曽根 理嗣

To further advance manned space exploration, a critical issue that must be addressed is recycling of resources, especially air revitalization and water reclamation. Japan is already a leader in terrestrial environmental technologies, and aims to apply this know-how to develop air and water recycling technologies for space applications. To support proposed post-ISS missions such as manned lunar or asteroid exploration and an Earth-Moon Lagrange point (EML1) space station, JAXA is developing an air revitalization system for an on-orbit demonstration on the International Space Station (ISS) early in the extended ISS operation period (2015-2020). The requirements for this technical demonstrator have been investigated and its specifications established. Regenerative life support functions include oxygen recovery from carbon dioxide using a combination of CO2 reduction by a Sabatier process and CO2 generation by electrolysis. Each air and water re-vitalization subsystem is planned to be transported to the ISS separately by successive H-II Transfer Vehicle (HTV) launches in the sequence Water Reclamation → Water Electrolysis → CO2 Reduction. This paper presents the air re-vitalization system developed by JAXA, and gives details of water electrolysis in microgravity.

The Sabatier reaction catalyzed by titania-supported ruthenium (Ru/TiO2) was investigated for the aim of practical water (H2O) generation from carbon dioxide (CO2) reduction and hydrogen (H2) at lower temperatures. Various Ru/TiO2 catalysts in powder form were prepared by dry processing. Hydrogenation of CO2 to methane successfully proceeded on the catalysts at temperatures below 300°C without the formation of carbon monoxide (CO). It is noteworthy that some of the Ru/TiO2 catalysts maintained their chemical properties after they were immobilized in a three-dimensional structure. In addition, use of the immobilized catalysts resulted in significant alleviation of not only catalyst weight but also temperature differences in the reactor. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Various space agencies are currently considering the moon and asteroids as way stations for astronauts bound for Mars. Under JAXA's long-term vision, JAXA2025, the agency will by 2015 finalize its development plans for the next period of manned space activity. To establish supporting technologies, JAXA is researching systems that will be indispensable for manned space activities beyond low earth orbit, including water and air recycling. Three types of assemblies are necessary for recycling air: a carbon dioxide separator to remove exhaled carbon dioxide from a spacecraft's atmosphere, a carbon dioxide reduction assembly to produce water from the separated carbon dioxide and added hydrogen, and water electrolysis equipment for oxygen production. This paper describes a carbon dioxide removal assembly and a water electrolysis assembly designed for operation in microgravity. © 2012 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

In this study, we analyzed the thermal characteristics of commercial cylindrical lithium-ion cells using an accelerated rate calorimeter (ARC) and by analyzing the electrochemical impedance spectroscopy (EIS) measurements. During the thermal runaway analysis, the cells were tested at different state of charges (SOCs) and the thermal deterioration was determined by monitoring the impedance at 1 kHz and the open circuit voltage as a function of the temperature. The mapping of the thermal runaway was obtained, ant the non-self heating, self-heating and thermal runaway regions were identified at different SOCs. The self-heating and thermal runaway behaviors showed a temperature dependence. In order to clarify the deterioration reaction in the non-self heating region, high temperature storage tests were carried out, storing the cell in the temperature range of 70-100 degrees C. We estimated the activation energy from the discharge capacities before and after the high temperature storage. In order to determinate the charge/discharge activation energy of the cells, EIS measurements were recorded. Based on our study, the activation energy of the deterioration was about two times greater in magnitude than the activation energy of the charge/discharge. (C) 2011 Elsevier B.V. All rights reserved.

