Introduction

Abstract

This chapter sets the scene for the story of the early years of the Square Kilometre Array by sketching the scientific, technical, funding and cultural context for the project.

This is a book about a grand vision radio telescope project called the Square Kilometre Array (SKA) and its transition from a global grass-roots collaboration among astronomers and engineers in the early 1990s to a formal legal entity two decades later, on the path towards an Inter-Governmental Organisation constructing a science mega-project.

The story of the SKA’s development is one of ground-breaking science ideas, innovative engineering, and global collaboration. It is one of the few examples of a community-driven global project that has demonstrated the perseverance and clarity of purpose needed to develop into a treaty-based science mega-project without the benefit of an existing large organisation to act as host in its formative years. There are striking similarities to the formation of the European Southern Observatory (ESO) which started as an astronomer-driven vision in 1953 to build a large optical telescope in the Southern Hemisphere and, a decade later, became a treaty organisation based on a Convention among governments largely modelled on the European Organisation for Nuclear Research (CERN) (Blaauw, 1991).

The development of the SKA has been a long and complex story, reflecting the many issues faced in creating a scientifically ground-breaking but affordable design, choosing a site, and creating a viable global organisation starting from a simple working group established by the International Union of Radio Science (URSI) in 1993. When complete, the SKA will take its place as one of the Great Observatories of the mid twenty-first century alongside the Atacama Large Millimetre/submillimetre Array (ALMA), the James Webb Space Telescope, the Cerenkov Telescope Array (CTA), the large optical telescopes under construction (ELT, TMT, and GMT), and the gravitational wave observatories (LIGO, VIRGO, KAGRA).

This historical account will take the reader from the emergence of the SKA concept through to the decision on where to locate the telescope, in 2012. A number of brief overviews of the SKA history, or elements of it, have already been published by Ekers (2012), Noordam (2012), Butcher (2015), Kellermann et al. (2020), and Kellermann and Bouton (2023). At the time of writing in 2023, construction of the first phase of the SKA has now started after a further decade of design and development involving hundreds of scientists, engineers and administrators around the world.

Like any big idea, the SKA did not emerge ex nihilo. As radio astronomy flourished and matured as a scientific discipline after World War II using technology pioneered in the war period,¹ many different concepts for radio telescopes were discussed, and some were built. In the process a rich legacy of radio astronomy projects, large and small, was created (see Chap. 2), several of which had direct influence on the SKA in terms of its design and ambition. Others had a more indirect influence in terms of defining the state of the art of what could be built at any particular epoch, or they were unfunded visionary proposals that provided a more distant goal for the community to strive towards.

It is beyond the scope of this book to describe the development of radio astronomy around the world, and the scientific insights generated, in the years before the emergence of the SKA. The reader is referred to a number of books that cover parts of the history, some from national perspectives—(Sullivan, 2009) covering all radio astronomy pre-1953; (Edge & Mulkay, 1976) primarily on UK radio astronomy; (Raimond & Genee, 2011) on The Netherlands; (Kellermann et al., 2020) on the USA; (Goss et al., 2023) on Australia; and (Baars, 2021) on global radio astronomy history from the perspective of the International Union of Radio Science (URSI).

In this Introduction, we will provide the context in which the SKA was born as a science mega-project.

