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NASDA English Translation

Why do spacecraft charge in sunlight? The first reason concerns differential charging between the sunlit and dark sides. A monopole-dipole model describing the differential charging potential distribution yields interesting theoretical results. We compare the results with observations. The second reason concerns reflectance. Much attention has been paid in recent years to the effect of surface conditions on secondary emission, which plays an essential role in spacecraft charging. In comparison, little or no attention has been paid to the effect of surface condition on photoemission, which plays a dominating role in spacecraft sunlight charging. We present theoretical reasoning why highly reflective mirrors generate substantially reduced photoemission. We have calculated, by using the Langmuir orbit-limited current balance equation in 1-D, 2-D, and 3-D, the different surface potentials of various surface materials under typical space plasma conditions, satellite surface reflectivity values, and sunlight incidence angles. We present numerical results confirming that with substantially reduced photoemission, highly reflective surfaces would often charge to high negative potentials in sunlight., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In this paper, we propose a quasi-neutral model with non-vanishing current describing the expansion of a plasma in an inter-cellular gap on a satellite solar array. Moreover, an electric arc cathode spot model is proposed in order to give suitable boundary conditions for the expansion model., JAXA Special Publication, 宇宙航空研究開発機構特別資料

We organized a working group for studying the reproduction and continuity of life under the space environment. The aim of our project is to get deep insight into the effect of space environment, especially the effects of gravity for long period of time, on reproduction. We discussed mainly two projects following this year. The first one was assessment of sperm quality. For human reproduction in space, the sperm quality of astronauts is one of the important factors. We noticed that it was necessary to progress the research about the effect of space environment on male reproductivity, sperm quality. We also discussed about Ciona intestinalis, as a new model animal for space biology. This animal has excellent features for the space experiments, such as relatively short life cycle, completed genome project, belonging to phylum Chordata that is close to vertebrate and so on. We move ahead on these proposals as the new project.

For telecommunication satellites, RF equipment switching can lead to coaxial cables electrically floating. In a geostationary orbit, space environment can charge floating cables to potentials as high as some tens of volts. With switches, the charge stored on the core flow out and the generated current can trigger interference or damages on MOS transistors. This paper deals with experimental results at electrostatic behavior level for such cables under electron irradiation. Two coaxial cables used in satellites (an overshield brand of seven coaxial cables and a cable connected to a switch) are irradiated by an electron beam source simulating geostationary orbit equivalent energy range and flux intensity. During these experiments, we monitored the current collection and the voltage gained on core and/or cables shielding after their irradiation in order to evaluate the probable occurrence of an electrostatic discharge., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In recent years, long-term employment and enlargement are becoming remarkable in space development. The increase in electric power may include discharges on the solar array panels of spacecrafts. Furthermore, the discharges involve the risk of producing surges which affect payloads in the spacecrafts. Testing with real satellites has many problems with time, effort, equipment, cost, etc., so an accurate evaluation by simulation is needed. In order to evaluate correctly, we have to imitate discharge currents that flow through a circuit. This discharge current can be obtained by modeling the plasma resistance generated by the discharges, as well as the equivalent circuit of the whole spacecraft. In this research, we modeled this plasma resistance. First, plasma resistance includes two resistance components, one of which exists in the discharging current path of the charges stored in the space body. The other resistance component exists in the inflowing current path of the charges stored on the surfaces of the solar cells. The former current and resistance are known as a blow-off current and blow-off resistance. The latter current and resistance are known as a flash-over current and flash-over resistance. In order to acquire experimental values of blow-off resistance, we measured the blow-off current using a solar cell, and analyzed it using SPICE simulation. From the results, it was confirmed that blow-off resistance decreased exponentially. Also, blow-off resistance had a relationship with discharge energy. In addition, we measured the flash-over resistance. We measured the flash-over current using a solar array coupon which had 50 cells on the coupon, and analyzed it using SPICE simulation. From the results, it was confirmed that flash-over resistance increased linearly in proportion to the distance from the discharge point. In the near future, we will create the equivalent circuit of the solar array panel. Moreover, there is a need to create the equivalent circuits

