Modeling the Optical System of NASA's EXCLAIM Mission

NASA's EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), is a balloon-borne instrument that designed to perform intensity mapping of CO and CII at redshifts as high z=3.5. It will map galaxy star formation history over cosmological time. EXCLAIM also demonstrate novel integrated silicon spectrometers using microwave kinetic inductance detectors (MKIDs) could be an enabling technology the Origins Space Telescope or other future mid- far-infrared space telescopes. Here we present progress toward full electromagnetic simulation EXCLAIM's optical system its operational frequencies. The goal these simulations verify design meets mission requirements. When combined with measurements instrument, our understanding complete. This work being done in preparation first flight mid 2022.