1.1 SKA: A Global Science Mega-Project Is Born

The proposed giant step in collecting area of the SKA compared to existing national telescopes operating in the same region of the electro-magnetic spectrum immediately put it in the class of “very large project”. Its size led directly to cost estimates well beyond those of any radio telescope built to that point (in 1990), costs that looked to be beyond the funding available for radio astronomy in any single nation. However, this was never seen as a problem. The telescope would be a global endeavour, building on the long tradition in radio astronomy of sharing ideas with colleagues, allowing open access to observatories by users from different institutes and countries (called “Open Skies”), and collaborating in observations involving national radio telescopes working in concert as a single telescope spanning the world (Very-Long-Baseline Interferometry, VLBI). The scale of the project dictated that in addition to a strong science case, innovative technologies would need to be developed to keep costs down, and national and international sources of design and construction funds would need to be sought. As the project progressed, its large scale brought science and governmental political aspects to the fore including its long-term governance structure, the location of the telescope itself and its headquarters, and the accommodation of differing national motivations for joining the project including the engagement of industry. In addition, the political, sociological and cultural differences across the global partnership were not always as easy to accommodate in more formal structures as had been the case in earlier simpler projects. We trace the paths taken in solving these many concurrent issues as well as the successes and failures along the way and reflect on SKA as an enterprise through the lens of hindsight.

1.2 The Initial Motivation for the SKA

1.2.1 Science Drivers

The SKA was initially conceived as an interferometer array providing a major advance in sensitivity of nearly a factor of 100 compared with the world’s most powerful radio telescope at the time, the Very Large Array (VLA) in New Mexico. Driving this desire for a very large collecting area was the goal of detecting the very faint neutral hydrogen emission in distant galaxies using the 21 cm spectral line (see Chaps. 2 and 5). Hydrogen is the most abundant element and its study is fundamental to our understanding of the formation and evolution of galaxies and their large-scale structure in the early universe. The large increase in sensitivity was to be achieved by pushing the boundaries of instrumental parameter space via a combination of much larger collecting area and developments in technology.

1.2.2 Exploration of the Unknown

In a study of scientific advances, Derek de Solla Price (1963) reached the conclusion that most advances follow laboratory experiments rather than theoretical predictions. Subsequently, Martin Harwit (1981) applied a similar analysis to astronomy and showed that most important discoveries result from technical innovation, in other words, technology leads discovery. The discoveries peak soon after new technology becomes accessible, usually within 5 years.

Throughout the history of radio astronomy new instruments utilised then state-of-the-art technologies to push the boundaries of instrumental parameter space and have made many fundamental discoveries about the universe (Sullivan, 2009; Kellermann & Bouton, 2023). The key instrumental parameters, then and now, were and remain the sensitivity set by collecting area and the system electronics, as well as the imaging quality and the frequency and time resolution.

There are many examples of unexpected discoveries from radio astronomy including Quasars, Pulsars, and the Cosmic Microwave Background. These are summarised in a book on the discoveries in radio astronomy called “Star Noise” (Kellermann & Bouton, 2023). They note that in almost all cases, the discovery had not been predicted before the observations. This has been called the “discovery of the unknown” and has been a key component of the science case for the SKA from its inception, illustrating the importance attached to ‘blue-sky’ research. It reflects the fact that a very large fraction of the discoveries made by radio telescopes were not anticipated at the time when the telescope construction was funded. The prominence given to this point by the SKA was not always seen by funding agencies and peer-review committees as being as strong an argument in justifying the expense of a science mega-project as having a set of key science projects with quantified improvements in performance supported as being important by a large fraction of the science community. However, quantifying the costs and outcomes of the exploration of the unknown is not straightforward. Successful telescopes that push the state-of-the-art are built by visionaries but often for reasons that turn out to be lower scientific priorities by the time the telescope begins operation.

1.2.3 Exponential Growth in Sensitivity

Between 1939² when Grote Reber made the first successful observations with the first purpose-built radio telescope and the early 1990s when the VLA had been in full operation for almost a decade, radio astronomy sensitivity increased by a factor of about one hundred thousand. Further upgrades to the VLA in the following decade took this increase to 1 million (see Sect. 2.2.2.3). Over the 65-year period from Reber’s first telescope, sensitivity increased exponentially with a three-year doubling time. The SKA’s proposed major advance in sensitivity by another factor of about 100 compared with the VLA in 1990 would have enabled it to stay on the same exponential curve for sensitivity assuming the telescope was operational by 2015 (see Fig. 1.1).

