Press release
June 27, 2024
The European Southern Observatory’s Extremely Large Telescope (ESO’s ELT), which is being built in the Chilean Atacama Desert, is one step closer to completion. The German company SCHOTT has given the go-ahead to the last of the 949 segments ordered for the telescope’s primary mirror (M1). With a diameter of more than 39 meters, M1 will be the largest mirror ever built for a telescope.
Because it is too large to be a single piece of glass, the primary mirror, M1, will be composed of 798 hexagonal segments, each about five centimeters thick and 1.5 meters wide, which will work together to collect tens of millions of times more light than the human eye. An additional 133 segments have been manufactured to facilitate maintenance and coating of the segments once the telescope is operational. ESO has also acquired 18 spare segments, bringing the total number to 949.
The M1 blanks – pieces of material that are shaped and then polished to become mirror segments – are made of ZERODUR©, a low-expansion glass-ceramic material developed by SCHOTT and optimized for the ranges extreme temperatures that occur at the ELT location, in the Chilean Atacama Desert. This company has also manufactured the blanks for three other ELT mirrors (M2, M3 and M4) at its facilities in Mainz, Germany.
“What ESO entrusted to SCHOTT is more than ZERODUR©“says Marc Cayrel, Head of Optomechanics at the ELT at ESO. “In close collaboration with ESO, SCHOTT fine-tuned each of the production steps, adapting the product to meet, and often exceed, the demanding requirements of the ELT. The excellent quality of the blanks has been maintained throughout the entire mass production of the more than 230 tons of this high-performance material. ESO is therefore very grateful for the professionalism of the qualified teams at SCHOTT, our trusted partner.”.
Thomas Werner, ELT project manager at SCHOTT, says: “Our entire team is delighted to conclude what has been the largest single order for ZERODUR® in our company’s history. For this project, we successfully completed mass production of hundreds of ZERODUR® mirror substrates, when we normally have a one-piece operation. It has been an honor for all of us to play a role in shaping the future of astronomy“.
Once manufactured, all segments follow a multi-stage international journey. After a slow cooling and heat treatment sequence, the surface of each blank is shaped by ultra-precise grinding at SCHOTT. The blanks are then transported to the French company Safran Reosc, where each one is cut into a hexagon shape and polished to a precision of 10 nanometers over the entire optical surface, meaning that irregularities in the mirror surface will be less than one thousandth of the width of a human hair. Also participating in the work carried out on the M1 segment assemblies: the Dutch company VDL ETG Projects BV, which produces the segment supports; the Franco-German consortium FAMES, which has developed and is finalizing the manufacture of the 4,500 nanometer precision sensors that monitor the relative position of each segment; the German company Physik Instrumente, which designed and manufactures the 2,500 actuators capable of positioning the segment with nanometric precision; and the Danish DSV, which is responsible for transporting the segments to Chile.
Once polished and assembled, each M1 segment is shipped across the ocean to reach the ELT technical facilities at ESO’s Paranal Observatory in the Atacama Desert, a 10,000 kilometer journey that has already seen more than 70 segments completed. M1. At Paranal, a few kilometers from the ELT construction site, each segment is coated with a layer of silver to make it reflective, after which it will be carefully stored until the telescope’s main structure is ready to receive them.
When it begins operations later this decade, ESO’s ELT will be the world’s largest eye to the sky. It will address the greatest astronomical challenges of our time and make discoveries still unimaginable.
Additional Information
The European Southern Observatory (ESO) makes available to the global scientific community the necessary means to reveal the secrets of the Universe for the benefit of all. We design, build and operate cutting-edge ground-based observatories – used by the astronomical community to address exciting questions and spread the fascination of astronomy – and promote international collaboration in astronomy. Established as an intergovernmental organization in 1962, today ESO is supported by 16 Member States (Germany, Austria, Belgium, Denmark, Spain, Finland, France, Ireland, Italy, Netherlands, Poland, Portugal, United Kingdom, Czech Republic, Sweden and Switzerland), together with Chile, the host country, and with Australia as a strategic partner. ESO’s headquarters and its planetarium and visitor center, the ESO Supernova, are located near Munich, Germany, while the Chilean Atacama Desert, a wonderful place with unique conditions for observing the sky, is home to our telescopes. ESO operates three observation sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope together with its Very Large Telescope Interferometer (VLTI), and survey telescopes such as VISTA. Also at Paranal, ESO will host and operate the Cherenkov Telescope Array South, the largest and most sensitive gamma-ray observatory in the world. At Chajnantor, together with international partners, ESO operates ALMA, a facility that observes the skies in the millimeter and submillimeter range. On Cerro Armazones, near Paranal, we are building “the world’s largest eye for looking at the sky”: the ESO Extremely Large Telescope (ELT). From our offices in Santiago (Chile), we support the development of our operations in the country and are committed to Chilean partners and Chilean society.
Translations of ESO press releases are carried out by members of the ESO Science Outreach Network (ESON), which includes outreach experts and science communicators from all ESO member countries and from other nations.
The Spanish node of the ESON network is represented by J. Miguel Mas Hesse and Natalia Ruiz Zelmanovitch.
Links
Contacts
Barbara Ferreira
ESO Media Manager
Garching near München, Germany
Telephone: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: [email protected]
Elizabeth Harvey
Marketing & Communications – SCHOTT AG
Mainz, Germany
Email: [email protected]
Francisco Rodríguez (Contact for media in Chile)
ESO and European Southern Observatory Science Outreach Network
Telephone: +56-2-463-3151
Email: [email protected]
Connect with ESO on social media
This is a translation of the ESO press release eso2410.