The power supply management system was originally developed at JAXA to manage the risk of electric power scarce due to excess access from each device. The main idea is to decrease the peak amount of limited power in a spacecraft by changing in switching time based on demand-response from each device. For realization, the system features "decentralized system" and "priority setting" on each device. The decentralized system, in which each device has its own controller and changes information each other, contributes to the robustness of the system since a defect of the controller does not affect other parts of the system while the limited power is allocated based on the priority level of each device. Experiments were taken for heater control equipment to demonstrate the practical performance of the novel power system. In the experiments, six devices were prepared with heater controllers which received duty signals, and set the target temperature for each of the devices. The experiments were initiated by providing sufficient power and checked if all the devices were fully working, and then decreased the power supply to observe the behavior of the temperatures under limited resource. As a result, all of the devices met the temperature requirements even under short energy supply. To quantitatively evaluate the benefits of the new system when applied to public infrastructure systems, multiple small electrical trains (HO gauge) whose electrical power provision system is basically the same as the real one have been arranged. The experiments also give the deeper understanding of behavior of first-order motor-driven system in view point of energy consumption. Presently, the priority setting system is being implemented to the small train system, to show whether similar results as the heater control case are also achieved. In conclusion, this paper will present the newly constructed power system and elaborate its ramifications together with the experimental and simulation results. Copyright © (2012) by the International Astronautical Federation.

The Japan Aerospace Exploration Agency (JAXA) is developing polymer electrolyte fuel cell (PEFC) systems that can be operated under isolated low-gravity and closed environments. In the present study, we combine the PEFC with an electrolyzer in order to realize a regenerative fuel cell. Ideally, if a single cell can be operated as a fuel cell and the cell can be made reversible through the electrolysis reaction, then compact, lightweight regenerative fuel cell systems can be realized. A unitized regenerative fuel cell was prepared, and its operability was demonstrated. During 100-W class operations, a stable fuel cell and electrolysis reaction was observed. (C) 2011 Elsevier B.V. All rights reserved.

A lithium-ion battery was developed using off-the-shelf pouch cells and launched with a small scientific satellite "REIMEI." The cells were potted with polyurethane or epoxy resin to protect the battery from vacuum in space. Preliminary experimental test results of pouch cells potted in a soft aluminum cap suggested that the cells tended to swell in vacuum, although they had been reinforced with the resins. Bread board models (BBMs), in which pouch cells were potted with resins in a hard aluminum case, were fabricated for cycle life performance tests in the laboratory. The test results indicated that the performance of epoxy-potted BBM was superior to that of the polyurethane-potted BBM. The measured cell resistance implied that the electrolyte solution leaked through the polyurethane resin, resulting in premature deterioration. The epoxy resin was used for the flight battery. The end-of-discharge-voltage (EoDV) trend of the flight battery on orbit was compared with the laboratory test results corrected based on a post-launch cycle test using a fresh cell. The corrected EoDV trend in the laboratory was in good agreement with the on-orbit trend for the early cycle period, indicating that the on-orbit battery was not inadvertently affected by conditions in space. (C) 2011 Elsevier B.V. All rights reserved.

This paper describes the outline and the five years' on-orbit results of the small scientific satellite REIMEI for aurora observations and demonstrations of advanced small satellite technologies. REIMEI is a small satellite with 72 kg mass, and is provided with three-axis attitude control capabilities for aurora observations. REIMEI was launched into a nearly sun synchronous polar orbit on Aug. 23rd, 2005, from Baikonur, Kazakhstan, by Dnepr rocket. REIMEI satellite has been satisfactorily working on the orbit for five years at present as of January, 2011. Three-axis control is achieved with accuracy of 0.1 degrees (3 sigma). Multi-spectrum images of aurora are taken with 8 Hz rate and 2 km spatial resolution to investigate the aurora physics. REIMEI is performing the simultaneous observation of aurora images and particle measurements. REIMEI indicates that even a small satellite launched as a piggy-back can successfully perform unique scientific mission purposes. (C) 2011 Elsevier Ltd. All rights reserved.

The Japan Aerospace Exploration Agency (JAXA) has been developing lithium-ion secondary cells for aerospace applications. Lithium-ion secondary cells were first used for the interplanetary spacecraft, HAYABUSA. For the long-term operations on the moon and interplanetary orbit, in-orbit performance of the lithium-ion battery demonstrated by HAYABUSA has been precisely examined. Furthermore, the regenerative fuel cell system is also one of the most important candidates to the future lunar and planetary missions where the higher energy density is required.