Fig. 1.1

A log-linear plot made in 2001 showing the relative sensitivity as a function of year for a selection of radio telescopes. Boxes indicate the sensitivity attained when the systems were first commissioned. Acronyms: WSRT—Westerbork Synthesis Radio Telescope; VLA—Very Large Array, VLA*—Extended VLA upgrade; GMRT—Giant Metre-wave Radio Telescope; and GBT—Green Bank Telescope. The SKA point was the expectation at the time when the plot was first made in 2001

1.3 How to Achieve the Sensitivity

Such a 100-fold increase in sensitivity would also be a significant step forward in capability and potential for discovery compared with the state of the art, as would be expected for such an expensive project. The increased sensitivity was to come from a combination of greatly increased collecting area (from 13,000 to 1 million square metres) and the exploitation of developments in low-noise wide-bandwidth detector technology. Innovation in all areas was thought to be the key factor in continuing the sensitivity increase (see Fig. 1.1). This exponential improvement in sensitivity would follow the experience in high energy physics with accelerator beam energies. Starting in 1930, each new particle accelerator technology provided exponential growth in energy and reduced unit costs up to a ceiling when the technology capability saturated, and a new technology emerged. The envelope of the exponential curves for each technology is also an exponential, and these are known as Livingston Curves.³ A factor of 10¹⁰ increase in energy was achieved in the 60 years to 1990 and the exponential envelope continued until the Large Hadron Collider became operational around 2010, after which it became impossible to sustain this rate of growth with the current technology (Riesselmann, 2009). The evolution of radio astronomy sensitivity is also a form of Livingston Curve. We return to the subject of innovation in the SKA in Sect. 11.4.3.

Two major classes of radio telescope emerged early on to exploit various combinations of these parameters. These were single dishes and arrays of dishes. As shown in Fig. 1.1, radio telescope sensitivity grew dramatically over time, initially as the collecting area of single dishes became much larger with increasing dish diameter. But by 1970 dish size reached a limit set by the effects of earth’s gravity, and single dishes were succeeded by the coherent combination of many smaller dishes that use aperture synthesis or beam-forming techniques⁴ to create a telescope whose total collecting area can be much larger than a single dish. The much larger array sizes possible also allowed much higher angular resolution than afforded by a single dish. In subsequent decades the number and size of elements in arrays also became larger, improving image quality as well as sensitivity. This time period also saw very substantial improvements in detector (receiver) technology which reduced instrumental noise, and in high-speed digital signal processing.

When the SKA emerged as a concept, substantially increasing the collecting area was the most obvious performance enhancement option available for a telescope whose main goal was the detection of the faint neutral hydrogen spectral line. This is why the collecting area envisaged, a square kilometre, provides the name of the telescope. In subsequent years several innovative concepts for the antenna elements were pursued in an effort to substantially reduce the cost per square metre of the collecting area. As we describe in Chap. 6, these initial options included arrays of about 50 very large diameter dishes or 3000 small diameter dishes, arrays of many tens of thousands of antenna elements fixed on the ground but steered electronically, lens antennas, and cylindrical paraboloid reflecting structures. A decision was made in 2005 on which avenues to follow and this was further refined in 2010 (see Chaps. 4 and 6). The first phase of the SKA now being built is only a tenth of the area of the original concept so cannot match the original science expectations, but the full SKA remains the long-term goal.

1.4 Big Science

The SKA was conceived to do “Big Science”. Derek De Solla Price (1963, 1986) introduced the terms ‘Little Science’ and ‘Big Science’ in his discussion of the pervasive presence of exponential growth in all areas of developing science. He was the first to apply quantitative measurement to the progress of science (scientometrics).

