Three-dimensional He+ pick-up ion velocity distribution functions observed with STEREO-A PLASTIC Duncan Keilbach, Verena Heidrich-Meisner, Lars Berger and Robert F. Wimmer-Schweingruber A&A, 696 (2025) A115 Published online: 09 April 2025 DOI: 10.1051/0004-6361/202453527