international SKA forum 2010 | june 9 - 16 assen, the netherlands
beyond astronomy
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index the promise of ska ....................................................................................4 universe awareness aims at the open minds of children ................. 12 from drenthe with love ......................................................................... 13 lofar - a bright outlook in every direction ........................................... 17 royal launch for international lofar telescope .................................... 20 more than a telescope ........................................................................... 23 sealed with a ciss ................................................................................... 25 precursors and pathfinders ................................................................... 30 radio astronomy’s golden age a new era for the transient universe .................................................... 32 in search of the eor: lights! camera! action! ....................................... 34 gastrophysics galore .............................................................................. 36 going to depths ...................................................................................... 38 colofon .................................................................................................... 40
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foreword
From 9-16 June 2010, the Netherlands Institute for Radio Astronomy (ASTRON), and its parent organisation, the Netherlands Organisation for Scientific Research (NWO), hosted the International Square Kilometre Array (SKA) Forum 2010 or ‘ISKAF2010’ for short. SKA is a global project whose aims are to build a next generation radio telescope that will be fifty times more sensitive and one million times faster in terms of survey speed than any existing radio telescope. ISKAF2010 represents the first time the International SKA Forum has been held in Europe; previous events were held in Australia (2008) and South Africa (2009). The main aim of the forum was to push the SKA project forward in all possible respects – scientifically, technically and politically. Many different events were organised during ISKAF2010, with locations spread around the North Netherlands, in particular in the province of Drenthe. In total almost a thousand people were involved! ISKAF2010 week kicked-off to a great start with the
astronomy meeting ‘A New Golden Age for Radio Astronomy’. This event attracted around 170 astronomers from around the world, all anxious to show the first results from the SKA pathfinder instruments now coming online, and to report progress updates on the SKA precursor telescopes under construction in Australia and South Africa. The concept design for SKA Phase 1 was also presented at the meeting. On Saturday 12 June 2010, one of the most prominent SKA pathfinder telescopes, the LOw-Frequency ARray (LOFAR), was opened by Her Majesty Queen Beatrix of the Netherlands. The opening was attended by more than seven hundred people, and the Queen was impressed by the progress that had been made since her last visit a few years ago.
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As the week progressed, the Agencies SKA Group met, in parallel with the astronomy meeting and the CISS (Connect Industry, Science and Society) workshop. The Agencies SKA Group consists of the major national funding agencies around the world (including NWO), that meet together in order to advance the SKA project. During ISKAF2010, the Agencies SKA Group agreed that, in order to progress toward construction of SKA, the next pre-construction phase should be governed and led through an appropriate legal entity that is adequately resourced. The agencies, together with the SKA community, will work toward this new governance structure over the next year, with a target date of mid 2011 for its implementation. This is good news for the SKA project and one of the key outcomes of ISKAF2010. One of the highlights of the week was the ISKAF2010 dinner at the Der Aa-church in Groningen – bringing together participants from all the various events in a relaxed and open atmosphere. The climax of the week was the SKA Forum itself, attended by scientists, engineers, industrialists and decision makers. The latter included representation at the highest levels – government ministers from Australia (Kim Carr, Minister for Industry, Innovation, Science and Research), South Africa (Naledi Pandor, Minister of Science and Technology) and the Netherlands (Maria van der Hoeven, Minister of Economic Affairs) were all present. Minister Van der Hoeven, together with the Queen’s commissioner Jacques Tichelaar, announced a new, four million euro financial investment in ASTRON’s SKA technology programme and re-stated the Dutch ambition to play a major role in establishing a European Centre for the SKA. As well as many presentations from the broad SKA community,
an exhibition was held at the Forum with around thirty companies and organisations represented. This successful week could not have been realised without the support of many different sponsors and partners; in particular we wish to recognise contributions from the European Commission’s FP7 programme, the Province of Drenthe, Sensor Universe and Marketing Drenthe. ISKAF2010 certainly achieved its aim of bringing
together all the main SKA proponents and stakeholders in one place in order to continue to develop and advance the international project. An ambitious programme for the next twelve months is now in place, with the creation of an appropriately resourced legal entity for the SKA being perhaps the most important outcome of the forum event. No doubt there will be a few obstacles to overcome along the road, but with the help of ISAKF2010, we can certainly say that the SKA journey has begun!
Michael A. Garrett Coordinator ISKAF2010 Chair, SKA Science & Engineering Committee
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Just eleven days after the International SKA Forum 2010, the TT Circuit in the town of Assen, the Netherlands, was the roaring scene of the 80th edition of the famous TT Motorcycle Races. But on June 15, a few hundred astronomers, engineers and policy makers gathered together in the TT Hall to discuss the wide-ranging impact of the Square Kilometre Array. “SKA is really cool.”
the promise of SKA 4
“Today, Assen has turned into one of the largest astronomical centres in the world,” said Jacques Tichelaar, the Queen’s Commissioner in the Dutch northern province of Drenthe. Indeed, the location for the third International SKA Forum – the first two events were hosted by Australia and South Africa – was a fitting one. Drenthe is also home to the 25-metre Dwingeloo radio telescope (the largest in the world when it was inaugurated in April 1956) and to the 14-element Westerbork Synthesis Radio Telescope. Moreover, just three days before the forum met, Queen Beatrix officially opened the International LOFAR Telescope (LOw-Frequency ARray), the core area of which lies just thirty kilometres southeast of Assen. According to Tichelaar, the construction of LOFAR in this rural part of the Netherlands had a big impact in fields beyond astronomy. For instance, the Hanze Institute of Technology in Assen now offers a bachelor course in sensor technology. Maria van der Hoeven, the Dutch Minister of Economic Affairs, also stressed that the impact of a big science project like LOFAR or SKA is “by no means limited to astronomy or to astronomers”. And Jos Engelen, chairman of the Netherlands Organisation for Scientific Research (NWO), welcomed the “many, many attractive aspects of big projects in big science”. According to Engelen, industrial contracts granted by SKA may enhance the profile of companies big and small, which, in turn, will lead to significant profits in other markets.
The impact of SKA is by no means limited to astronomy
A collection of superlatives The Square Kilometre Array will be by far the largest telescope ever built. With millions of antenna elements spread over an area as large as a small continent, SKA’s design headlines are “a collection of superlatives,” according to Richard Schilizzi, director of the International SKA Program Development Office. “A strong industrial engagement is absolutely critical.” In sketching the current status of the SKA project, Schilizzi
big questions and societal benefit Delegates meet at the exhibit hall (top) while Queen’s Commissioner of Drenthe Jacques Tichelaar addresses the ISKAF2010 forum (bottom).
What does SKA have in store for scientists? And what will it offer to society? Huib Jan van Langevelde, director of the Joint Institute for VLBI in Europe, moderated a forum discussion on SKA’s prospects of answering some of astronomy’s big questions and of offering added value to society at large.
Galaxies and the accelerating universe Steve Rawlings (Oxford University) explained how the One Billion Galaxy Survey of SKA will help astronomers to find out about dark matter, neutrinos and the accelerating expansion of the cosmos. The trick: mapping the 3D-distribution of matter will reveal the fundamental properties of the Universe. But to Trish Henning (University of New Mexico), individual galaxies are at least as interesting. “We don’t understand the origin of galaxies very well,” she said. And, referring to our own Milky Way Galaxy: “We really don’t know how the house was built; how the fuel for star formation – without which we wouldn’t be here – came together.”
Einstein on trial “Einstein’s theory of general relativity is our best description of gravity,” said Heino Falcke (Radboud University, Nijmegen). “But if just a tiny bit of general relativity is wrong, our entire picture of space and time might be wrong.” Using telescopes like SKA will enable Falcke and his colleagues to use the Universe as their laboratory to study extreme physics, such as strong gravitational fields and relativistic particles, and to put Einstein to the test. According to Falcke, “every time technology makes a leap, you discover something unexpected.”
Are we alone? “I’d be very surprised if we were alone in the Universe,” said Roy Booth (Hartebeeshoek Radio Astronomy Observatory, South Africa). “It’s inevitable that we will find Earth-like extrasolar planets shortly, and we have already found the building bricks of amino acids in interstellar space.” Booth said it would be fun to detect signals from an extraterrestrial civilisation, “but I believe SKA will have more success in detecting complex organic
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molecules in space at an unprecedented level of sensitivity.”
