Early Universe
The universe immediately after its birth is believed to have been in a state of high-temperature, high-density plasma, a phase known as the Big Bang. Radiation (such as light and gravitational waves) emitted during the Big Bang era—or even before—has traveled for 13.8 billion years to deliver a variety of information to us today.
In particular, the cosmic microwave background (CMB) has been observed to arrive almost uniformly from all directions outside our galaxy, providing direct evidence of the Big Bang. Moreover, it has been found that the CMB contains intensity fluctuations on the order of 10-4. From these patterns, properties such as the age and composition of the universe have been estimated with high precision. We are now in the era of precision cosmology. The Institute of Space and Astronautical Science (ISAS) is tackling the ultimate question: what existed before the Big Bang, and how did the universe begin? Gravitational waves emitted shortly after the birth of the universe are called primordial gravitational waves, and they are believed to be the key to understanding the origin of the cosmos. To detect these waves, research is being conducted using two approaches. The first is LiteBIRD, scheduled for launch in the 2030s, which aims to make the world's most sensitive measurements of CMB polarization and achieve the first detection of primordial gravitational waves through its patterns. The second approach is to directly detect primordial gravitational waves. To capture such extremely weak and long-period waves, it is necessary to construct gravitational-wave observatories in space, and foundational research and development toward this goal is currently underway.
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Hot Topics
- LiteBIRD aims to find evidence for the greatest expansion in the history of the Universe | Cosmos blog
- Implementing Arrangement with the Centre National d'Etudes Spatiales (CNES) for Lite (Light) satellite for the study of B-mode polarisation and Inflation from cosmic background Radiation Detection (LiteBIRD) | ISAS Topics
- 重力波観測のこれまで、これから | 宇宙科学研究所 読むISAS
Material Circulation and Chemical Evolution
Approximately 13.8 billion years ago, the Big Bang that occurred just after the birth of the universe produced light elements such as hydrogen and helium. In contrast, today’s universe is rich in heavy elements—such as carbon, oxygen, iron, and gold—that support life and civilization. These elements did not exist from the beginning; rather, their abundance has gradually increased through nuclear fusion processes accompanying the evolution of stars and supernova explosions. Heavy elements scattered into space by supernova explosions condense to form various compounds, becoming the seeds for the next generation of stars and planets. This entire process of element formation and the circulation of matter can be studied in detail through X-ray observations of massive stars and supernova remnants, as well as infrared observations of interstellar dust.
Some heavy elements are ejected from galaxies, overcoming their gravitational force and flowing into intergalactic space, where they become part of the plasma in galaxy clusters. By investigating the chemical composition of galaxies and galaxy clusters using X-rays, we can study the large-scale chemical evolution of the universe.
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Structure Formation of the Universe
The structure of the universe is formed through the growth of density “fluctuations” that existed in the very early universe, amplified by gravitational instability through the expanding universe. The nature of dark matter and dark energy, which determine the behavior of cosmic expansion, remains unknown and constitutes a major challenge in modern cosmology.
As density fluctuations grow, they eventually form individual astronomical objects as clumps of mass. When the gas within these structures cools, stars are formed and observed as galaxies. Outstanding issues in galaxy formation and evolution through cosmic structure formation include understanding the formation of the first stars and galaxies in the early universe, the mystery of how supermassive black holes form, and the processes that shape the internal structures of galaxies.
When the mass of a forming structure exceeds about ten trillion times the mass of the Sun, the gas cannot cool efficiently and instead becomes a high-temperature plasma at tens to hundreds of millions of degrees, emitting X-rays. A detailed understanding of the dynamical and thermal states of this hot plasma—especially in the central regions of galaxy clusters, including the influence of active supermassive black holes—is still awaited.
Galaxies are not only systems composed of dark matter halos and collections of stars, but also sites where various chemical elements are produced and circulated. Our home galaxy, the Milky Way, is just one among countless galaxies, yet for its individual stars we can measure three-dimensional positions, three-dimensional velocities, and even chemical compositions. By using such data, we can trace how the Milky Way formed from density fluctuations and how the evolution of celestial objects has led to the present-day universe.
Not all matter, however, has become luminous objects. In stars born from metal-rich interstellar material, gas accreting onto newly formed stars creates protoplanetary disks. Within these disks, the aggregation of solid particles is thought to eventually form terrestrial planets, giant planets with solid cores surrounded by accumulated gas, and icy planets. It is expected that these processes of planet formation will also be clarified through observations.
Thus, cosmic structure formation connects a wide range of phenomena—from the formation of galaxy clusters and galaxies from primordial density fluctuations, to star formation, matter circulation, planet formation, and even the chemical evolution that ultimately leads to life. Ongoing research aims to understand this entire picture while also providing physical and scientific explanations for each individual phenomenon.
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Space Plasma Physics
It is known that more than 90% of the baryonic matter in the universe exists in the state of plasma (ionized gas). For example, the cores of stars such as the Sun are composed of high-temperature, high-density fusion plasma exceeding ten million degrees. In addition, the largest structures in the universe, galaxy clusters, as well as the regions surrounding supermassive black holes, are filled with high-temperature plasma that has acquired enormous thermal energy through the release of gravitational energy.
From plasma, electromagnetic radiation (light) is emitted efficiently through interactions such as those between free electrons and positive ions. Extracting physical information about celestial objects through the observation of this radiation is a fundamental approach in astronomical research.
On the other hand, outer space serves as a natural “laboratory,” providing extreme environments—such as high temperature, high density, low density, and strong magnetic fields—that are difficult to reproduce with ground-based facilities. By taking advantage of these conditions and observing space plasmas, we not only test the fundamental laws of physics but also explore new physical phenomena.
