The WFIRST Galaxy Survey Exposure Time Calculator
  This document describes the exposure time calculator for the Wide-Field Infrared Survey Telescope (WFIRST) high-latitude survey. The calculator works in both imaging and spectroscopic modes. In addition to the standard ETC functions (e.g. background and S/N determination), the calculator integrates over the galaxy population and forecasts the density and redshift distribution of galaxy shapes usable for weak lensing (in imaging mode) and the detected emission lines (in spectroscopic mode). The source code is made available for public use. 
Christopher M. Hirata, Neil Gehrels, Jean-Paul Kneib, Jeffrey Kruk,   Jason Rhodes, Yun Wang, Julien Zoubian
astro-ph.IM