SKA’s beneficiaries Steven Tingay (Curtin University of Technology, Australia) believes SKA is for everyone, since it will offer vast technological improvements. But according to Heino Falcke, spin-offs are not the driver. “Some results will feature in textbooks and children’s books of the future,” he said, “but not because of advances in technology or industry, but because of progress in science.” Trish Henning added: “It’s incredible that we can do that kind of research from Earth. I don’t see mankind as a tiny speck in spacetime, since we have an extraordinary power to unravel the mysteries of the Universe.”
said that the new radio telescope should be fully operational by 2024. But construction of the smaller Phase 1 (SKA1) will already start in 2016. Built for 350 million euros, SKA1 is expected to deliver key science results by 2020. By then, construction of the final SKA2 will be well under way. With a price tag of some 1.2 billion euros, SKA2 provides fifty times the sensitivity and one million times the survey speed of current radio interferometers.
Emerging clarity According to John Wormersley, chairman of the Agencies SKA Group, SKA1 is now about to enter its pre-construction phase. “We see emerging clarity on SKA1,” said Wormersley. “The pre-construction phase will get us beyond detailed engineering, design and development. At the conclusion of that phase in 2015, we’ll be ready to dig holes and pour concrete, but we’re not there yet.” In two meetings, on 13 and 14 June, the Agencies SKA Group agreed on implementing a new legal entity to govern this pre-construction phase – something that should be completed by mid-2011. Reporting on the progress that has been made during the closed sessions of the Agencies SKA Group, Wormersley said that agreement had been reached on the terms of reference for the SKA Siting Group. “The idea is to put measurable criteria in place, so that we can arrive at a final figure of merit” he said. After collecting as much data as possible, a final site selection for SKA should be made in late 2011 or early 2012. Wormersley also described the societal benefits of a big science project like SKA. “The world faces very, very big challenges” he said, “and we’re not going to solve current problems with existing technology. Weathering a global recession demands an innovative and scientifically trained workforce. Our young people must be inspired to become part of that workforce. Particle physics and astronomy have always lured young people into science and technology. But SKA is not the only big global science project, and conveying our message to the public at large is a challenge.”
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Young people must be inspired to become part of an innovative workforce
Keynote speakers Mike Bode (left) and Niek Lopes Cardozo (right).
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SKA’s spin-offs
Maria van der Hoeven is Minister of Economic Affairs for the Netherlands. Below are some observations from her address at the International SKA Forum 2010.
On education At the LOFAR inauguration, we witnessed the excitement of schoolchildren – something that is being stimulated worldwide by the Universe Awareness programme. Our telescopes may fire their imagination.
On the role of LOFAR Sensor technology, safeguarding, dyke monitoring – spin-offs like these show the significance that new radio telescope technology can have for society at large. LOFAR is also a symbol of international collaboration and cooperation.
On the two candidate sites for SKA I know there’s a competition going on, but I hope this may turn into a win-win situation, where every partner in the project may end up playing an important role.
On technological spin-offs from SKA Astronomers haven’t yet discovered a crystal ball to predict the future, but I expect major breakthroughs in the fields of sustainability, information and communication technology (ICT), and sensor technology. SKA will definitely attract new talents.
On the Dutch role in SKA We believe that the Netherlands is the natural place to host the main European Regional SKA Centre, preferably in Dwingeloo. The Dutch government will also contribute two million euros for antenna development.
CSIRO’s Brian Boyle, supporting the case for Western Australia as the location for SKA.
Exciting times Although ‘SKA Beyond Astronomy’ was the theme of the International SKA Forum 2010, the scientific promise of the new telescope was an important topic of discussion during the meeting in Assen. In a keynote talk that could easily double as a crash course in modern astronomy, Mike Bode (Liverpool John Moores University) described the big questions in the field. Bode has been Task Leader of the 2008 ASTRONET Infrastructure Roadmap on the future of European astronomy, and he presented a comprehensive overview of cosmic mysteries, and the human
Why are big science projects seen as expensive toys for boys? 8
location, location, location... Two sites have been shortlisted as possible locations for the Square Kilometre Array: Southern Africa and Western Australia. Even though the Site Evaluation and Selection Committee won’t make a final decision before late 2011 or – more likely – early 2012, a fierce competition between the two candidate sites has commenced. At the International SKA Forum 2010 in the TT Hall in Assen, ministers and scientists from both countries extolled their country’s virtues, but ruffled some feathers along the way.
Next generation According to Naledi Pandor, Minister of Science and Technology for the Republic of South Africa, SKA comes at a very important moment for her rapidly developing country, and might be as inspiring as the 2010 World Cup Soccer. “SKA is a project for the next generation,” she said, pointing out that half of South Africa’s population is less than 15 years old. “As an ‘iconic project for world science’, SKA creates unique opportunities for young people,” said Pandor, who also announced that South Africa will commence a decade of science and technology in 2011. “We are keen and ready to host the Square Kilometre Array.”
search, acknowledged that SKA will generate great opportunities for industry, technology and education. “But,” he said, “It will only do so when it does excellent science. Nothing is more important than the opportunity to do the best possible science. Australia and New Zealand have much to offer, including an ideal site.” Brian Boyle, SKA Director for CSIRO (Commonwealth Scientific and Industrial Research Organisation), then surprised his audience with a remarkably outspoken talk on the qualifications of the Western Australia site. Thanks to the incredibly low population density, and the commitment of the Australian government, said Boyle, the radio quietness of the region is unmatched. “Compromise on requirements, and you compromise on science. The full benefits will only be achieved by building the best possible SKA at the best possible site. We only have one opportunity to get this right.”
Bernie Fanaroff, South Africa’s SKA Project Manager, focused on the unique characteristics of the arid and remote Northern Cape Province, where the core area of SKA could be located. He proudly reported on the progress of MeerKAT, the South African technology demonstrator and precursor of SKA. A seven-dish prototype (KAT-7) “already works end to end, within budget and schedule,” said Fanaroff.
Outspoken talk The Hon. Kim Carr, Australia’s Minister for Innovation, Industry, Science and Re-
Naledi Pandor (top) and Kim Carr (bottom) provide ministerial support for the Southern African and the Western Australian candidate location for SKA, respectively.
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two-step SKA science projects – both ground-based and space-based – to tackle them.
Richard Schilizzi is the director of the International SKA Programme Development Office (SPDO) in Cambridge, United Kingdom.
Does the development of SKA take longer than expected? When we started in the late 1990s, we thought we would be constructing the array in 2010. This has now slipped to 2016, so yes, it takes longer than originally envisioned. However, for a complex project like SKA, this is certainly not unusual, especially given the international component.
Isn’t it risky to build SKA in two phases? When Phase 1 starts to deliver science, you may not get enough funding for Phase 2. A stepwise approach can also be convenient in terms of funding. Phase 1 is really a step on the way to Phase 2. The science that is possible with the full array can never be carried out with the Phase 1 array, which is ten times smaller. Also, we hope to secure funding for Phase 2 before we start constructing Phase 1.
Aren’t you afraid that SKA will be based on technology that could be obsolete by the time the array is finally completed? We are pushing limits in all areas of technology. For instance, the exaflop computer technology envisioned for SKA is beyond current possibilities. Still, we build in as much flexibility as we can, in order to cope with future new developments.
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“This is one of the most exciting times to be in astronomy,” he said. “New telescopes and space missions will teach us a lot more about the origin of galaxies and stars. In studying pulsars, we witness strong gravity in action, and we may finally discover gravitational waves. SKA will shed new light on the astounding and totally unexpected mysteries of dark matter and dark energy in the Universe. And we will also start to address the biggest question of all: How did the Universe begin?” In the ASTRONET Roadmap, SKA and the European Extremely Large Telescope (E-ELT) share the number one position on the priority list for large-scale ground-based facilities. “They’re really complementary projects,” said Bode, whose talk was followed by the forum discussion ‘SKA’s reply to the big questions and societal benefit’ (see page ..).
Drivers of prosperity The second keynote speaker on the International SKA Forum 2010, Niek Lopes Cardozo (Eindhoven University of Technology), lamented the fact that so few people are aware of the benefits of big science projects like SKA. “Why are they seen as money sinks – as expensive toys for boys?” asked Lopes Cardozo. “It all starts with the big questions: what’s beyond the edge of the Universe, what was there before the beginning of time, and what’s inside the very smallest? ‘But these questions have inspired mankind on a quest that led to the development of learning and study, of instruments and technologies.” In his glowing talk ‘Big science for society’, Lopes Cardozo stressed that every euro invested in science and technology yields an economic return in the order of three euros. “Science and technology are the drivers of prosperity. Big science puts the bar very, very high. As a result, everybody gains. That’s the message we will have to communicate. Science is about the process as much as the anwers. It’s about the journey as much as the answers. We’ll have to explain what’s so good about the journey.” Lopes Cardozo wondered why scientists always have to fight for their science budgets. Just like countries are keen on or-
Concentration is evident among the forum audience (top) and during a live radio interview, broadcasted from the exhibit hall (bottom).
radio jumps
ganizing the Olympics, because of the economic benefits, they should be keen on investments in science and technology, because of the revenues, he said. “As an industry, you want to be part of the endeavour. It offers a showcase effect, and it opens up new markets. That’s something that everyone should recognize.”