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Exoplanets
Exoplanets are planets that orbit stars other than the Sun. The first exoplanet around a Sun-like star was discovered in 1995, and since then, exoplanets have been found around thousands of stars. Among them, Earth-like planets located within the habitable zone—where oceans could exist on their surfaces—are considered especially important from the perspective of future searches for life.
At ISAS, exoplanet surveys around late-type stars, which are smaller than the Sun, are being pursued through projects such as JASMINE and LAPYUTA. In addition, international collaborative missions are underway. These include plans to use microlensing observations with NASA’s Roman Space Telescope to detect planets even at large distances from their host stars and to reveal the overall distribution of masses and orbital properties of exoplanets. Other projects, such as ESA’s ARIEL mission and the Roman mission, aim to investigate the atmospheres of gas giant planets through transmission spectroscopy and direct observations.
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InstrumentDeve lopment
Our universe is known to contain a wide variety of celestial objects and astronomical phenomena, as well as cosmological phenomena and large-scale structures. In order to extract cutting-edge astrophysical information from these observational targets, the development of advanced observational instruments is essential.
The Department of Space and Astronautical Science conducts the development of detectors and optical systems covering a wide range of electromagnetic wavelengths, from radio waves and infrared to X-rays. These efforts strongly support the development of astrophysics missions such as LiteBIRD and JASMINE, while also contributing to the creation of new space science missions.
In addition to these activities, the department is also engaged in advanced experimental research, including laboratory plasma experiments and the development of key technologies required for future gravitational-wave observations.
The Department of Space Astronomy and Astrophysics engages in research on the genesis of our universe, such as how the universe was created, galaxies, stars, and black holes were formed, how various materials in the universe were produced, and what phenomena are occurring in the extreme environment of the universe. Furthermore, we pursue the possibility of life in the universe through research on planet formation, interstellar matter, and exoplanets.
In order to promote research such as using space telescopes and conducting experiments in space, the department researches and develops various devices covering X-rays, visible light, infrared, radio waves, and gravitational waves. We are performing developments for future missions.
Research at the Department of Solar System Sciences covers planetary science and Heliospheric system science. The underlying disciplines include solar physics, space plasma physics, magnetospheric and ionospheric physics, atmospheric science, planetary geology, planetary materials science, and theories governing the formation and evolution of planetary systems. In addition to fundamental academic research, we develop spaceborne science instruments and exploration methods, propose and plan new missions, conduct investigations such as using a collision test facility, and observations using balloons and sounding rockets.
Solar Physics
The Solar Physics Group focuses primarily on our “Sun” and aims to uncover its mysteries, such as:
- - How is the Sun’s high-temperature and dynamic outer atmosphere formed? [Coronal and chromospheric heating]
- - How do flares and plasma eruptions occur? [Magnetic reconnection, particle acceleration, space weather]
- - How is the Sun’s magnetic field generated and maintained? [Generation, evolution, and dissipation of magnetic fields; solar cycle activity]
Academic efforts addressing these questions also connect to broader goals, such as understanding how high-temperature plasmas in the universe are produced, how solar activity affects Earth and other planets, and how typical our life-supporting solar system is compared to others. Our research methods include observations and analysis of acquired data, development of instruments necessary for data acquisition, and numerical simulations required to interpret observations. By integrating these approaches organically, we tackle these challenges. The Solar Physics Group is currently operating the solar observation satellite “Hinode” in orbit. We promote research activities that produce scientific results by comprehensively analyzing data obtained from Hinode, along with data from other satellites and ground-based observatories around the world that collaborate with Hinode. In addition, we are advancing the development of observational instruments and techniques needed for future solar observations, including the next-generation solar physics mission SOLAR-C. We also carry out observational experiments using sounding rockets and high-altitude balloons (such as CLASP, FOXSI, and SUNRISE-3), which are essential steps toward realizing satellite-based observations.
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Hot Topics
- The behavior of the ultra-hot gas in sun-like stars can be predicted from the star's magnetic flux | ISAS Topics
- Global Space News: Could our Sun produce a superflare? | Cosmos blog
- Hinode-IRIS-ALMA Observations Reveal Behaviors at the Foot of Solar Microflares | GATEWAY to Academic Articles
- Sounding Rocket CLASP2 Elucidates Solar Magnetic Field up to the Base of the Corona | ISAS Topics
- SOLAR-C Project Team launched in JAXA (External link: NAOJ)
Space Plasma
The Space Plasma Group conducts research from various perspectives on the interaction between plasma and electromagnetic fields, which are ubiquitous in space. Due to this interaction, phenomena such as explosive plasma acceleration, the formation of massive plasma vortices, and shock wave structures are commonly observed in outer space. What mechanisms drive these phenomena? We are using a variety of methods to unravel these mysteries. Our research methods can be categorized into the development of science instruments for sounding rockets, satellites, and probes, analysis of observed data, and theoretical modeling and simulation. As each of these methods advances and works in concert, our understanding of these phenomena deepens. A key feature of Earth’s near-space environment for space plasma research is that it serves as the only experimental arena for space plasma where we can send satellites and probes to conduct in-situ observations. The Space Plasma Research Group analyzes data from both active and retired satellites and probes (such as ESA’s Jupiter Icy Moons Explorer “JUICE,” the Mercury magnetospheric orbiter “BepiColombo/Mio,” the geospace exploration satellite “Arase,” NASA’s magnetosphere exploration satellite “MMS,” and the lunar orbiter “Kaguya”), to produce scientific results. Additionally, the group is developing science instruments to be installed on satellites and probes currently under development (such as the Martian Moons eXploration ‘MMX’ and the lunar polar exploration “LUPEX”). In addition to fundamental academic research, the group develops new science instruments and exploration methods, plans and evaluates new missions, and conducts observations in the Arctic region using sounding rockets (such as the SS-520-3 sounding rocket and NASA’s LAMP sounding rocket).
