The purpose of the Exos D or Akebono mission was to investigate the particle acceleration regions above the auroral region in order to develop a better understanding of the acceleration mechanism and its relation to substorm phenomena.

The spacecraft was spin-stabilized with a rotation rate of 7.5 rpm. The attitude was magnetically controlled with the spacecraft axis pointing to the sun. All onboard operations such as command and data acquisition were controlled by an onboard computer permitting automatic operations for a full week.

JAXA stopped sending and receiving signals to and from EXOS-D on April 23, 2015, to terminate its operation after more than 26 years in orbit.