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Safran, eyes on the stars


Over a billion stars in the Milky Way were pinpointed by the Gaia European satellite with unequaled precision. Such a degree of precision was obtained with the use of two main mirrors polished by Safran Reosc, a subsidiary of Safran Electronics & Defense.

Launched into orbit on December 19, 2013, by a Souyouz rocket that took off from the Guiana Space Centre in Kourou, the Gaia spacecraft has pinpointed almost ten thousand times more stars than its predecessor, the Hipparcos satellite*.

To collect these astrometric data (precise measurements of the stars' position), Gaia features two telescopes in a single compact structure which provide two observing directions. Safran Reosc, a subsidiary of Safran Electronics & Defense, and leader in space optics, polished the entry mirrors for both telescopes. These parts are particularly challenging due to their size (150 x 55cm), aspheric shape, the great durability of the SiC material used and the required high precision of about 10 nanometers, something which is key to ensuring the precision of Gaia in its collection of astrometric measurements.

The telescope mirrors and all of the components of their supporting structures are made out of silicon carbide (SiC), a ceramic that offers several advantages in terms of stability and instrument precision.

Designed and manufactured by Airbus Defense & Space, the Gaia satellite represents a major leap forwards in terms of performance with resolution that is 100 times higher than that of Hipparcos. It actually works like an enormous space compass with a huge focal plane of almost one billion pixels.

The new mission, led by the European Space Agency (ESA), once again brings about genuine progress in the understanding of the faraway environment that surrounds the Sun and its planets.

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For 80 years now, Safran Reosc has been the world leader in large precision optics for astronomical, laser and space applications. Nowadays, the slow and painstaking polishing operations are carried out by robots under the supervision of Safran Reosc specialists. The company has also developed its own polishing layer for SiC material, the R-SiC polishing layer, which is easier to lay, easier to polish and reduces risks during the production process.

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* HIgh Precision PARallax COllecting Satellite, which pinpointed 118,000 stars and featured a beam-combining mirror from Safran Reosc.