NASDA Special Publication, 宇宙開発事業団特別報告

Secondary electron emission is a critical contributor to the current balance in spacecraft charging. Spacecraft charging codes use a parameterized expression for the secondary electron yield delta(E(sub 0)) as a function of incident electron energy E0. Simple three-step physics models of the electron penetration, transport and emission from a solid are typically expressed in terms of the incident electron penetration depth at normal incidence or range R(E(sub 0)), and the mean free path of the secondary electron. lambda(E). We recall classical models for the range R(E(sub o)): a power law expression of the form b(sub 1)E(sub o)(sup n1) and a more general empirical bi-exponential expression R(E(sub o)) = b(sub 1)E(sub o)(sup n1) + b(sub 2)E(sub o)(sup n2). Expressions are developed that relate the theoretical fitting parameters (lambda, b(sub 1), b(sub 2), n(sub 1) and n(sub 2)) to experimental terms (the energy E(sub max) at the maximum secondary electron yield delta(sub max), the first and second crossover energies E(sub 1) and E(sub 2), and the asymptotic limits for delta(E(sub o) approaches infinity)). In most models, the yield is the result of an integral along the path length of incident electrons. Special care must be taken when computing this integral. An improved fourth-order numerical method is presented and compared to the standard second-order method. A critical step in accurately characterizing a particular spacecraft material is the determination of the model parameters in terms of the measured electron yield data. The fitting procedures and range models are applied to several measured data sets to compare their effectiveness in modeling the function delta(E(sub o)) over the full range of incident energies, and in particular for determining crossover energies and critical temperatures., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In recent years, space debris increases because many rockets and satellites have been launched. A solar array of a spacecraft has become larger with the higher voltage and electrical power. Therefore, the risk of debris impact and possibility of discharge on the solar array is increasing. If space debris impacts solar array, it electric power decreases or loses. When space debris impact on the solar array, high-density plasma is discharged. The arc that led may generate the plasma. This is Temporary Sustained Arc. This discharge can lead to carbonize the insulation layer of the solar array by Joule heat due to the large current through the plasma, and form permanent short-circuit. If this phenomenon continues, a permanent short circuit course will be formed between a solar cell and a substrate. This is Permanent Sustained Arc. It causes decrease or loss of generating capacity of a solar array coupon. In this study, the first purpose is verified that sustained arc is discharged or not by space debris impacts on solar array. The second purpose is elucidated the threshold of sustained arc. We want to reduce the influence affect the missions of a satellite by those results. Therefore, we took notice a density and electron temperature of the plasma which induce to discharge and clarified the threshold of sustained arc generating for hypervelocity impact test by two-stage light gas gun. The triple probe method was used plasma measurement test. The results show that electron temperature and electron density have correlation with impact speed, and the plasma density is higher than the plasma environment on low earth orbit. A possibility of TSA (Temporary Sustained Arc) generation is large over 80 [V], and generating of PSA (Permanent Sustained Arc) was confirmed over 183 [V]-2.4 [A] of power supply voltage. The generating conditions of PSA are sustaining voltage is 50 [V], current is 2.2 [A] and dissipation power of discharge circuit is 110 [W]. Therefore, it is desirable t

プレスなどへの公開用資料として、ISS米国実験棟における中性子計測実験の概要をまとめたものである。1)中性子計測実験の概要、2)別添1:スペースシャトルシステムの概要、3)別添2:国際宇宙ステーション(ISS)の概要。, JAXA Research and Development Memorandum, 宇宙航空研究開発機構研究開発資料

The fatal anomaly of the Advanced Earth Observing Satellite-2 (ADEOS-2) on the polar earth orbit of 803 km altitude, that was due to an electric power loss from 6 kW to 1 kW, occurred off the coast of Peru from 16:12 to 16:16 UT on 24 October, 2003. It was considered to be caused by the short/open of the electronic cables in the harness connected the solar paddle and the satellite body. That had been probably triggered by electrostatic charging and subsequent discharging of the electronically floating Multi-Layer Insulation (MLI) blanket of the harness by the energetic auroral electron flux when the ADEOS-2 was passing through the northern aurora oval just before the anomaly. Measurements of the onboard energetic charged particle detector were not fully available around the anomaly due to the data transmission schedule. However the NOAA-17 satellite, that was almost 30 km just above the ADEOS-2, observed an extraordinary enhancement of the energetic electron flux at the nightside aurora oval. The total energetic electron flux (larger than 30 keV) is calculated to be 2.94 x 10(exp 10) (particles/sq cm). This total flux is supposed to be enough to charge the floating MLI blanket deeply and induce discharging for trigger arcs., JAXA Special Publication, 宇宙航空研究開発機構特別資料

