Final design for the Extremely Large Telescope (ELT) M1 local coherencer

Alexander Díaz; Gaizka Murga; Santiago Royo; Maialen González; Borja Vega; Afonso Teixeira; Juan Francisco Márquez; Noel Rodrigo; Pau Santos; Andreas Förster; Sebastian Schmid; Samuel Leveque; Philippe Gitton; Martin Dimmler

doi:10.1117/12.3019759

11 September 2024 Final design for the Extremely Large Telescope (ELT) M1 local coherencer

Alexander Díaz, Gaizka Murga, Santiago Royo, Maialen González, Borja Vega, Afonso Teixeira, Juan Francisco Márquez, Noel Rodrigo, Pau Santos, Andreas Förster, Sebastian Schmid, Samuel Leveque, Philippe Gitton, Martin Dimmler

Author Affiliations +

Proceedings Volume 13094, Ground-based and Airborne Telescopes X; 130942I (2024) https://doi.org/10.1117/12.3019759
Event: SPIE Astronomical Telescopes + Instrumentation, 2024, Yokohama, Japan

Abstract

The ELT M1 Local Coherencer is a non-contact metrology system aimed to simultaneously measure the relative pistons on the six sides of a target M1 segment with respect to neighbouring ones (reference segments) with an accuracy below 300nm in a range of ±250μm while it is supported by the M1 Segment Manipulator hanging from the M1 Segment Crane. For this purpose, the Local Coherencer is equipped with six Sensing Modules integrating a patented partially coherent light interferometer, an absolute tip-tilt sensor, a fine alignment system to orient the system normal to the reference segment and a coarse alignment detection system composed of a distance sensor and a border visualisation camera. The Preliminary Design described in a precedent paper has been further optimized to provide a better performance of the interferometer: a superluminiscent led (SLED) with a higher brilliance and spatial coherence has been selected to enhance the radiometry and contrast, the optical layout has been optimized to improve both the radiometric and wavefront degradation performance, additionally a detector with a bigger sensor area has been integrated to avoid the need of an afocal system to fit the output beam, thus further reducing the number of elements inducing beam degradation. As a part of the Final Design effort, an Early Unit of a Sensing Module has been built and tested to validate the expected performance, check the correct operation of the three measurement systems contained in the system as well as the local alignment system and tests the latency of the measurements. This paper describes the Final Design and the first results obtained with the aforementioned Early Unit of the Sensing Module.

Conference Presentation

(2024) Published by SPIE. Downloading of the abstract is permitted for personal use only.

Citation Download Citation

Alexander Díaz, Gaizka Murga, Santiago Royo, Maialen González, Borja Vega, Afonso Teixeira, Juan Francisco Márquez, Noel Rodrigo, Pau Santos, Andreas Förster, Sebastian Schmid, Samuel Leveque, Philippe Gitton, and Martin Dimmler "Final design for the Extremely Large Telescope (ELT) M1 local coherencer", Proc. SPIE 13094, Ground-based and Airborne Telescopes X, 130942I (11 September 2024); https://doi.org/10.1117/12.3019759

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