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Ultra-High Vacuum Engineering for Astronomical Observation
The Extremely Large Telescope (ELT), currently under construction in the Atacama Desert in Chile, represents a major turning point for ground-based astronomy. The performance of this instrument relies heavily on the optical quality of its mirrors. In partnership with AGC, Ceratec was commissioned to design and implement the automation of the High Vacuum Coating Plant. This facility is critical for the telescope’s operational maintenance.
A Dimensional and Geometric Challenge
The coating unit automated by Ceratec must handle a variety of complex optical geometries. Unlike the segments of the primary mirror (M1), the secondary and tertiary mirrors feature concave, convex, or flat curvatures, with diameters ranging from 2.4 meters to 4.25 meters.
The most critical component of this process is the secondary mirror (M2). With a diameter of 4.25 meters, it is the largest convex secondary mirror ever manufactured. The handling and surface treatment of such a piece allow for zero margin of error.
Mastery of the Vacuum Deposition Process
Ceratec’s scope involves the complete control of the thin-film deposition process. The ELT mirrors require periodic renewal of their reflective coating, which naturally oxidizes or degrades over time.
The developed automation system manages the following sequences:
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High Vacuum Control: Management of pumps to reach the pressure levels required for Physical Vapor Deposition (PVD).
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Magnetron Sputtering: Precise control of magnetrons to ensure uniform atomic deposition of the silver or aluminum layer across the entire optical surface.
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Recipe Management: Dynamic adaptation of process parameters based on the specific mirror loaded (M2, M3, M4, or M5).
This achievement demonstrates Ceratec’s ability to transpose its expertise in industrial automation to cutting-edge scientific applications, where precision and repeatability are absolute prerequisites.
