BE-C (Explorer 27) was a small ionospheric research satellite instrumented with an electrostatic probe, radio beacons, a passive laser tracking reflector, and a Doppler navigation experiment. Its primary objective was to obtain worldwide observations of total electron content between the spacecraft and the earth. The satellite was initially spin stabilized, but it was despun after solar paddle erection. Subsequent stabilization oriented the satellite axis of symmetry with the local magnetic field by means of a strong bar magnet and damping rods. A three-axis magnetometer and sun sensors provided information on the satellite attitude and spin rate. There was no tape recorder aboard so that satellite performance data and electrostatic probe data were observed only when the satellite was within range of a ground telemetry station. Continuous transmitters operated at 162 and 324 MHz to permit precise tracking by "Transit" tracking stations for navigation and geodetic studies. The satellite was turned off on July 20, 1973, due to frequency interference with higher priority spacecraft.