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Image Credit: JAXA.

Epsilon launch postponed due to unfavorable weather conditions

The launch of a Japanese Epsilon rocket from the Uchinoura Space Center in Japan has been postponed due to unfavorable weather conditions. The four-stage rocket was scheduled to blast off from the spaceport on October 07, 2021 at 00:51:21 UTC / 09:51:21 JST, carrying the RAISE-2 satellite and eight rideshare payloads into a 560 km high Sun-synchronous low Earth orbit. The launch was originally scheduled to occur on October 01, but had to be aborted 19 seconds prior to liftoff, due to a malfunctioning ground station. A new launch date has not yet been announced.

The flight will be the first rocket launch from Japan in 2021 and the first Epsilon launch since January 18, 2019.

The Epsilon rocket seen at the launch pad at the Uchinoura Space Center in Japan. Image Credit: JAXA.
The Epsilon rocket seen at the launch pad at the Uchinoura Space Center in Japan. Image Credit: JAXA.

The nine satellites will be launched as part of the Innovative Satellite Technology Demonstration Unit 2, the second mission of the Japan Aerospace Exploration Agency ‘s (JAXA) Innovative Satellite Technology Demonstration Program. This program enables companies, universities and research insitutes to launch and test new technologies on orbit, to improve spaceflight activities.

The first mission, known as the RAPid Innovative payload demonstration Satellite 1 ( RAPIS-1), launched on January 18, 2019 atop an Epsilon from the Uchinoura Space Center. The spacecraft hosted seven technology demonstrations and was in service for over one year until June 24, 2020.

The payloads


RAISE-2, or Rapid Innovative payload demonstration Satellite 2, is the primary payload and the largest and heaviest satellite launched as part of the second Innovative Technology Demonstration Program mission.

The spacecraft has a mass of 110 kilograms and is 0.75 x 1.00 x 1.00 m in size. RAISE-2 is operated by JAXA and carries six technology demonstrations selected from proposals from companies and research insitutes.


Hibari, the second largest payload atop Epsilon, is a 55 kilograms heavy and 0.59 x 0.59 x 0.55 m large satellite built and operated by the Tokyo Institute of Technology.

The spacecraft will test the feasibility of changing its orientation utilizing the reaction torque created by rotating its solar array paddles. As a secondary mission, Hibari’s fast response capability will be used to observe the origin of gravitational waves, once the waves are detected on Earth by ground-based observatories.


Z-Sat is a 0.50 x 0.50 x 0.51 m large and 46 kg heavy microsatellite developed by Mitsubishi Heavy Industries. The spacecraft will test the combined usage of near- and far-infrared cameras to more accurately measure heat sources on the planet. If the technology turns out to be feasible, it will be used for an orbital constallation of Earth monitoring satellites.


TeikyoSat-4, also known as Ooruri, is a 52 kg microsatellite built by the Teikyo University in Tokio. The spacecraft will be launched to observe the effects of microgravity on the growth of the slime mold “Dictyostelium discoideum”, which is housed inside TeikyoSat-4 in a pressurized and environmentally controlled chamber.


ASTERISC is a 4 kilograms heavy three-unit CubeSat built by the Narashino-based Chiba Insitute of Technology. The satellite will be launched to test a membrane-like dust sensor used for the observation of dust particles and space debris in low Earth orbit.


NanoDragon is a 3.8 kg heavy 3U CubeSat developed and built by the Vietnam National Space Center (VNSC) and the Vietnam Academy of Science and Technology (VAST) in cooperation with Meisei Electronics Co, Ltd. as the result of the nation’s Nano-class satellite development, launch and trial operation project.

The satellite was built to test a newly developed on-board computer, the attitude control system and the automatic identification system receiver, which is used to track and identify ships to avoid collisions.


KOSEN-1 is a 2U CubeSat operated by the Kochi National College of Technology. Once in orbit, the small spacecraft will conduct radio observations of Jupiter, the solar system’s largest planet. The satellite is therefore equipped with a seven-meters long deployable antenna, as well as two ultra-thin reaction wheels and a new on-board computer to allow for precise changes in orientation.


ARICA is a 1U CubeSat operated by the Aoyama Gakuin University in Tokio, Japan. The 1 kilogram spacecraft is equipped with a sensor to detect gamma-ray burst and will test the capability of real-time communication with ground stations via the Iridium and GlobalStar satellite constellations.

The Epsilon launch vehicle

The Epsilon is a three- to four-stage launch vehicle developed and operated by the Japan Aerospace Exploration Agency.

The rocket is 26 m in height, has a diamter of 2.6 m and a launch mass of 91 to 95.4 tonnes, depending on the configuration.

The launcher’s first stage, known as the SRB-A3, is a 11.7 m tall and 2.6 m wide solid rocket motor derived from the strap-on boosters of the Japanese H-IIA rocket. The SRB-A3 weighs about 75 tonnes fully loaded and has a burn time of 116 seconds. The stage provides around 2,271 kN of thrust.

The second stage, the M-35 is a solid rocket stage derived from the third stage of the former Japanese M-V launch vehicle. The M-35 is 4.3 m in height, 2.6 m in diameter and has a launch mass of 17 tonnes. It fires for 140 seconds, burning HTPB as a propellant, and generates 372 kN of thrust.

Epsilon’s third stage and the rocket’s final solid rocket motor is derived from the M-V’s fourth stage and is known as the KM-V2c. The stage burns for roughly 90 seconds and generates 99.8 kN of thrust. The solid motor is 2.3 m in lenght, 1.4 m in diameter and has a launch mass of 3.3 tonnes. In contrast to the SRB-A3 and the M-35, the KM-V2c is encapsulated under the launcher’s payload fairing together with the payload.

If required, the Epsilon rocket can be outfitted with a liquid-fueled fourth stage, known as the Post Boost Stage, or PBS for short. The PBS is 1.2 m in length, 1.5 m in diameter and has a launch mass of just 100 kilograms. It can be restarted multiple times and generates 0.4 kN of thrust in vacuum.

The Epsilon is able to launch up to 1,200 kg into a 250 x 500 km low Earth orbit (LEO) in the three-stage configuration, or 700 kg into into a LEO or 450 kg into a Sun-synchronous orbit in the four-stage configuration. The rocket is also capable of launching not only one single spacecraft, but multiple smalles satellites into orbit.

Irrespective of the amount of payloads, the Epsilon rocket features a 11.1 m tall, 2.6 m wide and 1.0 tonnes heavy two-halve payload fairing, which encapsulates the payloads, as well as the launcher’s third and fourth stage. The fairing gets jettisoned from the Epsilon once the SRB-A3 first stage has burned out.

The rocket had its maiden flight in September 2013 and has since conducted four successful flights.

An Epsilon rocket launches JAXA's RAPID-1 satellite into orbit. Image Credit: JAXA.
An Epsilon rocket launches JAXA’s RAPID-1 satellite into orbit. Image Credit: JAXA.


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