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Japanese lunar exploration long-term plan
Acta Astronautica 59 (2006) 68 – 76 www.elsevier.com/locate/actaastro
Japanese lunar exploration long-term plan Kohtaro Matsumotoa,∗ , Norimitsu Kamimoria , Yoshisada Takizawab , Manabu Katob , Mitsushige Odaa , Sachiko Wakabayashia , Satomi Kawamotoa , Tatsuaki Okadab , Takahiro Iwatab , Makiko Ohtakeb a Institute of Aerospace Technology, JAXA 7-44-1, Jindaiji-Higashi, Chofu, Tokyo 182-8522, Japan b Institute of Space and Astronautical Science, JAXA 3-3-3, Yoshino-Dai, Sagamihara, Kanagawa 229-8510, Japan
Abstract In the JAXA’s long-term vision, “JAXA 2025” at last March, the importance of exploration and utilization of the Moon is clearly identified as one of the major goals for the next two decades. The assigned long-term goal of the Moon exploration is the sound technology development for the lunar base after 2025. In this presentation, we will introduce the summary of this JAXA vision related to the Moon exploration, describe the interim result of the voluntary 60 days study team for the concrete plan of this JAXA’s Moon exploration vision, and present quick report of some technological examination. © 2006 Elsevier Ltd. All rights reserved.
1. Introduction Japan had started concept study of the human lunar outpost to utilize lunar resources, such as He3 and O2 , by the voluntary organization of researchers, at the end of 1980. As its first outcome, Japan had started its Moon exploration projects by LUNAR-A and SELENE, as “the first step to space frontier, start from the Moon” at early 1990. SELENE had started with two main missions, those are the orbital remote sensing and the Moon landing. The major purpose of SELENE was defined as the Moon science and investigation of the future Moon utilization, such as its resources and/or Moon platform for observatory. However, the Moon lander was separated from SELENE, and requested to improve the technological
∗ Corresponding author. Tel.: +81 422 40 3170.
E-mail address: [email protected] (K. Matsumoto). 0094-5765/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2006.02.020
readiness levels for the reliable obstacle avoidance capability and effective mechanics for sure landing. After three years study, we had proposed SELENE-B mission, which was designed to land very precisely and very safely. The design target of preciseness is within 100 m, with the autonomous optical obstacle avoidance and optical navigation. Moon night survivability was also examined as the future optional capability. The primary mission of SELENE-B was set as the technology development for the Moon science (Fig. 1). After the NASA’s new space vision, we also have started the re-examination of our Moon lander mission with more various mission targets, from the scientific exploration to the future Moon utilization, including the human lunar outpost. For the scientific Moon exploration road map, the low-frequency radio astronomy, the sample return, and so on, have also been discussed within the lunar exploration long scenario. In addition to those scientific missions, technology development and verification, Moon resource utilization, Moon observatory, and human beings on the Moon for the future space
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JAXA shall develop sound technologies for the establishment of a lunar base and its utilization. This will be done with the aim to maintain and strengthen the capability for technology development as the engine for expanding activities of Japan and achieving the world-class technological capability. In the Chapter II, that describes the long-term vision, lunar activities are described as: JAXA undertakes lunar explorations to establish its bridgehead base on the Moon. This will enable the expansion of the areas of activity on the Moon, and help strengthen Japanese technology development. JAXA develops the necessary technologies to achieve this goal.
Fig. 1. Japanese Moon lander 1st concept SELENE-B.
development and future human frontier have begun to be discussed widely. In correspondence with the start of integrated JAXA, JAXA have started to build its long-term vision for next two decades. The official version of the JAXA long-term vision, “JAXA 2025”, was fixed at the end of March 2005. In the discussion of this JAXA 2025 vision, the exploration and utilization of the Moon has been considered as one of the major goals. After finalizing JAXA 2025 vision, we have started the discussion for the concrete implementation of the lunar exploration, by the voluntary 60 days study team.
In Chapter III, that describes the detail of the vision, the “exploration and utilization of the Moon” is described in the section of “Advance the human knowledge and to expand the human frontier”. 2.2. Objectives of Moon exploration and utilization The objectives of Moon exploration and utilization are summarized as: • Contribution to the expansion of human frontier. • International recognition through challenge to develop advanced technologies. • Understanding the origin and evolution of the Moon and application of the findings. 2.3. Direction for the vision
2. Exploration and utilization of the Moon in JAXA 2025 vision In this section, the expectation and description for the Moon exploration and utilization in JAXA 2025 vision will be briefly introduced, based on the English version [1]. 2.1. Summary [3] In summary of the JAXA 2025 vision, the lunar exploration vision is described as: (2) Contribute to the advancement of knowledge and expansion of human frontier by exploring the mysteries and possibilities of the universe.
Recognizing the NASA’s new vision for space exploration and their invitation for the world cooperation, as background, JAXA 2025 vision sets four directions, that shall be pursued toward the implementation of this Moon exploration vision: • Promoting lunar science and examining possibilities of lunar utilization. • Taking the challenge to develop most advanced technologies toward future space exploration and innovative space utilization. • Preparing for the establishment of a human lunar base. • Establishing mutually complementary relationships with other countries.
