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The vibro-acoustic environment generated during a rocket launch induces dynamic loads which may damage critical components of spacecraft and scientific instruments. The research is focused on the vibro-acoustic response of the Wide Field Imager (WFI) instrument subjected to an intense diffuse sound field. Noise-induced structural vibrations in low- to mid-frequency can be computed by means of coupled FEM-BEM numerical models. Nevertheless, this approach is unsuited to calculations of cavity-structure interactions of light-weight and thin structures. In this paper the application and assessment of the elasto-acoustic FEM-FEM coupling approach for the cavity - optical blocking thin foil filter interactions is investigated. The diffuse sound field excitation is reconstructed by matching values of the sound pressure level to these obtained from experimental measurements. The viscosity effects on the wave propagation in thin layers are included by using the visco-thermal fluid model. The accuracy and efficiency of this approach are investigated and results obtained are compared to measured data from a reverberant test chamber. The results show that a very good agreement is obtained in terms of the acoustic pressure in the vicinity of the optical blocking filter. The behaviour of mechanical vibrations is correctly reproduced, although some considerable discrepancies in the levels of the vibrations are observed. The case of strong coupling between the cavity acoustic field and the filter membrane is finally discussed.

Ariane 5 rocket produces very high sound pressure levels during launch, what can influence structures located in the fairing. To reduce risk of damage, launch in vacuum conditions is preferred for noise sensitive instruments. In Wide Filed Imager (WFI) project, the main part of the filterwheel assembly is an extremely thin (~240 nm) filter of large area (170×170 mm), very sensitive to noise and vibrations. The aim of this study was to verify numerical calculations results in anechoic measurements. The authors also checked the influence of WFI geometry and sound absorbing material position on sound pressure level (SPL) affecting the filter mounted inside the assembly. Finite element method (FEM) simulations were conducted in order to obtain noise levels in filter position during Ariane 5 rocket launch. The results will be used in designing of WFI filterwheel assembly and endurance of the filter during launch verification.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. ATHENA is a Large high energy astrophysics space mission selected by ESA in the Cosmic Vision 2015-2025 Science Program. It will be equipped with two interchangeable focal plane detectors: the X-Ray Integral Field Unit (X-IFU) and the Wide Field Imager (WFI). Both detectors require x-ray transparent filters to fully exploit their sensitivity. In order to maximize the X-ray transparency, filters must be very thin, from a few tens to few hundreds of nm, on the other hand, they must be strong enough to survive the severe launch stresses. In particular, the WFI OBF, being launched in atmospheric pressure, shall also survive acoustic loads. In this paper, we present a review of the structural modeling performed to assist the ATHENA filters design, the preliminary results from vibration and acoustic tests, and we discuss future activities necessary to consolidate the filters design, before the preliminary requirement review of the ATHENA instruments, scheduled before the end of 2018.

Copyright 2018 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. The Wide Field Imager (WFI) is one of the two instruments of the ATHENA astrophysics space mission approved by ESA as the second large mission in the Cosmic Vision 2015-2025 Science Programme. The WFI, based on a large array of depleted field effect transistors (DEPFET), will provide imaging in the 0.2-15 keV band over a 40'x40' field of view, simultaneously with spectrally and time resolved photon counting. The WFI detector is also sensitive to UV/Vis photons, with an electron-hole pair production efficiency in the UV/VIS larger than that for X-ray photons. Optically generated photo-electrons may degrade the spectral resolution as well as change the energy scale by introducing a signal offset. For this reason, the use of X-ray transparent optical blocking filters (OBFs) are needed to allow the observation of X-ray sources that present a UV/Vis bright counterpart. The OBFs design is challenging since one of the two required filters is quite large ( 160 mm × 160 mm), very thin (< 200 nm), and shall survive the mechanical load during the launch. In this paper, we review the main results of modeling and characterization tests of OBF partially representative samples, performed during the phase A study, to identify the suitable materials, optimize the design, prove that the filters can be launched in atmospheric pressure, and thus demonstrate that the chosen technology can reach the proper technical readiness before mission adoption.