Opto-structural Analysis

Pepi, John W.

doi:10.1117/3.2317988

Cited by 8 publications

(6 citation statements)

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“…Uncertainty may be assessed as follows: assume the observable X that varies with the variation of the density X=g(Δρ/ρ). Evoking a linear operator (e.g., g:x→x for X carrying the density variations X(Δρ/ρ(D))=Δρ/ρ(D), or integration g:(x,u)→∫0ux(z)dz for X being the VRoC, i.e., X∝∫(Δρ/ρ(D(z)))zdz 39 ). Assuming a power law description of TID-induced strain (Δρ/ρ=A×DB) directly defines that the observable X is an homogeneous function of the irradiation exposure time t.…”

Section: Phenomenological Compaction Lawmentioning

confidence: 99%

Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic

Carré

Kirchhoff

Hull

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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The low thermal expansion glass ceramic ZERODUR ® has a long and successful history in spaceborne optical applications. This material is especially used where precise shape invariance is required, i.e., for the mirror substrates dimensional stability when subject to temperature gradients and transients. In space, temperature may not be the exclusive driving force impacting the form stability; influence from ionizing radiations require considerations. The real impact of ionizing radiation on ZERODUR ® has become a matter of reconciling, on the one hand, in situ experience, e.g., that the secondary mirror of low Earth orbit (LEO) Hubble Space Telescope crossing the South Atlantic Anomaly or the overall optics of geosynchronous equatorial orbit (GEO) Chandra X-ray Observatory are not reporting any specific problems related to dimensional stability at the optical form level. On the other hand, finite element simulation based on early lab experiments of ZERODUR ® compaction are suggesting the opposite. This debate was brought to the forefront with the SILEX mission, where radiative ageing models were significantly overestimating the deformation experimentally observed on the lab replicas and were in even stronger disagreement with the observations collected over the mission. It has been speculated that an erroneous form factor in the physical model used to derive the phenomenological compaction law was responsible for these discrepancies. Following this hypothesis, we readdressed the effect of ionizing radiation induced by γ, electron, and proton fluences on ZERODUR ® compaction. For each of these, we present and discuss the irradiation source, the experimental setup, the sample design, and the measurement procedure as well as the observations. Consistent with the feedback gathered over many different space missions, we confirm that the compaction observed is significantly smaller than the estimations available in the prior literature.

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Section: Phenomenological Compaction Lawmentioning

confidence: 99%

Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic

Carré

Kirchhoff

Hull

et al. 2023

J. Astron. Telesc. Instrum. Syst.

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“…The VRoC and the surface PV are provided on Figure 19. 2 The shielding due to the baffle induces only a weak radial dependence of the dose-depth field. In addition to this, the optic is fixed to the satellite, strengthening thus the overall stiffness of the satellite.…”

Section: D Estimated Change Of Curvaturementioning

confidence: 99%

ZERODUR stability in space environments

Carré

Hull²,

Schüller

et al. 2021

International Conference on Space Optics — ICSO 2020

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“…This implies the choice of structural materials like aluminium, titanium or silicon carbide, frequently used in space applications. For optics, deflection is a parameter often more critical than strength, especially for mirrors, quite sensitive to deformation errors [4]. In addition to stiffness, other parameters are important for the materials' choice, like density, thermal conductivity and thermal expansion.…”

Section: Modelling Of a Thermo-structural Fem Analysismentioning

confidence: 99%

“…A further solution is the use of low expansion materials; quartz glass is a common material for lenses and mirror, e.g. ULE® fused silica and ZERODUR® glass-ceramic show a nearzero coefficient of thermal expansion at room temperature, and for the optical elements mountings materials with very low CTE, such as Invar or SiC, can be used [4]. Otherwise, the thermal compatibility of different materials may be employed; for instance, in Comet Interceptor ESA mission, the structural casing of the EnVisS optical head is made of a titanium alloy, because of its thermal compatibility with res [8], even if its density is much higher than aluminium.…”

Section: Coupling With Thermal Interfacementioning

confidence: 99%

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Methodology for the analysis of a thermo-mechanically deformed optical system

Nordera

Chioetto

Zuppella

et al. 2021

International Conference on Space Optics — ICSO 2020

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The performance of as-built optical instruments strongly depends on thermal and structural loads, since these boundary conditions can affect the geometry of optical surfaces. Variations of temperature influence the volume, and the shape, of the structure proportionally to the coefficient of thermal expansion of the material, while mechanical loads, like gravity, may induce deformations on the optical elements according to the set of applied constraints. Those effects can introduce aberrations that degrade the performance of the optical system.Since software for optical and thermo-structural analysis are usually different, a coupling methodology between these two fields of physics is needed. This is a step-by-step procedure through many platforms.In this work, the procedure devised and used by the authors will be presented. At first, a thermo-mechanical analysis (depending on the loads involved) has to be performed, in order to obtain the final deformed geometry of the optical structure; COMSOL Multiphysics is the finite element solver (FEM) used for these analyses. Then an output data file, containing the coordinates of points belonging to the optical surface, can be generated. The output data are elaborated by a MATLAB routine that allows to convert the set of points into an n-th polynomial expression that best fits the surface data. The fitted polynomial surface is hence imported in ZEMAX ray-tracing software to study the optical performances of the system and the effects of thermo-mechanical loads.

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Opto-structural Analysis

Cited by 8 publications

References 0 publications

Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic

Comprehensive review of the effects of ionizing radiations on the ZERODUR® glass ceramic

ZERODUR stability in space environments

Methodology for the analysis of a thermo-mechanically deformed optical system

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