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2.4. Roadmap As the roadmap for the Moon exploration vision, the followings are its summary: Next decade roadmap: The development of advanced technologies for the decision to the full utilization of the Moon: (1) Implementation of SELENE project and other existing and planned Moon exploration missions. • Detailed map of the Moon surface of topography, geographical features and gravitational field. • For selecting a landing site on the Moon. • Establishing cooperation between SELENE and NASA lunar reconnaissance orbiter (LRO). (2) Exploration on the Moon and exploring possibilities of its utilization. • Acquire technologies for precise landing and roving on the Moon and other planets. • Planet and astronomical observations from the Moon surface. • Option list for decision of the full utilization of the Moon, in coming 20 years. (3) Advanced technologies development • Robotics, ISRU (in situ resource utilization), and so on. • Technology base. • Acquiring key technologies through the international space station (ISS) utilization and H-II transfer vehicle (HTV). • International cooperation in high performance sensors and a solar energy supply system. Coming 20 years roadmap: Technology establishment for the international human lunar base construction and utilization: (1) For the international human lunar base project. • Important role by fully utilizing the developed technologies. • Appropriate international contributions and share responsibilities. (2) Key technologies for long-term human presence at a lunar base. • Life-support, power generation, wireless power transmission, and so on. 3. Sixty days study for JAXA Moon exploration In correspondence with the finalization of the JAXA long-term vision, at the end of last March, we have vol-
untarily and informally started a 60 day’s study team to make a proposal for the concrete roadmap of the Moon exploration in JAXA 2025. The team members have been gathered to cover the various aspects of the Moon exploration, depicted in the JAXA long-term vision. The space technology researchers, the lunar scientists, and the astronomers have joined into this team. Most of the team members had also joined the study of the former Moon lander proposal SELENE-B. For the concrete roadmap of JAXA 2025 vision, as the major subjects, the study team discussions were started from the significance of the Moon exploration and human lunar base for the Japanese space development, to the definition of Moon landers as the precursor of the human lunar base. In the following, the interim report will be introduced. 4. Basic principles for Japanese Moon exploration As the principle of Japanese Moon exploration for the next decade, we have identified the following five basic principles. (1) As the first step for the next stage of Japanese space development: During the next two decades, human space activities will be expanded to the Moon and beyond, across the near-Earth boundaries. The technologies and resources, resulted from the Moon exploration and its utilization, would be essentially useful for the future exploration not only of the Moon itself but also of the solar system. Within about 20 years, there will be the lunar base/outpost for more human space activities. The lunar base will be constructed through international cooperation. Japan, with its advanced technologies, would join as one of the leading partner in this cooperation and would take appropriate responsibility. (2) Send landers within next decade before 2015: By SELENE, Japan could draw up high-resolution global mapping of the Moon surface, and precise Moon gravity map. Through SELENE, we would collect data that could determine the distribution profiles of lunar crust constituents, the crust structure, the exposed parts of the deep layers materials of lunar structure, areas of concentration of particular materials, and unique topographic features. Those data will be highly utilized to determine the future human landing site. Following the SELENE results, the exploration and investigation of Moon surface would go next steps using Moon landers and robotic vehicles for the possible full utilization of the Moon. The technologies developed by these landers and robotic exploration vehicles, will also work actively on other celestial bodies in the
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Fig. 2. Future lunar base: international lunar base, supported by lunar robot.
solar system, and will also contribute to the planet and astronomical observations from the Moon surface. International cooperation for these Moon landers would also be pursued. Based on the results and technologies during first decade, we will submit options for proceeding in the full utilization of the Moon. (3) Missions will cover technology development, lunar utilization, and lunar science: According to the objectives, identified in JAXA 2025, the exploration and utilization of the Moon will cover three fields, those are advanced technology development and verification for the future space development, utilization of lunar resources such as water/ice, oxygen, or Moon surface as the platform, and innovative scientific knowledge for the Moon itself. Those three missions will be assembled into a series of unmanned robotic precursors and human Moon explorations (Fig. 2). (4) For the international cooperation, and international human Moon exploration: In 20 years from now, it is anticipated that space infrastructures will be established on or around the Moon, for human space activities across the near-Earth boundaries. As the first step for such space infrastructure, the human Moon exploration project would start within next 10 years, as the next international human space program after ISS. In that case, Japan will join that international program as an international space partner. Through this participation, we will step-by-step ac-
quire and contribute technologies for human presence in space, utilizing and advancing the ISS experience. The common objectives of both of the SELENE and JAXA 2025 vision are Japan’s contribution to the expansion of human frontier. These objectives resonate with the principle shared by the United States and Europe in their space activities, i.e. the ultimate goal of space activities is “. . . to extend a human presence across our solar system. . .” and beyond. Japan will, therefore, establish mutually complementary relationships with other space partners, and will take steps forward in the journey into the universe by an effective and efficient manner. 5. Significance of human lunar base In the JAXA’s vision, the human lunar base/outpost is set as the long-term goal of our Moon exploration and utilization. However, for the human space activity and human lunar base, we still need more extensive and detailed discussions from the view points of cost/budget, schedule/when, effect/why, and so on. Thus, the 60 day’s study team has started its discussion to build common recognition of the human lunar base significance and roles for Japanese space development. The human lunar base has four major aspects for our space development, those are on the Moon, by the human, continuous and permanent activity, and international.
