The Solar Wind Experiment (SWE) will measure ions and electrons in the solar wind and the foreshock regions (particles whose energies are in the kiloelectronvolt range). From these measurements, the solar wind velocity, density, temperature and heat flux can be deduced. Electron and ion velocity distributions should reveal properties of the following plasmas and their pivotal role in the transfer of mass, momentum, and energy from the Sun to the Earth. Measurements made in the foreshock region will contribute to understanding the structure of the bow shock.