M1 segments testing


Operated by ESO, the Extremely Large Telescope (ELT) will be the most powerful giant telescope in the world, with a primary mirror of 39 meters in diameter.
ESO commissioned Safran Reosc to polish and test the 931 segments, each measuring approximately 1.40m in width.
Built-in Chile at an altitude of 3046 m, the ELT will enable significant progress in astronomy (stellar archeology, discovery and characterization of exoplanets, etc.).


To meet this industrial challenge, Safran Reosc has created a production facility in Poitiers, France, in which four SYMETRIE hexapods are installed: a hexapod is used to characterize the blanks of the segments, a hexapod positions the segments, a hexapod sets the reference, and another hexapod aligns the deflection mirror at the top of the tower of several meters.


SYMETRIE was chosen by Safran Reosc to supply the four hexapods used to test the segments of the ELT’s primary mirror.
The main characteristics of these hexapods are their very good resolution of 0.1 µrad and their excellent stability of 0.1 µrad over 1 hour.
Two of these hexapods incorporate a 360° turntable integrated into the hexapod mobile platform while having a load capacity of 2 tons.
According to Laurent-Daniel Haret, ELT-M1 Safran Reosc metrology project manager, « we now have a set of machines on site that will allow us to position our optical parts with remarkable precision and stability. »


■  Two out of the four hexapods integrate a 360° Rz rotation
 Heavy load for these two hexapods: 2 tons
 Resolution: 0.1 µrad
 Excellent stability of 0.1 µrad over 1 hour

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