The future European Extremely Large Telescope E-ELT: Reosc will manufacture the M4 mirror segments

Saint-Pierre du Perray, July 24, 2015

After an international competitive bidding process, Reosc, a subsidiary of Sagem (Safran), has just signed a contract with ESO (the European Southern Observatory) to produce all the optical segments of the M4 mirror for the E-ELT (European Extremely Large Telescope), the largest and most powerful telescope in the world (*).

For this program, Reosc will produce twelve mirror thin shells, the first six of which will be delivered in 5 years' time, with everything to be delivered by 2023.

The M4 is a circular, vitro-ceramic mirror measuring 2.4 meters in diameter and made up of six thin petals. This mirror, the consistent thickness of which is controlled on its whole surface with extreme precision, will be adaptive and capable of correcting turbulence caused by atmospheric conditions in real time.

The response to the technical requirements expressed for the competitive bidding process was the decisive factor that led to ESO selecting Reosc. Furthermore, Reosc had already demonstrated the very high performance of its offering in 2010 by supplying a prototype mirror to ESO, which fulfilled expectations for the validation phase of the M4 mirror for the E-ELT program.

Reosc develops and produces high-performance optics for satellites, large telescopes, high-energy lasers and the semiconductor industry. For example, the company produced single-piece 8-meter (26 ft) mirrors for ESO Very Large Telescope (VLT), and the international Gemini telescope. It also made the 11-meter (36 ft) mirror for the Gran Telescopio de Canarias, the mirrors for the Nirspec instrument on the James Webb Space Telescope and the Gaia astronomy satellite. The optics for Meteosat, Spot and Helios satellites were also provided by Reosc.

(*) The E-ELT is a large telescope equipped with a primary mirror measuring 39 m in diameter. Built in Chile on the Cerro Armazones (3,060 m above sea level), it will drive considerable progress in astronomy (stellar archeology, discovery and characterization of exoplanets, etc.). "First light' is scheduled for 2024.


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Reosc, a subsidiary of Sagem, a Safran high-technology company, is a world leader in the design, production and integration of high-performance optics for both civil and defense applications, including astronomy, space, high-energy lasers and the semiconductor industry. Founded by Henri Chrétien in 1937, Reosc has developed unique expertise in optics for earth-based astronomy. From research to design, from production to integration, Reosc currently offers a complete range of high-performance optics and high-precision opto-mechanical equipment.

Reosc employs 130 people and is located in Saint Pierre du Perray 35 km southeast of Paris.

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