The solar, anomalous, and magnetospheric particle explorer

The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) is one of two small explorer missions selected for flight by the Space Physics Division of NASA's Office of Space Science and Applications. The small explorers are roughly 400‐ lb. spacecraft that will be launched on Scout‐class expendable launch vehicles. The SAMPEX instruments will measure the electron and ion composition of energetic particle populations from ˜0.4 MeV/ nucleon to hundreds of MeV/nucleon from a zenith‐pointing small satellite in near‐polar orbit. They will use a coordinated set of detectors with excellent charge and mass resolution and higher sensitivity than previous instruments. While over the magnetic poles, the instruments will obtain the elemental and mass composition of anomalous cosmic rays, solar energetic particles, and galactic cosmic rays. At lower magnetic latitudes, geomagnetic cutoff effects will allow the ionization state of these particles to be determined at energies much higher than can be studied from interplanetary spacecraft. At sub‐auroral latitudes, SAMPEX will observe precipitating relativistic magnetospheric electrons, which undergo important interactions within the middle atmosphere.