NASDA English Translation

The Micro-Particles Capturer (MPAC) is a passive experiment designed to evaluate the micrometeoroid and space debris environment, and to capture particle residues for later chemical analysis. It is mounted on a frame about 1 m long, which it shares with the Space Environment Exposure Device (SEED), a materials exposure experiment. In this paper we focus on (1) Visual inspection of the whole surface of MPAC&SEED, and (2) Impact feature morphology and track analysis in the MPAC silica aerogel., JAXA Special Publication, 宇宙航空研究開発機構特別資料

NASDA Special Publication, 宇宙開発事業団特別報告

これからの宇宙開発・宇宙環境利用では長期飛行／長期有人活動が必須であり、ミッションを信頼性高く安心に遂行するためには、利用材料の寿命評価、特に地上では考えなくても良い数100キロメートルの環境に豊富な原子状酸素との共存性について、材料曝露試験を通して十分検討することが必要である。我が国の従来の実績としては、宇宙実験・観測フリーフライヤーの搭載実験機器部を用いて行った約10カ月間の材料曝露実験、STS(Space Transportation System)-85シャトルミッションによる12日間の材料曝露実験、宇宙環境信頼性実証システムプロジェクトの一環としての宇宙実証試験、などがある。米国では、1986年より6カ年間、長期曝露実験衛星でセラミック材料も含めた材料曝露実験を行っている。2001年10月15日より、国際宇宙ステーション(ISS)のロシアサービスモジュール(SM)の曝露部に材料曝露実験装置(SEED)を配置して、非酸化物系セラミック材料の材料曝露実験(SM/SEED)を3年計画で行っている。長期滞在が必須の状況では、「その場資源」と「宇宙エネルギー環境」が大きな活用対象であり、比強度の高い軽量材料としての本実験試料類の寿命評価は重要である。特に、炭化ケイ素は構造材としての重要性ばかりでなく、今後のエネルギー利用の高利用効率化(限られた資源を最大限に利用する)に重要なパワーデバイスとして注目されている。本発表では、2002年8月26日に回収した315日間の曝露結果と2004年2月26日に回収した865日間の曝露結果について報告する。, JAXA Special Publication, 宇宙航空研究開発機構特別資料

The conventional wisdom about solar array arcing in LEO is that only the parts of the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc plasma front. Mitigation techniques are also presented., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Ten different samples of thin film solar arrays were tested in a low density plasma. Tests were performed in the vertical vacuum chamber (2 m diameter and 3 m height) equipped with four oil diffusion pumps and in the horizontal chamber (1.8 m diameter and 2.5 m length) equipped with a cryogenic pump, which were providing background pressures below 1 micro-Torr. Cooled traps operation in the vertical chamber and cryogenic pump in the horizontal chamber secured quite clean environments with some traces of water vapor. Current collections and breakdown thresholds were measured for all samples. Degradation of some sample surfaces due to interaction with plasma electrons was established. The results obtained in this test were used to make recommendations to array manufacturers for further development of space grade solar arrays., JAXA Special Publication, 宇宙航空研究開発機構特別資料