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Atmospheric Science
The group studies various planetary atmospheres by utilizing probes (spacecraft, observation rockets, etc.) as well as ground-based observations. The Earth's atmosphere today is very much suited to foster life as a result of co-evolution of the planet and life. In contrast, the CO2-dominated atmospheres of Mars and Venus resulted in either a very thin and cold environment or a very thick and excessively hot one. Understanding how the three planets have become today's states is essential not only for science but also for civilization aspect. Our challenges include the NOZOMI Mars mission, the AKATSUKI Venus mission, the EUV planetary spectrograph HISAKI, and numerous observation rockets for the Earth atmosphere. AKATSUKI became the first Japanese orbiter of another planet, Venus, and acquired valuable data about the Venus atmosphere from December 2015 until the mission officially ended in September 2025. Our group plans and operates the missions, develops onboard instruments, and once data are acquired, they are intensively analyzed. The planetary exploration benefits from resources developed for the Earth's atmosphere, while new findings from other planets expand our horizons even to exoplanets. We continue our activities by conducting Mars missions (MMX and MIM), planning the post-AKATSUKI Venus mission, and joining international mission opportunities.
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Planetary Science
The Solid Planetary Science Group conducts research on the Moon, Mars, Venus, Mercury, asteroids, and the satellites of giant planets to better understand their origin, evolution, internal structure, surface geology, climate, and planetary environments. Our research combines spacecraft data analysis, numerical simulations, laboratory experiments, and theoretical studies.
A particular strength of the group is the integration of remote-sensing observations with laboratory analyses of returned samples and meteorites. By studying both spacecraft data and extraterrestrial materials, we seek to reveal the formation and evolutionary history of planetary bodies in the Solar System.
The group actively utilizes data from JAXA missions, including Kaguya (SELENE), Hayabusa, Hayabusa2, and the Hayabusa2 Extended Mission, as well as data from international planetary missions. We also contribute to future exploration through the development of scientific instruments for missions such as Martian Moons eXploration (MMX), Hera, JUICE, and Dragonfly, while pursuing new technologies and mission concepts for future lunar and planetary exploration.
Exoplanets
The Department of Solar System Sciences is conducting research on exoplanets based on our past work in the field of Solar System Science. More than 5,000 exoplanets have already been discovered, and many planetary systems have been found that appear to differ significantly from our own solar system. While observations to date have allowed us to determine the size, mass, and distance from the host star of these planets, their planetary environments remain unknown. Moving forward, in addition to increasing the number of detections, atmospheric observations will be particularly important for elucidating these planetary environments. Therefore, we are participating in Ariel, the ESA-led Exoplanet Atmospheric Infrared Spectroscopic Survey Mission, with the goal of determining the atmospheric compositions of 1,000 exoplanets. Furthermore, through the LAPYUTA ultraviolet space telescope project, currently under consideration, we aim to observe the upper atmospheres of exoplanets, particularly Earth-like exoplanets. Planets expected to be discovered by the infrared astrometric satellite JASMINE are also anticipated to become new observation targets, and technology demonstrations for the direct observation of exoplanets are underway on NASA’s Nancy Grace Roman Space Telescope, in which JAXA is participating. Furthermore, vigorous observations are being conducted using the James Webb Space Telescope (JWST) and large ground-based telescopes, and many more new research results are expected in the future.
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Planetary Materials Science
Astromaterials science is a field of research that seeks to uncover the origin and evolution of the Solar System and the universe through the analysis of extraterrestrial materials, including rocks from planets and asteroids. To advance this goal, JAXA has successfully carried out sample return missions such as Hayabusa and Hayabusa2, bringing back rock samples from previously unexplored celestial bodies to Earth and providing invaluable scientific data. Analyses of samples returned from asteroid Itokawa by Hayabusa have revealed the composition of early Solar System rocky bodies, as well as the processes of space weathering. Furthermore, studies of samples from asteroid Ryugu returned by Hayabusa2 have yielded important insights into the distribution of water and organic matter, contributing to key discoveries related to the origin of life. Looking ahead, the MMX mission, which will explore the Martian moons, is expected to provide new insights into the origin and formation of Mars and its satellite system, as well as the evolutionary history of the Martian surface environment. These research achievements not only deepen our understanding of the history of the Solar System but also have far-reaching implications for the study of extraterrestrial life and exoplanets. This field is led by the Department of Solar System Sciences, in close collaboration with the Astromaterials Science Research Group, which is responsible for the curation of returned samples, and is advanced through close partnerships with the astromaterials science community both in Japan and internationally.
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Heliospheric System Science
Heliospheric system science is a scientific field that seeks to elucidate the various phenomena that arise and are constantly evolving within the heliosphere—a region comprising Planetary System, Geospace, Interplanetary Space, and the Sun as subsystems—as these subsystems interact with each other. Members of the Solar Physics Group and the Solar Terrestrial Physics Group (Space Plasma Group and Planetary Atmospheres Group) are involved in this field, and significant scientific results are anticipated in the late 2020s from numerous satellite missions, including Hinode, Arase, Mio, and Solar-C (EUVST). Globally, observations at inner heliosphere are expanding with missions such as NASA’s Parker Solar Probe and ESA’s Solar Orbiter, accelerating efforts in which the fields of Solar Physics and Solar Terrestrial Physics collaborate to understand the heliospheric system, ranging from solar wind acceleration to solar wind dynamics. Ground-based observations and numerical simulation and modeling that help organically link multiple observations of the heliospheric system are also advancing, and even more scientific results are expected through collaboration between satellite and probe missions, ground-based observations, and numerical simulation and modeling.
