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Thousands of antennas… one radio telescope The Square Kilometre Array By Geoff Graham By any standards the Murchison region of Western Australia is an empty place. There are no towns, few roads and the population density is just one person for every 300 square kilometres. But there is a sense of excitement in the air. A high speed optical fibre has been run into the heart of the region, large semi-trailers regularly arrive loaded with high-tech equipment and scientists have become regular visitors. What is happening? A ustralia and New Zealand are engaged in a high stakes race that most people do not even know about. It is a race to host one of the largest scientific projects ever envisaged on the planet… the Square Kilometre Array. The Square Kilometre Array (abbreviated to SKA) is an international initiative to build the largest radio telescope in the world. The stakes are high. It will use technologies that have yet to be developed, will involve many countries from around the world and will cost billions of dollars. The SKA consortium started with a list of four possible sites and has whittled that down to a short list of two; one in South Africa and the other in the Murchison region in Western Australia. The Square Kilometre Array is a response to two of radio astronomy’s great issues: resolution and sensitivity. With an optical telescope you are dealing with light that has a wavelength of the order of 600 nanometres and it is relatively easy to construct mirrors and lenses that can reflect and focus these short wavelengths. Radio telescopes In a radio telescope the wavelengths are much longer and so the “mirrors” (reflecting dishes) need to be correspondingly larger. This and the need for sensitivity has led to an “arms race” in radio telescopes with dish sizes growing 14  Silicon Chip from the 76-metre dish of Jodrell Bank in the UK (1957) to the 305-metre dish used by the Arecibo Observatory in Puerto Rico (1963). With increasing size came improved resolution and sensitivity but it came at a cost. The Arecibo telescope is so large that it had to be built onto the walls of a valley and its view of the sky is determined by that part of the Earth is pointing to any particular time. Another way of addressing the size issue of radio telescopes is to use an array of smaller dishes and employ complex electronics and powerful computers which correlate the signals to simulate one large dish. The Very Large Array in New Mexico (USA) uses this technique, with the individual dishes spread out by up to 36km. This gives it the resolution of a single, very large steerable dish. While this was a great advance, the sensitivity of the telescope was still limited by the relatively small number of dishes and the resulting small collecting area. The Square Kilometre Array The Square Kilometre Array intends to get around this issue by using thousands of dishes with a total collecting area of one square kilometre; hence the name, Square Kilometre Array. The majority of the dishes will be concentrated in one area but some will be up to five thousand kilometres away. So the array will have a resolution implied by the 5000km siliconchip.com.au Artist’s impression of dishes that will make up the SKA radio telescope. Each dish is approximately 15m in diameter. Courtesy Swinburne Astronomy Productions/SKA Program Development Office baseline but a sensitivity However the rewards will derived from its one square be great. The SKA will be 50 kilometre of collecting area. times more sensitive and be The Australian and New Potential SKA array station placement in Australia able to survey the sky 10,000 Zealand bid for the SKA envis- and New Zealand indicating the 5,500km ‘baseline’ times faster than any imaging ages about 3000 dishes centred or maximum distance between the array stations. radio telescope array currently in the Murchison with some Image courtesy CSIRO running. dishes scattered as far away as the east coast of Australia Its high sensitivity means that it will be able to probe and New Zealand, giving that huge baseline. earlier in time towards the big bang and observe the very The signals from all these antennas will be correlated first black holes, stars and galaxies that shaped the develand reduced using massive super-computers, giving scien- opment of the universe. tists a detailed and far-reaching image of the sky at radio Other key projects include investigating the evolution frequencies. of galaxies, testing theories related to cosmology and dark One of many technical problems that must be addressed energy and answering questions related to the origin and is that current supercomputers are simply not capable of evolution of cosmic magnetism. Astronomers also want to processing the enormous amount of data involved. But the use the SKA to search for life and other planets outside our SKA is planned to become fully operational in about 2024 solar system and conduct tests of general relativity using and it is anticipated that by then, the evolution of electron- pulsars