PrepSKA electrifies Oxford

The annual Square Kilometre Array (SKA) meeting of Work Package 2 (WP2) of the PrepSKA programme took place over the weekend in Oxford, England.

PrepSKA is a preparatory phase building up to the SKA. It is an international programme partly funded by the European Commission.

According to Dr Carolina Odman, a SKA post-doctoral researcher, WP2 is the part of that programme that has to do with the design of the SKA, as well as the way the European Union structures projects they fund. “Each project is decomposed into work packages, which have milestones and deliverables.”

She says: “It is very exciting because this is where some of the new technologies are being developed. Much of the new technology development is taking place in the MeerKAT and Australian SKA pathfinder teams.”

The meeting, Odman says, is a place to share ideas and to compare the latest technological developments for the SKA.

“We can see what has happened elsewhere and we can showcase what we have achieved. The best scientists and engineers are all in one room so we can talk to all of them at once, which is hugely more efficient than travelling around the world to meet them all separately.”

The main purpose is to talk to some of the best scientists in the world and take their feedback into account for MeerKAT, for example, she says.

“At the same time, people come to us to learn about the innovations that come out of South African labs and research institutions.”

In the past, the WP2 meetings have been a place to demonstrate SA's capacity to pioneer new technologies, Odman says.

As well as the WP2 meetings, there have been meetings of the Agencies SKA Group (the national science funding agencies and governments) and the SKA Science and Engineering Committee (SSEC). These are the governing bodies of the international SKA project and SA participates in both.

In terms of the developments in SA's SKA technologies, Odman says that one new low frequency radio telescope called Lofar, has come online in the Netherlands (and in Europe).

“The people behind Lofar have had to solve some technological and infrastructure problems that are relevant for MeerKAT and the SKA.”

She states the specifications and technological requirements for phase one of the SKA are being narrowed down and that enables people to start working on execution plans. “This means that we know better where we should be going.”

According to Odman, SA is playing a leading role in digital signal processing and SKA SA is presenting a concept design for a correlator - the device that combines the signal from all the dishes- that comes out of its collaboration with the Centre for Astronomy Signal Processing and Electronics Research (Casper), based in Berkeley, US.

“The design proposed by the South African team has the advantage that it scales up naturally. From KAT-7 to MeerKAT it is easily extended to the full SKA scale.”

SA, she says, has developed innovative designs for the telescope dishes and the radio antennas and the MeerKAT team is collaborating with teams from the National Radio Astronomy Observatory from the US and Astron in the Netherlands to develop new methods of very fast massively parallel computing.

Judging from the meeting, Odman says SA is as competitive as ever in its bid to host the SKA. “All the site studies are still ongoing and even the site selection criteria as still being finalised.”

One of the things contributing to this is the new MeerKAT design announced last month. The offset design of the MeerKAT dishes was chosen to maximise the performance of the telescope in a regime where it is the most powerful scientifically, Odman says, and she adds MeerKAT will be the best radio telescope to look at neutral hydrogen very far away, in the distant past.

“It will also be the best instrument in the world to measure pulsars very accurately - stars that send radio pulses,” she says.

“In order to carry out those observations, two aspects of the telescope need to be maximised: sensitivity and dynamic range. Sensitivity means it can pick up very faint signals.

“Dynamic range means that while being very sensitive, it must also not easily be blinded. Imagine that you look through a telescope: you'll see stars you could never see with your naked eye but if you point the same telescope at the full moon, you'll hurt your eyes,” Odman points out.

She explains that this is because the dynamic range of our eyes is limited. “We want a telescope that is capable of seeing very faint and very bright at the same time, the equivalent of a faint star next to the full moon!”

Hence, Odman notes, the choice of design for the MeerKAT antennae is in response to the best science the telescope can produced. “That science is reflected in the recent MeerKAT observation announcement available on the site, about five years of observing time have been allocated to research groups around the world.”

The media release says: “Nearly 8 000 hours of observing time were allocated to a proposal to test Einstein's theory of gravity and investigate the physics of enigmatic neutron stars (radio pulsar timing survey), while 5 000 hours were dedicated jointly to two proposals to survey the distant universe with the MeerKAT (the ultra-deep survey of neutral hydrogen gas in the early universe).

“These science objectives also happen to be the prime science drivers for the first phase of the SKA telescope itself, confirming MeerKAT's designation as an SKA precursor instrument."

MeerKAT, Odman says, demonstrates “with flying colours” that SA is capable of building a world-class instrument on an excellent site.

“More than 500 astronomers from around the world responded to the call for observing proposals for MeerKAT, of which about 60 from Africa. This shows that the international community is very keen to use the South African telescope!”

The meeting in Oxford, she notes, has rendered important advances that have been made in establishing the SKA institution, an international central organ that will represent the whole SKA project.

“Many important discussions have taken place during the sessions and on the side for refining the design and technology options for the SKA and MeerKAT.”

SA has also brought substantial expertise on how to calculate how much everything will cost to the table, Odman says. “This is a very difficult exercise and the South African team has developed a very thorough method for costing the SKA.”

She adds that this is not simply a question of knowing how much money is needed to build and run the SKA, saying every possible design will have a different cost attached to it and one of the roles of meetings like these is to find the most cost-effective way of building the SKA: “Get the best science out of the cheapest - but best - quality instrument”.

On the scale of the SKA, Odman remarks, this is not trivial.

Australia has also brought interesting progress to the table, she says. The country has brought a different design that is still under development, she says. “They are focusing on antennae which can see in many directions at the same time but are less sensitive than the antennae for MeerKAT.”

My personal impression, Odman observes, is that this meeting is very fertile from an engineering point of view, “The scientists, managers and engineers find themselves all at the same place at the same time [and] the conversations mutually inspire them and it is very useful to be able to put together all the aspects of the project at once.”

She says each participant's ideas are matched to others' and to practicalities like power and cost.

“It is fascinating to see how the big picture takes shape: the SKA is a huge puzzle of a project with so many aspects, none of which exists independently from the others.”