Safran Reosc, a subsidiary of Safran Electronics & Defense, has signed a contract with the European Southern Observatory (ESO) to design and produce the M5 mirror, the fifth and final mirror for the Extremely Large Telescope (ELT).

The ELT is a giant telescope with a 39m primary mirror, that will be installed on the Cerro Armazones mountain in Chile at an elevation of 3,048m. The start of observations is planned for 2025. The ELT is expected to drive significant progress in astronomy, especially in areas such as stellar archaeology and the characterisation of exoplanets.

The M5 mirror is a flat elliptical silicon carbide mirror measuring 2.70m by 2.20m. It will be the world's largest mirror with optical precision in the 10 nanometer class built to date. Safran Reosc is also responsible for the development and construction of the high-precision optical test bench, which will be used to measure the mirror's optical quality throughout the polishing process.

Safran Reosc had previously won the contracts to make the thin glass petals of the M4 mirror in 2015, polish the M2 mirror in 2016 and polish the M3 mirror and all segments of the M1 mirror in 2017.