Science
ARASE (ERG)
Van Allen Radiation Belt Science Satellite · JAXA / ISAS
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Arase (ERG), launched by JAXA in 2016 to solve a mystery that has puzzled physicists since the Van Allen radiation belts were first discovered in 1958: what actually accelerates electrons trapped in Earth's magnetic field up to nearly the speed of light. Flying deep into the heart of the belt on a highly elliptical orbit, Arase carries nine instruments measuring particles and plasma waves simultaneously, directly observing the wave-particle interactions responsible. Nearly nine years after launch, it's still returning data — including observations of the extreme May 2024 geomagnetic superstorm, one of the strongest in two decades.
Its orbit
- Orbit
- Highly Ellipticalswings far out, then dives back close to Earth
- Altitude
- 254–19,754 mi (409–31,791 km)
- Inclination
- 31.9°
- One orbit
- 9.3 hours2.6 orbits a day
- NORAD ID
- 41896
- Int’l designator
- 2016-080A
- Launched
- 2016
Orbital elements from CelesTrak, as of 22 Sep 2026.
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