The Sabatier reaction with a titanium dioxide (TiO2)-supported ruthenium (Ru) catalyst (Ru/TiO2) was investigated with the goal of scaled-up carbon dioxide (CO2) methanation at lower temperatures than conventional catalysts. The catalytic reaction of stoichiometric amounts of CO2 and hydrogen (H2) without any diluting was conducted over a 0.75 wt% Ru/TiO2 (Ru/TiO2(0.75)) at several flow rates. The CO2 reduction was achieved with catalyst temperatures less than 300°C in good to excellent conversions. Transmission electron microscopy (TEM) and scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDX) images of Ru/TiO2(0.75) revealed highly dispersed Ru nanoparticles having one to a few nanometers' diameter on the TiO2 supports. The physical properties of Ru metals are considered to contribute the decrease of the reaction temperature. © 2010 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Proton exchange membrane fuel cell offers higher energy density than the existing battery technologies for high-energy applications, and it is a promising power source for various industries including aerospace vehicles. We have been developing and testing a non-external humidified fuel cell system for high-altitude balloons, which require simple, light, and easy-to-operate power systems. This system consists of three major subsystems-a fuel cell stack, a reactant supply subsystem, and an electrical control subsystem. Ground performance testing in a vacuum chamber simulating the high-altitude vacuum condition was performed before the flight. Then, a demonstration flight of the fuel cell system was launched using a large balloon for verifying its performance under practical high-altitude conditions. Cell voltage variations synchronized with oxygen pressure spikes were observed that were probably caused by condensed product water plugging the flow passages of the back pressure regulator. Flight results indicated that the fuel cell system operated better when water was expelled as vapor, rather than in the liquid form. In addition, a back pressure regulator should be installed to avoid the accumulation of water droplets for realizing a stable performance. (C) 2009 Elsevier B.V. All rights reserved.

Lithium-ion batteries are a candidate for the energy storage system onboard low-earth-orbit satellites. Cycle life performance under both orbital and terrestrial conditions must be investigated in order to evaluate any inadvertent effects due to the former and the validity of the latter, with a successful comparison allowing for the extension of terrestrial experimental matrices in order to identify the effects of ageing. The orbital Performance of LixMn2O4-based pouch cells onboard the microsatellite REIMEI was monitored and compared with terrestrial experiments, with the cells found to be unaffected by orbital conditions. A lifetime matrix of different cycling depths-of-discharge (DODs: 0,20,40%) and temperatures (25, 45 degrees C) was undertaken with periodic reference performance tests. A decrease in both the cell end of-discharge cycling voltage and capacity was accelerated by both higher temperatures and larger DODs. Impedance spectra measured for all ageing conditions indicated that the increase was small, manifested in a state-of-charge dependent increase of the high-frequency semi-circle and a noticeable increase in the high-frequency real axis intercept. An evaluation of the change of both the resistance and capacity of 3 Ah cells led to the development of a potential prognostic state-of-health indicator. The use of elevated temperatures to accelerate cell ageing was validated. (C) 2008 Elsevier B.V. All rights reserved.

Lithium-ion batteries area candidate for the energy storage system onboard low-earth-orbit satellites. Terrestrial experiments are able to capture the performance degradation of cells in orbit, therefore providing the opportunity for lifetime investigations. The lifetime performance of 3 Ah commercial LixMn2O4-based pouch cells was evaluated in a matrix of different cycling depths-of-discharge (DODs: 0, 20,40%) and temperatures (25, 45 degrees C). Aged cells were disassembled and the electrochemical performance of harvested electrodes investigated with two- and three-electrode pouch cells. The positive electrode had a larger decrease in capacity than the negative electrode. Both the positive and negative electrode contributed to the increase of cell impedance measured at high states-of-charge (SOCs). The data at low SOCs indicated that the increase of cell impedance was associated with the positive electrode, which showed a significant increase in the magnitude of the high-frequency semi-circle. This SOC-dependence was observed for cells cycled for either extended periods of time or at higher temperatures with a 40% DOD swing. Low-current cycling of positive electrodes revealed a change in the second potential plateau, possibly reflecting a structural change of the LixMn2O4. This could impact on the electrode kinetics and provide a possible explanation for the SOC-dependent change of the impedance. (C) 2008 Elsevier B.V. All rights reserved.

