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05-30-2017, Duryea, PA

World’s largest telescope to use SCHOTT mirror substrates for window to distant galaxies

The gigantic 39-meter primary mirror for the Extremely Large Telescope (ELT) will soon be made up of 798 ZERODUR® glass-ceramic components. SCHOTT is set to deliver a total of 949 mirror substrates made of ZERODUR® to the European Southern Observatory (ESO). Thanks to SCHOTT’s investment of more than $11 million, the company is well prepared to respond to the increased demand.
Signing Ceremony, Dr. Thomas Westerhoff (Director Strategic Marketing ZERODUR® at SCHOTT Advanced Optics), Prof. Tim de Zeeuw (ESO Director General), Christoph Fark (Executive Vice President of SCHOTT Advanced Optics) - Photo: ESO
Signing Ceremony, Dr. Thomas Westerhoff (Director Strategic Marketing ZERODUR® at SCHOTT Advanced Optics), Prof. Tim de Zeeuw (ESO Director General), Christoph Fark (Executive Vice President of SCHOTT Advanced Optics) - Photo: ESO
Chile’s Atacama Desert is home to the ESO’s Extremely Large Telescope – or ELT – the world’s largest telescope. With a planned launch in 2024, the telescope will deliver images of unprecedented quality, helping astronomers discover unexplored galaxies, study exoplanets, and investigate other objects and phenomena across the universe. The main function of the gigantic primary mirror, known simply as “Mirror 1” or “M1,” is to collect light from the cosmos and transfer it via additional mirrors onto the observatory’s scientific instruments. The international technology group SCHOTT has just been awarded the contract to provide the substrate components – 798 hexagons made of ZERODUR® glass ceramic for the assembly of the enormous primary mirror. With its use in the world’s largest telescope, ZERODUR®’s reputation as the standard material in substrates has been reconfirmed.

SCHOTT has already provided substrates for smaller ELT mirrors
After the first ZERODUR® components for the segmented fourth mirror (M4) left SCHOTT’s Mainz production facility in 2016, the next order followed at the beginning of 2017 for the substrates to be used in the secondary (M2) and tertiary mirrors (M3). Thus, the first four ELT substrates will soon be equipped with ZERODUR®.

“We are very proud to play a significant role in the ELT project. We are also extremely pleased that because of our know-how, distant galaxies can finally be viewed with unprecedented sharpness,” said Dr. Frank Heinricht, chairman of the board at SCHOTT AG. “The ESO order for the production of substrates for the ELT primary mirror represents the single largest contract for astronomical projects that SCHOTT has ever been awarded. At our ZERODUR® competency center in Mainz, we have invested more than 10 million Euros over the last several years to secure and expand our excellent market position for the future.”

Christoph Fark, Executive Vice President of Advanced Optics at SCHOTT said, “Providing more than 900 ZERODUR® panels for the hexagons, with the start of series production in 2020, will place a high workload on the manufacturing facility at our Mainz headquarters. However, with the addition of a second ZERODUR® melting tank, which was recently commissioned, we are certain that we will effortlessly meet the continuing high demand for the material. In addition, we have added more cutting-edge CNC machines at our facility that help fulfill growing customer requirements.”

Substrates made in Germany
The casting and grinding of the 949 ELT substrate elements takes place at SCHOTT headquarters in Mainz, Germany, while the polishing and coating of them is handled by the French company Reosc, which has many years of experience in working with ZERODUR®. The substrates for the primary mirror are scheduled to be gradually delivered from now through March 2024.

When it comes to the production of materials for astronomical applications, SCHOTT has accumulated decades of experience. Since 1903, the company, which is part of the Carl Zeiss Foundation, has been providing substrates in various dimensions for use in both space telescopes and terrestrial ones. In 2018, ZERODUR® will celebrate the 50th anniversary of its development. The de facto standard for substrates has proven its reliability in numerous mega telescopes around the world, including the Very Large Telescope, which is positioned not far from the ELT and has a primary mirror containing four ZERODUR® segments, with an overall diameter of 8.2 meters. The VLT is also known as having the world’s largest substrate cast as single unit.

Additional information about ELT
Further information focusing entirely on the fascinating astronomical project can be found at SCHOTT’s microsite, The site is home to interesting data and facts all about ELT as well as exclusive insights on the product properties and the production of ZERODUR®.

SCHOTT goes ELT – Microsite:
European Southern Observatory (ESO):
The Extremely Large Telescope:
A Window into Distant Galaxies: 
ELT’s optical system and how ZERODUR® contributes to it. Photo: ESO / Modifications by SCHOTT
ELT’s optical system and how ZERODUR® contributes to it. Photo: ESO / Modifications by SCHOTT
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Gregory FCA on behalf of SCHOTT
Mike Lizun
Phone: 610-642-1435
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Rina Della Vecchia
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Elmsford, NY 10523
Phone: 914-831-2286
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