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5.1. Moon exploration The Moon is the nearest neighbor celestial object for our earth with natural resources. The traveling cost is less than 5 days. If we, as human being, will continue to extend our space development, and to expand the human frontier from the earth surface to the outer world, the Moon shall be the next stage of the space development for the world and for Japan beyond the LEO activities. For the expansion of the human frontier via the lunar base, space technologies should be advanced drastically at the lunar base to support human astronaut in safe and comfortable condition. The lunar base will work as the technology development and verification test-bed. For those new space development activities, Japan already started SELENE project as our “first step”. We will continue our activities following SELENE with our advanced technologies, such as robotics, and so on. 5.2. Human lunar activity From the ISS to the Moon, human beings are striving to expand the boundary of our activities. For the human beings, the Moon will be the next stage across the nearEarth boundaries as a matter, of course. Without long stay and support technology on the nearest neighbor celestial, Moon, the expansion of the human exploration to mars and beyond might be too high goal for human technology and science. In 20 years from now, space infrastructures necessary for human space activities will be established on the Moon, as the most promising infrastructures for human space activities. Japan will participate in the next international human space program and will step-by-step acquire and contribute technologies needed for human presence in space. For the human transportation to the Moon, the human being shall have a couple of transportation measure for the maximum safety assurance for the crew safety. 5.3. Continuous lunar exploration The continuous activities at the lunar base will enable Moon exploration as non-disposable activities. The continuous and repetitive scientific observation, similar to the research on the ground, would create new field of lunar science. The human and robotic tasks for the lunar base construction and maintenance will also enable large facilities on the Moon, such as the optical observatory. Advanced technologies developed for the Moon
exploration could be tested and verified at the Moon base, for mars exploration, and solar system exploration.
5.4. International cooperation The technologies and investments for the human lunar base might be enormous for one country. The need of international cooperation is not only for this budgetary enormousness, but also the hopeful activity of the human beings. From Apollo era to till now, the human lunar base might be too high goal for the world space development. However, various advanced technologies in this century might enable such human lunar base as the realistic goal for our human beings, with affordable international cooperation. With the maximum international cooperation and competition, the human outpost establishment will become more realistic and more effective for Japan and the world. Thus on the Moon, international cooperation will be naturally organized. Advanced space development countries and Japan will compete sincerely to improve technologies and activities for the next generation. The human lunar base as the long-term target of Japanese space development would bring about the most advanced technologies, the contribution to the human frontier, and the national security for Japan. It will be used as the technology test-bed for our space technologies, for the utilization of lunar resources and/or lunar itself, for the space sciences, and as the stage of international cooperation and competition.
6. The roadmap for the human lunar base To realize to the human lunar base, the following series of Moon landers and human Moon explorations are proposed as the roadmap for next decade and for the international human lunar base (Fig. 3). In next decade: Japanese original orbiter and lander with international cooperation. In next decade, JAXA vision set the goal as the advanced technologies development for the decision of the full utilization of the Moon. For this goal, the series of the lunar orbitor and lunar landers should be projected, with the attached representative missions. SELENE: 2007 Orbitor. Precise global mapping; Moon gravity map; Sciences by remote sensing; Selection of first human exploration site. SELENE-2: 2011–2013 Lander for the polar region. Precise and safe landing; Lunar science on the Moon;
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Fig. 3. Proposed road map for next decade and for international human lunar base.
In situ resource investigation (water/ice); Moon night survival. SELENE-3: 2013–2015 Lander with rover for the polar region. Wide area investigation for science and utilization; Robotics for exploration; Long-term Moon night survival. In next two decades: Participation to the international project. After the decision of the full utilization of the Moon, Japan will join the international human lunar exploration to establish the technologies for the international human lunar base construction and utilization. For this goal, the series of the human lunar exploration will be projected. Human lunar lander: 2018–2020 3–14 days. Human landing; Human support (robotics, ISRU,. . .). Human lunar base: 2020–2025 60–90 days. Full scale lunar utilization and science; Long-term stay on the Moon. Permanent human lunar base: 2025–year. Extension of lunar utilization and science; Technology test-bed for manned mars exploration. 7. Technological subjects of polar region precursor exploration Although there might be so hard technological problems for the 1st Japanese Moon lander, our team has set the landing target area and exploration spot at the polar region, as SELENE-2. Recently the polar region, in particular, the permanently shadowed region (PSR), has been strongly expected that there would be water/ice, based on the Clementine and Lunar Prospector observation data.
If water ice will be found as the utilizable Moon resource, the Moon exploration will be drastically changed. The water ice could be used as the human support resource, fuel battery resource, fuel for Mars exploration, and so on. It might be the first mining rights in the space, or would be the situation similar to the Antarctica. Thus, the in situ investigation and observation of the water ice at the polar region will be very attractive not only for the science, but also more promising for the lunar utilization. However, for polar region and the PSR, there is almost no certain knowledge. Until now, no Moon lander did visit the polar region, and no orbiter did observe precisely, enough for the safe and/or sure exploration. Because of the very low sun angle, there could be expected no high-resolution image. The Moon polar region is really the un-explored Moon site. For the 1st landing exploration of such unknown region, we have examined technologies, those shall be added to the former Japanese Moon lander concept, SELENE-B, which was also designed to land the barren and un-explored vicinity area around a crater central peak. The followings are the major topics, examined until now. 8. Exploration scheme of PSR As the candidate scheme for PSR exploration, we have examined and compared the following schemes as its starting points. From the technological view points, PSR has many serious difficulties, those are no optical image, very low temperature estimation, such as around 40 K, no
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sun lighting, no more than speculated information, and so on. Thus, the bright vicinity of the PSR is also examined as the 1st landing target area, which will be close to the PSR and sun lighted. Based on the polar region elevation data, in some restricted sun-lighted PSR vicinity area, the severe night time is estimated nearly zero or very short, although the average Moon night time is 354 h at its equator. This short night period would be very attractive for Moon night survival. Some areas with 100% sun lighting are also called eternal lighted region (ELR), and might be ultimately attractive for future Moon base. Direct exploration of PSR: (a) Landing alone. (b) Landing with rover. (c) Landing by multiple exploration system. Exploration via the well-lighted vicinity of PSR: Fig. 4. PSR direct landing concept.
