Contracts Signed for ELT Mirrors and Sensors

Cover Photo : The optical system of the ELT showing the location of the mirrors

At a ceremony today at ESO’s Headquarters four contracts were signed for major components of the Extremely Large Telescope (ELT) that ESO is building. These were for: the casting of the telescope’s giant secondary and tertiary mirrors, awarded to SCHOTT; the supply of mirror cells to support these two mirrors, awarded to the SENER Group; and the supply of the edge sensors that form a vital part of the ELT’s huge segmented primary mirror control system, awarded to the FAMES consortium. The secondary mirror will be largest ever employed on a telescope and the largest convex mirror ever produced.


Sulutpos.com, Munchen – The construction of the 39-metre ELT, the largest optical/near-infrared telescope in the world, is moving forward. The giant telescope employs a complex five-mirror optical system that has never been used before and requires optical and mechanical elements that stretch modern technology to its limits.

The optical system of the ELT showing the location of the mirrors. This diagram shows the novel 5-mirror optical system of ESO's Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope's giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. Contracts for the casting of the M2 and M3 mirrors, their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters in January 2017. Credit: ESO
This diagram shows the novel 5-mirror optical system of ESO’s Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope’s giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. Contracts for the casting of the M2 and M3 mirrors, their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters in January 2017.

Contracts for the manufacture of several of these challenging telescope components have just been signed by ESO’s Director General, Tim de Zeeuw, and representatives of three industrial contractors in the ESO Member States.

Signatures for contracts with SCHOTT for the ELT M2 and M3 mirror blanks. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (right), signed two contracts with SCHOTT, represented by Christoph Fark, Executive Vice President, for the casting of the ELT's secondary and tertiary mirrors. Credit: ESO/M. Zamani
Signatures for contracts with SCHOTT for the ELT M2 and M3 mirror blanks. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (right), signed two contracts with SCHOTT, represented by Christoph Fark, Executive Vice President, for the casting of the ELT’s secondary and tertiary mirrors. Credit: ESO/M. Zamani

Introducing the ceremony, Tim de Zeeuw said: “It gives me great pleasure to sign these four contracts today, each for advanced components at the heart of the ELT’s revolutionary optical system. They underline how the construction of this giant telescope is moving ahead at full speed — on target for first light in 2024. We at ESO look forward to working with SCHOTT, SENER and FAMES — three leading industrial partners from our Member States.”

Signature of contract with SENER for the ELT's M2 and M3 mirror cells. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (right), signed a contract with the SENER Group, represented by Diego Rodríguez, Space Department Director, for the production of the ELT's secondary and tertiary mirror cells. Credit: ESO/M. Zamani
Signature of contract with SENER for the ELT’s M2 and M3 mirror cells. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (right), signed a contract with the SENER Group, represented by Diego Rodríguez, Space Department Director, for the production of the ELT’s secondary and tertiary mirror cells. Credit: ESO/M. Zamani

The first two contracts were signed with SCHOTT by Christoph Fark, Executive Vice President. They cover the casting of the ELT’s largest single mirrors — the 4.2-metre secondary and 3.8-metre tertiary mirror — from SCHOTT’s low-expansion ceramic material Zerodur© [1].

Signature of contract with FAMES consortium for ELT primary mirror edge sensors. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (centre), signed a contract with the FAMES consortium, represented by Didier Rozière, Managing Director FAMES (left) and Martin Sellen, Managing Director FAMES, CEO of Micro-Epsilon (right), for the production of edge sensors to help control the shape of the ELT's huge segmented primary mirror. Credit: ESO/M. Zamani
Signature of contract with FAMES consortium for ELT primary mirror edge sensors. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. In this picture ESO, represented by the Director General Tim de Zeeuw (centre), signed a contract with the FAMES consortium, represented by Didier Rozière, Managing Director FAMES (left) and Martin Sellen, Managing Director FAMES, CEO of Micro-Epsilon (right), for the production of edge sensors to help control the shape of the ELT’s huge segmented primary mirror. Credit: ESO/M. Zamani

Hanging upside-down at the top of the telescope structure, high above the 39-metre primary mirror, the secondary mirror will be largest ever employed on a telescope and the largest convex mirror ever produced [2]. The concave tertiary mirror is also an unusual feature of the telescope [3]. The ELT secondary and tertiary mirrors will rival in size the primary mirrors of many modern-day research telescopes and weigh 3.5 and 3.2 tonnes respectively [4]. The secondary mirror is to be delivered by the end of 2018 and the tertiary by July 2019.

Signature ceremony for contracts for casting ELT's M2 and M3 mirrors. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the casting of the ELT's M2 and M3 mirrors, both from SCHOTT and ESO. Credit: ESO/M. Zamani
Signature ceremony for contracts for casting ELT’s M2 and M3 mirrors. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the casting of the ELT’s M2 and M3 mirrors, both from SCHOTT and ESO. Credit: ESO/M. Zamani

The third contract was signed with the SENER Group by Diego Rodríguez, Space Department Director. It covers the provision of the sophisticated support cells for the ELT secondary and tertiary mirrors and the associated complex active optics systems that will ensure these massive, but flexible, mirrors retain their correct shapes and are correctly positioned within the telescope. Great precision is needed if the telescope is to deliver optimum image quality [5].

