Work starts on E-ELT mirror segments

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Cranfield University has begun work on producing seven of the mirror segments for the European Extremely Large Telescope (E-ELT).

The E-ELT will feature mirror segments machined at Cranfield University
Impression of the E-ELT (image courtesy of ESO)

A ground-based telescope, E-ELT will be 42m in diameter and made up of 1,000 hexagonal segments, each 1.4m wide and 5cm thick. According to Cranfield, the E-ELT will gather 15 times more light than the largest optical telescopes operating today.

Cranfield University claims to be the only university in the UK with the capability to undertake the various stages of the machining process for the mirror segments to the accuracy required.

Designed and developed at Cranfield specifically for realising these mirrors, the BoX (Big OptiX) machine has the ability to grind large optics in a matter of hours. In-depth coverage from The Engineer on the techniques for grinding and polishing optical surfaces can be read here.

The university also completes the process with a final machining phase on the Reactive Atom Plasma Technology (RAPT) machine, which allows final polishing of the surface of the component to an atomic level of accuracy to remove any imperfections of the final surface.

The E-ELT aims to find Earth-like planets around other stars in the ‘habitable zones’ where life could exist. It will perform ‘stellar archaeology’ in nearby galaxies and make fundamental contributions to cosmology by measuring the properties of the first stars and galaxies, as well as probing the nature of dark matter and dark energy.

Prof Paul Shore, head of the Cranfield Precision Engineering Centre, said: ‘At Cranfield we will be measuring the mirrors to ensure their accuracy, then grinding and mounting the feet that support them.

‘They will then be moved to Technium OpTIC (Opto-electronics Technology and Incubation Centre) in North Wales, the location of our Integrated Knowledge Centre in Ultra Precision and Structured Surfaces, where they will be polished to a form accuracy of 25 nanometres.’

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