Exploration of Energization and Radiation in Geospace (ERG): Development, Preliminary Flight Results, and Lessons Learned in JAXA’s Small Science Satellite Project

Exploration of Energization and Radiation in Geospace (ERG): Development, Preliminary Flight Results, and Lessons Learned in JAXA’s Small Science Satellite Project

The Geospace explorer, the ERG satellite or nicknamed “ARASE” satellite, is the second satellite in the series of small science satellite program by Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA). It was launched on December 20, 2016 by Epsilon launch vehicle. The satellite is now working quite well as designed, and preliminary mission data is being obtained. The purpose of the ERG project is to unravel how high energy electrons over MeV in the Earth’s radiation belt (Van Allen Belt) are generated and lost by measuring interaction between plasma wave and electrically charged particles. To measure these physical processes in-situ, ERG dives into the center of the radiation belt. The orbit of ERG is highly elliptic; apogee altitude is approximately 32,000 km and perigee altitude is 440 km. In this paper, we introduce the scientific background and the outline of the satellite system design to effectively achieve the scientific observations with a small satellite standard bus. Then preliminary flight results are introduced, and finally lessons learned are discussed.