Contract ceremony for the ELT's M2 and M3 mirror cells. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the ELT's M2 and M3 mirror cells, both from the SENER Group and ESO. Credit: ESO
Contract ceremony for the ELT’s M2 and M3 mirror cells. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the ELT’s M2 and M3 mirror cells, both from the SENER Group and ESO. Credit: ESO

The fourth contract was signed by Didier Rozière, Managing Director (FAMES, Fogale), and Martin Sellen, Managing Director (FAMES, Micro-Epsilon), on behalf of the FAMES consortium, which is composed of Fogale and Micro-Epsilon. The contract covers the fabrication of a total of 4608 edge sensors for the 798 hexagonal segments of the ELT’s primary mirror [6].

Contract ceremony for the ELT's M1 edge sensors. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the edge sensors for the ELT's primary mirror, both from the FAMES consortium and ESO. Credit: ESO/M. Zaman
Contract ceremony for the ELT’s M1 edge sensors. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved in the contract for the edge sensors for the ELT’s primary mirror, both from the FAMES consortium and ESO. Credit: ESO/M. Zaman

These sensors are the most accurate ever used in a telescope and can measure relative positions to an accuracy of a few nanometres. They form a fundamental part of the very complex system that will continuously sense the locations of the ELT primary mirror segments relative to their neighbours and allow the segments to work together to form a perfect imaging system. It is a huge challenge not only to make sensors with the required precision, but also to produce them quickly enough for thousands to be delivered to the necessarily short timescales.

Participants in the ELT contract signature ceremony at ESO Headquarters. Contracts for the casting of the M2 and M3 mirrors of ESO's Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO's Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved, both from SCHOTT, the SENER Group and the FAMES consortium, and from ESO. Credit: ESO/M. Zamani
Participants in the ELT contract signature ceremony at ESO Headquarters. Contracts for the casting of the M2 and M3 mirrors of ESO’s Extremely Large Telescope (ELT), their cells and sensors for the M1 segments were awarded at a ceremony at ESO’s Garching Headquarters on 18 January 2017. The picture shows representatives of teams involved, both from SCHOTT, the SENER Group and the FAMES consortium, and from ESO. Credit: ESO/M. Zamani

The signing ceremony was also attended by other senior representatives of the companies involved and ESO. It was an excellent opportunity for representatives of the contractors producing many of the giant telescope’s optical and mechanical components to get to know each other informally as they begin to help create the world’s biggest eye on the sky.

The optical system of the ELT showing the location of the mirrors. This diagram shows the novel 5-mirror optical system of ESO's Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope's giant concave 39-metre segmented primary mirror, it then bounces off two further 4-metre-class mirrors, one convex and one concave. The final two mirrors form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. An annotated version of this image is available here. Credit: ESO
The optical system of the ELT showing the location of the mirrors. This diagram shows the novel 5-mirror optical system of ESO’s Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope’s giant concave 39-metre segmented primary mirror, it then bounces off two further 4-metre-class mirrors, one convex and one concave. The final two mirrors form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. An annotated version of this image is available here. Credit: ESO

Notes

[1] Zerodur was originally developed for astronomical telescopes in the late 1960s. It has almost no thermal expansion, which means that even in the case of large temperature fluctuations, the material does not expand. Chemically, the material is very resistant and can be polished to a high standard of finish. The actual reflective layer, made of aluminum or silver, is usually vaporised onto the extremely smooth surface shortly before the telescope is put into operation. Many well-known telescopes with Zerodur mirrors have been operating reliably for decades. They include, for example, ESO’sVery Large Telescope in Chile.

[2] As it is a highly convex, aspherical mirror, fabrication of the secondary is a considerable challenge and the result will be a truly remarkable example of precision optical engineering. As with many elements of the ELT it will be a genuine first in this area of technology. The total weight of the secondary mirror and its support system is 12 tonnes — and since it hangs over the primary great care must be taken to prevent the mirror from falling!

[3] Most current large telescopes, including the VLT and the NASA/ESA Hubble Space Telescope, use just two curved mirrors to form an image. In these cases a tertiary mirror is sometimes introduced to divert the light to a convenient focus — that mirror is typically small and flat. However, in the ELT the tertiary also has a curved surface, the use of three mirrors delivering a better final image quality over a larger field of view than would be possible with a two-mirror design.

[4] The contract for the polishing of the secondary mirror has already been awarded.

[5] The M2 and M3 cells are complex mechanisms more than 6.5 metres wide and weighing close to 12 tonnes including the mirrors themselves. They provide alignment and tracking capabilities with a high precision hexapod with an absolute accuracy of tens of micrometres. The cells also compensate for mirror surface deformations in the order of tens of nanometres by means of an innovative solution using warping harnesses and lateral supports.

[6] At this time 3288 have been firmly ordered (for the ELT Phase 1) and an additional 1320 will be included in the ELT Phase 2, making 4608 in total.

ESOcast 93 Light: Kick-off for Mirrors and Sensors for Biggest Eye on the Sky

ESOcast 93 Light takes a quick look at four important contracts that were placed for big parts of ESO’s Extremely Large Telescope (ELT) at a ceremony on 18 January 2017 in Garching. The giant telescope is moving forward!

Credit: ESO. (youtube.com)

Visual Design and Editing: Martin Kornmesser and Luis Calçada.
Editing: Herbert Zodet.
Web and technical support: Mathias André and Raquel Yumi Shida.
Written by: Oana Sandu and Lars Lindberg Christensen.
Music: tonelabs (tonelabs.com).
Footage and photos: ESO, L. Calçada and ACe Consortium.
Directed by: Herbert Zodet.
Executive producer: Lars Lindberg Christensen.

More information

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries.

ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.

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