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Scientific Balloons
Scientific balloons (stratospheric balloons for space science research) are the only flight vehicles capable of staying at altitudes several times higher than those of aircraft. They make it possible to conduct challenging astronomical and cosmic-ray observations, in-situ observations of the upper atmosphere, and experiments in the rarefied atmospheric environment at high altitudes. In addition, because they can fly with relatively moderate constraints on experimental instruments, a short preparation period, and low cost, they also play a role in fostering space science as a “gateway to space” that can take on cutting-edge research in a timely manner. In interdisciplinary space science, we are advancing the development of scientific balloons as flight vehicles, the development of experimental apparatuses intended for installation on scientific balloons, and the analysis of experimental data acquired by scientific-balloon flights. With Antarctic flight data from the cosmic-ray observation experiment (BESS), we are particularly advancing detailed analysis of isotope ratios in cosmic rays. Based on Australian flight data from the MeV gamma-ray observation experiment (SMILE-2+), we achieved a significant detection of emission from the Crab Nebula and other sources, and demonstrated for the first time an observational sensitivity consistent with that expected from ground calibration. To further advance this field, we are preparing the next balloon experiment, SMILE-3. We are also promoting Antarctic experiments for the high-sensitivity observation of cosmic-ray antiparticles (GAPS), aiming to obtain knowledge on dark matter and other subjects. Furthermore, we are carrying out research and development on a balloon structure in which a net is placed over a super-pressure balloon (SPB) capable of long-duration flight. In the atmospheric gravity-wave observation experiment in Antarctica (LODEWAVE), we have taken the first step toward the first scientific observation using Japan’s small SPB. In addition to these activities, we contribute to maximizing the scientific outcomes created in collaboration with users of scientific balloon experiments.
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Sounding Rockets
ISAS provides opportunities for space observation at altitudes of around 300 km and for the demonstration of science and engineering technologies using the S-520, SS-520, and S-310 rockets. Going forward, ISAS plans to build connections with science and engineering fields with which it has had limited contact to date, while actively cultivating new research areas. Recently, ISAS has also been working to modernize its design and development processes through the broad use of digital information. In the future, it aims to shorten mission cycles and further enhance the functionality and operability of its sounding rockets as testbeds for spacecraft technologies. ISAS encourages the direct participation of graduate students and others in project activities aimed at carrying out the types of scientific missions described above. As an internship opportunity unique to ISAS, these activities provide a valuable setting for gaining practical experience that is difficult to obtain through classroom learning alone.
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Micro Spacecrafts
The trend of miniaturization and weight reduction of satellites has now extended to deep-space probes that reach and study various celestial bodies in the solar system. In 2014, the University of Tokyo and JAXA/ISAS successfully developed, launched, and operated PROCYON, the world's first 50-kg-class micro-spacecraft equipped with deep-space communication and orbit-control capabilities. Furthermore, in 2022, ten CubeSats were launched as piggyback payloads on NASA's first SLS launch, Artemis-1, and were injected into lunar transfer orbit. Among them, the 10-kg-class CubeSat EQUULEUS, jointly developed by JAXA/ISAS and the University of Tokyo, successfully performed precise orbit control using a lunar swing-by. In this way, the operational range of micro-satellites has now expanded from low Earth orbit to the Moon and beyond, and as these spacecraft become more sophisticated, they are increasingly capable of undertaking full-scale scientific exploration missions.
At JAXA/ISAS, the Department of Interdisciplinary Space Science is leading various research initiatives and projects to accelerate and advance this trend. Under the ESA-JAXA joint Comet Interceptor mission, three spacecraft, including a 30-kg-class micro-spacecraft provided by JAXA, will be used to visit and directly explore a long-period comet for the first time in human history. In addition, the outer solar system exploration technology demonstration mission (OPENS mission), which utilizes micro-spacecraft, aims to realize, for the first time in Japan, outer solar system exploration beyond Jupiter.
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Astrobiology and Planetary Protection
To elucidate the origin of life on Earth and whether life could exist elsewhere, questions that have been pondered throughout history, we investigate chemical evolution and prebiotic environments on celestial bodies within and beyond our Solar System. We also study the mechanisms by which life precursors are transported to the Earth via small bodies and cosmic dust, and by examining the survivability and reproductive capabilities of microorganisms in the extreme environments of the Earth-Moon system, we conduct research on the habitability of terrestrial planets and Ocean Worlds (classified as “Icy Worlds” under the COSPAR Planetary Protection Policy) in the outer planetary region, as well as the potential for the emergence and evolution of life there. Furthermore, to verify the hypotheses derived from these studies and to search for signs of life beyond Earth, we conduct astronomical observations, in-orbit experiments on Earth-orbiting platforms, in situ measurements by spacecraft, and microscopic analyses through sample return missions. We also develop scientific instruments and probes, contamination control protocols, and sample analysis techniques necessary to realize these endeavors. To realize such astrobiology exploration missions, we must adhere to the planetary protection policies established as an international consensus under COSPAR (Committee on Space Research). Planetary protection refers to activities aimed at both preserving the exploration destination from contamination by terrestrial life forms and protecting Earth’s biosphere from contamination by extraterrestrial life forms. We actively participate in the formulation of international policies and conduct related research with world-leading technologies that maximize scientific outcomes under the COSPAR Planetary Protection Policy. The results of these works have been utilized in the Hayabusa series and the Mars Moon eXploration (MMX) mission.
