  The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure
the interaction between the solar wind and ions created by atmospheric loss
from Pluto. These measurements provide a characterization of the total loss
rate and allow us to examine the complex plasma interactions at Pluto for the
first time. Constrained to fit within minimal resources, SWAP is optimized to
make plasma-ion measurements at all rotation angles as the New Horizons
spacecraft scans to image Pluto and Charon during the flyby. In order to meet
these unique requirements, we combined a cylindrically symmetric retarding
potential analyzer (RPA) with small deflectors, a top-hat analyzer, and a
redundant/coincidence detection scheme. This configuration allows for highly
sensitive measurements and a controllable energy passband at all scan angles of
the spacecraft.
