Associate Professor Otsuki Masatsugu receives the 2025 MEXT Commendation for Science and Technology

MMX Project member, Otsuki Masatsugu, has been awarded the 2025 MEXT Commendation for Science and Technology from the Ministry of Education, Culture, Sports, Science and Technology (MEXT).

Otsuki received the award for his “Contribution to international space exploration through observations of granular behaviour in a low-gravity environment”.

Otsuki is the PI (Principal Investigator) of the “Hourglass mission” that explored how granular materials such as planetary regolith behave in gravity environments weaker than on Earth. The award was issued jointly together with MMX Project System researchers and JAXA staff members who participated in this project:

• Ozaki Shingo (Professor)
  Yokohama National University, Faculty of Engineering, Division of Systems Research
  
• Ishigami Genya (Professor)
  Keio University, Faculty of Science and Technology, Department of Mechanical Engineering
  
• Maeda Takao (Associate Professor)
  Tokyo University of Agriculture and Technology, Graduate School of Engineering, Division of Advanced Mechanical Systems Engineering
  
• Sutoh Masataku (Chief R&D Engineer)
  JAXA, Human Spaceflight Technology Directorate

In 2018, the Hourglass mission was begun to observe the behavior of granular materials in a low-gravity environment. The mission was conducted onboard the International Space Station (ISS) in collaboration with the JAXA Human Spaceflight Technology Directorate, with the majority of members from the MMX Project at the JAXA Institute of Space and Astronautical Science, and researchers from universities who joined via the MEXT Joint Usage / Research Center that is designed to enable domestic researchers to share large-scale facilities.

Hourglass-shaped containers holding granular material (natural sand from Earth as well as simulated regolith) was brought into an artificial gravity generator (Centrifuge-equipped Biological Experiment Facility: CBEF) within the Japanese experiment module “Kibo” on the ISS, and observations were conducted for just under 60 hours. An example of granular material is the fine particle surface layer of solid celestial bodies, such as rocky planets and moons. Understanding how this regolith material responds during a spacecraft landing is essential to a mission design such as the Martian Moons eXploration (MMX) mission, where the landing gear must safely touchdown and take-off without being buried or overturning the spacecraft, or a rover such as IDEFIX that must run across the surface.

Analysis of the Hourglass mission data compared the difference in the granular flows between natural gravity and artificial gravity while in orbit (determining whether it was possible to reproduce natural gravity with this experiment), and explored how gravity affects the flow characteristics of granular material, and the effect on the adhesive forces between the granular particles. The results not only confirmed that the Hourglass mission could be used to check the behaviour of granular material in a gravity environment less than that on Earth, but also contributed valuable information to the fundamental study of the analysis of regolith dispersion and landing dynamics for the MMX landing gear. It has been demonstrated that the utilisation of low Earth orbit, commencing with the ISS, by the private sector will contribute to the pursuit of “exploration.”

Comment from Otsuki Masatsugu, upon receiving the award:

I am truly honoured to have received such a prestigious award. The Hourglass Mission, which is behind this award, began with words from the MMX Project Manager, “isn’t it time to go beyond extrapolation?” During tests on Earth, we had tried to somehow create the ground conditions that would occur at the time of landing on an asteroid, and acquire the parameters needed to predict interactions between the spacecraft and granular regolith. As a first step to improving this, we used the Hourglass Mission to quantify the forces acting on granular particles. From this, it became possible to estimate the adhesion force from the differences in the behavior of granular particles in various gravitational environments, allowing us to create a valid analysis for low gravity situations. I would like to extend my deepest gratitude to all the people involved at ISAS and the Human Spaceflight Technology Directorate, as well as all the related companies who supported this activity alongside us.

Decision on the recipients of the Minister of Education, Culture, Sports, Science and Technology Award (in Japanese):
https://www.mext.go.jp/b_menu/houdou/mext_01503.html