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- 地球帰還試料から探る化学進化とパンスペルミア仮説
- Martian Moons eXploration (MMX)
- 宇宙探査と惑星保護
- 宇宙探査における惑星保護と汚染管理 〜JAXA 宇宙科学研究所における取組み～
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Space Environment Utilization
In the field of space environment utilization, we mainly conduct scientific experiments on the International Space Station (ISS) and sounding rockets, and provide support to collaborators. In particular, the ISS is in an environment of microgravity and strong radiation. Taking advantage of these characteristics, various scientific experiments have been carried out to date. In the “Electrostatic Levitation Furnace” installed in the “Kibo” Japanese Experiment Module of the ISS, thermophysical property measurements of high-melting-point oxide melts, which are difficult to measure by conventional methods using containers, are being performed by utilizing the microgravity environment. To date, the density, surface tension, and viscosity coefficients of various materials, including rare-earth oxides (melting points of 2400°C or higher), have been obtained. Furthermore, on the Exposed Facility of the “Kibo” Japanese Experiment Module, the “Tanpopo” experiment was conducted to investigate the survivability of life in the space environment, and it was confirmed that certain microorganisms can survive for more than three years in the severe environment outside the ISS. These experimental results have reaffirmed the importance of space quarantine for planetary protection. In addition, by flying a sounding rocket on a parabolic trajectory, a microgravity environment lasting several minutes can be obtained. Using this, we are promoting research on the formation of cosmic dust and on cool-flame phenomena aimed at realizing safe engines through international cooperation.
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- Yuko Inatomi - My portal - researchmap
- Ishikawa Lab (Electrostatic Levitation Targeted Research Laboratory)
- Technical Demonstration of Electrostatic Levitation Furnace
- 橋本博文ホームページ
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International Space Exploration
International space exploration covers human space exploration activities promoted through international cooperation and robotic exploration activities conducted in advance of these efforts. For the time being, JAXA will focus its activities on the Moon and Mars. Because human space exploration is an extremely large-scale activity, it is carried out through international cooperation. In particular, lunar exploration under the U.S.-led Artemis program involves numerous international partners, including Japan. In addition to contributing to part of the lunar-orbiting outpost “Gateway,” Japan is moving forward with plans to contribute internationally through logistics resupply to Gateway and the lunar surface, a crewed pressurized rover for lunar surface mobility, and other means. At the same time, Japan is also pursuing activities based on its own strategy, while keeping international cooperation in mind. Possessing advanced technologies is essential for such cooperation. For this reason, various missions involving the Moon and Mars are being planned, including “SLIM,” which demonstrates pinpoint landing technology on the lunar surface; the Lunar Polar Exploration rover “LUPEX”; and “MMX,” a mission to return samples from the Martian moons. In addition, since fiscal year 2022, activities have also been underway to produce world-class scientific achievements on the lunar surface. By coordinating international space exploration activities with space science activities, JAXA aims to advance both technology and science efficiently and synergistically. The Department of Interdisciplinary Space Science plays a central role in integrating international space exploration and science.
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- JAXA Space Exploration Center (JSEC)
- Smart Lander for Investigating Moon (SLIM)
- Martian Moons eXploration (MMX)
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Information Technology
We are undertaking efforts to utilize information technologies that have developed rapidly in recent years for the creation of outcomes in space science, for outreach related to those outcomes, and further to support research and development.
In relation to space science data, which are the outcomes of our activities, we are examining methods associated with visualization and sonification. The target scope includes not only data obtained from scientific satellites, but also simulated data required for mission studies and training, and related future technologies. In connection with these visualization methods, we are also engaged in public relations, dissemination, and other production and production support of content for the general public.
We are practicing science communication in space science (dialogue between experts and non-experts), analyzing the responses to it, and examining effective science communication based on the analysis results. We plan, prepare, and operate venues for dialogue, analyze reactions on social networking services and in the media to the activities carried out, and conduct attitude surveys of non-experts, thereby exploring pathways to increase the number of space science enthusiasts among non-experts.
As activities directly connected to research and development, we conduct research and development related to computational science. Computational science, centered on numerical simulation technology, is referred to as the third pillar of science alongside theory and experiment, and is also an extremely important means of research and development in space science. Particularly from an engineering standpoint, we conduct research on numerical simulation technology, centered on analyses of high-speed flows related to aerospace vehicles, and on the high-performance computing technologies that support it.
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The Department of Interdisciplinary Space Science conducts related fundamental research, and research and development of flight systems as well as instruments and information systems intended for onboard installation on flight vehicles, in order to take responsibility for the development of interdisciplinary fields that extend across space science as a whole or span space science and its neighboring domains, and of new fields of space science.
The Department of Space Flight Systems is engaged in fundamental and applied academic research on space flight systems to contribute to space science projects. The main fields of research are engineering related to space exploration systems, space transportation systems, and various engineering disciplines. With the goal of realizing more flexible access to space, the department promotes fundamental research in various fields, such as inter-orbit transportation networks, various satellites and space exploration systems, space structure and materials engineering, space propulsion engineering, aerodynamics, thermal engineering, and orbital design and control.
Space Transportation Systems Engineering
To realize space science missions, it is necessary to transport probes and observation satellites from Earth into space. To achieve free access to space—from the ground to Earth orbit and even to more distant celestial bodies—the space transportation system is indispensable for space science research.
There are various forms of space transportation systems, but until now, the Institute of Space and Astronautical Science (ISAS) has launched many scientific satellites using solid-fuel rockets.
There are various types of space transportation systems. At ISAS, many scientific satellites have so far been launched by solid-fuel rockets. The M series built the history of Japan's rockets for launching scientific satellites, and the M-V rocket, one of the world's largest three-stage solid rockets, delivered "Hayabusa" and "Hinode" into space. This solid rocket technology has been passed on to the Epsilon rocket.
