Arase (satellite)

Arase
	Artistic rendering of Arase in orbit.
Mission type	Earth observation
Operator	JAXA
COSPAR ID	2016-080A
SATCAT no.	41896
Mission duration	7 years, 8 months and 7 days (elapsed)
Spacecraft properties
Bus	SPRINT
Launch mass	~350 kg
Power	≧700 W
Start of mission
Launch date	11:00:00, December 20, 2016 (UTC)
Rocket	Epsilon
Launch site	Uchinoura
Orbital parameters
Reference system	Geocentric
Perigee altitude	~460 km
Apogee altitude	~32110 km
Inclination	~31 degrees
Period	~565 minutes
Instruments
	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]

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.^[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.

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.^[4]

Instruments

Arase carries following instruments:^[3]

XEP-e (Extremely high-energy electron sensor)^[5]
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.^[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]