As the power level of Geostationary satellites increases, there is more demand of careful ground test on solar array insulation strength. International atmosphere surrounding commercial telecommunication satellites calls for common international standard on test conditions. In this paper, we review ESD tests of solar array carried out in recent years at Kyushu Institute of Technology jointly with the Japan Aerospace Exploration Agency. The purpose of this paper is to describe the test conditions with the reasons of selecting those conditions and how we certified the insulation strength of given solar array designs against electrostatic discharges in orbit. The paper is aimed to stimulate discussion among experts on the issue of international standardization of solar array ESD test., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Resistivity values were experimentally determined using charge storage methods for six samples remaining from the construction of the Internal Discharge Monitor (IDM) flown on the Combined Release and Radiation Effects Satellite (CRRES). Three tests were performed over a period of four to five weeks each in a vacuum of approximately 5 x 10(exp -6) torr with an average temperature of approximately 25 C to simulate a space environment. Samples tested included FR4, PTFE, and alumina with copper electrodes attached to one or more of the sample surfaces. FR4 circuit board material was found to have a dark current resistivity of approximately 1 x 10(exp 18) Ohm-cm and a moderately high polarization current. Fiber filled PTFE exhibited little polarization current and a dark current resistivity of approximately 3 x 10(exp 20) Ohm-cm. Alumina had a measured dark current resistivity of approximately 3 x 10(exp 17) Ohm-cm, with a very large and more rapid polarization. Experimentally determined resistivity values were two to three orders of magnitude more than found using standard ASTM test methods. The one minute wait time suggested for the standard ASTM tests is much shorter than the measured polarization current decay times for each sample indicating that the primary currents used to determine ASTM resistivity are caused by the polarization of molecules in the applied electric field rather than charge transport through the bulk of the dielectric. Testing over much longer periods of time in vacuum is required to allow this polarization current to decay away and to allow the observation of charged particles transport through a dielectric material. Application of a simple physics-based model allows separation of the polarization current and dark current components from long duration measurements of resistivity over day- to month-long time scales. Model parameters are directly related to the magnitude of charge transfer and storage and the rate of charge transport., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The Japan Aerospace Exploration Agency (JAXA) is performing a space environment exposure experiment (Experiment by the Russian Service Module/Micro-Particles Capturer and Space Environment Exposure Device experiment: SM/MPAC&SEED experiment) on the exterior of the SM on the ISS. The objectives of SM/MPAC&SEED experiment are to capture micrometeoroids and small space debris particles, and to investigate the degradation mechanism of materials for space use. In this paper, reported is outline of SM/MPAC&SEED experiment, and the inspection and analysis results on the first retrieved specimens are summarized., JAXA Research and Development Memorandum, 宇宙航空研究開発機構研究開発資料

We are studying the problems associated with high voltage power systems in space. Especially we are interested in the potential distribution of the solar array that is resistant to the electrical discharge. We have carried out experiments on the interaction between the high voltage solar array and the ambient plasma. In the experiment, an array of electrodes distributed on the insulation panel was used to simulate the inter-connectors of the solar array. An electrode array without the insulator panel was also used for comparison to study the effect of the insulator. One of major concerns in the usage of the high voltage solar array in space is the arc discharge on the array. Based on the plasma sheath theories, there is a possibility to control or to prevent the discharge by selecting a potential distribution of the electrode array. As the first step to find the potential distribution that is tolerate to the discharge, we measured the distribution of space potential surrounding an array of electrodes and measured the current to the electrodes. This paper presents the experimental results suggesting that we can control the discharge by selecting a proper potential distribution of the high voltage solar array., JAXA Special Publication, 宇宙航空研究開発機構特別資料

NASDA English Translation

JAXA Special Publication, 宇宙航空研究開発機構特別資料

会議情報: 第3回スペースデブリワークショップ (2008年1月21-22日. 日本科学未来館), 江東区, 東京, 形態: カラー図版あり, Physical characteristics: Original contains color illustrations

In recent years, a solar array of a spacecraft has become larger with the voltage higher. Therefore, the risk of debris impact and discharge on the solar array is increasing. There is danger that discharge through the plasma created by debris impact leads to a sustained arc and loss of the generated output from the solar array. In this study, hypervelocity impact test using two-stage light gas gun and the pseudo debris impact test using YAG (Yttrium Aluminum Garnet) laser was carried out to evaluate possibility of the sustained arc on solar array through the plasma created by space debris impact., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The total duration is evaluated in the condition that the Electrostatic Discharge (ESD) could occur and the number of expected trigger arcs for the secondary (sustained) arcs on solar array for the geostationary satellites, the Wideband InterNetworking engineering test and Demonstration Satellite (WINDS) and the Engineering Test Satellite 8 (ETS-8). For the evaluation, NASA Charging Analyzer Program (NASCAP) is used with the statistical plasma parameters observed by the Los Alamos National Laboratory geosynchronous satellites., 宇宙航空研究開発機構(JAXA)が開発中の静止軌道人工衛星のWINDS(超高速インターネット衛星)とETS-8(技術試験衛星8号機)について、NASA Charging Analyzer Program(NASCAP)を用いて表面帯電解析をおこなった。衛星表面帯電の影響として、衛星構造体(衛星アース)と誘電体、特に太陽電池表面のカバーガラスとの間の電位差により起こる放電(Electrostatic Discharge: ESD)の可能性がある帯電時間と、日照時での放電をトリガーとする持続放電による太陽電池の劣化とを見積もった。静止軌道の宇宙プラズマ環境パラメータとして、Los Alamos National Laboratory(LANL)の3つの静止衛星の延べ約12年間分のデータの統計解析結果を用いた。その結果、衛星により帯電特性が異なることが明らかになった。, JAXA Special Publication, 宇宙航空研究開発機構特別資料

