The Combined Release and Radiation Effects Satellite (CRRES) was launched on July 25, 1990, into a geosynchronous transfer orbit (GTO) for a nominal three-year mission to investigate fields, plasmas, and energetic particles inside the Earth's magnetosphere.

[3] CRRES carried an array experiments including chemical releases and a complement of sophisticated scientific instruments to accomplish these objectives.

Earthspace was the laboratory, and the releases were studied with an extensive network of ground-, aircraft-, and satellite-based diagnostic instruments.

[4] Other magnetospheric, ionospheric, and cosmic ray experiments were also included onboard CRRES and supported by NASA or the Office of Naval Research.

The spacecraft body was spun at 2.2 rpm about a spin axis in the ecliptic plane and kept pointed about 12 degrees ahead of the Sun's apparent motion in celestial coordinates.