and black holes. ics and computer technology will have reached the level The SKA project where it will be able to handle the data stream. As an illustration of the technology involved it has been The SKA project is a collaboration of 20 countries, comestimated that the combined data stream from the 3,000 prising Australia, Brazil, Canada, China, France, Germany, dishes will be thousands of Terabits per second, equivalent India, Italy, Japan, Korea, The Netherlands, New Zealand, to many times the world’s current internet traffic rate. Poland, Portugal, Russia, South Africa, Spain, Sweden, So this is a project that cannot work today but is critically United Kingdom and the United States. dependent on the relentless march of technical innovation. It is difficult to be precise on the details of the SKA as It’s a huge gamble, although some would say, a safe gamble! the design phase has only just started but it has been essiliconchip.com.au December 2011  15 A close look at CSIRO’s ASKAP prototype phased array feed which was installed on the Parkes Testbed Facility in July 2008. Photo: David McClenaghan, CSIRO. timated that the overall cost will be in the region of $2.5 billion. Much of that money will be spent in the contributing countries who will be building the technology – it will provide an extra powerful boost for the host country’s technical and scientific capabilities. It is one of a very few multi-billion dollar science projects in the world. Another often-quoted example is the Large Hadron Collider at CERN, situated on the border of France and Switzerland. Currently the headquarters for the SKA project has been selected (Jodrell Bank, UK) and some initial funding has been allocated. Also some progress has been made towards selecting the site, either in South Africa or the Murchison region in Western Australia. Key dates include the design phase starting in 2013-2015, initial construction in 2016, the first astronomical observations in 2020 and full operation in 2024. For Australia and New Zealand, the most anticipated event is the selection of the country that will host the SKA. Assembly of CSIRO’s first ASKAP antenna at the Murchison Radio-astronomy Observatory. Photo: Carole Jackson, CSIRO. Four of CSIRO’s new ASKAP antennas at the Murchison Radio-astronomy Observatory, October 2010. Photo: Graham Allen, CSIRO. 16  Silicon Chip siliconchip.com.au BRIGHT IDEAS. STOCKED HERE. Let element14 bring your ideas to life with an array of 10,000 lighting products and solutions, including design resources like application guides, white papers, notes and more. And with local service and technical help, you can count on us to support your needs – 24/7. As a part of the Premier Farnell group, element14 brings you 70+ years of trusted electronics distribution expertise, along with an innovative online engineering community, where you can collaborate with experts, access technical information and use helpful tools. So trust element14 to power all your bright ideas. Global portfolio of industry leading manufacturers: HOW MAY WE HELP YOU TODAY? WEBSITE: FAX: SALES: MOBILE SITE: m.element14.com TECHNICAL SUPPORT: FLEXIBLE PAYMENT OPTIONS: au.element14.com/lightingsolutions nz.element14.com/lightingsolutions PHONE: Australia 1300 519 788 New Zealand 0800 90 80 80 Australia 1300 361 225 New Zealand 0800 90 80 81 au-technical<at>element14.com nz-technical<at>element14.com au-sales<at>element14.com nz-sales<at>element14.com The new global face of Farnell Although the design of the SKA has not been finalised it will probably involve more than just the traditional radio telescope dishes. This is an artist’s impression of the SKA’s proposed dense aperture array antennas. These will operate at mid-frequencies and are closely packed antennas arranged in tiles within stations. The size of the dense aperture array stations is likely to be about 60m diameter. Courtesy Swinburne Astronomy Productions/ SKA Program Development Office This announcement will be made in late February 2012, just two months away. Government support The Australian and New Zealand governments were quick to provide high level support for the bid to host the SKA. In particular, Australia has pulled out all stops to demonstrate that the country has the technical capability and the will to host the SKA. To start with the Murchison region has been identified as the best site for the SKA and to support this proposal the Australian government has purchased a pastoral property, Boolardy Station. Typical of the properties in the area, at 3,467 square kilometres it is one third larger than the Australian Capital Territory. In this arid climate the number of animals must be restricted to give the natural vegetation time to regenerate after being grazed on, so Boolardy runs a small number of cattle which roam far and wide through the natural bush with hardly any human contact. The government has since leased the grazing rights back to the original owners so that they could continue doing that. As a result there could well be cattle grazing in the shade of the