Channeled infrared polarimeter (CHIRP) performance simulation

Modeling upper-tropospheric ice clouds remains one of the largest sources of uncertainty in quantifying Earth’s radiation budget. Polarimetric observations in the long-wave infrared (LWIR) are particularly sensitive to microphysical properties of small ice crystals (i.e. particle size, shape, and orientation), yet no current satellite mission includes LWIR polarimetry. The Channeled Infrared Polarimeter (CHIRP) is designed to address this observational gap by encoding linear Stokes parameters into spectrally varying fringe patterns. CHIRP’s performance requirement is to achieve polarimetric uncertainties on the order of 1 K for ice cloud targets as cold as 200 K. This work presents a comprehensive, end-to-end performance model of CHIRP that integrates spectral, radiometric, and polarimetric analyses. The optical design is evaluated through simulations of slit-width dependent resolving power, spectral blurring distributions, and pixel-level photocurrent generation, quantifying tradeoffs between throughput, resolution, and polarimetric efficiency. Simulations predict resolving powers up to <i>R</i> &asymp; 67 and polarimetric efficiencies of up to 94% for optimized configurations, with results highlighting the sensitivity of fringe contrast to spectral blurring and detector sampling. The modeling framework provides quantitative performance metrics that guide instrument design choices and establish the feasibility of CHIRP to achieve its science objectives.