This paper summarizes the cut-rent status of the BepiColombo Mercury magnetospheric orbiter (MMO) spacecraft design. The MMO is a spinning spacecraft of 223 kg mass whose spin axis is nearly perpendicular to the Mercury orbital plane. The current status of the overall MMO system and subsystems such as thermal control, communication, power, etc., are described. The critical technologies are also outlined. Furthermore, the outline of the international cooperation between Japan Aerospace Exploration Agency and European Space Agency is also presented. (C) 2008 Elsevier Ltd. All rights reserved.

'HAYABUSA' is a Japanese inter-planetary spacecraft built for the exploration of an asteroid named 'ITOKAWA.' The spacecraft is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage, in case it is required for a loss of attitude control. The capacity of the battery was measured during flight operations. Along with the operation in orbit, a ground-test battery was discharged, and both results showed a good agreement. This result confirmed that the performance of the lithium-ion secondary battery stored under micro-gravity conditions is predictable using a ground-test battery. (C) 2008 Published by Elsevier B.V.

The Japanese spacecraft, HAYABUSA, was launched on May 9, 2003 and spent more than 2.5 years approaching the asteroid ITOKAWA. This spacecraft used 13.2 Ah lithium-ion secondary cells. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery was maintained at ca. 65% during storage in case it is required for contingency operations. To maintain this SOC condition, the battery is charged once a week. After HAYABUSA touched down on ITOKAWA in December 2005, four of 11 lithium-ion secondary cells were over-discharged. However, the battery power was still indispensable for sealing the container with the asteroid sample. The seven remaining healthy cells were slowly recharged using minimum current. After its safety was confirmed, the lithium-ion secondary battery was used to transfer, latch, and successfully seal the sample container into the reentry capsule. The seven remaining cells have been slowlydischarged through the resistance of the monitoring circuit. The capacity by the discharge revealed that the storage performance of the lithium-ion secondary battery is predictable based on the ground-test results even after the storage for 5 years in space. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

A fuel cell (FC) /regenerative fuel cell (RFC) for space utilization has special system requirements, such as operational conditions and designs, because of its isolated low gravitational and closed environment, which differs greatly from that for terrestrial use. Over 1,000 h continuous and stable operation of PEFC using the developed prototype system was achieved. During conditions of no thermal control, no external humidifier, and low current density operation under low pressure, the voltage was maintained at a constant level under such low temperatures. No cross-leak or flooding phenomena were observed from these results: good performance was also obtained. These results suggest that the polymer electrolyte and other components used in this study were stable in such conditions. Copyright © 2008 by the American Institute of Aeronautics and Astronautics, Inc.

The Japanese spacecraft, HAYABUSA, was launched on May 9, 2003 and spent more than 2.5 years approaching the asteroid ITOKAWA. This spacecraft used 13.2 Ah lithium-ion secondary cells. After HAYABUSA touched down on ITOKAWA in December 2005, it could not communicate for seven weeks due to a malfunction of the attitude control. During this period, four of 11 lithium-ion secondary cells were over-discharged, and solar power was unavailable due to the spacecraft's tumbling motion. However, the battery power was still indispensable for sealing the container with the asteroid sample. The seven remaining healthy cells were slowly recharged using minimum current. During this time, ground simulation tests using similarly-built and intentionally short-circuited cells were carried out to evaluate the battery's operational safety. After its safety was confirmed, the lithium-ion secondary battery was used to transfer, latch, and successfully seal the sample container into the reentry capsule. The necessary power for these actions was supplied by the battery.

The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency's Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy gets transferred from the photosphere to the upper atmosphere and results in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-Ray Telescope (XRT). This paper provides an overview of the mission, detailing the satellite, the scientific payload, and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data. © 2007 Springer Science+Business Media B.V.