The Department of Space Flight Systems is engaged in research on future space transportation systems. By repeatedly using rockets, which have traditionally been expendable, we aim to significantly reduce transportation costs and to enable frequent, large-scale space transportation; accordingly, we are working on research into reusable space transportation systems. Along with research on a variety of elemental technologies, such as air-assisted engines aimed at dramatically improving propulsion performance and composite tanks aimed at reducing weight, system research using small-scale flight test vehicles is being conducted to practically acquire these technologies.
We are also working on research into an orbital transportation vehicle (OTV) for freely and frequently transporting probes into deep space, from near-Earth space to the Moon, Mars, and even more distant celestial bodies. By separating the roles of transportation as an infrastructure service and exploration that carries out missions, and by making common the functions for transporting in space that each probe has previously had individually, we aim to realize frequent deep-space exploration through a highly versatile, standardized transportation system. Our research goal is to build a transportation network connecting the ground, near-Earth space, and deep space through a reusable OTV.
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Space Exploration Systems Engineering
The exploration system leaves Earth orbit and approaches moons, planets, and small celestial bodies to conduct exploration and observations. Compared with satellites in Earth orbit, it tends to require more orbital maneuvers and longer-duration navigation, and it also needs to be adapted to environments different from those in Earth orbit. Because the distance is greater, communication delays are longer, and because it is also difficult to secure communication rates, it is necessary to grasp the system status with less data. Furthermore, because many orbital maneuvers are required, it becomes necessary to combine drastic weight reduction and more efficient propulsion systems compared with satellites in Earth orbit. At the Department of Space Flight Systems, research aimed at achieving more efficient exploration are conducted.
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Propulsion Systems Engineering
At the Department of Space Flight Systems, we conduct research on propulsion systems installed in space transportation systems such as rockets, as well as on exploration probes and observation satellites. As propulsion systems for space transportation systems, we are carrying out research and development of reusable rocket engines and air-breathing engines, along with activities aimed at flight demonstrations. As propulsion systems for exploration probes and observation satellites, we are conducting research on next-generation chemical and non-chemical propulsion, such as high-performance Hall cluster systems. In addition, we are also working on research into thrusters using low-toxicity propellants such as HAN, as well as research and development of advanced solid rocket technologies for utilizing solid rockets, which have traditionally been used for launch, in orbit.
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Structures and Materials
To efficiently carry out challenging missions that promote space science and exploration, it is important to pursue higher performance and higher reliability in the materials, structures, and mechanisms of space systems such as satellites and probes, as well as observation instruments such as telescopes. In terms of materials, in addition to high specific strength and high specific stiffness, recent requirements also include high weather resistance and the absence of thermal deformation or swelling deformation, and to achieve these, research and development are advancing on materials such as composites with special properties, shape-memory alloys, and metamaterials. In the area of structures and mechanisms, research and development are being pursued on structures that, in addition to high strength, high rigidity, and ultralightweight designs, have extremely high shape stability and shape accuracy against heat and minute vibrations; on large deployable structures with high stowage efficiency and highly reliable deployment mechanisms; on the behavior analysis and control of structures that involve buckling and large deformation, such as membrane structures; and on structures and mechanisms related to landing on celestial bodies and sample collection, as well as on integrated design of structures with fields such as control and thermal engineering. In this way, at the Department of Space Flight Systems, research that supports advanced space science observations and deep-space exploration are conducted.
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Thermal Engineering
In the space environment where there is no air, temperatures rise when exposed to intense sunlight and drop rapidly when entering the shade. For example, the solar panels of the spacecraft "Mio," which is currently heading for Mercury, have a surface temperature that rises to +240℃ in sunlight, while in the shade it drops to -160℃, exposing them to a maximum temperature difference of 400℃. In such harsh thermal environments to which satellites and spacecraft are exposed, the role of thermal control systems and thermal engineering technologies is to keep onboard equipment within an appropriate temperature range and lead the mission to success. The elemental technologies in spacecraft thermal control are broadly classified into radiative heat control, such as multilayer insulation and radiators; conductive heat control, such as thermal straps; thermal-fluid control, such as heat pipes and space cryocoolers; and heat generation/cooling control, such as heaters and Peltier devices. Keywords in the field of thermal engineering include "radiative heat transfer," "conductive heat transfer," "convective heat transfer," and "refrigeration cycles." Because the optimal form of a thermal control system changes depending on the orbit design, attitude control, heat generation by onboard equipment, and available power resources, it is important to combine the various elemental technologies and build a system that is as optimal and reliable as possible for the mission requirements. Researchers in the field of thermal engineering are broadly engaged in work ranging from basic research aimed at deepening the scientific foundations of advanced thermal control technologies needed for next-generation scientific satellites and probes, based on analyses of current issues and future plans from the perspective of heat, to research and development with an eye toward onboard implementation, and from mission creation to design and operations. To realize even more challenging missions, we are promoting, from the perspective of thermal engineering, activities that go beyond conventional technologies and their extensions to generate world-class research outcomes and free-thinking, reliable technology.
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Aerodynamics
Space transportation systems, such as rockets, that carry objects from the ground into space fly while accelerating through the atmosphere. Rocket aerodynamics is an important field of study for evaluating launch performance and has been applied to the aerodynamic design of rockets such as the M-V rocket. In the future, the reuse of space transportation systems will be essential in order to carry out space science missions at lower cost and with greater frequency. For this reason, we are also working on research into the aerodynamic design of reusable space transportation systems.
