Building the Irish LOFAR telescope

Birr is about to be at the forefront of astronomy — again. What may seem a quaint and unassuming town in the midlands, Birr, Co. Offaly, is steeped in astronomy history. Today, as the construction of a new telescope nears completion, the town is about to regain its scientific prominence.

In 1842, William Parsons, 3rd Earl of Rosse, began construction of a telescope on his estate which would colloquially come to be known as The Leviathan (a term used in mythology for large sea monsters). Not only was it the largest telescope in the world, it held this title for a staggering 72 years. This fact can be appreciated most in the current era of rapid technological improvements where the best of anything in the world holds that title for weeks rather than years before a better model comes along.

leviathanThe Leviathan telescope on the demesne of Birr castle. (credit: H. Warren)

Parsons was a brilliant man, inventing many of the techniques required for its construction due to its unprecedented size. His efforts were not in vain as, using The Leviathan, he discovered the spiral structure of galaxies – a key landmark in the history of astronomy. Perhaps most impressively, the construction and operation of the instrument was unhindered as the Great Famine decimated the population. First light for the telescope came in 1845 as the country was on the brink of starvation.

Messier51aThe spiral structure of Messier 51a, also known as the Whirlpool Galaxy, was discovered by the 3rd Earl of Rosse. Parsons sketched the structure of this galaxy in 1845.

In 2017, Birr is once again being thrust to the forefront of astronomy with the construction of a LOFAR station. Unlike The Leviathan, which is an optical telescope, LOFAR is a telescope used to detect radio waves arriving from space. LOFAR is a European project that is based in The Netherlands. The telescope is made up of stations which are scattered across the continent.

ILTThe location of the International LOFAR Telescope. (credit: ASTRON)

Using costly super computers and clever mathematics, all of the stations can be used in conjunction to act as one large dish. This is important as the resolving power of a telescope depends on its size. Combining all of the LOFAR stations equates to a telescope effectively the size of Europe. The Irish station marks a major addition to the project: As Ireland is situated on the western fringe of the continent, it will improve the overall resolution of LOFAR.

The LOFAR station in Birr detects radio waves using antennas and so bears little resemblance to the traditional single-dish telescopes. There are two sets of antennas with each being tuned to a different portion of the electromagnetic spectrum. Between the two styles of antenna, LOFAR can detect frequencies from 10 MHz to 240 MHz. The FM radio band lies right in the middle of this and contaminates the signal from space but this and other sources of interference are filtered out prior to analysis.

I-LOFARThe Irish LOFAR station. The Low Band Antennas are on the left and the High Band antennas are on the right. Cables run underground from each antenna to the container  in the middle. (credit: John Quinn)

The build took just several months to complete but initial plans for the €2 million project were formulated over a decade ago. The funding for the telescope has come from a diverse range of sources, including (but not limited to) Science Foundation Ireland, Enterprise Ireland, the Department of Jobs, Enterprise, and Innovation, and many Irish universities.

Getting this project off the ground was a major achievement for all involved, especially given the challenges at funding fundamental physics research in the current climate. LOFAR promises more than just science though — it generates more than 10 TB of raw data per second (or 6,000 episodes of Game of Thrones, which might be more familiar units to some), so manipulating, transporting, and storing this level of information presents the information and communications technology industry with fresh challenges. The timing also couldn’t be better, as big data is pertinent issue at present among technology companies — from start-ups to Google and Amazon.

I was involved in the build along with a group of astrophysicists from around Ireland, whose credentials ranged from students to professors. The first few weeks involved burying many kilometers of delicate coaxial cable. Beneath the surface, the cables are offered some protection against environmental factors (such as temperature changes) and wildlife. We then moved on to building the tiles that house the High Band Antennas. The quasi-modular design of the tiles and the fact that the majority of the components are polystyrene, made assembling the 96 tiles a simple process. The design of the Low Band Antennas was even less complicated, as the antennas did not have to be housed in any tile structure.

HBA_tileThe High Band Antenna tiles were built in the white tent in the background of the image and then laid in place using an excavator. The margin for error for the placement of the tiles was 3 cm.

I will be using the Irish LOFAR station as part of my research when it comes online. I am an astrophysics PhD student at University College Dublin and I examine the relativistic jets emitted by extragalactic super-massive black holes known as active galactic nuclei. I have already made observations of one active galactic nucleus in particular known as 3C 273 using the existing LOFAR telescope and I will extend my analysis to include the Irish station when it is available.

factorA mosaic of radio galaxies that I imaged using LOFAR. At the centre of each structure is thought to be a black hole which is emitting two oppositely-orientated jets of electrons at almost the speed of light. As the electrons collide with the intergalactic medium, they cool and emit low-energy radio waves.

Personally, I find the construction of the Irish LOFAR station to be an interesting venture, even leaving the use of it to one side for the moment. It stands at the unique intersection between phsyics, astronomy, engineering, technology. With the build pretty much done though, it’s time for it to start producing the science. For more information about the Irish LOFAR station, see the Irish LOFAR website.

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