This paper describes the on-orbit results and lessons-learned of the small scientific satellite "INDEX" (REIMEI) for aurora observation and demonstration of advanced satellite technologies. INDEX is a small satellite with 72kg mass, and is provided with three-axis attitude controll capabilities for aurora observation. INDEX was launched into a nearly sun synchronous polar orbit on Aug. 23rd, 2005 (UT) from Baikonur, Kazakhstan by Dnepr rocket. INDEX satellite has been satisfactorily working on the orbit for 24 months at present of August,2007. Three axis control is achieved with accuracy of 0.1 deg(3 σ). Multi-spectrum images of aurora are taken with 8Hz rate and 2 km spatial resolution to investigate the aurora physics. INDEX is performing the simultaneous observation of aurora images and particle measurements. INDEX indicates that even a small satellite launched as a piggy-back can successfully perform unique scientific mission purposes. Copyright IAF/IAA. All rights reserved.

Because structural change in lithium cobalt oxide (LiCoO2) cathode is primarily responsible for the performance degradation of lithium-ion cells in simulated satellite operation, it is important to investigate the operating-condition effect on cell-volume change. In this work, we used in situ strain- gauge measurement to probe the total volume change during charging and discharging of five 50 Ah- class lithium-ion cells with graphite anodes and LiCoO2 cathodes. Some interesting phenomena concerning the correlation of the taper voltage with the strain change at the end of the charge were found in the strain trend curve. To explain these phenomena, we examined the strain change of a commercial 0.65 Ah- class lithium- ion polymer cell with the same electrodes as a function of taper voltage by using in situ load- cell measurement and were able to deduce that the cell-volume change during charging correlated to the structure transition of the LiCoO2 cathode from the initial hexagonal phase (H1) to a new hexagonal phase (H2) at a taper voltage near 4.00 V. We conclude that the taper voltage should be maintained below 4.00 V to maximize the cycle life of lithium- ion cells with graphite anodes and LiCoO2 cathodes during practical satellite operation. (c) 2006 The Electrochemical Society.

Light element impurities in ultrathin silicon-on-insulator (SOI) wafers were characterized by photoluminescence (PL) spectroscopy under ultraviolet (UV) light excitation. Various commercial SOI wafers were irradiated by 1 MeV electrons with a fluence of 3 × 1016-1 × 1017 cm-2. The electron irradiation induces point defects, which react with light element impurities, resulting in the formation of strong radiative centers. We were able to successfully observe the C-line originating from the complex between interstitial carbon and oxygen in all the samples and also the G-line from the complex between interstitial and substitutional carbon in some of them. This demonstrates the presence of carbon and oxygen impurities in an ultrathin top Si layer with a thickness down to 62 nm. We investigated the difference in the impurity concentration depending on the wafer fabrication methods and the variation of impurity concentration in the respective wafers. © 2006 Elsevier B.V. All rights reserved.

We are conducting cycle-life testing of 10-100 Ah-class lithium-ion cells in a simulated satellite operation at the Japan Aerospace Exploration Agency (JAXA). This paper reviews the latest test results of these lithium-ion cells. Thus far, we have verified impressive life performance exceeding 30,000 cycles in a simulated low-earth-orbit (LEO) mode and 1800 cycles in a simulated geostationary-earth-orbit (GEO) mode for some of these cells. We optimized the thickness of the electrode layer to suppress cell-internal impedance and found that a lithium-ion cell with a thin electrode layer exhibited promising cycling performance in a simulated LEO operation. Since the electrode material is an important factor affecting the charge-discharge behavior of a lithium-ion cell, we also compared the cycling performance of lithium-ion cells with different cathode materials. (c) 2006 Elsevier B.V. All rights reserved.