It is clear that very large-scale facilities are having an increasing impact on science. One measure of this is the award of Nobel Prizes. To demonstrate the value of large facilities in astronomy (Ekers, 2010) plotted the scale of Nobel prize winning discoveries in astronomy as a function of time (see Fig. 1.2). This provides an independent way of assessing the increasing importance of the scale of the facility used to make the discovery. Large facilities like Hubble Space Telescope and the Laser Interferometer Gravitational-Wave Observatory (LIGO) are the ones that currently dominate Nobel Prize discoveries.

Fig. 1.2

Scale of Nobel Prize projects in experimental astronomy as a function of discovery date. The vertical axis is a logarithmic estimate of the project scale in arbitrary units. Updated by the authors from Ekers (2010)

Innovation in technology and growth in its capabilities led to the continuous stream of new discoveries. However, exponential growth in the capability of a new technology, with “Moore’s Law” as applied to semi-conductor devices as the classic example, cannot continue indefinitely and will plateau when a ceiling is reached, usually due to physical limitations, but sometimes due to finite funding or human resources. At this time either a new technology will be needed to continue the exponential and enable a new instrument or telescope, or an evolution from “little” to “big” science will be required to increase the resources to pay for increased instrument/telescope capability. This entails resources moving from local research institutes to national facilities and finally to global big science. Ekers (2010) shows how the development of astronomical facilities has followed this same trend from ‘Little Science’ to ‘Big Science’ as a field matures, but there are significant differences between the ‘Big Science’ culture in Physics and in Astronomy as we discuss briefly later in this Introduction.

As the scale of the projects developed to exploit the new technologies grew, the term “Mega-Science Project” was coined to categorise them. A more apt term is “Science Mega-Project” to emphasise the large-scale nature of the project required to carry out the desired science research. In recent years in astronomy, an additional descriptive term “Transformational Science” has been added to categorise what Big Science and Science Mega-Projects are expected to contribute to human understanding. A common phrase now used to promote a new, large telescope concept such as the SKA, is that it will “transform our understanding of the universe”. While such a slogan may appear trite, it does accurately capture the aspiration of such projects and their scientific user communities.

1.5 Complexities of Science Mega-Projects

Global science mega-projects are particularly complex to deliver, especially in cases where no single partner is dominant as is the case for SKA. They involve multiple nations and multiple players including large and small research organisations and universities, large and small industrial organisations, and governments and funding agencies, and they can involve inter-disciplinary research with different scientific requirements on the instrument. The various national and regional motivations for participating in the SKA project are discussed in Sect. 11.3.8.

Many challenges face a global science project, and in the SKA case not all the challenges were fully recognised by the early proponents. In the various countries taking part there are different funding cycles, different prior investment histories, different scientific interests, different levels of competence in technology development, different decision-making cultures, and different cultures of interaction between science and government. National and regional funding may be contingent on “juste retour/fair return” regarding industrial spin-off or location of the main or supporting facilities. Political considerations also influence some decisions on concept and location.

Holding a global collaboration together in the face of these challenges and complexity requires a clear and shared vision of the final goal, and good governance. While scientific questions are borderless, funding and legal frameworks are not. Experience shows that a lasting collaboration is based on mutual advantage, and good governance will seek to optimise that advantage for all parties. At the project management level, leaders need to understand and respect the agendas of the individuals and institutions involved.

1.6 Historical Funding Environment

When proposals for future radio astronomy developments were included on the agendas of the OECD Mega Science (Global Science) Forum meetings starting in 1996, science policy advisors in a number of governments in the OECD member countries were interested in information on the global level of funding on astronomy, and in particular in radio astronomy infrastructure. This interest continued throughout the following decade.

Figure 1.3 was compiled in 2005 to illustrate the capital funding levels for all ground- and space-based research facilities in astronomy. This does not include any estimate of the total funding support for research in astronomy, merely the investment in infrastructure. For the space-based category the funding is divided into the two distinctly different components, one focussing on exploration of the planets in the solar system, the other on observations of objects outside the solar system at wavelengths not accessible from Earth (X-ray, ultraviolet and infra-red). By 2020 funding commitments over the previous 15 years for the construction of the SKA Precursor and Pathfinder telescopes and the first phase of the SKA was roughly about €1.5 billion (in 2005 units). This indicates a fairly flat funding rate over the past two decades of about €100 million per year.

