause sparking and therefore does not cause RFI.” Ensuring that RFI does not interfere with the telescope is vital as otherwise the science capability will be significantly diminished with the result that expensive and time-consuming design modifications will have to be done and implemented. “You have to verify that any radiation is below the level that will impact on radio astronomy. Those levels are extremely low – in the order of 10,000 times lower than what is used in some of more rigorous military

applications,” Esterhuyse explains. “We refer to the SARAS (South African Radio Astronomy Service) levels, which has been signed into law and gives the minister of science and technology the power to intervene with any activity that will jeopardize the operation of our radio telescopes. Strictly speaking we are breaking the law if we do not comply too this requirement.” Equipment that does radiate is located inside a shielded room – the so called KAPB (Karoo Array Processor Building). It is a room that is cladded on the inside with metal panels, with special provision made where apertures are required. There is a double shielded door with copper fingers in order to allow getting in and out of the room without breaking the RFI seal. Special attention needs to be paid to cable, fibre and coolant entries as well as the joints between the panels to ensure that the RFI integrity of the building is not compromised in any way. The radiating equipment is firstly designed to emit as little radiation as possible by following best practice RFI design

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company profile

principles and is then housed inside this room, which results in minimum interference with the telescope. “You have to be very disciplined with RFI design and implementation, since you’ll compromise the entire instrument if the SARAS levels are exceeded. This is particularly important for long integration observations,” Esterhuyse says. The building, which sits five meters below ground level, will be used to house all the racks of digital data processing systems and the electrical power equipment. Being underground also enhances the RFI performance of the building as the soil provides additional attenuation.

LIGHTSPEED PROGRESS When talking to Esterhuyse about the general progress of the project in South Africa, you get the sense that this is a project that is moving quickly. Back in October 2012 when we spoke to Esterhuyse for the first time, the project was still at a stage where designs were being finalised for the antenna structure and

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all of the additional sub-systems. Then, in April 2013, infrastructure was being finalised and foundations were being planned. Today, all of the infrastructure is complete and the first MeerKAT antenna is on the ground with the second to come shortly. The focus right now is on testing and qualifying to ensure that everything is in good working order before full production of antenna and complimentary systems begins. “The second antenna is being manufactured, but has not been installed yet. The first antenna structure was installed in March 2014 and now we are busy with fitting the rest of the equipment to the antenna; the receivers, the optical fibre and other equipment to transform it into a working radio telescope that we can control remotely. Then we will run a series of stringent tests on it in order to qualify the antenna level design as well as all the sub-systems. Once qualification has been completed you can proceed to manufacture 64 of the antennas and the processing units. If you don’t do proper qualification before going into production you run the very real risk of costly and

Diesel Electric Services is proud to be associated with the SKA Project

SKA SA

Diesel Electric Services was awarded the contract for the design (along with Aurecon), manufacture, installation and commissioning of the Secure Power Supply for SKA Meerkat Radio Telescope. The site is located Âą90km from the town of Carnarvon, in the Northern Cape. The plantroom for the equipment is immersed in the ground to lower the interference it might have with the telescope. The scope included the Supply of the incoming 33kV domestic supply (indoor switchgear), from Eskom, stepped down by two 2500kVA Transformers to 22kV. The supply is then fed to the Dynamic rotary UPS (Euro Diesel No Break KSÂŽ) 22kV distribution Board, where the supply is conditioned and secured. The Dynamic Rotary UPS Plant consists of (x3) and future (x2) 1250kVA 400v units stepped up to 22kV, complete with 22kV input and output switchgear, all controls, ventilation and diesel supply system. The 22kV supply is then distributed through the ring network for the radio telescopes (stepped down at various places via 22kV mini-subs) and two 1600kVA transformers to the 400V supply for all the building requirements. The plant was commissioned in May 2014, and is online at present.

22kV MV Board, this will supply the load and the 400 transformers.

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company profile time-consuming re-work. One of our system engineers has summarized the system engineering development process as follows: ’you do development through this process as it is the quickest and easiest way of getting the desired result’.” A disciplined development approach and thorough testing is a very important part of the process and could make or break the SKA project as a whole. Without proper attention to detail and comprehensive testing and qualification, there could be some inconsistencies in the performance and this is why there are currently around 80 engineers working on site ensuring that testing is exhaustive. “The first antenna should be operational in the middle of September so we are pretty close to start system level testing. We should have the second antenna by the end of the year and antennas three and four should be installed by March 2015 at the latest. By that time we will have done all the testing and we will be going into full production. The infrastructure for the telescope has been completed – this refers to all the roads, shielded rooms, power facility and distribution, fibre duct reticulation, landing strip, construction camps and support buildings. With the ducting completed we are now in the process of installing the actual fibre to all antennas – this is required to communicate with and control antennas as well as to