To develop lithium-ion batteries for space applications, long-term evaluation on 10 - 100 Ah-class lithium-ion cells is being performed by simulating spacecraft's operation. So far, 23,000 cycles for LEO and 1,350 cycles for GEO satellite simulation testing have been completed. These results respectively correspond to about 4- and 15-year LEO and GEO satellite operations, indicating good applicability of lithium-ion cells as satellite power. The simulation testing of H-2A transfer vehicle (HTV) operation disclosed that lithium-ion cells were applicable for this short-term mission even with a strict operation condition of high charge rate and high taper voltage. The commercial laminated lithium-ion polymer cells (0.65 Ah) exhibited good performance in both cycle-life testing and space-environment endurance., JAXA Research and Development Memorandum, 宇宙航空研究開発機構研究開発資料

JAXA Special Publication, 宇宙航空研究開発機構特別資料

NASDA Conference Publication, 宇宙開発事業団会議報告

This paper describes a brief overview and research results of ISAS/MHI (Mitsubishi Heavy Industries) space-application microelectronics development project. The collaboration between ISAS and MHI have been developing radiation hardened VLSI components with a 0.2-micrometer fully-depleted silicon-on-insulator technology, and provides them as basic design units called standard cells. Chip designers can create various types of radiation hardened VLSI (Very Large Scale Integration) chips optimized for space research missions by properly combining the standard cells as they design conventional VLSI chips. The collaboration has also established an economically-efficient chip fabrication system. In FY2005, high-performance circuits have been included in the ISAS/MHI standard cells to realize high-performance space-application-specific microelectronics like a radiation hardened microprocessor with its operating frequency exceeding 100 MHz., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The space environment in Low-Earth orbit (LEO) has until recently been considered relatively benign to high levels of spacecraft charging. However, it has been found that the DMSP spacecraft at 840 km can charge to very large negative voltages (up to - 2,000 V) when encountering intense precipitating electron events (auroral arcs) while traversing the auroral zone. The occurrence frequency of charging events, defined as when the spacecraft charged to levels exceeding 100 V negative, was highly correlated with the 11-year solar cycle with the largest number of events occurring during solar minimum. This was due to the requirement that the background thermal plasma density be low, at most 10(exp 4)/sq cm. During solar maximum, the plasma density is typically well above that level due to the solar EUV ionizing radiation, and although the occurrence frequency of auroral arcs is considerably greater than at solar minimum, the occurrence of high-level charging is minimal. Indeed, of the over 1,600 events found during the most recent solar cycle, none occurred during the last solar maximum. A dependence of the magnitude of the spacecraft frame charge on density was observed with the largest negative voltages, approximately 2,000 V, only occurring at very low densities. A 'worst-case' charging electron spectrum for low-altitude was developed by applying a potential drop of 20 kV to source data that went into the MIL-STD-1809 specification for near-geosynchronous orbit and combining it with DMSP spectra consistent with a 20-kV drop. The results of this study have implications on a number of LEO satellite programs, including the International Space Station (ISS). The plasma density in the ISS orbit, at a much lower altitude than DMSP, is well above that at 840 km and rarely below 10(exp 4)/sq cm. However, in the wake of the ISS, the plasma density can be two orders of magnitude or more lower than the background density and thus conditions are ripe for significant charging eff, JAXA Special Publication, 宇宙航空研究開発機構特別資料

