ESO ELT optomechanics: construction status

Cayrel, Marc; Dierickx, Philippe; Förster, A.; Dérie, F.; Jochum, L.; Pettazzi, Lorenzo; Lucuix, Christian; Haupt, Christoph; Müller, Michael; Vernet, Elise; Pirard, Jean-François

doi:10.1117/12.2312665

Cited by 6 publications

(8 citation statements)

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“…The tip-tilt mirror M5 is a flat monolithic mirror sized � 2:2 m � 2:7m providing exclusively large tip and tilt corrections. M5 is actuated by three piezo-electric drives and its mirror tile is a lightweight structure made of silicon carbide [2,36].…”

Section: Metis-scao Systemmentioning

confidence: 99%

“…The reflective annulus has an inner diameter of � 0:5 m, an outer diameter of � 2:5m, and is realized via a thin ( , < 10 nm) aluminium layer on top of the segments. M4 can adopt arbitrary (out-of-plane) deformations with small amplitudes ( � 50 μm) and high spatial frequencies utilizing � 5350 actuators [2,37].…”

Section: Deformable Mirror M4mentioning

confidence: 99%

“…The METIS-SCAO system (see Figure 3) comprises the deformable mirror M4 (see Figures 1b and Figures 2), the tip-tilt mirror M5, the infrared pyramid wavefront sensor, and a controller implemented on a real-time computer [1,2]. M4 is a thin annular mirror composed of six identical independent plate segments which are supported via flat springs at their outer curved edges.…”

Section: Introductionmentioning

confidence: 99%

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Control oriented modelling and modal analysis of the deformable mirror M4 of the extremely large telescope

Neureuther

Schmidt

Bertram

et al. 2021

Mathematical and Computer Modelling of Dynamical Systems

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In this article, we derive a mechanical distributed parameter model for the annular sector plate segments of the Extremely Large Telescope's deformable mirror M4. Additionally, we modally analyse the derived model via analytical and numerical approaches. The deformable mirror M4 is used to reject wavefront disturbances and enhance the optical imaging quality. We present a control oriented annular sector Kirchhoff-Love plate model featuring an elastic boundary condition and its modal analysis for one of the six identical M4 segments. Subsequently, we show that the well-known method of separation of variables is incompatible with the modal analysis of the presented distributed parameter model in cylindrical coordinates. Moreover, we successfully modally analyse the model using a finite difference approximation and a realistic construction of an M4 segment via a finite element approximation to compare the results. The modal analyses provide consistent results and therefore, both models underlying the analyses are consistent.

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Section: Metis-scao Systemmentioning

confidence: 99%

Section: Deformable Mirror M4mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Control oriented modelling and modal analysis of the deformable mirror M4 of the extremely large telescope

Neureuther

Schmidt

Bertram

et al. 2021

Mathematical and Computer Modelling of Dynamical Systems

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“…A honeycomb is a construction that offers the largest volume (honey) for the minimum structure (beeswax) and it is created from two sets of hexagonal prisms ending in three rhomboidal faces placed back-to-back and offset to create a perfect tessellation, 20 as shown in Figure 15. A approximation to the honeycomb design has been an inspiration for several telescope mirror geometries 21,22 as well as mirror lightweighting structures; 23,24 however, applying the exact honeycomb cell geometry is challenging within traditional machining. The objective of this study is to apply the honeycomb construction that is seen in nature to create a lightweight sandwich mirror which exhibits two solid face plates and a rhombic dodecahedron interior.…”

Section: Honeycomb Designmentioning

confidence: 99%

Lightweighting design optimisation for additively manufactured mirrors

Atkins

Brzozowski

Dobson

et al. 2019

Astronomical Optics: Design, Manufacture, and Test of Space and Ground Systems II

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“…One example for such loads is bonded fixtures of mirror segments to support frames, which are planned for the European Extremely Large Telescope (ELT). 5 Glued bonds exert forces to the glass-ceramic due to glue shrinkage stress. Additional forces arise from the weight changing with different observation angles and from the inline segment shape optimization.…”

Section: Introductionmentioning

confidence: 99%

Minimum lifetime of ZERODUR® structures based on the breakage stress threshold model: a review

Hartmann

2019

Opt. Eng.

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Increasing demand for using the glass ceramic ZERODUR ® for optical elements with high mechanical loads called for strength data based on statistical samples larger than 20 specimens. The data now available for a variety of practical surface conditions (ground, lapped, and etched) allow stresses by factors 4 to 10 times higher than before. The larger samples revealed that breakage stresses of ground surfaces follow the threeparameter Weibull distribution. The threshold parameter of this distribution reflects the existence of an upper limit for the microcracks depth within such surfaces. It is equivalent to a minimum strength below which breakage probability is zero. Its use in the well-established crack growth theory allows calculating minimum lifetimes including fatigue using the stress corrosion constant for the prevailing environmental humidity. Long-term loading tests have confirmed the validity of the model. For fully etched surfaces, the Weibull statistics fails because in such cases failure mechanism is not unique anymore. Nevertheless, ZERODUR ® with fully etched surfaces that are free from other damages still exhibit minimum breakage stress above 100-MPa tensile stress. The successful satellite mission LISA Pathfinder has confirmed the possibility to apply ZERODUR ® for utmost precision experiments together with high mechanical loads.

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ESO ELT optomechanics: construction status

Cited by 6 publications

References 0 publications

Control oriented modelling and modal analysis of the deformable mirror M4 of the extremely large telescope

Control oriented modelling and modal analysis of the deformable mirror M4 of the extremely large telescope

Lightweighting design optimisation for additively manufactured mirrors

Minimum lifetime of ZERODUR® structures based on the breakage stress threshold model: a review

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