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ASTRON astronomy groups focus on LOFAR and SKA

Recently, the astronomy group within the A&O department of ASTRON went through a reformation: instead of several focus groups, it now consists of two groups: the LOFAR Science Group and the SKA Science Group. The LOFAR Science Group is led by André Offringa, the SKA Science Group by Joe Callingham.

Published by the editorial team, 21 February 2023

So why this change? “We felt that the old focus groups led, ironically, to a lack of focus,” Callingham explains. “The astronomers within the groups felt too many boundaries, while they tend to work across boundaries. So, the old setup felt a bit restrictive to them.”

Right now, ASTRON is – in terms of science – invested in two major telescopes: LOFAR and SKA. Therefore, it makes sense to make these two telescopes the focus of the two astronomy groups, even though the walls between the groups are very permeable. That also makes sense, given the fact that LOFAR is a pathway project for SKA and, right now, the SKA itself does not produce any scientific data yet.

However, that does not mean that astronomers within the LOFAR Science Group can only work with LOFAR, and those within SKA Science Group only with SKA. Nevertheless, their focus lies close to those instruments.

Joe Callingham. (Photo: Center for Astrophysics: Harvard, Smithsonian)

Forward focus

But what is the point of having an SKA Science Group if there isn’t any SKA science yet?

Callingham: “We have a more forward focused position for SKA. My role as head of this group is to make sure our science is represented, to make sure the telescope is commissioned and built in a way that we can do our science with it. We make sure that ASTRON is integrated heavily into SKA so that we can contribute to it.”

And ASTRON has a head start in this, since the data reduction required for LOFAR is similar to what will need to be done for SKA-Low. If an astronomer wants to do SKA-Low science now, they will be using LOFAR.


LOFAR in the meantime is undergoing a major hardware and software upgrade. Offringa: “LOFAR has two main observing modes: beamforming mode and imaging mode. In beamforming mode objects such as pulsars can be observed. The imaging mode is suited for observing the Epoch of Reionization or for localizing new, unknown phenomena. Thanks to the upgrade we can calibrate to higher levels, which means more accurate data. And we can also do more than one observation simultaneously, something that is not possible right now.”

The biggest challenge in this is not so much being able to do more observations but handling the larger amounts of data this produces. Offringa: “The big challenge is the increased data volume. Here lies one of the challenges we still have to solve to some level. Long-baseline surveys with the HBA’s take about a month of computing time to create the 10 gigapixel image for one observation. Ultimately, we would like to do these observations for all the sky. That means we need to write faster algorithms. Of course, we need the help of the I&S department for that, but we are optimistic that it is possible.”

Offringa’s optimism does not come out of the blue. “With LOFAR, we have made huge improvements since we’ve started operations with it. About a year ago imaging was by far the most expensive operation; the imaging part of the telescope took about 1.5 week. So, we focused on improving that part and now imaging calculations take around a day: it is that much better.”

André Offringa. (Photo: ASTRON)

Good deal

The expertise and experience with LOFAR, and the expertise with the WSRT – which is comparable to the techniques that SKA-Mid uses – are exactly the reasons Callingham is convinced that ASTRON will do very well with SKA. “The Dutch radio community with LOFAR and SKA will create exciting and never before achievable science opportunities.”

Callingham is certain that at least for the first couple of years of operation of SKA-Low, the ASTRON community will be the expert users. “The best SKA image will hopefully be made by someone in this building, or someone who has been trained in this building.”

So, what is next for both groups? Callingham: “For us, it’s making sure we’re integrated into the SKA community, making sure we’re heard and that things are built correctly for our own science groups.”

Offringa is already looking beyond LOFAR2.0. “Although first of course we need to get our science out of LOFAR2.0, we are already thinking very seriously what to do with LOFAR after that. Currently it is a world leading instrument, the biggest of its class in the world. And we are going to make sure it stays that way.”



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