(Upper panel) Schematic illustration of the core concept behind the interaction between solar radiation, solar wind protons, and interstellar neutrals leading to the formation of pickup ions through ionization and/or charge exchange in the supersonic solar wind. Pickup ions are tied to the heliospheric magnetic field and are transported outward by the solar wind. These processes generate energetic neutral atoms via charge exchange between solar wind protons, pickup ions, and interstellar neutrals in the inner heliosheath – the region between the termination shock and the heliopause. The outer heliosheath is the region in the very local interstellar medium adjacent to the heliopause. (Lower panels) Overview of the current understanding of ion distributions in the inner heliosheath, the availability of bulk solar wind data, and a flowchart summarizing the main ideas of the study.