福田 盛介

The exploration of energization and radiation in geospace (ERG) satellite, nicknamed "Arase," is the second satellite in a series of small scientific satellites created by the Institute of Space and Astronautical Science of the Japan Aerospace Exploration Agency. It was launched on December 20, 2016, by the Epsilon launch vehicle. The purpose of the ERG project is to investigate how high-energy (over MeV) electrons in the radiation belts surrounding Earth are generated and lost by monitoring the interactions between plasma waves and electrically charged particles. To measure these physical processes in situ, the ERG satellite traverses the heart of the radiation belts. The orbit of the ERG is highly elliptical and varies due to the perturbation force: the apogee altitude is approximately 32,200-32,300 km, and the perigee altitude is 340-440 km. In this study, we introduce the scientific background for this project and four major challenges that need to be addressed to effectively carry out this scientific mission with a small satellite: (1) dealing with harsh environmental conditions in orbit and electromagnetic compatibility issues, (2) spin attitude stabilization and avoiding excitation of the libration by flexible structures, (3) attaining an appropriate balance between the mission requirements and the limited resources of the small satellite, and (4) the adaptation and use of a flexible standardized bus. In this context, we describe the development process and the flight operations for the satellite, which is currently working as designed and obtaining excellent data in its mission.

<p>SLIM (Smart Lander for Investigating Moon) is the Lunar Landing Demonstrator which is under development at ISAS/JAXA. SLIM demonstrates not only so-called Pin-Point Landing Technique to the lunar surface, but also demonstrates the design to make the explorer small and lightweight. Realizing the compact explorer is one of the key points to achieve the frequent lunar and planetary explorations. This paper summarizes the preliminary system design of SLIM, especially the way to reduce the size.</p>

© The Authors, published by EDP Sciences, 2017. The lithium-ion secondary batteries have been widely used for the space programs, today. Among them, REIMEI was one of the first satellites using lithium-ion secondary battery. In 2005, the satellite was launched, and injected into the low earth polar orbit. Eleven years has passed since the launch and over 60,000 cycles of charge and discharge was experienced in space. The lithium-ion secondary cell of the REIMEI battery was designed using spinel manganese oxide type material for the positive electrode, and the graphitized type carbon for the negative electrode. The cell case was made of aluminium laminated film and the structure was reinforced by the epoxy resin and aluminium housing. After the operation of eleven years, the cells still maintain the appropriate uniform balance and operative. In order to identify the internal condition of the battery/cell, we calculated the ac impedance by the pulse duration to the on-board battery.

© The Authors, published by EDP Sciences, 2017. Understanding the behavior of Li-ion cells during thermal runaway is critical to evaluate the safety of these energy storage devices under outstanding conditions. Li-ion cells possess a high energy density and are used to store and supply energy to many aerospace applications. Incidents related to the overheating or thermal runaway of these cells can cause catastrophic damages that could end up costly space missions; therefore, thermal studies of Li-ion cells are very important for ensuring safety and reliability of space missions. This work evaluates the thermal behavior of Li-ion cells before and after storage degradation at high temperature using accelerating rate calorimeter (ARC) equipment to analyze the thermal behavior of Li-ion cells under adiabatic conditions. Onset temperature points of self-heating and thermal runaway reactions are obtained. The onset points are used to identify non-self-heating, self-heating and thermal runaway regions as a function of state of charge. The results obtained can be useful to develop accurate thermo-electrochemical models of Li-ion cells.

The lithium-ion secondary batteries have been widely used for the space programs, today. Among them, REIMEI was one of the first satellites using lithium-ion secondary battery. In 2005, the satellite was launched, and injected into the low earth polar orbit. Eleven years has passed since the launch and over 60,000 cycles of charge and discharge was experienced in space.The lithium-ion secondary cell of the REIMEI battery was designed using spinel manganese oxide type material for the positive electrode, and the graphitized type carbon for the negative electrode. The cell case was made of aluminium laminated film and the structure was reinforced by the epoxy resin and aluminium housing. After the operation of eleven years, the cells still maintain the appropriate uniform balance and operative. In order to identify the internal condition of the battery/cell, we calculated the ac impedance by the pulse duration to the on-board battery.