In this paper, we review our work on cycle-life testing of a 100-Ah class lithium-ion battery in a simulated geosynchronous-Earth-orbit (GEO) satellite operation. The battery consists often 100-Ah lithium-ion (10) cells in a series, with a high energy density exceeding 100 Wh kg L at the battery level. We simulate the eclipse period in real-time testing with five depth-of-discharge (DOD) patterns at an ambient temperature of 15 degrees C. We also simulate a sun-shine period in 8-day thermally accelerated full-charge storage at an ambient temperature of 25 degrees C, which in our experience corresponds to full-charge storage of a half-year operation at 0 degrees C. Eighteen eclipse seasons have presently been completed, corresponding to 9 years of GEO operation. The battery maintained a high voltage near 3.4 V at the end of the discharge, even when the DOD was set at 70%. The voltage dispersion of 10 cells was also sufficiently small in the range of 48 mV The cell temperature reached a maximum of 29 degrees C and maintained minimal dispersion smaller than 4 degrees C even when the battery was discharged at a high DOD of 70%. (c) 2006 Elsevier B.V All rights reserved.

The Japan Aerospace Exploration Agency (JAXA) is developing polymer-electrolyte fuel cell (PEFC) systems that can operate under isolated low-gravity and closed environments. Subsystems and operating methods such as the closed gas operation subsystem, the working gases counter-flow method, and a dehydrator using wicking material were developed to simplify assembly of the fuel cell system. We combined these subsystems with the 1 kW-class fuel cell stack and simulated the operations of a spacecraft in Earth orbit. The system performed stably for 1100 h under various operational conditions. © 2006 Elsevier B.V. All rights reserved.

Laminated lithium-ion polymer cells with gel electrolytes and laminate-film package are expected to replace the conventional alkaline batteries for space application due to their high energy density and high flexibility in configuration. To facilitate this, we assessed the effect of operation conditions, charge rate and taper voltage, on cycle-life testing of commercial lithium-ion polymer cells by simulating a satellite's LEO operation with 40% DOD profile in this work. So far, 6000 cycles have been completed. A lower charge rate was found to be promising for long-term satellite operation. Impedance analysis disclosed a little change in cell internal impedance with charge rate. This encouraged us to attribute the poor cycling performance at high charge rate to excessive lithium-ion exhaust in electrode surface-film formation due to a longer holding duration at taper voltage. The taper voltage was also found to affect charge performance of lithium-ion polymer cells. Good cycling performance, such as the minimum current at the end of the charge and the maximum voltage at the end of the discharge were observed when using taper voltage range from 4.05 to 4.10 V. Theoretical analysis deduced that low current at the end of the charge correlated to (1) a low cell internal impedance and (2) a large slope in the capacity-voltage charge curve measured at a low rate. We further evaluated cell cycling behavior at a low rate and indeed observed the largest slope of capacity-voltage charge curve at voltages ranging from 4.05 to 4.10 V. © 2004 Elsevier B.V. All rights reserved.

This paper summarizes the current status of the BepiColombo/MMO (Mercury Magnetospheric Orbiter) spacecraft design. The MMO is a spinning spacecraft of 223 kg mass whose spin axis is nearly perpendicular to the Mercury orbital plane. The current status of the overall MMO system and subsystems such as thermal control, communication, power etc are described. The critical technologies are also outlined. Furthermore, the outline of the international cooperation between JAXA and ESA are also presented.

A 100Ah Lithium ion cell for space applications has been developed and tested. It was evaluated for both calendar life and cycle life characteristics to confirm life performance for satellite applications. From these results, we established a simple formula to calculate cell capacity fade and impedance increase. In addition, we have been conducting GEO and LEO life simulation tests on other 100Ah cells from different manufacturing lots and confirmed that the cell satisfied general life requirements of these applications. We have verified the model by comparing calculated capacity fade estimates with the simulated life tests. Since our calculated life estimates match the experimental data with a high degree of precision, we feel this demonstrates the validity of our life model.

