The 12-sided polyhedron spacecraft JIKIKEN (EXOS-B) featured a 1-meter boom for a vector magnetometer in addition to extensible dipole antennae with lengths of 69.6 and 103 meters. 30 W were supplied to a battery and regulator system by a solar panel array.

With both sets of antennas extended, the spacecraft's spin decreased from 150 revolutions per minute to 3 revolutions per minute. A solar sensor was used to measure the angle with an accuracy of 0.5 degrees. Wideband 10 kHz or 3 kHz data was handled by a 2 W400 MHz PM system, while 256 or 1024 bps was handled by a 0.5 W136 MHz PCM/PM telemetry system. With the exception of a 10-Kbyte buffer used for housekeeping and plasma parameter data, data collecting was done in real time.