(d) Landing with rover. (e) Landing with multiple exploration system for PSR. 8.1. Direct exploration of PSR The PSR direct landing and exploration scheme have the following common problems: (1) Energy: Without nuclear energy or energy supply from outside, the lifetime of the lander will be strictly limited by the battery capacity. Only a few hours to few days lander lifetime may not be enough even for the single resource investigation mission. (2) Safe landing: In PSR optical camera image could never be expected for the obstacle avoidance and navigation sensors. The direct landing on PSR will require advanced active landing sensors, like LRF and so on, in addition to the optical camera for navigation during powered descent. (a) Lander with air bag could reduce the active LRF requirement. By the same design specification to mars exploration rover (MER), 123 m above the Moon surface will be the starting altitude of air bag protected Moon lander (Fig. 4). (b) In our rough concept study, the Moon rover exploration around the lander at PSR, might be too severe requirement for our 1st Moon lander. The rover on PSR shall move around the permanently shadowed area with very small body, with a little energy, and without any prior geographic knowledge. (c) A couple of penetraters or air bag landers, with a little resource investigation package, are possible explo-
ration sub system. Japan has developed the penetrater system in last decade for the Moon. With the penetrator, the under ground water/ice investigation will be easily done without power consuming excavation drill. However, very low temperature at PSR, lower than 100 K, the survivability of the penetrater could not be expected. 8.2. Exploration via the well-sun-lighted vicinity of PSR The well-sun-lighted vicinity of PSR, the landing and exploration scheme have the following common expectation and problems: (1) Well-lighted: The well sun-lighted regions will be better than a region near the equatorial, because of the short or zero night time, for the night survival energy. At the limited well-lighted vicinity of PSR, sun light could be used as the energy resource with more than 80–90% of one Moon day. At north pole, some regions are also expected with 100% sun light. (2) Safe landing: The sun angle is very low, nearly zero. Thus even in those sun-lighted areas, the expectation for the optical images will be limited, because of the very long shadow of the distributed rocks. (d) Rover: For the rover the long distance traverse will be essentially required from the lander to PSR, without any geophysical knowledge. If we intend to explore the highly expected PSR for water/ice exploration, the required traverse distance for rovers might be more than 10 km.
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Fig. 5. Possible concept of polar PSR exploration.
Fig. 6. Fuel weight for lander hopping.
And because of the very low sun angle, even around the lander, the rovers shall traverse over the too much shadowed zone before the PSR. The energy supply from the lander or the energy station might be essential requirement of the small rover without long life battery or the nuclear battery. (e) The ejection of a couple of single point exploration system (SPES) might be more effective than rovers. During the descent phase, over the PSR, SPES would be shot as penetraters, or soft landed by the air bag. SPES will be ejected during the descending phase or after landing, to overcome the long and severe traverse by the rover (Figs. 5 and 6). 9. Unknown region landing scheme The following four types of landing system were examined for the polar region landing.
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(a) Landing leg: For this traditional landing system, the autonomous obstacle avoidance capability will be essential to avoid and prevent fall down during the touch down. The current Moon orbiters, such as SMART-1, SELENE, LRO, Chandrayaan, are expected to supply the more detailed Moon surface information. The most precise surface resolution by the LRO will be improved up to nearly less than 1 m or 50 cm. However, in addition to this precise terrain image, the active LRF and optical image camera will be required for more sure obstacle identification and precise positioning. (b) Air bag: For SPES landing, air bag landing system will be hopeful, to reduce the excessive weight of rocket and legs by more simple and light air bag, and increase safety of landing. By the air bag design specification for mars rover MER landing, SPES could be ejected from about 123 m above the target PSR, or fly over a few hundreds meter to the PSR from landed lander (Fig. 5). (c) Air bag landing from orbit: This concept is the combination with the rocket descent from Moon orbit, and the final touchdown by the air bag from suitable altitude, defined by the air bag collision performance. Parachute and air bag scheme will increase the landing safety for the unknown polar region much more than the rocket and leg scheme. But because of the high vacuum environment on the Moon, parachute has no use. Thus, for the descent phase, the rocket is used to reduce the landing speed to almost zero. And the air bag is used against the final collision impact with less possibility of tumble even for the unknown barren land (Fig. 4). (d) Penetrater: Penetrater is the combination with rocket descent and hard landing. Instead of soft landing, the penetrater concept will utilize the high touch down speed to penetrate into the Moon regolith and to utilize the thick regolith as thermal chamber. However, in polar region, the too low regolith temperature would cancel the thermal chamber effect.
10. Conclusion In this paper, the Moon exploration and utilization approach in the JAXA 2025 vision is briefly introduced. The concrete plan to realize this scenario is proposed as the interim report of the 60 days study team in JAXA. As a part of this study team activity, initial study results for technological subjects were also introduced with possible schemes for polar permanently shadowed region exploration.
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References [1] JAXA 2025, 2005.3, JAXA http://www.jaxa.jp/about/ vision_missions/long_term/. [3] K. Matsumoto, et al., Japanese long term Moon exploration plan, ILC-2005.
Further reading [2] M. Kato, et al., The science scenario of the SELENE-2 mission, ILC-2005.
[4] K. Matsumoto, et al., Night survival and long stay for Japanese Moon landing, IAC-04-IAA.3.6.2.10, 2004. [5] D. Ben, J. Bussey, et al., Illumination conditions at the lunar south pole, Geophysical Research Letters 26 (9) (1999) 1187–1190.