dishes but this is OK; they do not emit radio noise! Kilometre Array Pathfinder project (abbreviated to ASKAP). This project involves much of the technology required for the SKA but on a smaller scale. This includes 36 dishes, a high-speed fibre network and a supercomputer facility in Perth. The ASKAP is currently under construction at the Murchison Radio Observatory and should become operational in 2013. This is why the small population in the Murchison are seeing so much activity. The high-speed fibre optic data link is required to connect the site to the rest of Australia and the large semi-trailers are carrying the components to build the telescope. Why the Murchison? The primary reason for choosing the Murchison region is the very low level of radio noise in the area, mostly due to the small number of people living there. With a population density of less than one person for every 300 square kilometres and no radio stations, no mobile phone towers or most other sources of radio pollution, it is a very quiet place especially as far as the radio spectrum is concerned. There is no town or city within the area and the nearest reasonable-sized town (Geraldton) is over 300km away. It does have some disadvantages though. It is hot and dry and the remoteness is a logistical challenge but to the scientists that is nothing when compared to the advantages of a region with almost total radio silence. The proposed site of the SKA lies in the Murchison Shire which is in Western Australia, about 738km north of Perth and 250km inland. This shire is unique in Australia as it is the only local government body that has no town or city or even a large Murchison Radio Observatory Part of Boolardy has been excised and named the Murchison Radio Observatory (MRO) and will be the core site for the SKA should it come to Australia. In addition, the Australian Communications and Media Authority have established a “radio quiet zone” band plan which outlines the purposes for which the radio spectrum may be used within 150km of the MRO. This seeks to manage all frequencies from 70MHz to 25.25GHz, with an inner zone of 70km where the requirements of radio astronomy will have precedence over other activities. The most potent demonstration of Australia’s determination is the funding of the CSIRO Australian Square 18  Silicon Chip This “graphically” explains why the Murchison area was proposed as the location for the Square Kilometre Array. The top graph shows the typical level of RF “noise” for Sydney; the centre graph is for Narrabri (where the Australia Telescope Compact Array is located) and the bottom graph is for the Murchison Shire. Courtesy Ant Schinckel, CSIRO. siliconchip.com.au The phased array detector under construction. Phased array feeds will be used by ASKAP’s 36 antennas to detect and amplify faint radio waves, a development being pioneered the CSIRO for the ASKAP telescope. Both photos: Courtesy Ant Schinckel, CSIRO settlement within its boundaries. The Murchison Shire is not small; it is 50,000 square kilometres or a little bigger than the Netherlands. However its total population is only 100 to 160 (estimates vary) with just 29 pastoral properties as the major ratepayers. Imagine, the Netherlands with only 29 farms! The shire has its offices and maintenance depot located in the Murchison Settlement (population about 25) which is also the only place to buy petrol in the shire. Most telling of all, there is no pub or hotel anywhere in the shire. As well as being the proposed site for the SKA, the Murchison Radio Observatory will also host a number of other radio astronomy projects. These include the SKA pathfinder project (ASKAP) and the $30 million Murchison Wide Field Array project developed by Australian, Indian and American scientists. So this purchase will not go to waste if Australia loses its bid to host the SKA. The ASKAP project The Australian Square Kilometre Array Pathfinder (ASKAP) project is being driven by the CSIRO and is a very large project in its own right. When completed it will be the world’s most powerful survey radio telescope by a factor of 10. While it will be a potent scientific tool it will also demonstrate that Australia has the capacity to host a mega science project such as the SKA and will provide a base for training our future engineers and scientists. The completed ASKA phased array detector, the heart of the telescope. A phased array feed array acts as a multiple pixel sensor and is much faster than conventional telescope sensors which can see only one pixel. The ASKAP telescope will consist of 36 steerable dishes each 12 metres in diameter linked to a telescope in New Zealand to give an extended baseline. The estimated cost is over $150 million; a lot of money for a pure science project in Australia. Normally the scarce research dollars are reserved for solving practical problems in agriculture and the like. Each dish will have a completely new and unique radio “camera” that will be able to record multiple points in the sky. A normal radio telescope has all the radio energy focused