Contract signed for ELT M5 Mirror
11 maart 2019
ESO has signed contracts for the manufacture of the Extremely Large Telescope (ELT) M5 Mirror with the French companies Safran Reosc and Mersen Boostec. Safran Reosc will supply the M5 Mirror along with the auxiliary equipment required for its handling, transport, operation and maintenance. Mersen Boostec will supply the mirror’s lightweight substrate to Safran Reosc’s specifications, and will also be responsible for the supply of the M5 replacement blanks if necessary .
The contracts were signed by Philippe Rioufreyt, CEO of Safran Reosc, Jérôme Lavenac, Operations Managing Director of Mersen Boostec, and Xavier Barcons, ESO Director General, at a ceremony held today at ESO Headquarters in Garching, Germany. Also in attendance were French Consul General in Munich, Pierre Lanapats, and Deputy Consul General in Munich, Benoît Schneider, as well as ESO Council Delegate for France, Laurent Vigroux.
The contract with Safran Reosc builds on an existing cooperative relationship with the high-performance optics company, who is already responsible for the manufacture and polishing of several other optical components of the telescope.
When complete, M5 will be a flat, elliptical mirror measuring 2.70 by 2.20 meters constructed from 6 lightweight silicon carbide segments brazed together . Its unique contribution to the function of the ELT will be the stabilisation of any image movements induced by vibrations due to telescope mechanisms or atmospheric turbulence and wind conditions. It will be mounted on a tip/tilt mechanism that will constantly move — up to 10 times per second — requiring the mirror to be simultaneously very light and very rigid.
ELT first light is planned for 2025, when it will begin to tackle the biggest astronomical challenges of our time. The colossal telescope will allow the exploration of completely unknown realms of the Universe — it will be “the world’s biggest eye on the sky”.
 The substrate, or main body of the mirror, will be created by Mersen Boostec and then polished and integrated by Safran Reosc.
 Silicon carbide has mechanical properties which are ideally suited to the requirements of the M5 mirror. In particular, the low thermal expansion coefficient and high rigidity provides a stable structure for the mirror that will not expand or contract due to changes in temperature. This technology was already successfully used for the primary mirror of the Herschel Space Observatory, but the optical quality required for the M5 mirror is around 100 times more demanding.
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