Japanese lunar exploration long-term plan Kohtaro Matsumotoa,∗ , Norimitsu Kamimoria , Yoshisada Takizawab , Manabu Katob , Mitsushige Odaa , Sachiko Wakabayashia , Satomi Kawamotoa , Tatsuaki Okadab , Takahiro Iwatab , Makiko Ohtakeb a Institute of Aerospace Technology, JAXA 7-44-1, Jindaiji-Higashi, Chofu, Tokyo 182-8522, Japan b Institute of Space and Astronautical Science, JAXA 3-3-3, Yoshino-Dai, Sagamihara, Kanagawa 229-8510, Japan
Abstract In the JAXA’s long-term vision, “JAXA 2025” at last March, the importance of exploration and utilization of the Moon is clearly identified as one of the major goals for the next two decades. The assigned long-term goal of the Moon exploration is the sound technology development for the lunar base after 2025. In this presentation, we will introduce the summary of this JAXA vision related to the Moon exploration, describe the interim result of the voluntary 60 days study team for the concrete plan of this JAXA’s Moon exploration vision, and present quick report of some technological examination. © 2006 Elsevier Ltd. All rights reserved.
1. Introduction Japan had started concept study of the human lunar outpost to utilize lunar resources, such as He3 and O2 , by the voluntary organization of researchers, at the end of 1980. As its first outcome, Japan had started its Moon exploration projects by LUNAR-A and SELENE, as “the first step to space frontier, start from the Moon” at early 1990. SELENE had started with two main missions, those are the orbital remote sensing and the Moon landing. The major purpose of SELENE was defined as the Moon science and investigation of the future Moon utilization, such as its resources and/or Moon platform for observatory. However, the Moon lander was separated from SELENE, and requested to improve the technological
∗ Corresponding author. Tel.: +81 422 40 3170.
E-mail address: [email protected] (K. Matsumoto). 0094-5765/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.actaastro.2006.02.020
readiness levels for the reliable obstacle avoidance capability and effective mechanics for sure landing. After three years study, we had proposed SELENE-B mission, which was designed to land very precisely and very safely. The design target of preciseness is within 100 m, with the autonomous optical obstacle avoidance and optical navigation. Moon night survivability was also examined as the future optional capability. The primary mission of SELENE-B was set as the technology development for the Moon science (Fig. 1). After the NASA’s new space vision, we also have started the re-examination of our Moon lander mission with more various mission targets, from the scientific exploration to the future Moon utilization, including the human lunar outpost. For the scientific Moon exploration road map, the low-frequency radio astronomy, the sample return, and so on, have also been discussed within the lunar exploration long scenario. In addition to those scientific missions, technology development and verification, Moon resource utilization, Moon observatory, and human beings on the Moon for the future space
K. Matsumoto et al. / Acta Astronautica 59 (2006) 68 – 76
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JAXA shall develop sound technologies for the establishment of a lunar base and its utilization. This will be done with the aim to maintain and strengthen the capability for technology development as the engine for expanding activities of Japan and achieving the world-class technological capability. In the Chapter II, that describes the long-term vision, lunar activities are described as: JAXA undertakes lunar explorations to establish its bridgehead base on the Moon. This will enable the expansion of the areas of activity on the Moon, and help strengthen Japanese technology development. JAXA develops the necessary technologies to achieve this goal.
Fig. 1. Japanese Moon lander 1st concept SELENE-B.
development and future human frontier have begun to be discussed widely. In correspondence with the start of integrated JAXA, JAXA have started to build its long-term vision for next two decades. The official version of the JAXA long-term vision, “JAXA 2025”, was fixed at the end of March 2005. In the discussion of this JAXA 2025 vision, the exploration and utilization of the Moon has been considered as one of the major goals. After finalizing JAXA 2025 vision, we have started the discussion for the concrete implementation of the lunar exploration, by the voluntary 60 days study team.
In Chapter III, that describes the detail of the vision, the “exploration and utilization of the Moon” is described in the section of “Advance the human knowledge and to expand the human frontier”. 2.2. Objectives of Moon exploration and utilization The objectives of Moon exploration and utilization are summarized as: • Contribution to the expansion of human frontier. • International recognition through challenge to develop advanced technologies. • Understanding the origin and evolution of the Moon and application of the findings. 2.3. Direction for the vision
2. Exploration and utilization of the Moon in JAXA 2025 vision In this section, the expectation and description for the Moon exploration and utilization in JAXA 2025 vision will be briefly introduced, based on the English version [1]. 2.1. Summary [3] In summary of the JAXA 2025 vision, the lunar exploration vision is described as: (2) Contribute to the advancement of knowledge and expansion of human frontier by exploring the mysteries and possibilities of the universe.
Recognizing the NASA’s new vision for space exploration and their invitation for the world cooperation, as background, JAXA 2025 vision sets four directions, that shall be pursued toward the implementation of this Moon exploration vision: • Promoting lunar science and examining possibilities of lunar utilization. • Taking the challenge to develop most advanced technologies toward future space exploration and innovative space utilization. • Preparing for the establishment of a human lunar base. • Establishing mutually complementary relationships with other countries.
