AMPTE-Charge Composition Explorer, also called as AMPTE-CCE or Explorer 65, was a NASA satellite designed and tasked to study the magnetosphere of Earth, being launched as part of the Explorer program. The AMPTE (Active Magnetospheric Particle Tracer Explorers) mission was designed to study the access of solar wind ions to the magnetosphere, the convective-diffusive transport and energization of magnetospheric particles, and the interactions of plasmas in space.

The AMPTE-CCE is one of the three components of the international space mission AMPTE, which also included AMPTE-IRM (Ion Release Module), designed by Germany, and AMPTE-UKS (United Kingdom Subsatellite), provided by the United Kingdom.

The mission consisted of three spacecraft: AMPTE-CCE; AMPTE-IRM, which provided multiple ion releases in the solar wind, the magnetosheath, and the magnetotail, with in situ diagnostics of each; and AMPTE-UKS, which uses thrusters to keep station near the AMPTE-IRM to provide two-point local measurements. The AMPTE-CCE (Charge Composition Explorer) spacecraft was instrumented to detect those lithium and barium tracer ions from the AMPTE-IRM releases that were transported into the magnetosphere within the AMPTE-CCE orbit. The spacecraft was spin-stabilized at 10 rpm, with its spin axis in the equatorial plane, and offset from the Earth-Sun line by about 20°. It could adjust attitude control with both magnetic torquing and cold gas thrusters. The AMPTE-CCE used a 2.E8-bit tape recorder and redundant 2.5-watts S-band transponders. The spacecraft battery was charged by a 140-watt solar array.

AMPTE-CCE was launched with the two other satellites of the AMPTE program on 16 August 1984, at 16:48 UTC, from a Cape Canaveral launch pad by a Delta 3924 launch vehicle. It was placed in an equatorial orbit of 1,100 × 50,000 km (680 × 31,070 mi) with an inclination of 4.8°.

Charge Composition Explorer was instrumented to detect those lithium and barium tracer ions from the IRM released that were transported into the magnetosphere within the CCE orbit. The spacecraft was spin-stabilized at 10 rpm, with its spin axis in the equatorial plane, and offset from the Earth-Sun line by about 20°. It could adjust attitude with both magnetic torquing and cold gas thrusters.

The satellite carries 5 scientific instruments that are used to measure the composition of the particles in the magnetosphere throughout their energy spectrum and the changes that affect them with the objective of determining the main processes governing their excitation, their displacement and their disappearance. CCE must also detect the lithium and barium ions released by the MRI satellite and transported in the magnetosphere:

The instrument was a triaxial fluxgate magnetometer mounted on a 2.4 m (7 ft 10 in) boom. It had seven automatically switchable ranges (from ± 16 nT to ± 65,536 nT) with resolution commensurate with a 13-bit analog-to-digital converter, and was read out at 8.6 vector samples/second. The signals from two sensors (one parallel to the spin axis and one orthogonal) were also fed into 5-50 Hz bandpass channels that were read out every 5 seconds.

The instrument consisted of an entrance collimator and electrostatic analyzer section followed by a time-of-flight and total-energy-measurement section floating at a 30 kV acceleration potential. The energy range covered was from 1 to 300 keV/Q, with a geometric factor of 2.E-3 cm²-sr and 32-sector angular resolution. Energy resolution was 5 to 18%, and all charge states and isotopes of Hydrogen (H) and Helium (He), the charge states of Lithium (Li), and the major elements and charge states up to and including Iron (Fe) were resolved.