The effectiveness of the photoluminescence (PL) and electroluminescence (EL) spectroscopy and their mapping was demonstrated for a diagnostic characterization of radiation effects in InGaP2/GaAs/Ge triple junction (3J) cells and Cu(In,Ga)Se2 (CIGS) cells. The degradation of the band-edge emission under 1 MeV electron irradiation became larger in the order of InGaP2, Ge, and GaAs sub cells, suggesting the lowest radiation tolerance for the GaAs cell. Irradiation of 3 MeV protons on CIGS cells degraded the band-edge emission and induced the deep-level emission at 0.8 eV. We believe that the deep level is responsible for the degradation of the solar cells. The potential of PL and EL mapping was shown for the microscopic and macroscopic defect recognition.

We tested the effect of two new additives, cyclo hexane (CH) and 1-methyl-2-pyrrolidinone (NMP), on the cycling performance of a carbon-coated artificial graphite (AG) anode on a lithium-ion cell to investigate suppression of irreversible capacity loss of the graphite anode during the first-cycle charge. Both CH and NMP additives effectively increased the coulombic efficiency of the graphite anode during the first cycle. We attribute this phenomenon to the dissolution of the poly (vinylidene fluoride) (PVdF) binder of the AG anode due to CH or NMP addition, which improved the PVdF elasticity and reduced the contact area between the AG particles and the electrolyte. Consequently, adding CH or NMP reduced the loss of lithium ions in the first-cycle charge. Cycle-performance testing of the Li/AG half-cell indicated that we could achieve maximum discharge capacity and coulombic efficiency by applying an additive amount ranging from 2 to 5% for both CH and NMP. The cycling performance testing of the LiCoO2 half-cell suggested that these two additives also have good oxidation stability and are therefore worth applying in lithium-ion cells with graphite anodes. © 2005 The Electrochemical Society. All rights reserved.

This paper describes the initial on-orbit results of the small scientific satellite "INDEX" (REIMEI) for aurora observation and demonstration of advanced satellite technologies. REIMEI is a small satellite with 72kg mass, and is provided with three-axis attitude controlled capabilities for aurora observation. REIMEI was launched into a nearly sun synchronous polar orbit on Aug. 23rd, 2005 (UT) from Baikonur, Kazakhstan by Dnepr rocket. After REIMEI was separated from the Dnepr rocket, REIMEI successfully performed a sun-pointing acquisition with spinning motion. A week later REIMEI switched into three-axis attitude control mode. REIMEI satellite functions works satisfactorily in the orbit. The first imaging observations of aurora were successfully performed above the southern polar region in Sep. 16th, 2005. Multi-spectrum images of aurora were taken with 8Hz rate and 2 km spatial resolution.

The Japanese satellite 'HAYABUSA' is currently en route to an asteroid named ITOKAWA. The satellite is powered by a 13.2 Ah lithium-ion secondary battery. To realize maximum performance of the battery for long flight operation, the state-of-charge (SOC) of the battery is maintained at ca. 65% during storage in case it is required for contingency operations. To maintain this SOC condition, the battery is charged once a week. We further charge the battery up to 4.1 V/cell using bypass circuits to balance the cells every four months. The capacity of the battery was measured during the flight operation, which revealed the appropriate capacity for the HAYABUSA mission.

The Japan Aerospace Exploration Agency (JAXA) is developing a polymer electrolyte fuel cell (PEFC) system for aerospace missions. A fuel cell stack, gas circulator, and dehydrator were prepared. We combined these components and operated the fuel cell system without external humidification. The performance of the fuel cell was verified for 250 hours while it continuously generated 60 A. We then varied the current level from 30 to 150 A, and continued the test for 400 hours. We did not change gas flow or circulation rate and observed a stable performance by our PEFC system without external humidification.

Polymer electrolyte fuel cell (PEFC) systems targeting applications to transfer vehicles for short-term missions and larger spacecraft in the future are being developed at NASDA. First, we designed and manufactured a system with a 100 W class fuel cell. Through our tests, we found that a humidifier is not necessary when using pure hydrogen and oxygen supplied from opposite directions. In a closed simulated environment, the tests could also demonstrate the stable operation of the fuel cell system where the oxygen was recycled and the hydrogen stream was dead-ended. © 2004 Elsevier B.V. All rights reserved.