Fig. 1.3

The international funding environment for astronomy facilities from 2000–2005

1.7 The Culture of Radio Astronomy

Astronomy is a technique-oriented observational science. (Sullivan, 2009) in Chap. 17.4 discusses the significance of this distinction and calls radio astronomy a “techno-science”.

Astronomers cannot, in general, carry out experiments following the traditional scientific method. There is only one universe to observe. They can only observe it, and then interpret these observations, using a variety of instruments at ‘observatories’; these often have longer lifetimes than the individual instruments they host. We return to the observatory concept in Sect. 11.6. Compared to particle physics, for example, where recent mega-science facilities are used by large teams brought together by the desire to address a small number of key questions, one of the distinguishing characteristics of the astronomy culture is that multiple groups of astronomers use flexible instruments for a diverse range of experiments. As discussed in Chap. 5 and Sect. 11.4.2, this difference generated some tension in the radio astronomy community because the notion of an SKA with a few well-defined and focussed science cases was not consistent with a more general-purpose instrument that would support a diverse range of science, including exploration of the unknown. There were also tensions arising from the engineering design compromises needed for different science cases (see Sect. 5.7).

This cultural difference with respect to high energy physics was significant, because in the minds of many governments and funders, high energy physics was the archetypal field of big science. It was seen as a natural example to follow when areas like radio astronomy moved into the same scale of investments. This difference has also impacted the way the SKA concept developed at low frequencies. The main scientific and technical driver of the low frequency component of the SKA is the detection of the Epoch of Reionisation in the early universe (see Chap. 5) which is a classic-style scientific experiment rather than being one of the programs for a low-frequency observatory. In radio astronomy, input on telescope design and data handling from collaborating organisations in many countries is taken for granted. There are even sets of observations such as those with the highest angular resolution Very Long Baseline Interferometers including the Event Horizon Telescope (see Sect. 2.3) or the International Pulsar Timing Array (Manchester, 2013) which are only possible through international collaboration among diverse groups with instruments straddling the globe. Sharing of ideas, staff exchanges, and the open skies policies mentioned below, are the norm. It was natural for the radioastronomy groups from around the world to be thinking of an international collaboration to jointly build a very large telescope like the SKA, rather than competing.

Another important aspect of the radio astronomy culture is the close interactions between scientists and engineers. These interactions were a critical element for the development of the SKA as design tradeoffs had to be made between scientific opportunities and practical solutions. This has always been part of the culture in radio astronomy which itself was born from the engineering innovations of the early pioneers.

Open access to radio astronomy facilities for scientists with good projects independent of institutional or national affiliation has always been part of the radio astronomy culture and is seen as the most effective way to make scientific progress. This concept has become known as “Open Skies” and is employed in many radio observatories around the world (see Sect. 4.2).

1.8 This Book

With the context sketched above in mind, subsequent chapters go on to examine the instrumental heritage of the SKA and the emergence of the SKA concept, the global collaboration and governance structures put in place during the journey from working group in 1993 to legal entity in 2011, the evolution of the science case and its presentation, the twists and turns of telescope design, the decade-long story of telescope site selection from 2001 to 2012, the two SKA headquarters selection rounds in 2007 and 2011, and efforts to engage industry in the SKA. It concludes with some thoughts on SKA as a science mega-project, reflections on key issues that arose, and decisions made.

At the time of writing (2023), a decade after the end of the period covered in this book, the first phase of SKA construction by the SKA Observatory, a new Inter-Governmental Organisation, is underway. This is the culmination of the decades of global collaboration at government, institute and personal levels on SKA research and development and planning by hundreds of scientists, engineers and administrators in many countries.