SCHOTT to equip the main mirror of the world’s largest telescope with ZERODUR® glass-ceramic

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, including spares, made of ZERODUR® to the European Southern Observatory (ESO).

SCHOTT to equip the main mirror of the world’s largest telescope with ZERODUR® glass-ceramic
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)
SCHOTT has just been awarded the contract to provide the substrate components for the main mirror of the ELT. 798 hexagons made of ZERODUR® glass-ceramic form the enormous primary “mirror 1” or “M1”. Thus, the reputation of ZERODUR® as the standard material in substrates has been confirmed once again with its use in the world’s largest telescope.


SCHOTT earlier provided substrates for other 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®.


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 Safran-Reosc, which has many years of experience in working with ZERODUR®. The substrates for the primary mirror are scheduled to be gradually delivered through to March 2024.
This artist's video takes the viewer into the dome of ESO's Extremely Large Telescope on Cerro Armazones in northern Chile. It reveals the complex and massive telescope structure and the 39-metre segmented main mirror. The final moments show night falling and the telescope starting work by switching on multiple lasers to create artificial stars high in the atmosphere.