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transport the data back to the central processor building. “One can’t perform system level testing on telescope level before you have an installed antenna, but wants to eliminate as many risks as possible before you get to that point - for that reason we do a lot of lab testing and component or subsystem testing. As an example all of the components that will be installed on the telescope that has any active electronics will have gone through RFI testing in a reverberation or anechoic chamber (RFI testing facility) so they will already be qualified for RFI performance. If you consider the data and science processor we would have done lab tests where the entire signal path has been simulated with the use of test data to verify that data processing is performed accurately and that automated RFI flagging for example has been implemented correctly,” Esterhuyse says. “The best case scenario is that there will be no modifications required after testing and we can go straight into production. Realistically, there will be some re-work but we are confident that this will be minor detail changes as we have followed a disciplined development process. Once the qualification has been completed and the required updates has been done, manufacturing can start and then the prototype (1st antenna) will be retrofitted to production status. “We have planned the project well and execution so

SKA SA

Through SKA things are looking up. We are extremely proud to deliver our West Africa Cable System ( WACS) capacity to a project of significant scientific discoveries. Let Broadband Infraco assist your discovery even more with its vast product portfolio. Contact Broadband Infraco for your national and International bandwidth requirements: Business@infraco.co.za

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SKA SA far has followed the plan closely so at this point we don’t foresee that there’s a significant risk of anything serious going wrong,” explains Esterhuyse.

KAT-7 KAT-7 is the seven-dish MeerKAT precursor array and is the world’s first radio telescope array consisting of composite antenna structures. It was completed in 2010 and has already delivered images of the Centaurus A, a galaxy 14-million light years away. During development of the MeerKAT project, KAT-7 has proved to be a useful tool. Obviously, its scientific value is significant and the experience that have been obtained with the roll-out, testing and commissioning of the instrument has been invaluable during the advancement of MeerKAT. “KAT-7 has been used for science observations and additionally it has been very useful for the project team in developing the CAM (Control and Monitoring software) and on an operating level. We have essentially developed the KAT-7 solution further to arrive at a solution for MeerKAT and have been careful to ensure backwards compatibility in order to allow us to roll out and test these developments on KAT-7. It’s a great test bay and when we deploy the software on MeerKAT we have a high level of confidence that it will work. “On the science processing side KAT-7 has been equally useful as we have been able to successfully test our algorithms for features such as automated RFI removal. There is also a high level of interest from scientist (that will eventually be involved on MeerKAT) to do observations on KAT-7 – this has the benefit that science data interfaces are defined and a working relationship with your stakeholders are established early in the life of your premier instrument,” explains Esterhuyse. MeerKAT development remains on track with Esterhuyse expecting between 10 and 12 antennas to be installed by June 2015 and 30 installed by the end of 2015. After March next year, full production should be underway.

interest from radio astronomers to be involved in the MeerKAT project,” says Esterhuyse. “When we started out with MeerKAT we requested formal input from the science community as to the fundamental, cutting edge science that could be performed with an instrument like MeerKAT. The high-impact science cases were selected by a group of international scientists and over 5000 hours of time on MeerKAT has been allocated to these programs. These science cases are then used to drive your high-level system requirements. This process was completed in October 2010 – our system requirements were finalised in January 2011 and the system level preliminary design review was passed in July 2011. That was followed with allocation of requirements to the various subsystems and the development and testing of these systems that are now being integrated and tested on a system level.” All of these challenges and ups and downs that is inherent to an extended technically challenging project such as this, Esterhuyse says there is no time to be bored. He is still excited to come to work every day and happy that a number of his colleagues are longstanding members of the team. “We definitely still enjoy it a lot,” he says “primarily because we realise the long term objective. For an engineer, if you work on a project like this, your ultimate satisfaction is to have the instrument completed and get the first observation off the full array. Of the guys that started this journey at the beginning, just about everybody is still here and we’ve been very lucky to keep the key people involved. I can’t talk for others but I am confident in saying that most of the key personnel see themselves involved till at least the successful completion of MeerKAT.” In just two and a half years’ time, the full SKA project will be underway; MeerKAT will be delivering science, and the focus on South African science will have grown even further. It’s quite the achievement and has a long way still to go and IndustrySA will be following everything in the future very closely!

SCIENCE, MORE SCIENCE

RFI is any source of transmission that is within the

Since the site selection for the SKA project back in 2012, the scientific community has been drawn closer and closer to South Africa and Australia as they realized that would be where premier radio astronomy science would be performed in the coming decades. The wider scientific community has been vital in the development of the project, providing ideas and notions for exactly how the telescope should be used. “We have definitely seen a pick-up in momentum and

observed frequency band other than the celestial sources themselves. Even the sun and some other natural sources can cause RFI. For more information on the SKA project, check back to IndustrySA’s Oct 2012 and Apr 2013 editions.

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