Whitepaper #382 in the Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033. Main topics: basic research. Additional topics: outer heliosphere; space-based missions/projects; emerging opportunities.
Interstellar pickup ions (PUIs) hold most of the internal solar wind pressure and are preferentially accelerated at shocks in the outer heliosphere. In the whitepaper, we briefly present limitation of existing PUI observations and identify related knowledge gaps. We recommend prioritizing a dedicated PUI instrument to observe PUIs in the heliosheath and beyond.