PUFIN (Profiling Upper altitudes For Ice Nucleation) is a lightweight sampler flown on the U.S. Department of Energy’s Atmospheric Radiation Measurement user facility’s tethered balloons to measure ice nucleating particles at multiple altitudes. Deployments in Maryland and Alabama show it can detect low concentrations in under an hour and capture changes with height. All data are publicly available, and future flights will help track seasonal and vertical patterns of these unique particles.