Breathe or drink A second forum discussion covered more or less the same ground as the CISS-meeting (Connect Industry, Science and Society) on 14 June (see page ...). Surprisingly, a quick vote among the audience revealed that the vast majority of attendees believed that science results are much more important than economic benefits. Australian radio astronomer and former International Astronomical Union President Ron Ekers was one notable exception. “Nations that put money into it need some national return,” he explained. “Science benefits are for all mankind, so if there wouldn’t be any economic benefits, governments wouldn’t invest.”
Ron Ekers is former director of the Australia Telescope National Facility and former president of the International Astronomical Union. He was also a member of the International SKA Steering Committee.
Can you comment on the development of radio astronomy? Radio astronomy developed very rapidly between 1950 and 1980. Around that time, optical, infrared, X-ray and gamma-ray astronomy received a big technological boost, and radio astronomy became eclipsed somehow. But the past five years have seen huge advances again. SKA will be our next big jump forward.
But according to Ralph Wijers (University of Amsterdam), it doesn’t make sense to choose one over the other. “It’s like asking someone to choose between being able to breathe and being able to drink. These are two kinds of benefits for two slightly different groups. It adds up. Why should we care which one is more important? Unavoidably, you’ll have them both.”
To which big jump forward in optical astronomy could this SKA jump be compared?
Louis Brennan (Trinity College, Dublin), who presented the white book from the COST Workshop (European Cooperation in Science and Technology), said that SKA could act “like a catalyst for seeking solutions to current problems in data storage and processing, green energy, and sensor technology.” And Bruce Elmegreen (IBM) believed that SKA would be the benchmark in a new era of exploration. “It’s sure to expand our technological horizon again,” he said.
What’s the next jump beyond SKA?
I would say it’s similar to what the Hubble Space Telescope had to offer. It’s also comparable in terms of money. Of course, maps of the radio sky are less familiar and maybe less spectacular than Hubble pictures, but SKA will make superb images and deliver exciting new science.
History teaches us that you often get wrong answers when trying to predict future developments. But it’s important to realize that the concept of SKA is not limited by aperture size. In the future, SKA could certainly go into space. Or, if space technology enables it, we might even build a SKA-like array on the far side of the Moon.
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Carolina Ödman received a long, loud applause after her presentation on ‘SKA and Education’. Granted, it was the last talk of a long double morning session, and lunch was waiting. But the audience’s enthusiasm was mainly due to Ödman’s inspiring thoughts – and her inspiring movie – about astronomy education. “Young children have open minds,” she says. “Astronomy can bring something positive to the foundation of their world view.”
universe awareness aims at the open minds of children 12
Over the past few years, Carolina Ödman has been the manager of Universe Awareness (also known as UNAWE, see www.unawe.org). The goal of this international programme, founded by Leiden astronomer and IAU vice president George Miley, is to use astronomy for the benefit of young children, with an emphasis on the underprivileged, be it in developing countries or in the run-down suburbs of western society. Universe Awareness was one of the cornerstone projects during the IAU’s successful International Year of Astronomy 2009. It has representatives in some forty countries all over the world. According to Ödman, astronomy is “an outstanding ambassador” if you want to bridge geographical and cultural gaps. After all, she adds, “there are no lines between countries” if you look at our home planet from space. In Ödman’s heart-warming movie, school children in the Netherlands, South Africa and Australia shared stories, songs and details about their daily lives over the Internet, using video conference tools. “Like nothing else, astronomy provides a unique and profound perspective on our place in the world,” says Ödman. By focusing on underprivileged children, Universe Awareness hopes to reduce existing gaps in wealth, health and education. The Square Kilometre Array offers great opportunities for educational projects. Says Carolina Ödman: “Turning almost half of the planet into a big eye is amazing and exciting. It’s very, very new.” Providing understandable radio images is important for educational programmes, she adds, but radio astronomy in itself isn’t too abstract for children to grasp. “If SKA were to be built in South Africa, Universe Awareness would certainly use it to give local children pride in where they come from.”
from drenthe with love Luxury resort ‘Hof van Saksen’ was the scenic venue for the ISKAF2010 forum.
When a few hundred radio astronomers, engineers, industrialists and policy makers flock together for a few days at a luxury resort in a rural part of the Netherlands to discuss the largest telescope ever built, it’s no wonder that they also enjoy the relaxing atmosphere, the good company of colleagues, the unspoilt scenery in the province of Drenthe, and the great food. These pages provide a good impression of the various social events during the International SKA Forum 2010, including scenes from the welcome reception on 9 June, the excursions and the informal dinner in the Drents Museum on the 13th, and the lively ISKAF2010 dinner in the Der Aa Church in Groningen on 14 June. Please take some minutes to relive your good time in the Netherlands! You may even discover yourself in one of the photographs.
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Receptions, cocktail parties and exhibits provided ample opportunity for informal contacts.
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from drenthe with love
ISKAF 2010 dinner in the Der Aa Church in Groningen.
Dinners at the Drents Museum in Assen (top) and in the Der Aa Church in Groningen (right).
Some delegates visited the venerable 25-meter radio telescope at Dwingeloo (top), while others spend their spare time at their laptop computers (bottom).
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from drenthe with love
Beyond astronomy: Alien visitors (top) and the 2010 FIFA World Cup (bottom) provided dramatic spectacles during the ISKAF2010 forum.
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LOFAR (LOw-Frequency ARray)
is the first operating telescope based on the phased-array principle: an array of cheap, basic antennas and very sophisticated data processing. The array consists of a central antenna area, called the ‘Superterp’, a circle of more antenna stations at a
few kilometres distance, and sparse ‘spiral arms’ of additional stations that spread out over Germany, Belgium, Great Britain, France, and Sweden, creating base lines up to 1500 kilometres long. The signals from the antennas are combined in each station,
and then sent over dedicated optical fibre cables to a fast supercomputer in Groningen. This IBM number cruncher acts as a correlator: it combines the signals from all the stations in such a way that a virtual telescope is synthesised with the same angular resolution – though not the same sensitiv
a bright outlook in every direction
If you are given a tour of the world’s most advanced radio telescope, you could very well suspect a hoax. ASTRON’s public relations officers take you to a muddy meadow where a few PVC tent poles are erected on pieces of black plastic sheet. The sheets are held down by a square of coarse metal grating like you can buy at any hardware shop; each PVC pipe is held upright by four metal wires, kept taut by rubber ’ligaments’. The miracle is this: things that happened billions of light years away, when the Universe was not even half its present age, send electromagnetic ripples through space that reach our Earth and wiggle the free electrons in the metal wires, which causes tiny voltage differences between the ends. There is nothing magical in the metal wires, but it takes an IBM supercomputer, the fastest optical fibre network connections in the world, and fine-tuning by some pretty sharp minds, to separate these cosmic voltage differences from the much larger ones caused by terrestrial events, collect them, and amplify them a billion times, so they can be turned into stunning images and real understanding of what goes on in remote parts of the cosmos.
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founding father
George Miley, former director of the Leiden Observatory, is the founding father of LOFAR. Since his retirement in 2008, he has been the driving force behind Universe Awareness, a UN-supported astronomy outreach project for developing countries.
tral window cheaply; it is a test bed for SKA technology; it is a new radio telescope in the Netherlands with high visibility for astronomy. And, last but not least, it is scientifically useful. It will be able to find radio galaxies at z > 6 in the very early universe.
How was the idea of a LOw Frequency ARray conceived?
How do you sell “we can see radio galaxies at z > 6” to a ministerial cabinet without a single scientist?
In the nineties, ASTRON was very much focused on developing the phased-array technology for SKA. But that goal was a long way away, somewhere around 2020 .As a result, between 1990 and 1995, academic interest in radio astronomy dwindled. We needed an intermediate, science-driven project to get things going again. I wrote a proposal and mailed it to ASTRON Director Harvey Butcher on June 13, 1997. That was the first time the name LOFAR was used.
