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June 28, 2024
Today, ESO’s Extremely Large Telescope (ELT) took another step towards on-time completion. At ESO’s headquarters in Garching, Germany, the organisation signed a contract with Glyndwr Innovations Limited (a wholly owned subsidiary of the University of Wrexham) in Wales, United Kingdom, for the production of the preliminary mirror for the ELT’s M5. In the event of delays in production of the M5, it will be used as the fifth mirror in the ELT’s innovative five-mirror design when the telescope sees first light.
The M5 mirror is a crucial part of the design of the ELT’s adaptive optics system: it will adjust its position up to 10 times per second without bending to allow the telescope to obtain the sharpest possible images. Like the rest of the ELT, the M5 pushes technology to the limit: at 2.7 by 2.2 meters, it is the largest mirror ever produced made from silicon carbide, a very rigid but very light material. The M5 block, the molded piece of material that is then polished to become the mirror, was recently completed. Six segments of silicon carbide were welded together and then covered with a very thin layer of the same material, deposited atom by atom. This deposition layer was necessary to be able to polish the mirror to a precision less than one-hundredth the thickness of a human hair, the next stage of the manufacturing process.
Since such a large silicon carbide mirror has never before been produced, with such strict polishing requirements, there are risks associated with its manufacture. Specifically, the ELT team at ESO has deduced that the current production risk is high enough to potentially delay the schedule of the entire ELT project.
To ensure that the ELT is ready to observe the skies before the end of the decade, ESO has partnered with Glyndwr Innovations to create an alternative M5 mirror, called the M5 Preliminary Mirror, which will be used to put the telescope into operation and demonstrate its performance. This mirror will be made up of a single piece of the more conventional ZERODUR©, a glass-ceramic material that has been used in astronomical telescopes for decades. Because the properties of ZERODUR© are different from those of silicon carbide, this preliminary mirror will be smaller than the M5, 2.2 by 1.8 meters, and will not be able to demonstrate the telescope’s full adaptive optics capabilities. However, it is an excellent substitute for the first months of operation of the ELT, when various observations will be made to test and calibrate its various systems.
The Glyndwr Innovations team now has the exciting task of grinding and polishing the preliminary M5 mirror block (which is being produced by German company SCHOTT), as well as assembling the interfaces onto the mirror and delivering the finished product safely and on time to the ELT construction site at Cerro Armazones in the Atacama Desert in Chile. Glyndwr Innovations will also design, manufacture and supply the ancillary equipment required to handle, store and transport the mirror, and develop a test rig to accurately measure the shape of the mirror during manufacture.
When the ELT begins observations later this decade, it will be the world’s largest eye on the sky, and is expected to advance our understanding of dark energy, exoplanets and the early epochs of the Universe.
Contacts
Barbara Ferreira
ESO Media Manager
Garching near München, Germany
Tel: +49 89 3200 6670
Email: [email protected]
