Artistic rendering of Arase in orbit.
Mission typeEarth observation
COSPAR ID2016-080A Edit this at Wikidata
SATCAT no.41896
Mission duration6 years, 11 months and 18 days (elapsed)
Spacecraft properties
Launch mass~350 kg
Power≧700 W
Start of mission
Launch date11:00:00, December 20, 2016 (UTC) (2016-12-20T11:00:00Z)
Launch siteUchinoura
Orbital parameters
Reference systemGeocentric
Perigee altitude~460 km
Apogee altitude~32110 km
Inclination~31 degrees [1]
Period~565 minutes
  • Extremely high-energy electron sensor (XEP-e)
  • High-energy particle sensor – electron (HEP-e)
  • Medium-energy particle sensor – electron (MEP-e)
  • Low-energy particle sensor – electron (LEP-e)
  • Medium-energy particle – ion (MEP-i)
  • Low-energy particle – ion (LEP-i)
  • Magnetic Field Experiment (MGF)
  • Plasma Wave Experiment (PWE)
  • Software Wave-Particle Interaction Analyzer (S-WPIA)

Arase, formerly known as Exploration of energization and Radiation in Geospace (ERG), is a scientific satellite to study the Van Allen belts. It was developed by the Institute of Space and Astronautical Science of JAXA. While there was a scientist working on a similar project with the surname Arase, the satellite's name has nothing to do with him but instead named after a river beside the launch point.

It was launched aboard Epsilon launch vehicle at 11:00:00, 20 December 2016 UTC into apogee height 32250 km, perigee 214 km orbit. Subsequent perigee-up operation moved its orbit to apogee 32110 km, perigee 460 km of 565 minutes period.[2]


The Arase spacecraft is the second satellite based on SPRINT bus, after Hisaki (SPRINT-A). Arase weighs about 350 kg, measures about 1.5 m × 1.5 m × 2.7 m at launch.[3] Once in orbit, it will extend four solar panels, two 5 m masts, and four 15 m wire antennas.[3] The spacecraft is spin-stabilized at 7.5 rpm (8 seconds).[3]

Planned mission duration was for one year of scientific observation, [3] but the mission remains active over 5 years later.


Arase's launch on the enhanced Epsilon's maiden flight was originally scheduled for 2015, but was postponed to the 2016 financial year due to satellite development delays.[4]


Arase carries following instruments:[3]

MGF is located at the end of 5 m extended mast.[3]

PWE consists of a search coil (PWE-MSC) located at the end of another 5 m extended mast, four 15 m wire antennae (PWE-WPT), and associated electronics unit (PWE-E).[3]

S-WPIA will analyse the data obtained by other instruments.[3]

See also


  1. ^ "Arase (ERG) Geospace Probe - JAXA". JAXA. Retrieved 2018-03-14.
  2. ^ ジオスペース探査衛星「あらせ」(ERG)の軌道変更運用(近地点高度上昇)の完了について (in Japanese). JAXA. 13 January 2017. Retrieved 18 January 2017.
  3. ^ a b c d e f g h プレスキット/2016年11月18日(木) (PDF) (in Japanese). November 18, 2016. Archived from the original (PDF) on December 26, 2016. Retrieved November 27, 2016.
  4. ^ Shogo Matsuda (16 January 2015). "Japan's Epsilon rocket shoved aside?". Nikkei Asian Review. Retrieved 6 February 2015.
  5. ^ "Exploration of energization and Radiation in Geospace (ERG)". JAXA. 2012. Archived from the original on 2013-10-30. Retrieved 2013-09-08.