Acoustic Simulation’s Verification of WFI ATHENA Filterwheel Assembly

Abstract

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.

Design and acoustic tests of the ATHENA WFI filter wheel assembly development model towards TRL5

“…The WFI FWA acoustic-demonstrator model (A-DM) was built to reproduce the expected acoustic environment around the filters, and to check if the filters are able to survive the acoustic loads in this environment. 6 The geometry of the system has been designed so that it reflects the current state of the project, in particular regarding the closed air volumes and masses of individual elements. Besides the FW itself and MGU mockup (with dummy motor and bearings), other important acoustic components are included: baffle, detector mockup, and top and bottom covers (WFI primary structure mockup) (see Figs.…”

“…The WFI FWA acoustic-demonstrator model (A-DM) was built to reproduce the expected acoustic environment around the filters, and to check if the filters are able to survive the acoustic loads in this environment 6 . The geometry of the system has been designed so that it reflects the current state of the project, in particular regarding the closed air volumes and masses of individual elements.…”

“…Separate filters will be mounted on a filter wheel (FW), two thin optical blocking filters (OBF) one for the LDA and one for the FD, and one thick x-ray blocking filter (XBF) for the FD, specifically designed to attenuate the soft emission (E < 2 keV) from x-ray bright sources. 4 The FW will have seven functional positions, namely: (1) both detectors closed, (2) LDA thin OBF, (3) FD thick XBF, (4) both detectors open, (5) LDA calibration (Fe55 radioactive source), (6) FD calibration (Fe55 radioactive source), and (7) FD thin OBF.…”