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Glyndwr scientists exceed polishing specifications for E-ELT telescope mirror

Less than a year after the European Southern Observatory approved plans for the first primary mirror segment of the European Extremely Large Telescope (E-ELT) to be produced at Glyndŵr University St Asaph in Wales, the team has now demonstrated a polishing process that achieved 7.5nm accuracy on the 1.5-metre optics.

The Glyndŵr scientists hope that the success will help them to procure a £200 million contract for mass production of the 798 mirrors that will make up the final primary mirror of the telescope.

The University’s unique polishing process and metrology system was used to produce the measurement, which signifies a world’s first and a major achievement for UK’s optical manufacturing industry, and may open up many UK jobs if the team manage to secure the contract.  

Once completed, the E-ELT will be the largest optical infrared telescope in the world − it will measure 39 metres across and collect 15 times more light than the largest telescopes in operation today. In June, part of the 3,000-metre peak of the Cerro Armazones Mountain in Chile was blasted away in preparation for its construction, which is due for completion in 2022.

The 39m primary mirror will be segmented because it is not feasible to build such a large mirror in one piece, as Professor Walker, Professor of Optics at Glyndŵr University explained: ‘You would not try to buy one enormous tile to go on your bathroom wall; you would buy a box of tiles and put them on the wall. It is exactly the same analogy that these very big telescopes are always segmented.’

Therefore, 798 segments, which are all 1.4m in size, corner to corner, and 50mm in thickness, will make up the primary mirror. 

The metrology measurement of 7.5nm for the second mirror prototype is an improvement on the ESO compliance figure of less than 15nm which Glyndŵr scientists achieved in October 2013. ‘Reaching 7.5nm is a significant achievement by the team here in St Asaph and marks another major milestone for the UK’s optical manufacturing industry,’ said project manager Tony Fox-Leonard. ‘The specifications for the E-ELT primary mirror segments issued by ESO were recognised as severely challenging… by the optical component manufacturing industry. But we did it, and have gone even further in achieving a measurement of 7.5nm – we must now maintain and improve on that standard.’

In order to be able to participate in the £200 million contract to produce all of the segments required for the telescope’s primary mirror, the group are now searching for potential project partners across the globe to collaborate with. It is expected that this would lead to hundreds of jobs being created when the mirrors are mass produced in the UK.

Last year, Chancellor George Osborne committed £88 million towards the construction of the E-ELT, which helped the team produce the mirror. Glyndŵr vice chancellor and chief executive Professor Michael Scott pointed out that the team at St Asaph deserves huge credit for achieving the ESO specification and explained they will now look to contribute to procuring the eventual manufacturing contract for all of the mirrors required for the telescope, securing high technology jobs in Denbighshire, UK.

‘[The team in St Asaph] have helped to put Glyndŵr University on the map and garnered the respect of the global optics industry,’ said Scott. ‘We are all extremely proud of them and would again like to congratulate Tony and his team for their hard work and innovation.’

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Further Information

Glyndŵr University St Asaph



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