What is the strategic rationale for LOFAR, in a few words?
This project would never have been funded without the collaboration of geophysics or agriculture. It is very important that LOFAR is not only a radio telescope, but also a sensor network that can be used for other sciences such as seismic measurements, or to give farmers precise information on the usage of pesticides. Also, after frantic lobbying, we were given a lot of support in 2003 by Maria van der Hoeven, who was then Minister of Science and Education. She was the one who really convinced her fellow ministers to do this.
It will be exploring the last unexplored spec-
ity – as a single, 1500-kilometre radio telescope would have. At the highest detectable frequency of 240 megahertz, and using the longest base lines, LOFAR should be able to discern details as small as 0.13 arc seconds, equivalent to taking a 150-megapixel image of the Full Moon.
RISKS AND REVENUES Like a scientific venture capitalist, LOFAR director Michiel van Haarlem arranges the telescope’s science targets on a scale from ‘risky’ to ‘secure’, with potential revenues to match. “Detection of the Epoch of Reionization (EoR) is certainly the most risky,” he says. At the start of the EoR, the Universe was mainly filled with neutral hydrogen gas, produced
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during the Big Bang. Only when the first generation of stars was born, did their ultraviolet light start to ionize pockets of this hydrogen. Gradually, those pockets grew until all the hydrogen in intergalactic space was ionized, like it is now. This process is thought to have taken place in the redshift range from z = 15 to z = 6, corresponding to the earliest history of the Universe.
is designed to detect these very low frequencies. Van Haarlem: “Maybe it won’t be technically feasible. But everybody agrees that detecting the EoR is going to earn someone a Nobel Prize.” Less risky are observations of radio galaxies and
Detecting the Epoch of Reionization is going to earn someone a Nobel Prize
LOFAR hopes to detect the
characteristic radio waves from neutral hydrogen in the redshift range from z = 11.4 (at 115 MHz) to z = 6 (at 180 MHz). Only LOFAR
clusters at distances of only a few billions of light years. Huge efforts have already gone into studying galaxies and clusters at closer range, but looking deeper into the history of the Universe with LOFAR should finally provide
eyeing the rare universe us with a full understanding of their birth and evolution. The most secure investment is doing all-sky surveys, simply listing all sources down
cause radio waves travel at the speed of light, this delay can be calculated precisely. For instance, radio waves from a source just above the
Up to a point, we can predict what we will find, but there will be surprises too to the lowest detectable brightness, so other astronomers can do more detailed observations later. “Don’t underestimate this work,” warns Van Haarlem. “There is less of the glamour of cosmology here, less hype. But remember, until now this low-frequency range was not part of the astronomers’ palette. Up to a point, we can predict what we will find – many more pulsars, for instance – but there will be surprises too.”
horizon in the East will first arrive at the easternmost antennas in German, then at the ‘Superterp’ near Exloo, Drenthe, and finally at the antenna station in the United Kingdom. Because ‘pointing’ merely involves making a selection of the total data stream, it is possible to switch between observing directions very fast, and even to point the ‘software telescope’ in up to eight different directions at the same time!
SOFTWARE TELESCOPE
The phased-array principle can even be used to upgrade more conventional radio telescopes. In a project called Apertif, the dishes of the Westerbork Synthesis Radio Telescope (WSRT) are now fitted with a focal plain array – a miniature array that replaces the conventional receiver in the focus of the parabolic dish, enlarging the field of view 25 times.
LOFAR can do the same as
conventional radio telescopes with their impressive parabolic dishes, and more. A radio dish only collects radio waves from one particular direction in the sky, and has to be rotated each time another target is chosen. But the LOFAR antennas collect signals from every direction above the horizon. To ‘point’ the telescope, the software just selects signals that have arrived at the various antennas with the appropriate time delay. Be-
Ralph Wijers of the University of Amsterdam is Principal Investigator of the LOFAR Transients project, which will focus on short-lived phenomena in the radio universe.
How difficult was it to make LOFAR a reality? In 2006 we got funding for all the hardware from the ‘aardgasbaten’ – a national foundation for large innovative projects, financed by the profits from natural gas. But it was a real struggle to get the last five million euros for developing software and expertise. Finally, ASTRON and NOVA (an astronomical collaboration of Dutch universities) decided to shoulder this burden together. But there is a very satisfying side to this. Because we are all in this together now, we all know how we can make the most of LOFAR’s scientific potential. It has truly become a national alliance.
In December 2009, you received a personal, 3.5 million euro European Research Council Advanced Grant. What will you do with that? It will fund my project Aardvark. With extra software and computing power, we can turn all the low-frequency antennas at the central ‘Superterp’ of LOFAR into a radio fish-eye lens. For the first time, we will be able to monitor the entire radio sky all the time for rare, transient phenomena. Just think of all the fun you have with this instrument. .
What will LOFAR have discovered five years from now? It will be great when LOFAR detects a radio flash simultaneously with a signal in a gravitational-wave detector such as LIGO. When you see a signal like this in two completely different instruments, you can be sure you have detected a very rare event: the merging of two neutron stars. Also, gravitational waves travel exactly with the speed of light, while the radio waves are slowed down a little by intergalactic ionised gas. We know the gas is there, but we know very little about it. Even if this happens only once, the time difference between the two signals will tell us a lot about the intergalactic medium.
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royal launch for international lofar telescope
It was a beautiful, sunny afternoon on Saturday June 12 near the village of Exloo, as it should be, since there was no plan B for taking Her
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Majesty Queen Beatrix to one of the LOFAR antenna stations in a pouring rain. More than seven hundred
people were invited for the first part of the ceremony, to be held in a temporary party centre as big as a circus. Among the guests gathered
before the arrival of the Queen, it was observed that LOFAR had already succeeded in speeding up the formation of a new govern-
ment, because that same day, Beatrix had to appoint an ‘informateur’ (cabinet matchmaker) at her palace
in The Hague, before leaving for Exloo by helicopter. In his speech, LOFAR director Michiel van Haarlem
stated with obvious relief: “This ends the phase when LOFAR only belongs to the engineers.” In an interview
later on the day he added: “I expect the first science results before the end of this year.”
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Her Majesty Queen Beatrix visits the LOFAR antennas after officially inaugurating the telescope array near Exloo, the Netherlands.
On stage, Van Haarlem briefly interviewed a number of LOFAR stakeholders. For LOFAR is not just a radio telescope, it is also a multi-purpose sensor network connected by glass fibres. It is already being used as a test bed for precision agriculture, for the study of infrasound in the atmosphere and for geophysical research. Also, the central part of the telescope is a protected area for wildlife.
single-dish radio telescope, which was the largest in the world for several months.
A nostalgic note was struck when grainy black-andwhite footage was shown of another inauguration, by Beatrix’ mother, Juliana. In April 1956, she ceremonially pushed a button to start the 25-metre Dwingeloo
While the 700 guests reflected on the event over a drink, the Queen was invited to visit one of the antenna stations in the field. On a red carpet – hastily secured against gusts of wind with some of the
This ends the phase that LOFAR belongs only to the engineers
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This time the stage was set with a dazzling, full colour display of countless LEDs and spotlights, but once again a Dutch Queen inaugurated a radio telescope that will be unique in the world for some years to come. As in sport, no scientific instrument stays at the top for very long. Michiel van Haarlem put it: “We hope to learn many valuable lessons that we can pass on to the Square Kilometre Array.”
rocks from the last ice-age that still litter the fields here – Beatrix ventured from her bus to one of the deceptively simple looking antennas in the clay. She was accompanied by half a dozen officials, and filmed in close-up by at least as many camera crews. “Fifteen years ago, we could not have done this,” Van Haarlem explained to her, “Because the computers were not powerful enough.” Her Majesty’s answer is lost to posterity: everything the Dutch royal family says in personal conversation is strictly off the record.
more than a telescope In the 1990s, the attention of the Netherlands Institute for Radio Astronomy (ASTRON) was largely focused on a very long-term project: the Square Kilometre Array, to be completed somewhere around 2015. It would be an array of hundreds of 12-metre parabolic telescopes. Leiden astronomer George Miley conceived LOFAR as a mid-term project to keep Dutch radio astronomy alive while it waited for SKA. For LOFAR director Michiel van Haarlem, the telescope has become considerably more than that: “The initial idea can be seen as a precursor to SKA, but the size and frequency range of LOFAR have increased beyond that. LOFAR has been funded on its own merits; it would be here even if SKA had never been proposed. Moreover, it is not clear if SKA will cover the really low frequencies, below 70 or 80 megahertz.
