The New Horizons mission made the first up-close and detailed observations of Pluto and its moons. These observations include measurements of the solar wind interaction with Pluto. The Solar Wind Around Pluto (SWAP) instrument is designed to measure the tenuous solar wind at large distances from the Sun and its interaction with Pluto, as well as making unprecedented measurements of interstellar pickup ions. SWAP directly addresses the Group 1 science objective for the New Horizons mission to “characterize the neutral atmosphere of Pluto and its escape rate”. In addition, SWAP makes measurements critical for the Group 2 objective of characterizing Pluto’s ionosphere and solar wind interaction. Finally, SWAP makes observations relevant to two Group 3 science objectives for New Horizons, both in support of characterizing the energetic particle environment of Pluto and Charon and in searching for magnetic fields of Pluto and Charon.
The SWAP instrument was designed to measure the solar wind and pickup ions out at ∼33 au, as the New Horizons spacecraft repeatedly rotated to point its various cameras during the flyby of Pluto and Charon. Because of the great distance and large range of viewing directions, SWAP was designed to have an extremely high sensitivity and a very large field-of-view. These attributes allowed SWAP to make fundamental measurements of the Jovian magnetosphere and magnetotail, and Pluto’s interaction with the solar wind. SWAP continues to make observations of the solar wind and interstellar pickup ions out to at least ~41 au.