Preliminary mechanical design of the ATHENA Wide Field Imager (WFI) Large Detector Array (LDA) Optical Blocking Filters (OBF)

Athena is one of L-class missions selected in the ESA Cosmic Vision 2015-2025 program for the science theme of the Hot and Energetic Universe. The Athena model payload includes the Wide Field Imager (WFI) is one of the two scientific instruments proposed for Athena. The WFI will provide imaging in the 0.2-15 keV energy band over a wide field, simultaneously with spectrally and time-resolved photon counting. The instrument is designed to make optimal use of the grasp (product of collecting area and solid angle) provided by the optical design of the ATHENA mirror system, by combining a sensitive approx. 40'x40' field of view DEPFET detector with a pixel size properly sampling the angular resolution of 5'' on-axis (half energy width). The present document shows the preliminary design of the optical blocking filters (OBF) for the large detector array (LDA) in full size and one quadrant. The filters consist of aluminium coated thin polypropylene film supported by a SS mesh and an aluminium cross stiffening structure. During the launch, filters are subject to many loads, and the most dangerous for their survival are the mechanical accelerations at the interface with the filter wheel, the acoustic pressure and the differential pressure due to the cargo venting