So, probably, LOFAR will remain an instrument with unique capabilities for many years to come.” Planning for an instrument ten years in the future, one must make an educated guess about the increase in capabilities and costeffectiveness of computers and other technology in that period. “The kind of problems we all expected, we actually encountered,” says Van Haarlem. “The balance between computing power and speed of data handling shifts over time, because of what the users want. LOFAR at present has a smaller number of detectors than originally planned, but its overall size is bigger. The first plan was to build more antenna stations at a maximum separation of 350 kilometres, while the maximum separation now is 1500 kilometres.”
PATHFINDER PROGRAMMES Like LOFAR, SKA will also be a phased-array telescope. Two official pathfinder
projects for SKA are now being built: MeerKAT in South Africa (eighty 12-metre dishes) and ASKAP (Australia SKA Pathfinder) in Western Australia (thirty-six 12-metre dishes). South Africa and Western Australia are the two remaining candidates for the location of SKA, which will require huge investments in people and hardware . LOFAR is ahead of these two
competitors. According to Van Haarlem, the telescope is now 75 percent finished. “It attracts young people to Dwingeloo – international PhD students and postdocs who would not have come here without LOFAR. ASTRON definitely is a world leader in this technology.” Van Haarlem stresses, though, that LOFAR does not to present itself as a pathfinder for SKA. In fact, he doesn’t even want to present it as a telescope; it is a multi-purpose sensor network for geophysics, agriculture and atmospheric science as well as for radio >
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changes and challenges
Raffaella Morganti is Head of the Astronomy Group at the ASTRON Netherlands Institute for Radio Astronomy. She organised the multi-day science meeting ‘A New Golden Age for Radio Astronomy’ at the International SKA Forum 2010.
What is the most important step forward that SKA has to offer? Sensitivity, without any doubt. We are reaching the limit of what can be done with the current generation of radio telescopes. SKA provides not just a small step, but a really big jump in sensitivity. By mapping the gas content of extremely remote galaxies, we will be able to study galaxy evolution.
Is SKA driven by science or by technology? It’s a complicated process. One pushes the other. Science is an important driver by setting priorities. Astronomers always want bigger telescopes and more collecting area. But their demands need to be matched by technology and money. That’s why pathfinders like LOFAR are important. We encountered problems, we struggled, and we solved them. As a result, we are now confident that SKA will do great low-frequency science.
Which other changes do you foresee in radio astronomy? We’ve always been a very closed community. That needs to change. We need to get better at turning data into images that can be appreciated by nonradio astronomers. We also need to attract people from other fields – that’s another challenge.
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more baskets for the eor-egg astronomy. Van Haarlem: “Much more than radio astronomy, these other fields of research are relevant to society. Precision agriculture touches on animal welfare and dealing with food shortages in the world. Seismic research with LOFAR can be relevant for storing CO2 underground. The extent of their projects is smaller, but researchers at the Royal Dutch Meteorological Institute (KNMI), at Delft University of Technology, and at Wageningen University and Research Centre are as passionate about LOFAR as astronomers are.”
Colin Lonsdale, Director of the Massachusetts Institute of Technology’s Haystack Observatory, was one of the early contributors to LOFAR design studies. The National Science Foundation (NSF) is now putting its money in the Australian Murchison Widefield Array (MWA).
What happened? The phased-array technique is revolutionary, and in whatever form LOFAR would be built, we wanted to get into the science. Initially, NSF gave us two million dollars to participate in designing the correlator. But later, the project went in a direction that made it impossible for us to get additional funding. There would be no copies of LOFAR built outside the Netherlands, and we felt we could not make a strong case that it would detect the Epoch of Reionization (EoR), because the widefield correlator would not be specially designed for that.
Are your early contributions still part of LOFAR? I look back on this scientific collaboration as an extremely productive, valuable period. Several aspects of our design studies are still part of LOFAR, for instance the fact that it became apparent that the telescope array needed more than one type of antenna. Also, we thought of the array configuration itself, with the logarithmic spiral arms.
So, will the MWA or LOFAR discover the Epoch of Reionization? It is an extremely difficult measurement. Nobody has yet proven it can be detected with any telescope. Maybe they are right, maybe we are, or maybe we’re both right. It is healthy not to put all your eggs in one basket. I have no doubt that on a personal level, the collegiality of the early years will continue. We have been comparing notes for the last six years, and we will keep on doing that.
The Square Kilometre Array will never be built without the help of industry. And industry is very interested in high-tech big science projects like SKA. But what are the best ways to bring those two parties together? And how do you get governments involved? The CISS (Connect Industry, Science & Society) workshop tried to provide some answers.
sealed with a ciss
“Astronomers are a clever bunch, but they shouldn’t reinvent what industry has already produced.” Bruce Elmegreen (IBM Research) knows what he’s talking about: he used to be an astronomer himself. Elmegreen was one of the speakers at the CISS workshop (Connecting Industry, Science and Society) on 14 June. “Astronomy is a highly talented community,” he says, “and industry has unique capabilities. Bring them together, and you get the best of both worlds.” Organised by Sensor Universe (see page …), the CISS workshop focused on possible ways of cooperation between science and industry. “We may need to change our standard way of thinking,” says Elmegreen. Traditionally, industry replicates and produces components that have been designed and prototyped by astronomers and astronomical engineers. But it might often be better to cooperate from the very start. In many cases, existing products or technologies can be modified to meet the needs of the scientists. Or astronomers can just pay industry to invent and design what they’re looking for. They might even get that service for free, if there are attractive non-science markets for the new technologies. According to Elmegreen, the Square Kilometre Array is a good case in point. The projected data rate produced by SKA is enormous – it is expected to be comparable to the full data rate of the World Wide Web in 2020. This will require new data compression techniques and new communication protocols, which of course will have applications
beyond astronomy. Also, experience with the remote control of high-tech systems located in inaccessible and inhospitable areas will benefit other areas, like deep-sea drilling, mining, or even the construction of ‘smart buildings’. Says Elmegreen: “There are many remote areas in our midst that could profit.”
Expensive commodity Justin Jonas, Associate Director for Science and Engineering in the SKA South Africa Project Office, agrees that SKA is “a new iconic project”. First of all, he says, it’s important to retain human capital and expertise, and to attract bright young people. But it’s also clear that SKA will need industry, and that industry is interested in SKA. In finding the best possible model of interaction, says Jonas, it’s vital to focus on risk factors. “Most risks need to be retired in the earliest possible stage. Risk is a very expensive commodity.”
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coherence and complexity Justin Jonas (Rhodes University, South Africa) is the Associate Director for Science and Engineering in the SKA South Africa Project Office. He is also the Project Scientist for MeerKAT, one of the precursors for the Square Kilometre Array.
In what respect is MeerKAT different from the other SKA precursors and pathfinders? We will have more dishes than others. But we have a so-called single-pixel feed: we are trading a larger field of view for a much
higher sensitivity and a large dynamical range. MeerKAT is also the largest mid-frequency pathfinder, and our dishes are more like the mid-frequency SKA dishes.
We don’t want to raise too much interest among SMEs [small and medium enterprises].
Is it hard to work together with government and industry on a science project like this?
To me, it’s quite surprising that there’s such a coherent view on the necessary cooperation between science, industry and government. People are also very realistic about this interaction. What was new to me was the urgency in understanding the various procurement models – there are many complexities here.
We are a top-down project, driven by the government. There are really high levels of contact. As for industry: cooperation is good, but also very focused. We’ve identified the industries that are really appropriate.
Building KAT-7 – the prototype array for MeerKAT, which is a SKA precursor in the South African Karoo desert – has taught Jonas some lessons. First of all: some radio astronomy requirements, like the need to prevent RFI (radio frequency interference), are foreign to industry, he says. Secondly, the common standards and practices in industry are not always what radio astronomers want; in some cases they just can’t afford it. And, last but not least: the build-to-spec approach, where industry designs and produces components on the basis of specifications that are laid down by astronomers, doesn’t work.
Clarity
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What do you take away from this CISS workshop?
Artist’s conception of the MeerKAT array in the South African Karoo (top).
Astronomers are a clever bunch, but they shouldn’t reinvent the wheel
According to John Humphreys, Chairman of the Australian SKA Industry Consortium (ASKAIC), competent project management and clarity on both the project definition and on possible shared goals are the success drivers for fruitful cooperation between science and industry. Moreover, he says, it’s very important to have common ground and language. “Industry requires clarity on how they can participate, and customer engagement. The challenge for SKA is how to achieve this engagement.”
sensor universe organises serendipity Humphreys sees three important areas where this might be possible: SKA is a globally operated facility, it deals with huge computer processing power and data flows, and it has equally huge energy requirements. “Clearly, SKA is not business as usual,” he says, “but to industry, the telescope is not necessarily bigger than other large infrastructure projects. We’re ready to start, as soon as there’s more clarity, for instance on the site, the budget, the design trade-offs, etcetera.”
