June 8, 2004
The Solar Wind Around Pluto (SWAP) instrument is designed to measure the interactions of Pluto and Charon with the solar wind, the high-speed stream of charged particles flowing out from the Sun. Understanding these interactions will expand researchers' knowledge of the astrophysical processes affecting these bodies and that part of the solar system.
SWAP uses detectors that are sensitive to energetic atoms, energetic electrons and ultraviolet light. Because SWAP is targeting energetic particles only, ultraviolet light is considered "noise." To eliminate ultraviolet photon counts, researchers build serrations into the instrument so that when ultraviolet photons enter SWAP, they will reflect off the serrations and out of the instrument in as few as three bounces. This technique does not affect the energetic particle counts.The incredible distance of Pluto from the Sun required that the SWAP team build the largest aperture instrument ever used to measure the solar wind - it will allow SWAP to make measurements even when the solar wind is very tenuous.