Spaceflight Insider

Japan’s Epsilon rocket sends Van Allen belt spacecraft into orbit

Epsilon-2 Launch with ERG aboard

Epsilon-2 Launch with ERG aboard. (Click for full view) Photo Credit: JAXA

Using an upgraded Epsilon rocket, Japan sent its Exploration of Energizing and Radiation in Geospace (ERG) spacecraft into a high-energy orbit that will repeatedly pass through the Van Allen belts to allow the probe to study how geomagnetic storms form. Liftoff from Kyushu Island took place at 8 p.m. Japan Standard Time (6 a.m. EST / 11:00 GMT).

This was only the second time Japan had launched an Epsilon rocket, which made its debut flight in 2013. It replaces the country’s M-V rocket, more expensive and larger, which was retired in 2006.

ERG observing Van Allen belts

An artist’s rendering of the ERG spacecraft observing and studying Earth’s Van Allen belt. Image Credit: JAXA

Epsilon is a three-stage, 85-foot (26-meter) tall Japanese solid-fuel rocket. The booster was derived from the strap-on motors used on Japan’s H-2A launcher. It is designed to lift payloads smaller than 2,600 pounds (1,200 kilograms) – depending on the orbit and altitude required for payload insertion.

At ignition, the first stage propelled the stack to more than 5,000 mph (8,000 km/h), pushing it out of the atmosphere to allow for the payload fairing at the top to reveal the spacecraft. After about 116 seconds, the first stage burned out and dropped away.

Firing several seconds later, the second stage burned for about two minutes before it too separated and fell away. While that was ongoing, the thrusters on the Epsilon rocket started to spin the vehicle to stabilize it on its way into orbit.

The third stage fired for another minute-and-a-half to place it into a 136-mile (219-kilometer) by 20,600-mile (33,200-kilometer) orbit with an inclination of 31.4 degrees relative to the equator.

After separating from the third stage, the ERG spacecraft separated and extended its four solar arrays.

The whole flight from liftoff to separation took about 13 minutes and 27 seconds. The Japan Aerospace Exploration Agency (JAXA) confirmed the successful separation in a press release not long after the launch.

According to the release, signals were received at 8:37 p.m. Japan Standard Time (6:37 a.m. EST / 11:37 GMT) by the Santiago Ground Station in the Republic of Chile.

The ERG spacecraft is nicknamed “ARASE”. This is a Japanese word for a river raging with rough white water. The mission team named it that due to the conditions the spacecraft will undergo. It will study Earth’s inner magnetosphere where energetic charged particles are trapped, forming belts – the Van Allen belts.

ARASE is also the name of the Arase River, which runs through Kimotsuki, Kagoshima, where JAXA’s Uchinoura Space Center is located.

The ERG spacecraft weighs about 772 pounds (350 kilograms). Its SPRINT bus measures about 4.9 feet (1.5 meters) by 4.9 feet (1.5 meters) by 8.9 feet (2.7 meters). With the solar panels extended, it measures 18 feet (5.5 meters) from end to end in each direction. Those panels will generate 700 watts of power.

The spacecraft was spin stabilized at about 7.5 rotations per minute, or one every 8 seconds. Its orbital period is 538 minutes.

It carries with it nine instruments to study the radiation belts: 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 – electro), MEP-i (Medium-energy particle – ion), LEP-i (Low-energy particle – ion), MGF (Magnetic Field Experiment), PWE (Plasma Wave Experiment), and S-WPIA (Software Wave-Particle Interaction Analyzer).

The primary mission is expected to last for one year, with the possibility of an extension.

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Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity. You can find him on twitter @TheSpaceWriter.

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