THE ENERGETIC PARTICLES - ACCELERATION, COMPOSITION, AND TRANSPORT (EPACT) INVESTIGATION ON THE WIND SPACECRAFT

The Energetic Particles: Acceleration, Composition, and Transport (EPA CT) investigation is designed to make comprehensive observations of so lar, interplanetary, and galactic particles over wide ranges of charge , mass, energy, and intensity using a combination of and different par ticle telescopes. This paper summarizes the scientific goals of EPACT and provides a detailed description of the instrument design and capab ilities. Electrons are measured from 0.2 to 10 MeV, primarily providin g time markers for injections of solar particles. Hydrogen is measured from 1.4 to 120 MeV, and Helium is measured from 0.04 to 500 MeV nucl (-1). The collection powers and energy ranges for heavier nuclei up to iron are ideal for observations of quiet-time populations such as par ticles accelerated by interplanetary shocks and the anomalous cosmic r ays (thought to be accelerated at the boundary of the heliosphere). Th e large collection power available is also ideal for observations of H e-3, He-4, and heavier nuclei in impulsive He-3-rich solar events. The re is even the possibility of observing ultra heavy nuclei (Z > 30) in large solar events for the first time. Finally, there is a telescope designed to measure isotopes from He (3.4-55 MeV nucl(-1)) to Fe (12-2 30 MeV nucl(-1)), which is intended for solar particles, the anomalous cosmic rays and galactic cosmic rays. The overall capabilities of EPA CT provide scientifically interesting measurements over all phases of the solar cycle. There will also be important opportunities for combin ed studies with other spacecraft, such as SAMPEX, Ulysses, and Voyager s 1 and 2.