Validation test cases for the SPARCS code (S. Clerc et al., 8th SCTC, 2003) are presented. More specifically daylight charging of spacecraft is addressed. The main mechanism for charging in daylight is the formation of a potential barrier which leads to partial recollection of secondary electrons and photo-electrons. We first validate the recollection of photo-electrons using the particle tracking capabilities of SPARCS. The test cases involve a positively biased metallic surface. The spherically symmetric and the plane configurations are studied. Numerical results for the net total yield agree with the analytic expression. To validate the potential barrier formation due to surface charging, we compute the charging of a dielectric sphere in sunlight. Due to the complexity of this problem, an exact analytical solution cannot be found. Instead, a simplified monopole-dipole approximation is shown to give a reasonable agreement. Finally, the computation of daylight charging benchmark of a model telecom spacecraft is presented. Agreement with published results (Davis et al. 8th SCTC, 2003) is good., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Possibility of arcing in high voltage arrays have necessitated the theoretical and experimental study of charging and arcing by Indian Space Research Organisation (ISRO), which is planning to increase the satellite bus voltage above the current level of 42 volt. The study, named Spacecraft Plasma Interaction eXperiment (SPIX) was undertaken, together with Institute for Plasma Research (IPR), India to (1) develop software, which is able to predict the floating potential of an object of simplified geometry in space plasma typically of geosynchronous bimaxwellian type, which is also able to calculate the differential potential between two such objects, (2) to develop software to solve the differential equations describing primary arcing phenomena developed by Cho, a pioneer in the field, (3) to study the primary arcing threshold and frequency and to identify the arcing sites of a solar array coupon immersed in a LEO (Low Earth Orbit) like laboratory plasma and to (4) find out the arcing threshold of sustained arcs by introducing a solar array simulator voltage between adjacent strings in a solar array coupon immersed in a LEO-like plasma environment. The experiments have largely yielded results akin to that of other investigators, although some differences have been observed in some experiments. A short term future aim would be to increase the sample space in the last type of experiments mentioned above., JAXA Special Publication, 宇宙航空研究開発機構特別資料

JAXA Special Publication, 宇宙航空研究開発機構特別資料

We present event studies and results of a statistical investigation on charging events seen by the Freja satellite in the auroral zone at 1,500-1,700 km altitude. Charging up to kilovolts is sometimes observed, though lower values are more normal. Comparing to DMSP at 840 km, Freja experiences fewer charging events, but some of them are found in sunlit conditions, which has not been seen on DMSP. No charging event occurred for a density above 2,000 cu cm, though correlation between density and charging otherwise was weak. All charging events show enhanced electron fluxes around or above 10 keV, including enhanced tails up to 100 keV, while electrons around 1 keV instead counteracts charging, as is expected from high secondary yields in this energy range. Simulations using POLAR reproduced moderate charging events, but not the events with kilovolt charging., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The response of a plasma to Very Low Frequency (VLF) (3 kHz to 20 kHz) antennas at orbital altitudes of 1,000 to 10,000 kilometers has been a subject of scientific interest for many decades. As this antenna frequency is less than either the plasma frequency or the electron gyrofrequency (both nearly 300 kHz for a plasma density of 10(exp 9)/cu m and a magnetic field of 0.1 gauss), only certain modes can propagate as an electromagnetic (EM) wave, and the near field is dominated by electrostatic (ES) effects. Although a comprehensive self-consistent EM-ES simulation would be the desired goal, there are many computational challenges to be overcome, so we begin with a quasi-static simulation so as to sort out the dominant ES effects. We present antenna simulations using Nascap-2k modeling the plasma using both an explicit Particle-In-Cell (PIC) approach and a hybrid approach with PIC ions and fluid barometric electron densities. In the latter, electron plasma oscillations are suppressed, while in the former they are excited. Accuracy of the simulations is assessed by comparison with lower-dimensional simulations of similar cases., JAXA Special Publication, 宇宙航空研究開発機構特別資料

