Open-source simulator for ATHENA X-ray telescope optics

The ATHENA (Advanced Telescope for High Energy Astrophysics) X-ray observatory is the European Space Agency - selected L2 class mission, with launch scheduled in early 2030s. The observatory hosts a large X-ray telescope designed to have 5 arcseconds resolution with an effective area larger than 1.4 m² at 1 keV. To meet these performance requirements ESA developed the Silicon Pore Optics technology: ribbed Si plates are shaped on a proper mould to copy the defined optical design and then stacked into modules. This technological solution, taking advantage of both replica process and modular implementation, is effective to populate ATHENA's large aperture (diameter of ~2.5 m). As a result the optical pupil of an SPO will be very different than the classical nested shell one since it would be composed by a high number of small channels (about 10⁶ channels of ~ 1 mm² in ATHENA current design) and hence requires specific tool to be studied. To this end ESA financed the SIMPOSIuM project aimed to develop an open source, user-friendly SPOs simulation tool. The project is now at a good level of maturity and it offers 2 Graphical User Interfaces implementing a variety of simulation features. The SPORT GUI manages a full ray-tracing code and an analytical effective area calculator. The SWORDS GUI runs a SPOs diffraction effects simulator. In this paper we present the SImPOSIuM package and its collocation in ATHENA optics development framework.