Henk Koopmans is an entrepreneur pur sang. He started out in accountancy, but soon earned his money by buying, restructuring and selling companies, mostly in the field of ICT and electronics. Now, as Director of Sensor Universe, he helps both the science and the business community to benefit in ways they never would have imagined. “Some scientists are very open to the idea,” he says, “others not at all, probably because of a lack of interest in what’s happening in society beyond their own horizon.”
As for risks, Humphreys quotes John F. Kennedy: “There are risks and costs to a programme of action. But they are far less than the long-range risks and costs of comfortable inaction.”
Position paper Finally, Niels Kramer of NXP Semiconductors in Eindhoven presented a Dutch Industry Position Paper on SKA, produced by NXP, Siemens, and IBM. The position paper describes the importance of SKA to the Netherlands from an industry perspective. “We wanted to make a clear statement to the Dutch government,” says Kramer, “and to outline what SKA means to Dutch industry.”
Sensor Universe is a Dutch institute that brings together science, industry and government in the field of sensor technology. Initiated by the Netherlands Institute for Radio Astronomy (ASTRON), the province of Drenthe, and the municipality of Assen, Sensor Universe traces its roots to the development and construction of the International LOFAR Telescope (LOw Frequency ARray). “There was an urgent need to bridge the gap between the various parties,” says Koopmans. “They even speak a different language. When scientists talk about ‘results’, they refer to data and publications. For companies, ‘results’ equals cash flow.” Radio astronomy plays a pioneering role in sensor technology, and in the storage and processing of huge volumes of data. The needs of radio astronomers create unique opportunities for industry, and Koopmans saw exciting possibilities for new forms of collaboration.
Cross-fertilization “Our aim is to organise serendipity,” he says. “That may sound counterintuitive, but by bringing people together in workshops and network meetings, we facilitate cross-fertilization, which often leads to surprising new initiatives.” Over the past years, some fifteen workshops have been organised. “Unfortunately, getting gov-
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ernment bodies involved turns out to be more difficult,” says Koopmans. “Governments tend to work on the basis of projects instead of programmes.” According to Koopmans, the ‘triple helix model’, in which science, industry and government play an interwoven role, is recognised elsewhere, too. “There have been similar conferences in South Africa and in Australia, and in both cases we have been invited to explain our approach, which is now gaining momentum all over the world.” Sensor Universe also organised the CISS workshop (Connect Industry, Science and Society) at the International SKA Forum 2010. Says Koopmans: “We need to speed up economical activities. Industry should be connected to science and society as early as possible. In that case, both science and industry will benefit. The Square Kilometre Array is a prime example of a promising collaboration.”
Sensor Universe Director Henk Koopmans, addressing the Connecting Industry, Science and Society workshop (right).
According to Kramer, government involvement – and financial support – is essential. “The Netherlands have always had a strong tradition in radio astronomy, and there has always been interaction between science and industry. But in the case of SKA, we need a different kind of collaboration. We have research and development capabilities to offer, as well as risk mitigation, and cooperation at all levels.”
Clearly, SKA is not business as usual
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The Dutch Industry Position Paper recommends a clear cabinet decision in 2010, to show where the Netherlands stands when it comes to the SKA. The Netherlands’ top position in the world in terms of radio astronomy has been reconfirmed by the opening of the LOFAR telescope on June 12. A clear positive statement of the new Dutch government regarding its SKA ambitions will help to retain our top position for the next several decades. In the Netherlands and at large, the industry is ready to support the ambitions and truly help make the SKA a reality.
carrots for funding countries
IBM’s Bruce Elmegreen (centre) during the panel discussion at the CISS workshop. At the end of the CISS Workshop, Chairman Henk Koopmans and the four speakers took part in a panel discussion, answering questions from the audience. Below are some quotes from this panel discussion.
On the possible effects of scale growth of the SKA pathfinders “There haven’t been big changes at a fundamental level, partly because procurement is a short-term process. But some ways of industrial involvement might not have worked as well with smaller pathfinders.” (Bruce Elmegreen)
On the role of SMEs “SMEs are often complementary to big companies. They are more clever in some areas than we are.” (Niels Kramer)
“There needs to be some form of just return for various countries, maybe beyond astronomy.” (Justin Jonas)
On non-science benefits “It’s important to keep SMEs up to date all the time, so they can join whenever they see an opportunity.” (Henk Koopmans)
On procurement rules
“Those are the carrots for funding countries. We need new communication protocols to sell what exaflop computing and 24/7 renewable energy can do for society.” (John Humphreys)
“We all agree we need rules. But who makes the rules? We need to agree on that as well. These issues have been solved in other cases, like the Large Hadron Collider and the International Space Station.” (Bruce Elmegreen)
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precursors and pathfinders
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Acronym:
LOFAR or ILT
Full name:
LOw-Frequency ARray or International LOFAR
Acronym: Full name:
ASKAP Australian Square Kilometre Array Pathfinder
Partners:
CSIRO, ATNF, with partners in Australia, Canada, the Netherlands, United Kingdom and Germany
Location:
Murchison Radio Observatory, Western Australia
Description:
Array of 36 12-metre dishes with phased-array feeds
Status:
Under construction (six antennas operational in 2011, fully operational in 2013)
Website:
www.atnf.csiro.au/SKA
Telescope
Partners:
Netherlands Institute for Radio Astronomy (ASTRON) with a consortium of Dutch institutes
Location:
Core area near Exloo (Drenthe), the Netherlands
Description:
Array of many thousands of low-band (10-90 MHz) and high-band (110-250 MHz) antennas, concentrated in dozens of stations across North-western Europe
Status: Website:
Completed; inaugurated on 12 June 2010 www.lofar.org Acronym: Full name:
MWA Murchison Widefield Array
Partners:
MIT, the Harvard-Smithsonian Center for Astrophysics, the Raman Research Institute, and an Australian consortium of universities
Location:
Murchison Radio Observatory, Western Australia
Description:
Large field-of-view, low-frequency array (80-300 MHz), consisting of 512 cross-correlated phased tiles of 16 dipoles each
Status: Website:
Construction nearing completion www.mwatelescope.org
Acronym: Full name:
MeerKAT Karoo Array Telescope
Partners:
National Research Foundation of South Africa / SKA South Africa
Location:
Karoo desert, Northern Cape Province, South Africa
Description:
Array of 80 12-metre antennas with wideband single-pixel receivers
Status: Website:
Under construction (fully operational in 2013) www.ska.ac.za/meerkat/overview.php
Acronym:
SKADS and AAVP
Full name:
SKA Design Studies / Aperture Array Verification Program
Partners: Location:
26 institutes in 13 countries (SKADS) -
Description:
EC-supported European programmes to investigate and develop technical work onaperture arrays
Status:
AAVP is the successor to SKADS, a 4-year programme completed in late 2009
Website:
www.skads-eu.org www.ska-aavp.eu
Acronym: Full name:
ATA Allen Telescope Array
Partners:
UC Berkeley Radio Astronomy Lab and the SETI Institute
Location:
Hat Creek Radio Observatory, California
Description:
Radio interferometer array of (eventually) 350 6-metre dishes
Status: Website:
Partly completed and operational (42 dishes) www.seti.org/Page.aspx?pid=503
Acronym: Full name: Partners: Location:
TDP Technology Development Project Cornell University / U.S. SKA Consortium -
Description:
NSF-supported 4-year effort to develop technologies for metre- and centimetre-wavelength astronomy
Status: Website:
In progress http://skatdp.astro.cornell.edu
Acronym:
KAT-7 or MPA
Full name:
Karoo Array Telescope-7 or MeerKAT Precursor Array
Partners:
National Research Foundation of South Africa / SKA South Africa
Location:
Karoo desert, Northern Cape Province, South Africa
Description:
Seven-dish prototype interferometer array; precursor for MeerKAT
Status: Website:
Completed; fully operational www.ska.ac.za/meerkat/overview.php
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radio astronomy’s golden age 34
As part of the International SKA Forum 2010, a multi-day astronomy meeting was organised by Raffaella Morganti, who heads the Astronomy Group at the Netherlands Institute for Radio Astronomy (ASTRON), the host of the forum. The meeting’s title, ‘A New Golden Age for Radio Astronomy’, nicely captured the excitement of the world’s radio astronomy community. With new facilities coming online, such as ASTRON’s LOwFrequency ARray (LOFAR), and with promising new technologies being developed for future telescopes like the Square Kilometre Array, radio astronomy is entering an era that will be rife with revolutionary discoveries. After an introductory session, four science sections covered the most intriguing and challenging fields that the new generation of radio telescopes are already exploring, or will deal with in the foreseeable future.
a new era for the transient universe For centuries, western philosophers believed the heavens to be unchanging, just like Aristotle had told them. In the year 1572, however, Danish astronomer Tycho Brahe saw something that made him doubt this rule: a bright new star. Although Brahe didn’t know he was looking at a supernova, he did realise the event wasn’t taking place in the Earth’s atmosphere, but somewhere far away. The heavens did change after all.
empty, except for a huge question mark. “This is a great era to live in, as far as the transient sky is concerned, because there simply has not been a large survey of this part of phase space,” Cordes said.