In missions such as Hayabusa and Hayabusa2, which aim to return samples from asteroids, and the MMX mission, which aims to return samples from the Martian moon Phobos, the aerodynamic design and thermal protection system development of Earth atmospheric reentry capsules for delivering collected samples back to Earth are essential technologies for successful sample return, and they are among the cutting-edge technologies in which Japan is at the forefront.
In addition, Japan may also conduct landing exploration on celestial bodies with atmospheres and gravity, such as Mars, and the development of EDL technologies for atmospheric entry (entry, descent, and landing technologies) is also required.
In 2021, the United States became the first country in the world to successfully fly a drone in the Martian atmosphere. Going forward, research on the use of drones on celestial bodies with atmospheres and gravity, such as Mars, is also expected to become important.
The Department of Space Flight Systems will take on a central role in researching and developing these technologies.
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Orbit Design and Control
Technology for designing trajectories to send spacecraft into orbit around a body or to the Moon and planets, and for actually controlling spacecraft, is one of the fundamental research areas that underpin more flexible space science and exploration.
In research on "trajectory design," the challenge is to design better trajectories (for example, with less propellant) while taking into account celestial gravity acting on the spacecraft and onboard propulsion systems. To achieve better trajectory design, techniques such as swingbys, the three-body problem, and low-thrust trajectory control are actively used. In addition, gaining a deep understanding of the nonlinear behavior of orbital dynamics is also key to better trajectory design. In recent years, there has been active research on transfer trajectory design and orbit design (for asteroid vicinity operations, constellations, etc.) using cutting-edge technologies such as dynamical systems theory, optimization theory, and machine learning.
In research on “control,” the challenge is how to manipulate a spacecraft’s trajectory freely by using onboard sensors and orbit determination information. As control technology improves, it directly leads to better quality in space science and exploration, for example by expanding the range of samples that can be collected and the terrain that can be accessed in planetary exploration. In recent years, research has been active on robust trajectory control against disturbances, ultra-precise relative motion control (formation flight), optimal trajectory control during landing descent, and trajectory control of spacecraft that actively uses disturbances.
Research results in the field of trajectory design and control have made major contributions to the realization and development of small-body and lunar/planetary exploration, astronomical observation, launch rockets, and more.
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Robotics Technology
The Robotics Group conducts research in all fields related to robotics for the purpose of exploring the surfaces of extraterrestrial bodies, including those with strong gravity, such as the Moon and Mars, and those with weak gravity, such as asteroids and comets.
Research topics include sophisticated mobile systems for traversing uneven terrain on the surfaces of these celestial bodies, obstacle detection based on the images, localization to determine the position of the robot on the surface, artificial intelligence enabling autonomous navigation and observation using sensors mounted on the robots, X-teramechanics to model the interactions between the robot and the celestial surface, and the operational machinery used by the robots.
We currently focus on using acquired images to enable automatic terrain recognition through learning technologies. We also create new exploration methods using robots. Recently we have conducted research on new collaborative exploration using multiple small robots. Based on these research activities, we sometimes propose robotic missions and payloads to make an actual field test of the robots on the surfaces of extraterrestrial bodies.
Spacecraft Systems
The Spacecraft Systems field focuses on the technologies and system architecture required to realize astronautical science and exploration missions by integrating a wide range of specialized disciplines and ensuring overall mission feasibility. Research and development are carried out across diverse areas of engineering to address challenges such as enhancing functionality while reducing the size and mass of scientific satellites and spacecrafts, as well as improving development methodologies. These efforts have led to the establishment of a standard bus system for small scientific satellites, first demonstrated on Hisaki and Arase, which is now being widely adopted in subsequent satellite missions. Also, the lightweight lunar landing technologies developed through SLIM are expected to serve as an important heritage for future landing missions. Research is also being pursued at multiple levels—including system architecture, components, and implementation technologies—to reduce the size, weight, power consumption, and development time of satellite buses. While actively incorporating commercial technologies, research activities are simultaneously being conducted to improve the reliability of micro- or nano-satellites and their onboard components. Looking ahead, ultra-small spacecrafts are expected to become increasingly important platforms for achieving scientific and exploratory objectives in space. To support this vision, new development methodologies—including approaches to quality assurance and reliability—are being investigated and validated to enable faster, lower-cost, and more efficient spacecraft development, with the Comet Interceptor B1 and OPENS-0 serving as a representative model case.
Spacecraft Control Technology
We conduct research on the motion control of satellites and spacecraft.
In the area of attitude control, our work focuses on technologies necessary to realize high-performance, advanced missions. Specifically, we investigate high-precision pointing control methods, primarily for space telescope missions used in astronomical observation. We also study tracking control techniques—coordinated with onboard telescopes—that enable spacecraft to perform observations while flying in close proximity to celestial bodies.
For lunar and planetary landing missions, we conduct research on guidance, navigation, and control (GNC) to improve landing accuracy, as well as on landing strategies and control methods that enhance mission safety.
We also work on spacecraft formation flight, where multiple satellites coordinate their relative positions to accomplish a single mission. Our research includes propellant-efficient control strategies with practical mission applications in mind, as well as novel approaches that utilize electromagnetic forces. In addition, we explore control methods for satellite swarms based on these technologies.
Furthermore, we engage in foundational research, including high-precision attitude estimation and control, as well as the development of control-related hardware and instrumentation.
A key feature of our laboratory is its broad research scope, covering topics from fundamental studies to mission-oriented applications in spacecraft motion control.
Orbit Determination and Design
Research topics include precise orbit determination, navigation, guidance, and radio measurement technologies for deep-space missions, as well as planetary radio science, which uses these technologies as probes to measure the gravity fields and atmospheres of Solar System bodies. The research covers both theoretical aspects, such as orbital mechanics, estimation theory, and relativity, and engineering approaches, such as radio measurement technologies at ground stations. Practical research is conducted using actual deep-space missions.
