SWAP (New Horizons)

[2] One idea is the photoionization of escaping neutral particles might alter the flow solar wind around the dwarf planet.

[2] One of the areas of investigation is the relationship between high altitude atmospheric loss and the solar wind.

[7] It was determined that NH crossed the plutopause, that separates the solar wind plasma from one bound to Pluto, and then passed through a heavy ion tail.

[8] SWAP was also designed to be used in conjunction with PEPPSI and REX, to study how the solar wind changes with greater distance from the Sun.

[9] Starting in 2012, while the rest of the spacecraft was in hibernation most of the time, SWAP was turned on to collect data about the Solar wind as it journeyed out to Pluto at 33 AU.

[9] SWAP has a barrier known as the Retarding Potential Analyzer (RPA) that can be open or shut depending on the conditions.