The event Brahe witnessed is what today’s astronomers would call a transient: an astronomical event that can only be observed for a short period of time. Events in this category were the subject of the second session of the astronomy meeting at the International SKA Forum 2010.
Transient phase space The first talk was by Cornell University’s Jim Cordes. He emphasised the importance of studying transients by showing a graph of the so-called transient phase space, with the decay time along the x-axis and the observed brightness along the y-axis. At the right side of the graph, numerous events with decay times longer than a day were depicted: various bursts, supernovas, classical novas, etc. The left side, however, was virtually
SKA will use precise pulsar timing measurements to detect gravitational waves.
So, what can we expect to find here? Many examples were mentioned; millisecond pulsars for instance, which could be a million times brighter at radio wavelengths than the ‘regular’ pulsar in the Crab Nebula. Also, we may see radio bursts
caused by merging neutron stars, or evaporating black holes. Maybe even signals from extra-terrestrial intelligence will be detected. But, as Jean-Mathias Griessmeier of ASTRON explained, transients can also be found a lot closer to home. Lightning on other planets in our solar system, notably Saturn, also causes short bursts of radio emission.
taking the pulse
These kinds of events can be studied by a number of projects. Of course, LOFAR was mentioned a number of times, but observations by the Allen Telescope Array in California and the Australian SKA Pathfinder were also discussed.
The Moon as a detector A very interesting technique to detect transients was described by Heino Falcke of the Radboud University in Nijmegen. He studies transients at the highest time resolution (lasting from ten nanoseconds to hundreds of milliseconds), among which are ultrahigh-energy cosmic rays. “These things are extremely rare,” Falcke explained. “We are talking here about a few events per century per square kilometre. You have to measure these with a detector millions of square kilometres in size, and that’s very difficult to buy these days.” The solution, which was first suggested in a Russian paper by Rustam Dagkesamansky and Igor Zheleznykh, is to use the Moon as a detector. “A cosmic ray particle hits the lunar surface and produces a radio flash, which will be detectable from the ground.”
This is a great era to live in, as far as the transient sky is concerned
One aspect of studying transients that was mentioned by several speakers is the fact that wave fronts of the radiation emitted by pulsars and the like are distorted by the intervening medium. While this might sound like nothing but a nuisance, it also has its advantages, Cordes explained. “You can find transients and use them as a tool to probe the interstellar or the intergalactic medium.” In other words: while signals from transients may not get through to us the way we would like them to, the way they get mangled on their way to Earth tells us something about the Universe as well.
Jason Hessels is a staff astronomer at the Netherlands Institute for Radio Astronomy (ASTRON). In 2005, he discovered the fastest spinning pulsar known to date.
Which of the early LOFAR results would you say is the most impressive? I think the observation in which we simultaneously used LOFAR to make a sharp image of a pulsar as well as detect its pulsations is very impressive. This observation shows how LOFAR is both a high-resolution and high-speed radio camera.
What results would you have loved to be able to show, but couldn’t? In the lead-up to the conference we were trying to put all the stations on the central ‘Superterp’ of LOFAR into phase with each other. Once this is achieved, we’ll be getting the maximum possible sensitivity from the combination of these stations. We came very close to getting this working before the conference and we were even processing data ten minutes before my talk! Now we have the time to finish the job at a more relaxed pace.
Some of the earliest pulsar observations by LOFAR were done by undergraduate students. How did that go? They were very excited to be among the first users of the telescope, and they learned quite a bit about radio astronomy in the one week we worked together. Some of them have decided to continue further studies in astronomy, so I think that means they’ve caught the astronomy bug.
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radio astronomy’s golden age 36
in search of the eor: lights! camera! action! In the beginning, the Universe was ionized: some fifteen minutes after the Big Bang, nuclei of light elements and electrons floated separately in space. Some 380,000 years later, this changed; by then, the temperature and the density of the Universe had sufficiently decreased to allow the ions and the electrons to form neutral atoms mainly hydrogen. However, this was not to be the final stage of matter. A few hundreds of millions of years after the Big Bang, energetic objects formed in the early Universe and broke up the neutral hydrogen atoms again. This era was aptly named the Epoch of Reionization (EoR). The third session of the astronomy meeting focused on this process, which is still shrouded in mystery. “We have not yet seen the sources responsible for reionization,” Martin Haehnelt (University of Cambridge) said during the first talk. “Most likely they were faint galaxies below current survey limits, but more exotic solutions are certainly possible.”
times stronger than the cosmological neutral hydrogen emission astronomers want to study, he explained. “Searching for the EoR signal can truly be compared to searching for a needle in a haystack.” After this disheartening statement, however, Jelić presented results of the EoR foreground model developed by LOFAR astronomers, which is the first detailed foreground model that includes both
Four problems One project to learn more about the EoR, by studying the emission of neutral hydrogen in the early Universe, is LOFAR. These will be very complicated observations though, Saleem Zaroubi (University of Groningen) warned. Four problems will have to be dealt with: foreground emissions, the ionosphere, the noise caused by the telescope itself, and Radio Frequency Interference (RFI), mostly by man-made sources. “To be sure that what you are doing is correct, you have to simulate every step and see if you can dig out the signal,” Zaroubi said. ASTRON’s Vibor Jelić provided more details on
the foregrounds, which he called “the largest problem from an astrophysical point of view”. This amalgam of radiation, emitted by galactic as well as extragalactic sources, is hundreds of
galactic and extragalactic components. At the end of his talk, he concluded: “With the expected EoR sky and receiver noise levels, and with idealized instrumental response, we should be able to statistically reconstruct the EoR signal.”
PAPER work Don Backer (University of California) discussed another experiment to study the EoR: the Precision Array for Probing the Epoch of Reionization, or PAPER. This set of arrays started out with a number of antennas in Green Bank, West Virginia, Backer explained, which are now complemented by thirty-two antennas in the South African Karoo.
snapshot cosmology
Lincoln Greenhill is Senior Research Fellow at Harvard University and Project Scientist for the Murchison Widefield Array (MWA). A computer simulation depicting the distribution of matter in the early Universe at the Epoch of Reionization.
Having arrays in both the Northern and the Southern hemisphere allows the PAPER team to map the entire sky.
The hunt for the EoR signal is like searching for a needle in a haystack
In the final talk, Steve Rawlings (Oxford University) discussed the possibilities of the Square Kilometre Array (SKA) with regard to the EoR and other cosmological points of interest. “Phase one of SKA can, well before the end of this decade, achieve fundamental scientific breakthroughs,” he said. “Its aperture arrays can improve on LOFAR sensitivity by a factor of ten and hence image the EoR.” Also, Rawlings added, the telescope can be used to map out gravitational waves, caused by merging supermassive black holes. Further down the line, during phase two, SKA will be able to use hydrogen and pulsars to attack what Rawlings referred to as “beyond-Einstein questions,” such as dark energy and quantum gravity. Exciting times are ahead!
What will MWA tell us about the Epoch of Reionization that other telescopes can’t? MWA will be a high-dynamic range, wide field of view radio camera for snapshots. In this respect, it will be the best of any of the projects. We will make our detection of the early universe by coadding the MWA snapshots.
“Only crazy people would throw away their observations,” you said in your talk. Yet this is what happens with MWA. All the other radio arrays store raw data. For small volumes, this is practical and certainly preferable. However, in order to make beautiful snapshots with MWA, huge data volumes have to be manipulated. If we tried to store these, this would amount to about a petabyte per week for many months, so we had to make a trade-off. The price is in forced discarding of the raw data – and in having to develop new techniques from scratch.
