The ACT vision mission study simulation effort

The Advanced Compton Telescope (ACT) has been selected by NASA for a one-year “vision mission” study. The study’s main goal is to determine feasible instrument configurations to achieve ACT’s sensitivity requirements, and to give recommendations for technology development. Space-based instruments operating in the energy range of nuclear lines are subject to complex backgrounds generated by cosmic rays, earth albedo radiations, trapped particles, and diffuse gamma rays; typically measurements are significantly background-dominated. Therefore accurate, detailed simulations of the background induced in different ACT configurations, and exploration of event selection and reconstruction techniques for reducing these backgrounds, are crucial to determining the capabilities of a given instrument configuration. The ACT simulation team has assembled a complete suite of tools that allows the generation of particle backgrounds for a given orbit, their propagation through any instrument and spacecraft geometry – including delayed photon emission from instrument activation – as well as the selection and reconstruction of Compton events in the given detectors. We describe here the scope of the ACT simulation effort and the suite of tools used.