title: Arase (satellite)
text: # Arase (satellite)
  
  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.
  
  ## Spacecraft
  
  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. Once in orbit, it will extend four solar panels, two 5 m masts, and four 15 m wire antennas. The spacecraft is spin-stabilized at 7.5 rpm (8 seconds).
  
  Planned mission duration was for one year of scientific observation, but the mission remains active over 5 years later.
  
  ## Launch
  
  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.
  
  ## Instruments
  
  Arase carries following instruments:
  
  * XEP-e (Extremely high-energy electron sensor)
  * HEP-e (High-energy particle sensor – electron)
  * MEP-e (Medium-energy particle sensor – electron)
  * LEP-e (Low-energy particle sensor – electron)
  * MEP-i (Medium-energy particle – ion)
  * LEP-i (Low-energy particle – ion)
  * MGF (Magnetic Field Experiment)
  * PWE (Plasma Wave Experiment)
  * S-WPIA (Software Wave-Particle Interaction Analyzer)
  
  MGF is located at the end of 5 m extended mast.
  
  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).
  
  S-WPIA will analyse the data obtained by other instruments.
  
  