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Japanese Space Research and Development on the International Space Station

Shoji Torii
Professor, Faculty of Science and Engineering, Waseda University

Space research and development has a technical side of opening up space in mankind’s pursuit of new frontiers and a scientific side of studying the universe. The International Space Station (ISS) was built with the unique idea of achieving both sides through international collaboration. The ISS was completed over a 13-year period from 1999 to 2011 with the participation of 15 countries including Japan, the US, Russia, Canada, the European Space Agency (ESA), and others.

Different countries operate their own unique facilities, and Japan in particular conducts research and development utilizing the features of its Japanese Experiment Module (JEM), also called Kibo, a manned space experiment facility comprised of a Pressurized Module (PM, an on-board laboratory) and Exposed Facility (EF, an external experiment platform). Japan has also developed the H-2 Transfer Vehicle (HTV), or Kounotorii, for delivering cargo to the ISS with its payload of around six tons and highly acclaimed automatic navigation technology. Above all, the recent remarkable work of astronaut Koichi Wakata as a commander of the Space Station also obviously demonstrates how Japan has gained even greater knowhow concerning space exploration since its first opportunity of manned activity.

In scientific experiments and observations, a crucial role is played by research using the microgravity environment of the PM and space science observations in the EF. In this article, I outline the Japanese equipment on board JEM-EF before giving an overview of CALET (CALorimetric Electron Telescope) , the apparatus for observing high-energy electrons and gamma-rays on which I am a leading researcher, and explaining the significance of its observations.

As Figure 1 shows, JEM-EF is a multipurpose experiment platform providing an exposed environment for conducting scientific observations, earth observations, communications, science and engineering experiments, and so on, and has 12 ports to which experiment equipment can be connected. Currently installed on JEM-EF are three Japanese experiment payloads: SEDA-AP, which measures space environment data, MAXI, which monitors all-sky X-ray images, and SMILES, which observes superconducting sub-millimeter wave limb-emissions. Also installed is MCE, a multi-mission port-sharing payload with a mixture of earth observation equipment, science and engineering experiments, and consumer high vision cameras. Japan’s fifth payload, CALET, is due for launch in 2014 and will be installed as a replacement to the port currently occupied by SEDA-AP.

Figure 1: Conceptual image of the installation of CALET to the JEM-EF platform as of 2014.

The targets of CALET’s observations are the high-energy subatomic particles and atomic nuclei radiating from space called cosmic rays. The study of cosmic rays is conducted from the perspective of particle physics or nuclear physics, that is, the generation and disappearance of particles, and the perspective of astrophysics, that is, the acceleration and propagation of particles. To gain a comprehensive understanding of the structure of the universe and individual celestial phenomena, it is essential to not only observe electromagnetic waves such as visible light, infrared and X-rays but also figure out both elementary particle cosmology and astronomical cosmology by observing cosmic rays and high-energy gamma rays. Such observations, however, are in unchartered territory due to difficulties with measurement technologies, and the origin of these high-energy particles is one of the remaining frontiers of space science. Electrons or gamma rays of 100 gigaelectronvolts (GeV) or more are a particularly unexplored field due to the difficulty of measuring them directly, and it is hoped in the future that dramatic observations will be achieved, including new discoveries such as explanations for dark matter, one of the great mysteries of astrophysics, and particle acceleration bodies.1 Figure 2 conceptually shows the origin of cosmic rays.

Figure 2: The source of subatomic particles pouring in from outer space

Figure 3: Conceptual image of CALET

CALET, illustrated in Figure 3, is an observation system with an imaging calorimeter (CAL) as its main detector, designed on the basis of our experience in balloon observations spanning two decades.2 The AMS-02, already operating on the ISS,and the Fermi gamma-ray satellite include similar observation equipment, but whereas they are both very large observation devices with a gross mass of seven tons each, CALET has the advantage of weighing only a tenth of that while being able to observe higher energies due to its optimized observation system. Significant synergistic results can be expected from the complementary observations of CALET and these other devices.

Although international collaboration such as that on ISS is essential for space research and development due to the enormous budget needed, the main point is for countries to conduct projects based on their own ideas within this collaborative relationship. I believe that the key to the future growth of Japanese space research and development, including international collaborative research, is to combine the international cooperation already started on the ISS with international competition.

References

1. “Observing Cosmic Rays in Space [Uchuusen wo chokusetsu toraeru]” by Shoji Torii
Nihon Butsuri Gakkaishi journal (The Centenary of the Discovery of Cosmic Rays), Volume 67 pp. 821-826 (2012)

2. “CALET Mission - Explaining the High-Energy Universe [Kou enerugii uchuu wo kaimei suru CALET misshion]” by Shoji Torii
IEEJ Transactions on Fundamentals and Materials Vol.132 pp.603-608. (2012)

Shoji Torii
Professor, Faculty of Science and Engineering, Waseda University

[Profile]
Professor, Department of Physics, School of Advanced Science and Engineering, Graduate School of Advanced Science and Engineering, Faculty of Science and Engineering, Waseda University.
Graduated from the Faculty of Science, Kyoto University in 1972, left the doctoral program of the Graduate School of Science, Kyoto University in 1977 after completing the required courses, and became a Doctor of Science at Kyoto University in 1978. He worked as a Japan Society for the Promotion of Science grant-in-aid researcher at the Institute for Cosmic Ray Research, University of Tokyo from 1977, researcher at the same institute from 1979, research associate at the Physics Department of Utah State University, US from 1982, and assistant, lecturer, assistant professor and professor on the Faculty of Engineering, Kanagawa University from 1983 before taking up his current position in 2004. His area of specialization is cosmic ray physics.

[Publications]
“Modern Astronomy Series, Volume 17: Space Observation III - High-Energy Astronomy” [Shiriizu gendai tenmongaku dai 17 kan Uchuu no kansoku III ―Kou enerugii tenmongaku], cowriter, “3.2 Flying object observation and observation technologies [hishoutaikansoku to kansoku gijutsu” (Nippon Hyoronsha Co., Ltd., 2008)