The satellite borne batteries should be composed by safe materials if we don't want to have a risk of explosion caused by batteries. Therefore, we focused on two safe batteries. One is a lithium-ion battery with an ionic liquid electrolyte, and the other is a LiFePO4/C type lithium-ion battery. To check whether the batteries are suit for space applications or not, we demonstrate the ionic liquid type batteries and LiFePO4/C type battery in orbit by mounting on "Hodoyoshi-3" microsatellite, and test LiFePO4/C type cell on the ground at various conditions for a better understanding.On the ground tests, AC impedance and capacity of the cells were initially measured, and charge/discharge cycling was constantly repeated at 10, 23 and 45 degrees C. The cells were discharged by constant current (CC) protocol to DOD 50% with 1.0 C for 30 minutes. They were then charged by a constant-current/constant voltage (CC-CV) protocol to 3.6 V for 65 minutes with 0.5 C. For capacity check, the cells were charged at 1.0 C in CC-CV mode until their charge current becomes 60 mA, and discharged at 1.0 C in CC mode to 2.0 V at 23 degrees C. The AC impedance was measured by applying 100 mA of AC oscillation over the frequency range from 0.01 Hz to 10 kHz at SOC 50%.As a result, the decrease in the impedance for the charge transfer through the cycles was observed at each test condition. Furthermore, especially in over recommended charge condition at 10 degrees C, cells that were charged and discharged at 1.1 A/1.1 A were led to internal short circuit. The results suggested that the negative electrode performed as a "lithium-ion excess" by cycles. We define "lithium-ion excess" that lithium-ion happens to stay inside the negative electrode without desorption after cells discharge.

For planetary exploration missions using a lander, autonomous pinpoint landing capability whose precision is less than 100-meter must be needed in order to land on limited investigation areas. This capability cannot be realized with an inertial navigation system in terms of accuracy, so that the inertial error should be reduced in some way. One of solutions is image-based velocity measurement in a navigation path of the planetary lander. However, images taken by the lander have probrems such as frame rate limit and motion blur. Moreover, the available onboard resources of computation are limited. This paper proposes a velocity estimation method using a single blurred image for the pinpoint planatary landing. We present the method based on cepstral analysis and discuss feasibility through resource evaluation with a space-grade FPGA.

© The Electrochemical Society of Japan, All rights reserved. The AC impedance of the LiFePO4 type lithium-ion secondary cells was initially measured, and charge/discharge cycling was constantly repeated at 10, 23, and 45°C to understand their electrochemical characteristics. The decrease in the impedance for the charge transfer was observed at each temperature even though the SOC was set in 50%. We assumed from the impedance changing and discharge trend that the negative electrode performed as a "lithium-ion reservoir" by cycles.

The AC impedance of the LiFePO4 type lithium-ion secondary cells was initially measured, and charge/discharge cycling was constantly repeated at 10, 23, and 45 degrees C to understand their electrochemical characteristics. The decrease in the impedance for the charge transfer was observed at each temperature even though the SOC was set in 50%. We assumed from the impedance changing and discharge trend that the negative electrode performed as a "lithium-ion reservoir" by cycles. (C) The Electrochemical Society of Japan, All rights reserved.

Lithium-ion secondary cells are widely used for the space applications, today. Among these applications, REIMEI, which was launched in 2005, was one of the first satellites using lithium-ion battery. The off-the-shelf type cells designed using spinel manganese oxide for the positive and the graphitized carbon for the negative electrode were used. The cell case was made of aluminum laminated film and the structure was reinforced by the aluminum case filled with epoxy resin. Today, ten years has passed, and the battery experienced 55,000 cycles for charge and discharge. The current distribution between two batteries almost coincided together even after the long term operation, which revealed the stable performance of the lithium-ion secondary cells under the microgravity in space. (C) The Electrochemical Society of Japan, All rights reserved.