When solar array is operated at a high voltage, arcs occur on the array surface. Our task is to examine the effects of conductive current generated by arcing on solar array circuit of spacecraft. First, equivalent circuits of small solar array module are modeled. The equivalent circuits are made for various types of solar cells such as silicon, gallium arsenic (hetero-junction), and triple junction cells, etc. The equivalent circuit is composed of current source, diode, resistance, inductance and capacitance. First, we measured the frequency characteristic and I-V characteristic of a given solar array, and modeled the equivalent circuit to have the same characteristics by electronic circuit simulation software (SPICE). Next, an electric equivalent circuit of the arc inception was made, and was compared with the ground test result. We simulated the transient current and surge voltage resulted from the ground test using the equivalent circuit. The circuit is being adjusted to experimental results at present. We plan to add the effect of arc expansion to the circuit., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Geospace Environment Simulator (GES) has started as one of the advanced computing research projects at the Earth Simulator Center in Japan Marine Science and Technology Center since 2002. By using this computing resource, a large scale simulation which reproduces a realistic physical model can be utilized not only for studying the geospace environment but also for various human activities in space. ES project aims to reproduce fully kinetic environment around a satellite by using the 3-dimensional full-particle electromagnetic simulation code which includes spacecraft model inside. Spacecraft can be modeled by the unstructured-grid 3D FPEM code. We will report current status of porting our simulation codes onto the ES and our concept of achieving the satellite environment in conjunction with the space weather., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In the Earth's magnetosphere where the spacecraft potential is usually positive, photoelectrons emitted from the spacecraft surface are attracted back to the spacecraft and some of them are detected by electron analyzer onboard. Then photoelectrons are unnecessary contamination. By analyzing such a component detected by LEP/EA-e onboard GEOTAIL spacecraft, we examined velocity/energy distribution functions of photoelectrons, and their relationship to the spacecraft potential. We found that the ratio of the duskward photoelectron flux to the dawnward flux increases when the spacecraft potential is large, and decreases when it is small. Further analysis revealed, by plotting the ratio as a function of the photoelectron energy normalized by the spacecraft potential (E/V(sub sc)), that it is the largest when E/V(sub sec) is about one third. This result implies the existence of azimuthal component of electric field as well as the radial component which is regarded to be dominant in an ordinary case around the spacecraft surface, although it is not clear why such an electric field is generated around GEOTAIL., JAXA Special Publication, 宇宙航空研究開発機構特別資料

JAXA Special Publication, 宇宙航空研究開発機構特別資料

The characterization of the electromagnetic interaction for a solar sail in the solar wind environment and identification of viable charging mitigation strategies are critical solar sail mission design tasks. Spacecraft charging has important implications both for science applications and for lifetime and reliability issues of sail propulsion systems. To that end, surface charging calculations of a candidate 150-meter-class solar sail spacecraft for the 0.5 AU solar polar and 1.0 AU L1 solar wind environments are performed. A model of the spacecraft with candidate materials having appropriate electrical properties is constructed using Object Toolkit. The spacecraft charging analysis is performed using Nascap-2k, the NASA/AFRL sponsored spacecraft charging analysis tool. Nominal and atypical solar wind environments appropriate for the 0.5 AU and 1.0 AU missions are used to establish current collection of solar wind ions and electrons. Finally, a geostationary orbit environment case is included to demonstrate a bounding example of extreme (negative) charging of a solar sail spacecraft. Results from the charging analyses demonstrate that minimal differential potentials (and resulting threat of electrostatic discharge) occur when the spacecraft is constructed entirely of conducting materials, as anticipated from standard guidelines for mitigation of spacecraft charging issues. Examples with dielectric materials exposed to the space environment exhibit differential potentials ranging from a few volts to extreme potentials in the kilovolt range., JAXA Special Publication, 宇宙航空研究開発機構特別資料

JAXA Special Publication, 宇宙航空研究開発機構特別資料

NASDA English Translation

Spacecraft are exposed to a harsh environment where high-energy charged particles, such as electrons and protons, are scattering. When a large amount of the charged particles is irradiated onto insulating materials of the spacecraft, an electrostatic discharge may occur. The electrostatic discharge sometimes gives a serious damage to the systems of the spacecraft. To investigate the process how the charged particles accumulate into the bulk of the insulating materials, we have developed the internal charge measurement system using optical method. We have already confirmed using Pulsed Electro-Acoustic method (PEA method) that the irradiated electrons accumulate in the bulk of an acrylic resin when the electron beam is irradiated to it. However the PEA method is available under only a restricted measurement condition. Therefore, we have attempted to develop a widely usable measurement system using optical method. In this report, to estimate the reliability of the optical measurement system, we compare the distribution of the accumulated charge observed using the optical method with that obtained using PEA method., JAXA Special Publication, 宇宙航空研究開発機構特別資料

国際宇宙ステーションロシアサービスモジュール利用微小粒子捕獲実験および材料曝露実験装置(Service Module/Micro-Particles Capturer and Space Environment Exposure Device: SM/MPAC&SEED)の実験概要、目的などについて述べる。, JAXA Special Publication, 宇宙航空研究開発機構特別資料

