The CubeSat Infrared Atmospheric Sounder (CIRAS) is a proposed small satellite IR sounder developed in response to the challenges of high cost and possible data gaps for currently operational hyperspectral IR sounders, such as Atmospheric Infrared Sounder, Infrared Atmospheric Sounding Interferometer, and Crosstrack Infrared Sounder. A key objective of CIRAS is to demonstrate the technologies required for a low cost-to-orbit, operational IR sounder. CIRAS was designed by National Aeronautics and Space Administration’s Jet Propulsion Laboratory, with 625 channels measuring upwelling IR radiation of the Earth in the mid-wavelength IR spectrum region. Through observational system simulation experiments, the impact of assimilating CIRAS on global numerical weather prediction was assessed. CIRAS was simulated by applying the Community Radiative Transfer Model to profiles extracted from the Goddard Earth Observing System Model, Version 5 nature run for an afternoon polar orbiting sensor, and then assimilated by the National Centers for Environmental Prediction Global Data Assimilation System. Assimilating CIRAS improved global analysis and forecasts, when added to the currently operational observing configuration and to a data gap scenario.