FINCH: time-dependent simulation of nulling interferometry for the DARWIN mission

Within the scope of the DARWIN Technology and Research Programme, the European Space Agency (ESA) initiated the development of a dynamic system simulator (called FINCH "Fast Interferometer Characterization") for the spaceborne nulling interferometry mission DARWIN.The FINCH project is realized by two parallel activities: (1) a simulator for the Guidance, Navigation and Control (FINCH/GNC) of the free-flying satellite array, and (2) a simulator for the optical subsystems and the beam propagation within the system (FINCH/OPT). While the GNC activity is handled by EADS Astrium, France, the optical part is performed in a joint effort by EADS Astrium, Germany, and the European Southern Observatory (ESO). In this paper we focus on FINCH/OPT aspects and describe: • DARWIN and the corresponding overall end-to-end simulation approach • the completed FINCH/OPT development for modelling of point sources • modelling of extended objects, exact and with suitable approximations • details of optical modelling of DARWIN configurations within FINCH • applications of FINCH