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

Abstract

The filter wheel (FW) assembly (FWA), developed by the CBK Institute, is one of the critical subsystems of the wide field imager (WFI) instrument on board the Advanced Telescope for High Energy Astrophysics-mission of the ESA Cosmic Vision 2015-25 space science program (launch scheduled around 2035). The instrument has to collect soft x-rays with very high quantum efficiency, thus WFI requires extremely thin optical blocking filter (OBF). Due to its thickness (∼150 nm) and large area (∼170 mm × 170 mm) needed to achieve a 40 0 × 40 0 instrument field of view, the filter is extremely vulnerable to acoustic loads generated during Ariane 6 rocket launch. On the other side, FW mechanism has to provide high overall reliability, so it is more favourable to launch the instrument in atmospheric pressure (without vacuum enclosure for filter protection). Design efforts of the FW subsystem were focused on two issues: providing maximal possible sound pressure level suppression and smallest possible differential pressure across the OBF, which should prevent filters from damaging. We describe the design of a reconfigurable acoustic-demonstrator model (DM) of WFI FWA created for purposes of acoustic testing. Also, the acoustic test campaign is described: test methodology, test criteria, and results discussion and its implication on future FWA design. In general, tests conducted with the FWA DM showed that current design of WFI is feasible and the project can be continued without introducing a vacuum enclosure, which would significantly increase system complexity and mass.

Elastic characterization of nanometer-thick polymeric film for astrophysics application with an experimental-numerical method

“…The wide field imager (WFI) OBFs will be launched in atmospheric pressure and, for this reason, they will have to withstand simultaneously the vibration loads and the powerful acoustic spectrum transmitted inside the launcher cargo. 6 The nanometric film thickness and the severe static and dynamic loading conditions, combined with the existence of different PI stoichiometries that could change the mechanical properties, need a characterization of the membrane material. The modification of the material properties moving from bulk to thin sheets and the dependence of the mechanical properties on the microstructure (grain size, texture, and defects) are studied topics.…”