The JWST/NIRSpec instrument performance simulator software

NIRSpec is the near-infrared multi-object spectrograph for the future James Webb Space Telescope (JWST). It is developed by EADS Astrium for the European Space Agency. The Centre de Recherche Astrophysique de Lyon (CRAL) has developed the Instrument Performance Simulator (IPS) software that is being used for the modeling of NIRSpec's performances and to simulate raw NIRSpec exposures. In this paper, we present the IPS software itself (main simulation modules and user's interface) and discuss its intrinsic accuracy. We also show the results of simulations of calibration exposures as they will be obtained during the NIRSpec on-ground calibration campaign.