Part of MWA is now up and running. What will happen the next few months? The 5% aperture that we have running in the Australian outback has enabled us to test the system, end to end. However, the best way to learn about a new telescope is to use it. Recognizing this, we are pursuing a science programme that pushes the limits of the instrument.
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radio astronomy’s golden age 38
gastrophysics galore Because there is so much of it throughout the Universe, hydrogen gas is the single most important tracer of what goes on in the space between the stars and between the galaxies. Conveniently, all neutral atomic hydrogen emits radio waves at a wavelength of 21 centimetres (a frequency of 1.42 gigahertz). When we observe objects at distances of billions of light years, these waves have been stretched by the expansion of the Universe. By detecting the range of wavelengths from 21 centimetres up to a metre or more, we can trace cosmic evolution all the way back to the era when the first galaxies formed, presumably only some four hundred million years after the Big Bang.
are now revealing the turbulent lives of hydrogen clouds much closer to home.
Magellanic Stream Starting out in our own Galaxy, the Milky Way, Snezana Stanimirovic from the University of Wisconsin Madison used the giant Arecibo radio telescope in Puerto Rico to investigate the Magellanic Stream – a large cosmic river of gas that is falling in from our closest neighbour in intergalactic space, the Small Magellanic Cloud. It is well known – and actually observed – that stars are born in contracting gas clouds in galaxies. In elliptical galaxies, the reservoir of gas becomes depleted and star formation comes to a halt. In spiral galaxies like the Milky Way, star
The Magellanic Stream (pink, bottom) dominates the radio sky south of the Galactic equator.
LOFAR will take us into that era, but at the fourth session of the astronomy meeting, several speakers reported results from radio telescopes that
formation continues to this day. In her talk, Stanimirovic put it this way: “To maintain a healthy rate of star formation, you need a large accretion
constant change
of gas from outside the plane of the galaxy.” In a sense, the gas gets ‘eaten’ by newly formed stars, while old stars return part of their contents back into space – a complicated process for which astrophysicists have coined the word ‘gastrophysics’. The fact that gas even streams between neighbouring galaxies adds to the complexity.
The loneliest galaxies Traditionally, astronomers focused much of their attention on galaxies in clusters. These are the largest gravitationally bound structures in the universe. They are connected by filaments and walls of galaxies, creating a spongy distribution of matter on the largest scale.
Ninety-five percent of space consists of voids
Jacqueline van Gorkom (Columbia University) focused on the rare orphan galaxies in the huge voids within this cosmic sponge. “In our cosmic neighbourhood, ninety-five percent of space consists of voids,” she says. With specialized statistical methods, Van Gorkom selected the ‘loneliest’ galaxies from the ‘deepest underdensities’ in an existing database, the Sloan Digital Sky Survey . These void galaxies, she found, are on average smaller than cluster galaxies, but they form stars more quickly and efficiently than ‘normal’ galaxies. Her hypothesis is that isolated galaxies still accrete gas from the void surrounding them, which fuels star formation. The ongoing accretion of intergalactic gas by galaxies is a research subject for several other astronomers who spoke at the session. It seems that, in a certain sense, the formation of galaxies from the primordial hydrogen gas that pervaded the Universe shortly after the Big Bang is still going on today.
Nissim Kanekar is Ramanujan Fellow at the National Centre for Radio Astrophysics (TIFR) in Pune, India. His radio observations of a remote gas cloud may indicate that the constants of Nature are changing over time.
We’ve heard this before: in 1999, observations of distant quasars suggested that the fine structure constant was changing. Follow-up observations could not support this result. For the quasar observations, the result could have been an artefact of looking through several aligned gas clouds at different distances. We have observed a cloud that contains a natural maser – the microwave equivalent of a laser. That’s why we are sure we are looking at only one cloud. Also, we used two telescopes on different continents, so interference from a terrestrial source cannot be the cause.
So now you just have to convince theoretical physicists? The best we can do right now is to go deeper – look longer, at fainter and more distant sources. We were allocated one hundred hours of observing time on the Green Bank Telescope, and 160 hours on the Arecibo telescope in Puerto Rico. By the end of this year, we hope to have enough data to confirm our result.
Will LOFAR give us a definite answer to this question? Even LOFAR will not have enough sensitivity for that, but SKA would. In fact, SKA would be able to map the changing of the constants over the history of the Universe.
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radio astronomy’s golden age 40
going to depths Even before the official opening on June 12, and long before the last LOFAR antenna station is due to be switched on, this telescope is producing actual science data. The central part – the ‘Superterp’ and nearby stations – forms a large telescope in its own right, and Leiden astronomer Huub Röttgering showed that it can produce ‘deep’ images of radio galaxies and clusters. Also, the first long-baseline experiments, connecting the ‘Superterp’ with an antenna station in Effelsberg, Germany, are well under way. Many technical hurdles remain to be overcome, though, as explained by ASTRON staff astronomer Ger de Bruyn during the fifth session of the astronomy meeting. Calibration is more challenging for LOFAR than for conventional radio telescopes, because the LOFAR antennas pick up radio waves from the entire sky. Only at a later stage, during data processing, is an actual observing direction decided upon. In fact, LOFAR still has to do a complete sky survey to make a Global Sky Model with which to calibrate is own data.
Ionosphere of influence One peculiar issue with low-frequency radio waves is that they are distorted by the ionosphere, a layer of ionised gas high in the Earth’s atmosphere. This distortion can be dealt with by looking at well-known radio sources, and using them as calibration for the actual radio sources of interest. However, this is technically complicated, because the ionosphere can look different in appearance to antenna stations that are far away from each other, and it can change in seconds, notably because of unpredictable changes in the solar wind. Despite all this, the conclusion arrived at by Olaf Wucknitz of Bonn University was unequivocal: “Long-baseline LOFAR works!” Considering these first long-baseline experiments, Wucknitz had
more good news: “I was pleasantly surprised, the ionosphere seemed very quiet.” Röttgering went on to show images taken by LOFAR just days ago. “Look at this really amazing structure, the Sausage Cluster,” he said, almost lyrically. On the large screen behind him, on a canvas dotted with galaxies and foreground stars, appeared a complicated blob that indeed resembled a sausage. But this one is seven million light years long, three times the distance between the Milky Way and the Andromeda Galaxy.
Colliding clusters According to Röttgering, the Sausage Cluster is actually two clusters crashing into each other. The individual galaxies within the clusters are not colliding, much less the individual stars in the galaxies. Instead, the LOFAR image is the spectacular radio signature of the collision between the halos of very tenuous gas and dark matter that presumably surround each cluster. Although it has been studied for a long time, the radio emission from galaxies and clusters is not very well understood. It is unclear why some galaxies emit a lot of it, and others nothing at all. Also, radio astronomers would like to know a lot more about the magnetic fields in galaxies and those between the galaxies in a cluster, which probably influence their evolution. Magnetic fields
Long-baseline radio astronomy with LOFAR works!
Astronomers at the science meeting ‘A New Golden Age for Radio Astronomy’ (top), listening to Annalisa Bonafede’s talk (left).
cause polarisation of radio waves, so polarisation measurements – which LOFAR can perform – give a handle on how magnetic fields evolve in clusters . In some senses, these images are only a proof of principle. Once the full LOFAR machinery is in place, Röttgering has a more ambitious pro-
gramme: “Our goal is to detect a hundred radio galaxies at a redshift (z) larger than 6, and a hundred radio clusters of galaxies at z > 0.6.” Redshift is caused by the expansion of the Universe, and is a measure of distance. Says Röttgering: “LOFAR is really going to tell us wonderful things about clusters.”
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Members of the ISKAF2010 Project Team and collaborators (from left to right): AndrĂŠ van Es, Marjan Tibbe, Femke Boekhorst, Peter Bennema, Mariska Pater, Jaap Westerhuijs, Roel Barkhof, Truus van den Brink, Diana van Dijk, and Ria Moraal.
Organisation | Groningen Congresbureau
colofon
Opening LOFAR | Arjan van Dijk Public relations | Roel Barkhof Text | Arnout Jaspers, Jean Paul Keulen and Govert Schilling Edit | Stuart Clark Photography | Hans Hordijk Graphic Design | Gilbert Terpstra, Pam van Vliet Print | Flevodruk Production and coordination | Govert Schilling
42 This activity is supported by the European Community Framework Programme 7, ISKAF2010, grant agreement no.: 262168 (INFRA 2010-1)
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