With construction of the Square Kilometre Array Observatory (SKAO) under way, director-general Philip Diamond describes what it took to launch the largest radio telescope ever built and what its key science goals are.
Having led the SKAO for almost a decade, how did it feel to get the green light for construction in June this year?
The project has been a long time in gestation and I have invested much of my professional life in the SKA project. When the day came, I was 95% confident that the SKAO council would give us the green light to proceed, as we were still going through ratification processes in national parliaments. I sent a message to my senior team saying: “This is the most momentous week of my career” because of the collective effort of so many people in the observatory and across the entire partnership over so many years. It was a great feeling, even if we couldn’t celebrate properly because of the pandemic.
What will the SKA telescopes do that previous radio telescopes couldn’t?
The game changer is the sheer size of the facility. Initially, we’re building 131,072 low-frequency antennas in Western Australia (“SKA-Low”) and 197 15 m-class dishes in South Africa (“SKA-Mid”). This will provide us with up to a factor of 10 improvement in our ability to see fainter details in the universe. The long-term SKA vision will increase the sensitivity by a further factor of 10. We’ve got many science areas, but two are going to be unique to us. One is the ability to detect hydrogen all the way back to the epoch of reionisation, also called the “cosmic-dawn”. The frequency range that we cover, combined with the large collecting area and the sensitivity of the two radio telescopes, will allow us to make a “movie” of the universe evolving from a few hundred million years after the Big Bang to the present day. We probably won’t see the first stars but will see the effect of the first stars, and we may see some of the first galaxies and black holes.
We put a lot of effort into conveying the societal impact of the SKA
The second key science goal is the study of pulsars, especially millisecond pulsars, which emit radio pulses extremely regularly, giving astronomers superb natural clocks in the sky. The SKA will be able to detect every pulsar that can be detected on Earth (at least every pulsar that is pointing in our direction and within the ~70% of the sky visible by the SKA). Pulsars will be used as a proxy to detect and study gravitational waves from extreme phenomena. For instance, when there’s a massive galaxy merger that generates gravitational waves, we will be able to detect the passage of the waves through a change in the pulse arrival times. The SKA telescopes will be a natural extension of existing pulsar-timing arrays, and will be working as a network but also individually.
Another goal is to better understand the influence of dark matter on galaxies and how the universe evolves, and we will also be able to address questions regarding the nature of neutrinos through cosmological studies.
How big is the expected SKA dataset, and how will it be managed?
It depends where you look in the data stream, because the digital signal processing systems will be reducing the data volume as much as possible. Raw data coming out of SKA-Low will be 2 Pb per second – dramatically exceeding the entire internet data rate. That data goes from our fibre network into data processing, all on-site, with electronics heavily shielded to protect the telescopes from interference. Coming out from there, it’s about 5 Tb of data per second being transferred to supercomputing facilities off-site, which is pretty much equivalent to the output generated by SKA-Mid in South Africa. From that point the data will flow into supercomputers for on-the-fly calibration and data processing, emerging as “science-ready” data. It all flows into what we call the SKA Regional Centre network, basically supercomputers dotted around the globe, very much like that used in the Worldwide LHC Computing Grid. By piping the data out to a network of regional centres at a rate of 100 Gb per second, we are going to see around 350 Pb per year of science data from each telescope.
And you’ve been collaborating with CERN on the SKA data challenge?
Very much so. We signed a memorandum of understanding three years ago, essentially to learn how CERN distributes its data and how its processing systems work. There are things we were able to share too, as the SKA will have to process a larger amount of data than even the High-Luminosity LHC will produce. Recently we have entered into a further, broader collaboration with CERN, GÉANT and PRACE [the Partnership for Advanced Computing in Europe] to look at the collaborative use of supercomputer centres in Europe.
SKAO’s organisational model also appears to have much in common with CERN’s?
If you were to look at the text of our treaty you would see its antecedents in those of CERN and ESO (the European Southern Observatory). We are an intergovernmental organisation with a treaty and a convention signed in Rome in March 2019. Right now, we’ve got seven members who have ratified the convention, which was enough for us to kick-off the observatory, and we’ve got countries like France, Spain and Switzerland on the road to accession. Other countries like India, Sweden, Canada and Germany are also following their internal processes and we expect them to join the observatory as full members in the months to come; Japan and South Korea are observers on the SKAO council at this stage. Unlike CERN, we don’t link member contributions directly to gross domestic product (GDP) – one reason being the huge disparity in GDP amongst our member states. We looked at a number of models and none of them were satisfactory, so in the end we invented something that we use as a starting point for negotiation and that’s a proxy for the scientific capacity within countries. It’s actually the number of scientists that an individual country has who are members of the International Astronomical Union. For most of our members it correlates pretty well with GDP.