Electron emission and concomitant charge accumulation near the surface of insulators is central to understanding spacecraft charging. We present a study of changes in electron emission yields as a result of internal charge build up due to electron dose. Evolution of total, backscattered and secondary yield results over a broad range of incident energies are presented for two representative insulators, Kapton and Al2O3. Reliable yield curves for un-charged insulators are measured and quantifiable changes in yields are observed due to less than 100 fC/sq mm fluence. We find excellent agreement with a phenomenological argument based on insulator charging predicted by the yield curve; this includes a decrease in the rate of change of the yield as incident energies approach the crossover energies and as accumulated internal charge reduces the landing energy to asymptotically approach a steady state surface charge and unity yield. We also find that the exponential decay of yield curves with fluence exhibit an energy dependent decay constant, alpha(E). Finally, we discuss physics based models for this energy dependence. To understand fluence and energy dependence of these charging processes requires knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and transport within the insulator, and how the profile of trapped charge affects the transport and emission of charges from insulators., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Charges accumulate on spacecraft surface trough various processes such as including conduction, irradiation, ionization and polarization. These charges can affect the space system operations via an electric current flowing in the structure or a locally generated electric field. This work is focussed on the analysis of electron behavior in polymeric films such as PolyMethylMetaAcrylate (PMMA) and Teflon, subjected to an electronic irradiation. The charge distribution is detected in-situ by Pulsed Electro-Acoustic (PEA) method. Surface potential and surface current measurements are also performed to get further information on the charge displacement with time., JAXA Special Publication, 宇宙航空研究開発機構特別資料

Recently, satellite anomaly is mainly caused by charging and discharging. It is important to check the charging hazard in the satellite development phase. There are some charging analysis code such as NASCAP, but the latest version of NASCAP is not available in Japan because of the export license limitation in USA. So we started the development of charging analysis tool called MUSCAT (Multiutility Spacecraft Charging Analysis Tool). MUSCAT will be used to evaluate the risk of charging and discharging hazard not only at the development phase but also at satellite operation in LEO, PEO and GEO. Development plan and current status is reported., JAXA Special Publication, 宇宙航空研究開発機構特別資料

In the space development and utilization, it is very important to understand the interactions between spacecraft/structures and space plasma environment as well as the natural phenomena occurring in space plasma. In order to evaluate the spacecraft-plasma interactions quantitatively to contribute to the progress of space utilization and space technology, we aim to develop a proto model of Geospace Environment Simulator (GES) by making the most use of the conventional full Particle-In-Cell (PIC) plasma simulations. For the development of GES, we have been using the Earth simulator which is one of the fastest supercomputer in the world. GES can be regarded as a numerical chamber in which we can virtually perform space experiments and analyze the temporal and spatial evolution of spacecraft-plasma interactions. GES will be able to provide fundamental data regarding various engineering aspects such as the electrostatic charging and electromagnetic interference of spacecraft immersed in space plasmas, which will be useful and important information in determining designs and detailed specifications of spacecraft and space systems., JAXA Special Publication, 宇宙航空研究開発機構特別資料

The scintillating fiber camera is a type of three-dimensional track detector. Using this camera, we can observe the scintillation track produced along the path of a charged particle, and from its scintillation yield can determine the linear energy transfer (LET) distribution of the charged particle. Such observations are also possible for recoil (charged) particles produced by fast neutrons. From these data, we can estimate the LET distribution of individual charged particles or that of recoil particles produced by neutrons; and finally, we can estimate the dose equivalent due to charged particles and/or fast neutrons. For use as a dosimeter for fast neutrons produced by the interaction between cosmic-ray particles and wall materials of a manned spaceship in space, a 52 mm cubic scintillating fiber camera with a 75 mm diameter gated-image intensifier with a maximum counting rate of 30 Hz was constructed. The dosimeter consists of a stack of scintillation fibers with a sensitive volume of 52 mm x 52 mm x 52 mm and a 75 mm diameter image intensifier for readout from the scintillation fibers. The scintillation yields were measured for high-energy heavy ions such as carbon and argon ions. An energy resolution of 12 percent full-width half-maximum (FWHM) was obtained for penetrated argon ions of 650 MeV/n. These results demonstrate that this type detector is very useful as a dosimeter for high-energy cosmic rays and their secondary neutrons., JAXA Special Publication, 宇宙航空研究開発機構特別資料