ELT M1 edge sensors in the figure control loop: simulations and test results

Andreas Reinacher; Babak Sedghi; Martin Dimmler; Ulrich Lampater

doi:10.1117/12.2627790

26 August 2022 ELT M1 edge sensors in the figure control loop: simulations and test results

Andreas Reinacher, Babak Sedghi, Martin Dimmler, Ulrich Lampater

Proceedings Volume 12182, Ground-based and Airborne Telescopes IX; 1218220 (2022) https://doi.org/10.1117/12.2627790
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

The primary mirror of ESO’s Extremely Large Telescope contains 798 hexagonal segments, which are equipped with edge sensors (ES) to measure the relative segment displacement. These ES are used for M1 figure control, i.e. for maintaining the reference shape of the primary mirror. Measuring with nanometric precision in three axes with a large dynamic range of hundreds of microns, the figure loop needs to be frequently calibrated. In this paper we present a combination of simulated case studies of operational scenarios and test results gained with a test setup (M1 Test Facility) comprising seven M1 segments, 21 position actuators, and 24 ES (12 around the inner segment, 12 between the outer segments), running a scaled down version of the figure control loop. The impact of ES uncertainties originating from calibration and linearization errors on the figure control of ELT‘s primary mirror is investigated with the purpose of improving the understanding of the ES performance in the ELT covering their complete lifecycle. The paper starts with a description of the relevant subsystems before comparing performance data of the ES validation models against specification values. Then the figure loop that controls the M1 shape is described as well as the simulation environment, including a FE model of the M1 and an ES model. A brief description of the M1 Test Facility is followed by simulations of operational scenarios to study the interaction of ES uncertainties with M1 figure control. Finally, some test results measured with the figure control of the M1 Test Facility are presented.

Citation Download Citation

Andreas Reinacher, Babak Sedghi, Martin Dimmler, and Ulrich Lampater "ELT M1 edge sensors in the figure control loop: simulations and test results", Proc. SPIE 12182, Ground-based and Airborne Telescopes IX, 1218220 (26 August 2022); https://doi.org/10.1117/12.2627790

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