The Active Magnetospheric Particle Tracer Explorers (AMPTE) will carry out the release and monitoring of tracer ions (lithium and barium) in the solar wind and within the distant magnetosphere in order to study access of solar wind ions to the magnetosphere and the convective-diffusive transport and energization of magnetospheric particles. In addition, a single massive release of barium in the dawn magnetosheath will create a visible artificial comet in the flowing solar wind plasma within which studies of diamagnetic effects, ionization, momentum exchange, ion transport, and visible phenomena will be made. The AMPTE spacecraft will also obtain comprehensive measurements of the composition and dynamics of the ambient Z≥2 magnetospheric particle populations at the geomagnetic equator, including the energy interval (˜20 to ˜200 keV) of importance to the ring current. Implementation of these objectives utilizes two primary spacecraft, the Ion Release Module (IRM) and the Charge Composition Explorer (CCE), launched into elliptical orbits of apogee 19.5 RE and 9.0 RE, respectively. A supporting instrumented spacecraft, the United Kingdom Subsatellite, positioned a few hundred kilometers from the IRM, provides two-point in situ plasma diagnostic measurements. All three spacecraft are currently scheduled for launch on a Delta 3924 vehicle in August 1984. The AMPTE program is a collaborative effort between the United States and the Federal Republic of Germany (FRG) and between Germany and the United Kingdom (UK).