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2.4. Roadmap As the roadmap for the Moon exploration vision, the followings are its summary: Next decade roadmap: The development of advanced technologies for the decision to the full utilization of the Moon: (1) Implementation of SELENE project and other existing and planned Moon exploration missions. • Detailed map of the Moon surface of topography, geographical features and gravitational field. • For selecting a landing site on the Moon. • Establishing cooperation between SELENE and NASA lunar reconnaissance orbiter (LRO). (2) Exploration on the Moon and exploring possibilities of its utilization. • Acquire technologies for precise landing and roving on the Moon and other planets. • Planet and astronomical observations from the Moon surface. • Option list for decision of the full utilization of the Moon, in coming 20 years. (3) Advanced technologies development • Robotics, ISRU (in situ resource utilization), and so on. • Technology base. • Acquiring key technologies through the international space station (ISS) utilization and H-II transfer vehicle (HTV). • International cooperation in high performance sensors and a solar energy supply system. Coming 20 years roadmap: Technology establishment for the international human lunar base construction and utilization: (1) For the international human lunar base project. • Important role by fully utilizing the developed technologies. • Appropriate international contributions and share responsibilities. (2) Key technologies for long-term human presence at a lunar base. • Life-support, power generation, wireless power transmission, and so on. 3. Sixty days study for JAXA Moon exploration In correspondence with the finalization of the JAXA long-term vision, at the end of last March, we have vol-
untarily and informally started a 60 day’s study team to make a proposal for the concrete roadmap of the Moon exploration in JAXA 2025. The team members have been gathered to cover the various aspects of the Moon exploration, depicted in the JAXA long-term vision. The space technology researchers, the lunar scientists, and the astronomers have joined into this team. Most of the team members had also joined the study of the former Moon lander proposal SELENE-B. For the concrete roadmap of JAXA 2025 vision, as the major subjects, the study team discussions were started from the significance of the Moon exploration and human lunar base for the Japanese space development, to the definition of Moon landers as the precursor of the human lunar base. In the following, the interim report will be introduced. 4. Basic principles for Japanese Moon exploration As the principle of Japanese Moon exploration for the next decade, we have identified the following five basic principles. (1) As the first step for the next stage of Japanese space development: During the next two decades, human space activities will be expanded to the Moon and beyond, across the near-Earth boundaries. The technologies and resources, resulted from the Moon exploration and its utilization, would be essentially useful for the future exploration not only of the Moon itself but also of the solar system. Within about 20 years, there will be the lunar base/outpost for more human space activities. The lunar base will be constructed through international cooperation. Japan, with its advanced technologies, would join as one of the leading partner in this cooperation and would take appropriate responsibility. (2) Send landers within next decade before 2015: By SELENE, Japan could draw up high-resolution global mapping of the Moon surface, and precise Moon gravity map. Through SELENE, we would collect data that could determine the distribution profiles of lunar crust constituents, the crust structure, the exposed parts of the deep layers materials of lunar structure, areas of concentration of particular materials, and unique topographic features. Those data will be highly utilized to determine the future human landing site. Following the SELENE results, the exploration and investigation of Moon surface would go next steps using Moon landers and robotic vehicles for the possible full utilization of the Moon. The technologies developed by these landers and robotic exploration vehicles, will also work actively on other celestial bodies in the
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Fig. 2. Future lunar base: international lunar base, supported by lunar robot.
solar system, and will also contribute to the planet and astronomical observations from the Moon surface. International cooperation for these Moon landers would also be pursued. Based on the results and technologies during first decade, we will submit options for proceeding in the full utilization of the Moon. (3) Missions will cover technology development, lunar utilization, and lunar science: According to the objectives, identified in JAXA 2025, the exploration and utilization of the Moon will cover three fields, those are advanced technology development and verification for the future space development, utilization of lunar resources such as water/ice, oxygen, or Moon surface as the platform, and innovative scientific knowledge for the Moon itself. Those three missions will be assembled into a series of unmanned robotic precursors and human Moon explorations (Fig. 2). (4) For the international cooperation, and international human Moon exploration: In 20 years from now, it is anticipated that space infrastructures will be established on or around the Moon, for human space activities across the near-Earth boundaries. As the first step for such space infrastructure, the human Moon exploration project would start within next 10 years, as the next international human space program after ISS. In that case, Japan will join that international program as an international space partner. Through this participation, we will step-by-step ac-
quire and contribute technologies for human presence in space, utilizing and advancing the ISS experience. The common objectives of both of the SELENE and JAXA 2025 vision are Japan’s contribution to the expansion of human frontier. These objectives resonate with the principle shared by the United States and Europe in their space activities, i.e. the ultimate goal of space activities is “. . . to extend a human presence across our solar system. . .” and beyond. Japan will, therefore, establish mutually complementary relationships with other space partners, and will take steps forward in the journey into the universe by an effective and efficient manner. 5. Significance of human lunar base In the JAXA’s vision, the human lunar base/outpost is set as the long-term goal of our Moon exploration and utilization. However, for the human space activity and human lunar base, we still need more extensive and detailed discussions from the view points of cost/budget, schedule/when, effect/why, and so on. Thus, the 60 day’s study team has started its discussion to build common recognition of the human lunar base significance and roles for Japanese space development. The human lunar base has four major aspects for our space development, those are on the Moon, by the human, continuous and permanent activity, and international.