Lithium-ion secondary cells are widely used for the space applications, today. Among these applications, REIMEI, which was launched in 2005, was one of the first satellites using lithium-ion battery. The off-the-shelf type cells designed using spinel manganese oxide for the positive and the graphitized carbon for the negative electrode were used. The cell case was made of aluminum laminated film and the structure was reinforced by the aluminum case filled with epoxy resin. Today, ten years has passed, and the battery experienced 55,000 cycles for charge and discharge. The current distribution between two batteries almost coincided together even after the long term operation, which revealed the stable performance of the lithium-ion secondary cells under the microgravity in space.

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. Energy storage devices are very important for space missions, Li-ion cells are used to supply energy to spacecrafts or satellites during the eclipse/night time. These cells possess a high energy density but can cause catastrophic incidents that could end up costly space missions, those incidents are manly related to the overheating or thermal runaway of Li-ion cells, leading to possible fire and explosion as observed by incidents in the electronics and aerospace industries. The thermal analysis of Li-ion secondary cells is very important for ensuring safety and reliability of space missions. The thermal behavior of a Li-ion cell is dominated by the exothermic reactions between its electrolyte and electroactive materials. Thermal runaway occurs when the exothermic reactions go out of control, thus the self-heating rate of the cell increases to the point that it begins to generate more heat than what can be dissipated. Understanding the behavior of Li-ion cells during thermal runaway is critical to evaluate the safety of these energy storage devices under outstanding conditions. In this work we analyze the thermal runaway behavior of 18650 Li-ion cells before and after storage and cycling degradation at high temperatures. The thermal behavior of the cells is analyzed using accelerating rate calorimetry. Non-self-heating, self-heating and thermal runaway regions of the cells as a function of state of charge and temperature are identified and compared among the cells. Li-ion cells were tested inside an accelerating rate calorimeter (ARC) 2000™ to record their thermal behavior under adiabatic conditions. Onset temperatures of self-heating and thermal runaway reactions are identified, and by using these onset points thermal mapping plots are made. We are able to identify non-self-heating, self-heating and thermal runaway regions of degraded and non-degraded Li-ion cells as a function of state of charge. The results shows that degraded Li-ion cells tend to be thermally unstable at low state of charges.

A prototype lithium-ion battery with a bis(fluorosulfonyl)imide (FSI)-based ionic liquid electrolyte was developed. The prototype was mounted on a demonstration module of the "Hodoyoshi-3" microsatellite, which was successfully launched on June 20, 2014. Qualification tests for space application, including radiation tolerance and vacuum tests, revealed negligible degradation of the ionic liquid-based lithium-ion battery (IL-LIB) cell. According to the flight data, the IL-LIB cell can exist stably in an ultra-high vacuum environment despite its thin and flexible pouch casing without any rigid anti-vacuum reinforcements. Furthermore, the power unit showed the same charge-discharge performance as that predicted by the charge-discharge behavior of an identical cell on the ground, suggesting that the IL-LIB cell maintains performance in high vacuum a microgravity environment. These results prove that LIB cells with FSI-based ionic liquids can be used as a power source for space applications. (C) The Electrochemical Society of Japan, All rights reserved.

© 2014, The Author(s). HISAKI (SPRINT-A) satellite is an earth-orbiting Extreme UltraViolet (EUV) spectroscopic mission and launched on 14 Sep. 2013 by the launch vehicle Epsilon-1. Extreme ultraviolet spectroscope (EXCEED) onboard the satellite will investigate plasma dynamics in Jupiter’s inner magnetosphere and atmospheric escape from Venus and Mars. EUV spectroscopy is useful to measure electron density and temperature and ion composition in plasma environment. EXCEED also has an advantage to measure spatial distribution of plasmas around the planets. To measure radial plasma distribution in the Jovian inner magnetosphere and plasma emissions from ionosphere, exosphere and tail separately (for Venus and Mars), the pointing accuracy of the spectroscope should be smaller than spatial structures of interest (20 arc-seconds). For satellites in the low earth orbit (LEO), the pointing displacement is generally caused by change of alignment between the satellite bus module and the telescope due to the changing thermal inputs from the Sun and Earth. The HISAKI satellite is designed to compensate the displacement by tracking the target with using a Field-Of-View (FOV) guiding camera. Initial checkout of the attitude control for the EXCEED observation shows that pointing accuracy kept within 2 arc-seconds in a case of “track mode” which is used for Jupiter observation. For observations of Mercury, Venus, Mars, and Saturn, the entire disk will be guided inside slit to observe plasma around the planets. Since the FOV camera does not capture the disk in this case, the satellite uses a star tracker (STT) to hold the attitude (“hold mode”). Pointing accuracy during this mode has been 20–25 arc-seconds. It has been confirmed that the attitude control works well as designed.

