Coating the Extremely Large Telescope mirrors with silver | ELT Updates

ESO’s Extremely Large Telescope (ELT) will have a 39-m wide primary mirror, comprised of 798 hexagonal segments working together with manometric accuracy. The segments are coated with a thin layer of silver to reflect the light from the cosmos. But how does the coating process work? In this video we take you on a behind-the-scenes tour of the ELT’s Technical Facility in Chile where this process takes place.
Learn more about the ELT: elt.eso.org/
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Credits:
ESO
Directed by: Angelos Tsaousis and Martin Wallner.
Editing: Angelos Tsaousis.
Written by: Barbara Ferreira.
Narration: Graeme Mackenzie/voicearchive
Music: Jon Kennedy - Inner Resting, Andrea Michele Vincenti - New Visions.
Web and technical support: Gurvan Bazin and Raquel Yumi Shida
Footage and photos: ESO / Luis Calçada, Angelos Tsaousis, Jose Porte,
Max Nadjar, Boris Häußler, Herbert Zodet, Juan Carlos González Herrera,ACe/Cimolai.
More information and download options: www.eso.org/pu...

[@EmilianoGirina]

The level of technology and engineering behind this telescope is amazing. I can't wait to see how much, and what kind of science it can produce.

[@jaspyjiindust.9227]

The world needs to cooperate more!

[@bazpearce9993]

Looking forward to see what this beastie can do.

[@mariadaluzmoutinho5701]

Incrível a minúcia e cuidado...o engenho e arte para ver o reflexo mágico, a prata para moldar de forma nítida e mais brilhante que nunca e vamos sorrir! Que história épica ...mais uma etapa de algo maravilhoso e extraordinário do ELT!!

[@Nivola1953]

I used to work in a microelectronics wafer fab, my job included the process of coating the wafers with thin layers of alloys of Al/Si that will provide the electrical connections. I’m very surprised at the little attention paid in the video to the substrate cleaning process, because I remember the trouble caused by any trace of contaminants, especially organic compounds, which were thoroughly removed with acids baths followed by an extensive rinsing and drying process. I guess you used a sputtering type of deposition, I’m really curious about who built your coating tool.

[@ImieNazwiskoOK]

With the amount of mirrors this telescope will need, I think it can be safely considered a literal factory for mass production(and not some manufacturing site for a one off very specific thing). Out of curiosity what is the goal(it seems to currently still be in development so it will probably change) for time needed to make a single mirror?

[@sanjaygatne1424]

केव्हा पहिले छायाचित्र बघायला मिळेल असे झाले आहे. खुप खुप शुभेच्छा. दुर्बीण लवकर तयार व्हावी.

[@ESOobservatory]

Hi! First light is currently planned for 2028.

[@ptonpc]

This is what happens when humans work together for the betterment of the world.

[@ESOobservatory]

Yes! It takes a lot people with very different backgrounds and a lot of dedication to make something like this happen.

[@ValidatingUsername]

@@ESOobservatoryMore importantly it is one of if not the last step in training the next generation of graduates in the field to produce what they have specialized into as their educational career progressed. With that being said we can slow down the pipeline now that we have JWST and LHC focusing on replacement and a telescope for 75 years from now 😊

[@danbaker7191]

When imaging, are all segments adjusted in real-time? Is there a web pointer for details how the surface shape control system works?

[@BanterMaestro2-y9z]

The actuator structures that both support and deform the main-mirror segments are called _whiffle trees._ Today's large, segmented telescope mirrors all use them. They are used to compensate the overall mirror shape for sag and thermal effects, but the wavefront correction is typically done at the secondary mirror because its much smaller size allows for a much shorter response time measured in milliseconds.

[@mael1515]

Zeiss makes these?

[@ESOobservatory]

There are different companies involved. The blanks are made of Zerodur, and they're cast by SCHOTT in Germany. They're later polished by Safran Reosc in France. At Safran they also install the blanks on supports manufactured by VDL ETG Projects B.V. in the Netherlands. Once ESO verifies that the segments are ok they're shipped to Chile, where we coat them with silver following the workflow explained in this video.

[@mael1515]

@@ESOobservatory thank you for this detailed answer! I am fascinated how far engineering has pushed the envelope.

[@andreamichelevincenti]

💜🎵💜

[@rjung_ch]

👍💪✌

[@anonimes4005]

well... thats a big mirror