Is there a sufficient volume of contracts for industries across the participating nations?
Absolutely. The SKA antennas, dishes and front-ends are essentially evolutions of existing designs. It’s the digital hardware and especially the software where there are huge innovations with the SKA. We have started a contracting process with every country and they’re guaranteed to get at least 70% of their investment in the construction funds back. The SKAO budget for the first 10 years – which includes the construction of the telescopes, the salaries of observatory staff and the start of first operations – is €2 billion. The actual telescope itself costs around €1.2 billion.
Why did it take 30 years for the SKA project to be approved?
Back in the late 1980s/early 1990s, radio astronomers were looking ahead to the next big questions. The first mention of what we call the SKA was at a conference in Albuquerque, New Mexico, celebrating the 10th anniversary of the Very Large Array, which is still a state-of-the-art radio telescope. A colleague pulled together discussions and wrote a paper proposing the “Hydrogen Array”. It was clear we would need approximately one square kilometre of collecting area, which meant there had to be a lot of innovation in the telescopes to keep things affordable. A lot of the early design work was funded by the European Commission and we formed an international steering committee to coordinate the effort. But it wasn’t until 2011 that the SKA Organisation was formed, allowing us to go out and raise the money, put the organisational structure in place, confirm the locations, formalise the detailed design and then go and build the telescopes. There was a lot of exploration surrounding the details of the intergovernmental organisation – at one point we were discussing joining ESO.
Building the SKA 10 years earlier would have been extremely difficult, however. One reason is that we would have missed out on the big-data technology and innovation revolution. Another relates to the cost of power in these remote regions: SKA’s Western Australia site is 200 km from the nearest power grid, so we are powering things with photovoltaics and batteries, the cost of which has dropped dramatically in the past five years.
What are the key ingredients for the successful management of large science projects?
One has to have a diplomatic manner. We’ve got 16 countries involved all the way from China to Canada and in both hemispheres, and you have to work closely with colleagues and diverse people all the way up to ministerial level. Being sure the connections with the government are solid and having the right connections are key. We also put a lot of effort into conveying the societal impact of the SKA. Just as CERN invented the web, Wi-Fi came out of radio astronomy, as did a lot of medical imaging technology, and we have been working hard to identify future knowledge-transfer areas.
It also would have been much harder if I did not have a radio-astronomy background, because a lot of what I had to do in the early days was to rely on a network of radio-astronomy contacts around the world to sign up for the SKA and to lobby their governments. While I have no immediate plans to step aside, I think 10 or 12 years is a healthy period for a senior role. When the SKAO council begins the search for my successor, I do hope they recognise the need to have at least an astronomer, if not radio astronomer.
I look at science as an interlinked ecosystem
Finally, it is critical to have the right team, because projects like this are too large to keep in one person’s head. The team I have is the best I’ve ever worked with. It’s a fantastic effort to make all this a reality.
What are the long-term operational plans for the SKA?
The SKA is expected to operate for around 50 years, and our science case is built around this long-term aspiration. In our first phase, whose construction has started and should end in 2028/2029, we will have just under 200 dishes in South Africa, whereas we’d like to have potentially up to 2500 dishes there at the appropriate time. Similarly, in Western Australia we have a goal of up to a million low-frequency antennas, eight times the size of what we’re building now. Fifty years is somewhat arbitrary, and there are not yet any funded plans for such an expansion, but the dishes and antennas themselves will easily last for that time. The electronics are a different matter. That’s why the Lovell Telescope, which I can see outside my window here at SKAO HQ, is still an active science instrument after 65 years, because the electronics inside are state of the art. In terms of its collecting area, it is still the third largest steerable dish on Earth!
How do you see the future of big science more generally?
If there is a bright side to the COVID-19 pandemic, it has forced governments to recognise how critical science and expert knowledge are to survive, and hopefully that has translated into more realism regarding climate change for example. I look at science as an interlinked ecosystem: the hard sciences like physics build infrastructures designed to answer fundamental questions and produce technological impact, but they also train science graduates who enter other areas. The SKAO governments recognise the benefits of what South African colleagues call human capital development: that scientists and engineers who are inspired by and develop through these big projects will diffuse into industry and impact other areas of society. My experience of the senior civil servants that I have come across tells me that they understand this link.