We are in progress to develop a system for automatic operation of a satellite in order to reduce human load at satellite steady operation phase. The ground station for small satellite REIMEI (INDEX : INnovative-technology Demonstration EXperiment) is used as a test bench for verification of the proposed method. In our new automatic operation system, a scheduler software as a substitutive operator manages all the operations through a unified procedure, including sending command, receiving telemetry, and driving antenna in accordance with an operation time line which is prepared before the operation pass. The scheduler also performs diagnostics of satellite anomaly based upon the received telemetry data and status of the ground station. In case that some anomaly of the satellite is detected, the scheduler initiates an emergency schedule that was prepared depending on the emergency level. The automatic operation system is nearly completed for downlink operations of the data recorder that account for 75% of REIMEI steady operation. This approach is very effective to reduce psychological and physical load of operators.

本論文は,高分解能な合成開口レーダ(Synthetic Aperture Radar : SAR)画像のスペックル低減処理において,テクスチャやエッジなどの特徴量を保存する手法を提案している.提案する手法は,Gamma-Gamma MAPフィルタにおける局所領域からのオーダパラメータの推定に際して,オーダパラメータの推定精度を向上させるために,比較的広い領域を選択し,注目画素と同様の性質を有する領域に含まれる画素で構成されるウィンドウを新たに設定し,得られたウィンドウ内に含まれる画素を用いて,オーダパラメータを推定する.得られたオーダパラメータを基に,事後最大確率推定を行うことで,同一領域におけるテクスチャ情報を保持しつつ,スペックルを低減する.計算機シミュレーション画像による性能評価により,特徴量の保持性能と平滑性能を確認した上で,実際のSAR画像に適用することにより,従来手法と比較して高い視覚的自然性を確認した.

This paper describes the outline and the five years&apos; 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.

After the success of remotely-sensed global observation by SELENE orbiter, Japan has been focusing on the in-situ exploration of the Moon. To know more about the Moon, numerous missions have to be launched to the Moon for surveying different interesting places. Naturally the cost of single mission must be reduced. Japan has been considering a landing mission for about ten years as a next mission to the Moon. This has a few tons of weight and costs a few million euros including the launch vehicle because it also features the future manned mission. Obviously it is not suitable for scientific in-situ exploration, which must be conducted repeatedly. The authors have been studying a small lander on the Moon or the planets in order to enable the multiple in-situ explorations cheaply. With the technologies developed in our studies, the mission named SLIM (Smart Lander for Investigating Moon) has been proposed to demonstrate an autonomous, accurate and soft landing on the specified place of the Moon. SLIM is also helpful to increase the success probability of the nation-led flagship landing mission when it is conducted as a precursor. This paper describes the proposed SLIM mission.

The Institute of Space and Astronautical Science JAXA is developing a landing radar comprising a radio altimeter and a velocity meter, which are two of the mandatory navigation sensors for a planetary lander. A BBM of the landing radar has been evaluated on natural terrains by using a helicopter. This paper introduces the BBM hardware and discusses the dynamic performance in field experiments.

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.

比較的安価な小型月着陸実験機でピンポイントに月面の目標地点に着陸し，科学探査を行う小型ミッションを検討している．観測機器の重量制限，ミッション期間が最長で月の昼間に限定，月の表側のみに着陸可能など，制約は多い．しかし，単目的でも小回りの利く探査は，大型で高価な周回衛星や着陸機と相補的な役割を果たすことができ，さらに将来の惑星表面探査への技術ステップとしても重要性は高い．本研究では、小型月着陸機による探査構想とミッション候補の検討、搭載機器の可能性を検討した結果を報告する。

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.

