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The OMOTENASHI (Outstanding MOon exploration TEchnologies demonstrated by NAno Semi-Hard Impactor) mission is a JAXA (Japan) and University of Tokyo technology demonstration mission. The ONOTENASHI spacecraft is a 6U cubesat that will make a semi-hard survivable landing on the Moon with the primary objective of testing the technologies and trajectory maneuvers that allow for such a landing. It will also be measuring the radiation environment beyond low-Earth orbit. OMOTENASHI is scheduled to launch on the Artemis 1 mission as a ride-on secondary satellite on the Space Launch System (SLS) Block 1 in late 2021.

Spacecraft and Subsystems

OMOTENASHI is a 6U cubesat, 10 x 20 x 30 cm, with a mass of approximately 14 kg. It comprises a small (0.715 kg) Surface Probe, a Retromotor Module (~4.3 kg), and an Orbit Module (~8.5 kg). The Surface Probe has an inflatable airbag and shock absorption system comprising crushable material and an epoxy filling, designed to allow survival in surface impacts at target speeds of 50 m/s vertical and 100 m/s horizontal, corresponding to a few hundred meters of lunar free fall. It has a P-band transponder for communications and an 18 Whr lithium battery for power. The Retromotor Module contains a 500-N solid rocket motor capable of about 2500 m/s deceleration and forms the core of the cubesat. The Orbit Module guides the spacecraft trajectory. It also carries a radiation monitor. Spacecraft attitude is maintained with four 25-mN axial thrusters using R236fa propellant. The total mass of propellant is 0.74 kg, stored in a 589 ml tank. Fine control is achieved by 3 reaction wheels. Positional knowledge is via a star tracker, 4 Sun sensors, and a 3-axis IMU. Spacecraft power is provided by body-mounted solar cells and batteries. Attitude control is via cold gas jets mounted on either side of the solid rocket motor.

Mission Profile

After separation from the SLS, OMOTENASHI will make a single maneuver, a lunar impact orbit, combining lunar orbit insertion and descent. The cubesat then spins up and the airbag is inflated. At the end of the descent phase, the Orbit Module is jettisoned and the solid rocket motor is fired, bringing the spacecraft almost to a vertical standstill at an altitude of 100 - 200 meters. The surface probe is then released and makes a free-fall to the lunar surface, impacting at a shallow angle at roughly 30 m/s vertical velocity and under 100 m/s horizontal. The airbags and shock absorption mechanism are designed to ensure a survivable landing.

Alternate Names

    Facts in Brief

    Launch Date: 2021-11-01
    Launch Vehicle: SLS Block 1 Crew
    Launch Site: Cape Canaveral, United States
    Mass: 14 kg

    Funding Agency

    • Japan Aerospace Exploration Agency (Japan)


    • Planetary Science
    • Engineering

    Additional Information

    Questions and comments about this spacecraft can be directed to: Dr. David R. Williams



    NameRoleOriginal AffiliationE-mail
    Dr. Tatsuaki HashimotoMission Principal InvestigatorInstitute of Space and Aeronautical
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