onto one detector so it can be thought of as recording a single “pixel” of an image of the sky. By contrast, the ASKAP dishes will have 188 active elements in an array, so they will be able to record multiple “pixels” giving the telescope the ability to simultaneously sample large areas of the sky much faster than a conventional radio telescope. This Phased Array Feed (PAF), as it is called, comprises a checkerboard phased array, analog and digital signal processing systems and the associated support systems required to run this unique receiver. It was developed in Australia by the CSIRO for ASKAP. It, along with the entire ASKAP project, is a good demonstration to the rest of the world of the level of Australia’s capabilities in building and designing the high-tech com- The ASKAP telescope will generate 72 Terabits of raw data every second. Onsite processing will reduce that to 40Gb/s which will be transferred to a new supercomputer facility in the suburbs of Perth which in turn will reduce the data volume to the equivalent of one DVD per second; still an awful lot! The SKA is expected to generate many thousand times this data rate. Courtesy Ant Schinckel, CSIRO. siliconchip.com.au December 2011  19 “Mr WiFi” One scientist who was involved in the design of the ASKAP telescope is Dr John O’Sullivan. He helped design the unique multiple pixel sensor used in the telescope. Dr O’Sullivan is also noted as the lead scientist involved in the development of the ubiquitous wireless networking technology IEEE 802.11a – also known as WiFi. As most of our readers know, WiFi has stormed the consumer world and is used all types of gadgets from mobile phones to cameras and much more. While researching this story SILICON CHIP had a rare opportunity to meet and talk with Dr O’Sullivan about the development of WiFi. It makes an interesting tale. The story began in the early 1980s as scientists were using more and more exotic technology in the pursuit of the faint signals from radio telescopes. During this period, one technology that became pivotal was the implementation of Fast Fourier Transform (FFT) processing in hardware. At about the same time, the then new CSIRO Chief of Radiophysics, Dr Bob Frater, set a challenge to the scientists in the division: to develop some commercial application from these technologies. As Dr O’Sullivan simply put it “there was a need to network our laptops” so the CSIRO formed a team of scientists to focus on just that. Their target was way beyond anything then available: a 100Mb/s wireless local area network for offices and meeting rooms. The technology they used (later to become WiFi) was based on multiple carriers, all transmitting part of the data stream and is called OFDM (Orthogonal Frequency-Division Multiplexing). The team built on the idea that FFT technology could be used to divide up the spectrum in such a way that the severe and complex reflections found inside buildings could be compensated for at the receiver. The development effort involved many CSIRO scientists in associa20  Silicon Chip CSIRO Fellow, Dr John O’Sullivan and a prototype of the phased array feed being developed for ASKAP. Dr O’Sullivan also led the CSIRO team that developed 802.11a or WiFi Photo: Chris Walsh, Patrick Jones Photographic Studio tion with Macquarie University and led to an Australian patent in 1992 and a USA patent in 1995. These patents covered the technology behind the wireless transmission, not the idea of wireless networking itself as believed by many people. With more development and an overseas promotional campaign, OFDM was eventually adopted as the basis of the IEEE 802.11a standard in 1999. The early implementations of WiFi were hampered by the level of semiconductor technology available at the time, as the digital processing power required was bulky and consumed a lot of power. Now everything can be packed into a few integrated circuits using very little power. This is another example of a technology which needed the ongoing march of semiconductor development to make it a practical reality. From 2000 to 2009 WiFi saw an enormous take-up but most vendors implementing the standard were ignoring the CSIRO’s patents. The result was increasing litigation against companies such as 3Com, Asus, Belkin, D-Link, Fujitsu and Toshiba. In response, the industry formed a single heavyweight group including HP, Apple, Intel, Dell, Microsoft and Netgear in an effort to quash the CSIRO’s claims. Fighting this case was a high stakes gamble undertaken in foreign courts with legal costs running into many tens of millions. Full credit is due to the tenacity of the CSIRO in pursuing this strategy as a loss would have been very expensive. As most Australians know, the CSIRO did have a win in 2009, with a number of manufactures agreeing to pay royalties. Bolstered by this the CSIRO is now pursuing other companies and is steadily reaching agreement on royalties. The terms of the agreements are confidential but they are expected to bring hundreds of millions of dollars to the CSIRO who will invest it in new