Research is also being carried out on hybrid orbit determination methods that combine radio and optical measurements from ground stations, such as Delta-DOR, Doppler, ranging, SLR, and optical observations of right ascension and declination, with measurements by onboard spacecraft sensors that observe target bodies, such as LIDAR and OP-NAV, in order to simultaneously estimate the orbits of multiple objects. The objective of this research is to establish methods for determining, with high precision, the orbits of spacecraft and small Solar System bodies, as well as the positions of landers and rovers, across a broad region of the Solar System, from deep space beyond Jupiter to the lunar surface.
Communication and RF navigation and control measurement technology
We are responsible for communication systems required by exploration missions and space science missions, associated navigational guidance measurement technology based on them, and fundamental research and development related to them. These systems span both the onboard and ground layers and even refer to end-to-end technology development extending to the link layer like error correction technology for communication systems, regardless of radio waves or light waves in the physical layer. Furthermore, navigational guidance measurement is a unique field that requires analog accuracy calibration even in the context of digitization. Key technologies mainly include antennas, front-ends, amplifiers, and their assembled communication systems. Some studies have focused on device development and signal processing technologies included in them. In recent developments applying higher frequencies such as Ka-band radio waves and optical signals, not only equipment development but also operational technologies for their efficient utilization are becoming important research topics. Because our research has been mission-oriented, data from long-term operations in actual exploration and space science missions has been accumulated. Analyzing these operational data and applying it to learning systems will make it a promising research field. Another important feature of our system is that the system should be mutually compatible with overseas space agencies. This aspect includes research activities focused on standardization.
Data Processing Technology
We conduct research and development on all data processing for spacecraft and their corresponding ground systems. In recent years, as observational instruments have become more highly advanced, the volume of data they acquire has grown exponentially.It is necessary to organize and process this data onboard and efficiently transmit it to the ground. We are establishing standard specifications for these data processing and storage methods and promoting the development of equipment that complies with them. We also consider the advancement of ground systems for transmitting and receiving commands to and from spacecraft to be important. We are researching spacecraft status management and automated operations using technologies such as AI.
Sensor and Device Technology
We conduct basic research on semiconductor devices installed in spacecraft, and we also develop flight models.
Examples of basic research include advanced Si devices, diamond semiconductors aimed at improving the power conversion efficiency of wireless transmitters, MEMS multifunctional devices, standby-power-free systems, and flexible thin-film devices.
As development for installation on spacecraft, we are developing a small inertial navigation unit equipped with a MEMS gyroscope and a coherent LiDAR for spacecraft use.
As achievements in flight model development, there are the development of the dedicated IC for optical pulse detection for the laser altimeter onboard the Martian Moons Exploration (MMX) mission, the development of the 3D image sensor for the Flash LiDAR onboard HTV-X, and the development of the next-generation space microprocessor (in cooperation with the Research and Development Directorate).
Energy Systems
Power management, power generation technologies, energy storage technologies and energy transmission technologies for spacecraft such as planetary probes and scientific satellites have been studied.
Spacecraft and satellites generate electricity using solar panels during sunshine period. The excess electricity is stored in the batteries, and then used to maintain power during the eclipse period. The loss of power sub-system is quite a critical event that determines the lifespan of the spacecraft. Moreover, because the use of spacecraft requires resistance to vacuum environments, radiation environments, and the like, it requires the development of specialized technologies. Accordingly, research is very important on solar cell technologies that are lightweight, highly efficient, and highly resistant to radiation; on storage devices such as lithium-ion secondary battery technologies; and on power-system management methods that make it possible to operate spacecraft over extremely long periods. In addition, research is also being advanced on fuel cells and regenerative fuel cells for future large-scale space exploration.
Furthermore, as a future energy system, research is being conducted on a solar power satellite that generates electricity using a large-scale solar array in orbit and transmits it to the ground via microwaves or lasers. To realize this satellite, it is necessary to develop a wide range of technologies, from large-scale space power generation to long-range, high-power wireless power transmission, and construction /maintenance of very large space structures.
In addition, as a contribution to lunar exploration, which has attracted attention in recent years, its use as an energy supply system from lunar orbit to the lunar surface is also being considered.
Sounding Rocket Support Technologies
This research activity aims to propose and develop new technologies for space experiments and observations using JAXA’s S-310/S-520 series sounding rockets. It focuses on technologies that are not currently available but are expected to add scientific and technical value. From the viewpoint and expertise of the Department of Spacecraft Engineering, we identify such needs, propose practical concepts, develop prototypes, and prepare them for in-space demonstration.
We have applied this approach to low-cost systems for attitude control and separation-probe experiments. These include control software for a compact attitude control device and a small probe system with power and communication functions that operates after separation from the rocket. A key aim is to make such systems simple and affordable for researchers using sounding rockets for the first time. Our technical focus is on control, devices, and embedded systems that can be implemented at very low cost while remaining easy to use.
A major feature of this activity is its rapid cycle from idea to in-space demonstration. We aim to reach flight demonstration within a few years, obtain early feedback from actual use, and reflect the results in the next development cycle. Several outcomes have already been implemented as common equipment within less than ten years from the start of development, including a communication protocol converter based on commercial microcontrollers, a data acquisition unit, and a deployable camera system. We are also applying this approach to motion stages and deployable masts, with the aim of making them common equipment for future sounding-rocket experiments.
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The Department of Spacecraft Engineering performs research on rockets, artificial satellites, planetary probes, exploration robots and spacecraft ground systems, as well as on fundamental technologies in the fields of electrical and electronics engineering, measurement and control engineering, and energy engineering.