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5.1. Moon exploration The Moon is the nearest neighbor celestial object for our earth with natural resources. The traveling cost is less than 5 days. If we, as human being, will continue to extend our space development, and to expand the human frontier from the earth surface to the outer world, the Moon shall be the next stage of the space development for the world and for Japan beyond the LEO activities. For the expansion of the human frontier via the lunar base, space technologies should be advanced drastically at the lunar base to support human astronaut in safe and comfortable condition. The lunar base will work as the technology development and verification test-bed. For those new space development activities, Japan already started SELENE project as our “first step”. We will continue our activities following SELENE with our advanced technologies, such as robotics, and so on. 5.2. Human lunar activity From the ISS to the Moon, human beings are striving to expand the boundary of our activities. For the human beings, the Moon will be the next stage across the nearEarth boundaries as a matter, of course. Without long stay and support technology on the nearest neighbor celestial, Moon, the expansion of the human exploration to mars and beyond might be too high goal for human technology and science. In 20 years from now, space infrastructures necessary for human space activities will be established on the Moon, as the most promising infrastructures for human space activities. Japan will participate in the next international human space program and will step-by-step acquire and contribute technologies needed for human presence in space. For the human transportation to the Moon, the human being shall have a couple of transportation measure for the maximum safety assurance for the crew safety. 5.3. Continuous lunar exploration The continuous activities at the lunar base will enable Moon exploration as non-disposable activities. The continuous and repetitive scientific observation, similar to the research on the ground, would create new field of lunar science. The human and robotic tasks for the lunar base construction and maintenance will also enable large facilities on the Moon, such as the optical observatory. Advanced technologies developed for the Moon
exploration could be tested and verified at the Moon base, for mars exploration, and solar system exploration.
5.4. International cooperation The technologies and investments for the human lunar base might be enormous for one country. The need of international cooperation is not only for this budgetary enormousness, but also the hopeful activity of the human beings. From Apollo era to till now, the human lunar base might be too high goal for the world space development. However, various advanced technologies in this century might enable such human lunar base as the realistic goal for our human beings, with affordable international cooperation. With the maximum international cooperation and competition, the human outpost establishment will become more realistic and more effective for Japan and the world. Thus on the Moon, international cooperation will be naturally organized. Advanced space development countries and Japan will compete sincerely to improve technologies and activities for the next generation. The human lunar base as the long-term target of Japanese space development would bring about the most advanced technologies, the contribution to the human frontier, and the national security for Japan. It will be used as the technology test-bed for our space technologies, for the utilization of lunar resources and/or lunar itself, for the space sciences, and as the stage of international cooperation and competition.
6. The roadmap for the human lunar base To realize to the human lunar base, the following series of Moon landers and human Moon explorations are proposed as the roadmap for next decade and for the international human lunar base (Fig. 3). In next decade: Japanese original orbiter and lander with international cooperation. In next decade, JAXA vision set the goal as the advanced technologies development for the decision of the full utilization of the Moon. For this goal, the series of the lunar orbitor and lunar landers should be projected, with the attached representative missions. SELENE: 2007 Orbitor. Precise global mapping; Moon gravity map; Sciences by remote sensing; Selection of first human exploration site. SELENE-2: 2011–2013 Lander for the polar region. Precise and safe landing; Lunar science on the Moon;
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Fig. 3. Proposed road map for next decade and for international human lunar base.
In situ resource investigation (water/ice); Moon night survival. SELENE-3: 2013–2015 Lander with rover for the polar region. Wide area investigation for science and utilization; Robotics for exploration; Long-term Moon night survival. In next two decades: Participation to the international project. After the decision of the full utilization of the Moon, Japan will join the international human lunar exploration to establish the technologies for the international human lunar base construction and utilization. For this goal, the series of the human lunar exploration will be projected. Human lunar lander: 2018–2020 3–14 days. Human landing; Human support (robotics, ISRU,. . .). Human lunar base: 2020–2025 60–90 days. Full scale lunar utilization and science; Long-term stay on the Moon. Permanent human lunar base: 2025–year. Extension of lunar utilization and science; Technology test-bed for manned mars exploration. 7. Technological subjects of polar region precursor exploration Although there might be so hard technological problems for the 1st Japanese Moon lander, our team has set the landing target area and exploration spot at the polar region, as SELENE-2. Recently the polar region, in particular, the permanently shadowed region (PSR), has been strongly expected that there would be water/ice, based on the Clementine and Lunar Prospector observation data.
If water ice will be found as the utilizable Moon resource, the Moon exploration will be drastically changed. The water ice could be used as the human support resource, fuel battery resource, fuel for Mars exploration, and so on. It might be the first mining rights in the space, or would be the situation similar to the Antarctica. Thus, the in situ investigation and observation of the water ice at the polar region will be very attractive not only for the science, but also more promising for the lunar utilization. However, for polar region and the PSR, there is almost no certain knowledge. Until now, no Moon lander did visit the polar region, and no orbiter did observe precisely, enough for the safe and/or sure exploration. Because of the very low sun angle, there could be expected no high-resolution image. The Moon polar region is really the un-explored Moon site. For the 1st landing exploration of such unknown region, we have examined technologies, those shall be added to the former Japanese Moon lander concept, SELENE-B, which was also designed to land the barren and un-explored vicinity area around a crater central peak. The followings are the major topics, examined until now. 8. Exploration scheme of PSR As the candidate scheme for PSR exploration, we have examined and compared the following schemes as its starting points. From the technological view points, PSR has many serious difficulties, those are no optical image, very low temperature estimation, such as around 40 K, no
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sun lighting, no more than speculated information, and so on. Thus, the bright vicinity of the PSR is also examined as the 1st landing target area, which will be close to the PSR and sun lighted. Based on the polar region elevation data, in some restricted sun-lighted PSR vicinity area, the severe night time is estimated nearly zero or very short, although the average Moon night time is 354 h at its equator. This short night period would be very attractive for Moon night survival. Some areas with 100% sun lighting are also called eternal lighted region (ELR), and might be ultimately attractive for future Moon base. Direct exploration of PSR: (a) Landing alone. (b) Landing with rover. (c) Landing by multiple exploration system. Exploration via the well-lighted vicinity of PSR: Fig. 4. PSR direct landing concept.