and innovative projects within Australia. Dr O’Sullivan has since retired and has been made a CSIRO Fellow – a great honour. To date, over one billion WiFi chipsets have been manufactured. When asked if he was surprised by this success, Dr O’Sullivan replied “Well not completely. We thought it could be big but I am blown away by how big.” “Nowadays when I see the amazing number of portable and mobile devices I have to think that even my rosiest predictions have been exceeded!” siliconchip.com.au Its starting capacity will be 100 teraflops, later rising to one petaflop as demand increases (a teraflop is one million million floating point calculations per second and a petaflop is a thousand teraflops). After this processing effort, the data stream will have been reduced to the equivalent of one DVD every two seconds. This data will be stored in disk arrays at the Pawsey facility for later retrieval and analysis by researchers across the world. Remember, this is just for the Australia’s pathfinder telescope (ASKAP). The amount of data from the Square Kilometre Array will be many, many times this. SKA site selection If you want to know what it is like driving to the Murchison SKA site, staring at this photograph for four hours is a fair approximation – but you will still miss out on the bumps, heat and the dust. Photo credit: Paul Bourke and Jonathan Knispel. Supported by WASP (UWA), iVEC, ICRAR, and CSIRO. ponents required for today’s radio telescopes. ASKAP technologies It is not possible to talk at length about the technical details of the SKA because design decisions and funding arrangements are still being made. It is not even certain what antennas and frequencies will be included in the final design and anyway, there will undoubtedly be changes in direction as the project progresses. It is much easier to talk about the technology being used in the ASKAP project as that is already underway. Currently the ASKAP project has installed nine dishes in the Murchison, with another in Warkworth, New Zealand to give a long baseline of 5,500 kilometres. When finished, the telescope will display an amazing array of technologies, mostly developed in Australia. The data stream starts with the 188 pixel sensors at the focal point of each telescope. These will produce an enormous 1.9 Terabits/second resulting in a total data stream of 72 Terabits/second from all 36 dishes. To put this into perspective, it is estimated that the world’s current total internet traffic is only 20 Terabits/second. This is for the ASKAP project alone, the SKA telescope will generate more than a thousand times this rate. The data stream from each telescope is carried via an 18-fibre optical ribbon cable to a rack of equipment called a Beamformer, with one of these for each telescope. The output of each of these goes to more electronics which correlate and further reduce the data streams. The processing requirements are enormous with one Peta operations per second (that is one thousand million million operations per second) needed to reduce the total data stream to 40Gb/s. This is still a very high data rate and it will be piped via fibre cable to Perth for processing. The federal government has made a grant of $80 million to build a supercomputer facility in the suburbs of Perth to process this data stream. The facility will be known as the Pawsey High Performance Computing Centre for SKA Science and it will rival supercomputer facilities overseas. siliconchip.com.au As mentioned before, the competition for hosting the SKA is between South Africa and Australia/New Zealand. South Africa is also pulling out all the stops in an effort to attract the project. It has proposed the Karoo Desert in the Northern Cape as the preferred site for the SKA and has joined in partnership with eight neighbouring countries in its bid. Not to be outdone in proving its capabilities, South Africa has proposed the MeerKAT, a 64-dish array that it claims will be the “largest and most sensitive radio telescope in the southern hemisphere until the SKA is completed.” This is an enormous investment for the country; the money allocated to their overall SKA bid is many times the current annual budget of the country’s main research organisation, the NRF, and a significant component in the nation’s finances. In conducting this international competition the international SKA project is also striving for a win/win outcome for all participants. An important feature of this contest is that both telescopes and the SKA will have differing characteristics, so none will be made directly redundant when future decisions are made. Regardless, there is still a lot of money being invested in this area of science. The two countries made their final submissions to the project’s site selection committee in September and now they have a nail biting wait for the decision. An independent SKA Science Advisory Committee will evaluate the bid documents which represent eight years of work and announce the decision in late February 2012. So stay tuned for the big announcement. SC December 2011  21