Intensity fluctuation of synthetic aperture radar (SAR) images, due to speckle and texture, statistically brings series connections of dark pixels. Resolution enhancement of SAR systems can provide texture with correlation properties. In this paper, simulation studies are carried out to investigate the relation between the occurrence of the stochastic dark line features and texture correlation.

Intensity fluctuation of synthetic aperture radar (SAR) images, due to speckle and texture, statistically brings series connections of dark pixels. Resolution enhancement of SAR systems can provide texture with correlation properties. In this paper, simulation studies are carried out to investigate the relation between occurrence of the stochastic dark line features and texture correlation.

In the previous works [1], [2], we developed the classification method of land cover from polarimetric SAR data using support vector machines (SVMs). As the extended study of the SVM-based classification method, an unsupervised approach is presented in this paper. Since SVM, originally a technique for pattern recognition, can not be applied to unsupervised classification straightforwardly, we propose the automatic selection scheme of representative training areas based on the number of the closest training samples to the separating hyperplane in the feature space; such samples are called the support vectors. In the experiment for a part of the AIRSAR Flevoland data including five classes of agricultural crops, the scheme performs successful classification, which can bear comparison with the supervised result.

Support vector machines (SVMs), newly introduced in the 1990s, are promising approach to pattern recognition. They are able to handle linearly nonseparable problems without difficulty, by combining the maximal margin strategy with the kernel method. This paper addresses a novel SVM-based classification scheme of land cover from polarimetric synthetic aperture radar (SAR) data. Polarimetric observations can reveal existing different scattering mechanisms. As the input into SVMs, the polarimetric feature vectors, composed of intensity of each channel, sometimes complex correlation coefficients and textural information, are prepared. Classification experiments with real polarimetric SAR images are satisfactory, Some important properties of SVMs, for example the relation between the number of support vectors and classification accuracy, are also investigated.

Support vector machines (SVMs) have much attention recently as promising approach to pattern recognition. They are able to handle linearly nonseparable problems by combining the maximal margin strategy with the kernel method. This paper addresses a novel SVM-based classification scheme of land cover from polarimetric synthetic aperture radar (SAR) data. The SVMs are successfully applied to the feature vectors which consist of several polarimetric features or the texture measure, and perform efficient image classification. Some important properties of SVMs, for example the relation between the number of support vectors and classification accuracy, are also discussed.

Speckle statistically brings series connections of dark pixels, which can be observed as dark line features in synthetic aperture radar (SAR) images. The dark lines have no physical meaning. In this paper. line features of that kind in high-resolution SAR images whose intensity obeys a K-distribution are studied. It is stochastically explained that the dark line features in 1-look K-distributed images can be observed more distinctly than those in exponential distributed images. It is further revealed that such line features are detectable enough, even if the K-distributed images are multilooked. The experiments on simulated images as well as on actual SAR images confirm the explanation.

Texture is an essential key to the classification of land cover in SAR images. A wavelet-based texture feature set is derived in this paper. It consists of the energy of subimages obtained by the overcomplete wavelet decomposition of local areas in SAR images, where the downsampling between wavelet levels is omitted. The feature set has been successfully applied to multifrequency polarimetric images of the Flevoland site, an agricultural area in The Netherlands. The methods of polarization selection and feature reduction are also discussed.

The smoothing effect of the wavelet-based speckle filtering that we proposed is investigated. The filtering reduces the amplitude of wavelet coefficients, and a theoretical investigation with the Haar basis derives a functional relation between the ENL and two parameters: the wavelet level and the degree of the amplitude reduction.

A filter for suppressing speckle in synthetic aperture radar (SAR) images utilizing wavelet is proposed. The filter suppresses speckle by reducing the amplitude of the detail images in wavelet subspaces, while preserving edges by releasing the amplitude reduction around edges; information on edges, contained in the detail images, is utilized for edge detection. Simulations and application to SAR images have shown that the performance of the filter is satisfactory in both smoothing and edge preservation, and in generating visually-natural images as well.