(d) Landing with rover. (e) Landing with multiple exploration system for PSR. 8.1. Direct exploration of PSR The PSR direct landing and exploration scheme have the following common problems: (1) Energy: Without nuclear energy or energy supply from outside, the lifetime of the lander will be strictly limited by the battery capacity. Only a few hours to few days lander lifetime may not be enough even for the single resource investigation mission. (2) Safe landing: In PSR optical camera image could never be expected for the obstacle avoidance and navigation sensors. The direct landing on PSR will require advanced active landing sensors, like LRF and so on, in addition to the optical camera for navigation during powered descent. (a) Lander with air bag could reduce the active LRF requirement. By the same design specification to mars exploration rover (MER), 123 m above the Moon surface will be the starting altitude of air bag protected Moon lander (Fig. 4). (b) In our rough concept study, the Moon rover exploration around the lander at PSR, might be too severe requirement for our 1st Moon lander. The rover on PSR shall move around the permanently shadowed area with very small body, with a little energy, and without any prior geographic knowledge. (c) A couple of penetraters or air bag landers, with a little resource investigation package, are possible explo-
ration sub system. Japan has developed the penetrater system in last decade for the Moon. With the penetrator, the under ground water/ice investigation will be easily done without power consuming excavation drill. However, very low temperature at PSR, lower than 100 K, the survivability of the penetrater could not be expected. 8.2. Exploration via the well-sun-lighted vicinity of PSR The well-sun-lighted vicinity of PSR, the landing and exploration scheme have the following common expectation and problems: (1) Well-lighted: The well sun-lighted regions will be better than a region near the equatorial, because of the short or zero night time, for the night survival energy. At the limited well-lighted vicinity of PSR, sun light could be used as the energy resource with more than 80–90% of one Moon day. At north pole, some regions are also expected with 100% sun light. (2) Safe landing: The sun angle is very low, nearly zero. Thus even in those sun-lighted areas, the expectation for the optical images will be limited, because of the very long shadow of the distributed rocks. (d) Rover: For the rover the long distance traverse will be essentially required from the lander to PSR, without any geophysical knowledge. If we intend to explore the highly expected PSR for water/ice exploration, the required traverse distance for rovers might be more than 10 km.
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Fig. 5. Possible concept of polar PSR exploration.
Fig. 6. Fuel weight for lander hopping.
And because of the very low sun angle, even around the lander, the rovers shall traverse over the too much shadowed zone before the PSR. The energy supply from the lander or the energy station might be essential requirement of the small rover without long life battery or the nuclear battery. (e) The ejection of a couple of single point exploration system (SPES) might be more effective than rovers. During the descent phase, over the PSR, SPES would be shot as penetraters, or soft landed by the air bag. SPES will be ejected during the descending phase or after landing, to overcome the long and severe traverse by the rover (Figs. 5 and 6). 9. Unknown region landing scheme The following four types of landing system were examined for the polar region landing.
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(a) Landing leg: For this traditional landing system, the autonomous obstacle avoidance capability will be essential to avoid and prevent fall down during the touch down. The current Moon orbiters, such as SMART-1, SELENE, LRO, Chandrayaan, are expected to supply the more detailed Moon surface information. The most precise surface resolution by the LRO will be improved up to nearly less than 1 m or 50 cm. However, in addition to this precise terrain image, the active LRF and optical image camera will be required for more sure obstacle identification and precise positioning. (b) Air bag: For SPES landing, air bag landing system will be hopeful, to reduce the excessive weight of rocket and legs by more simple and light air bag, and increase safety of landing. By the air bag design specification for mars rover MER landing, SPES could be ejected from about 123 m above the target PSR, or fly over a few hundreds meter to the PSR from landed lander (Fig. 5). (c) Air bag landing from orbit: This concept is the combination with the rocket descent from Moon orbit, and the final touchdown by the air bag from suitable altitude, defined by the air bag collision performance. Parachute and air bag scheme will increase the landing safety for the unknown polar region much more than the rocket and leg scheme. But because of the high vacuum environment on the Moon, parachute has no use. Thus, for the descent phase, the rocket is used to reduce the landing speed to almost zero. And the air bag is used against the final collision impact with less possibility of tumble even for the unknown barren land (Fig. 4). (d) Penetrater: Penetrater is the combination with rocket descent and hard landing. Instead of soft landing, the penetrater concept will utilize the high touch down speed to penetrate into the Moon regolith and to utilize the thick regolith as thermal chamber. However, in polar region, the too low regolith temperature would cancel the thermal chamber effect.
10. Conclusion In this paper, the Moon exploration and utilization approach in the JAXA 2025 vision is briefly introduced. The concrete plan to realize this scenario is proposed as the interim report of the 60 days study team in JAXA. As a part of this study team activity, initial study results for technological subjects were also introduced with possible schemes for polar permanently shadowed region exploration.
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References [1] JAXA 2025, 2005.3, JAXA http://www.jaxa.jp/about/ vision_missions/long_term/. [3] K. Matsumoto, et al., Japanese long term Moon exploration plan, ILC-2005.
Further reading [2] M. Kato, et al., The science scenario of the SELENE-2 mission, ILC-2005.
[4] K. Matsumoto, et al., Night survival and long stay for Japanese Moon landing, IAC-04-IAA.3.6.2.10, 2004. [5] D. Ben, J. Bussey, et al., Illumination conditions at the lunar south pole, Geophysical Research Letters 26 (9) (1999) 1187–1190.