NASA's Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX) satellite, an international collaboration with Germany, is the first of a series of scientific research missions called “Small Explorers.” In 1989, NASA chose three initial missions to research energetic radiations observed near Earth and radio frequency emissions given off by stars in early development. In addition to the pursuit of scientific research, the Small Explorer program emphasizes small spacecraft and rapid development of each mission—in 3 years or less [Baker et al., 1991].

The SAMPEX mission yields new information on the high-velocity radiations arriving at Earth from the Sun and interstellar space. SAMPEX is named after the primary sources of the radiations: [Solar] ions and electrons, which are swept up by huge explosions in the solar atmosphere, [Anomalous] cosmicrays, which are believed to be interstellar gas atoms accelerated at the edge of the solar system, and [Magnetospheric] electrons, which plunge into the upper atmosphere and may influence its chemistry.