記述言語：英語   掲載種別：研究論文（学術雑誌）

1U CubeSats often use the 430-MHz band for communication due to their size and power limitations, and half-wavelength dipole antennas are employed. A 430-MHz-band dipole antenna requires a deployable structure for a 1U CubeSat. However, a 1U CubeSat has a small volume margin for redundant systems, so the antenna deployment system can be a single point of failure. In this paper, the 1U CubeSat structure itself was used as an antenna. As a sub-mission of the BIRDS-4 project, three 1U CubeSats (GuaraniSat-1, Maya-2, and Tsuru) demonstrated this antenna structure. The results of the ground tests showed a maximum gain of −5.7 dBi with the flight model. These satellites were deployed from the International Space Station on 14 March 2021. Radio signals were alternately transmitted from the dipole antenna and the structure antenna onboard Tsuru for on-orbit demonstration on 15 December 2021, and the received signal strength on the ground was compared using RTL-SDR, SDR# and several codes. The ground station was able to receive both dipole and structure CW signals. The received power strength indicates that a gain of −8.1 dBi is being demonstrated with the structure antenna.

DOI： 10.3390/electronics11071163

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Electrostatic dust transportation is one of the fundamental sources for dust activity on airless planetary bodies. Even though a series of laboratory experiments have been performed to improve our understanding of the physics behind the electrostatic dust mobilization, there are several factors to investigate such as the launch angles, the lofted particle sizes, the traveling distance of the lofted grains, the initial acceleration to the launching velocities and so on. In this experimental study, an electron beam is used with 450 eV energy to produce secondary electrons to initiate lofting of the silica microspheres in the vacuum chamber, and the particle trajectories are recorded with a microscopic telescope and a high-speed camera. The dust samples are prepared as a mixture of particles with sizes from several micrometers to approximately 90.0 μm in radius. In addition, a polyimide tape with the adhesive surface is placed around the dust sample to collect the lofted particles up to approximately 10.0 cm distance. The collected silica microspheres are studied under the microscope to measure the size variation over the distance from the dust source. The experiment results show that spherical particles and residues effortlessly reach up to 10 cm distance, whereas the fluffy dust aggregates are observed particularly near the dust sample. In addition, the analysis of trajectories shows that the dust grains accelerate rapidly to their launching velocities below 12.0 ms due to the repulsion between the neighboring dust particles. Finally, the peak of the dust launching angle distribution is determined to be around 43.5–45° from the surface normal.

DOI： 10.1016/j.asr.2021.03.037

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

Pulsed electrothermal thrusters use kiloampere discharge currents for polytetrafluoroethylene (PTFE) ablation and sublimation. However, higher arc currents cause higher electromagnetic interference (EMI). A 10 J surface arc thruster (SAT), which adopts current regulating diodes (CRD), was developed that enables significant reduction in EMI. A CRD limits the discharge currents to 5 A in spite of the applied voltage. A low-melting-point sulphur propellant has been used that enables low-discharge currents to efficiently ablate it and accelerate it electrothermally. In this paper, the near-term potential for elemental sulphur propellant in SAT is investigated. The advantages of sulphur with respect to PTFE are presented. First, we measured the pulse width of the main discharge. Then sulphur propellant proved superior to PTFE propellant in discharge duration. The mean pulse widths of PTFE and sulphur are 3.38 and 22.1 ms, respectively. Second, we measured the pressure rise in the vacuum chamber after each discharge. The mean pressure rises of PTFE, sulphur powder and sulphur solid are 0.43, 0.94 and 1.9 mPa, respectively. Sulphur powder experienced the least intensity of discoloration in comparison with other propellants. The discharge initiator misfired frequently during PTFE ablation, but it ignited successively during sulphur ablation. Experimental results indicate sulphur is a suitable propellant for surface discharge propulsion, and for low arc currents is superior to PTFE.

DOI： 10.1007/s42423-021-00074-5

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

In a researchers considered the influence of flashover discharge current on the solar cell array circuit in spacecraft. In the experiment, solar cell coupons were placed 4 m in the longitudinal direction in a large chamber at the Japan Aerospace Exploration Agency Sagamihara Campus. The surface of the coverglass was positively charged with respect to the solar cell by negatively biasing the solar cell coupon and irradiating with an electron beam and the discharge current. A flashover discharge current waveform with a peak of about 4 A and continuing for about 400 μ s confirmed. In addition, when the surface of the coverglass was neutralized by electrons, photoluminescence was confirmed from magnesium fluoride, and the progress rate of flashover discharge was calculated based on time-resolved imaging using an image intensifier. It was observed that the current waveform estimated from this progress rate was in good agreement with the experiment.

DOI： 10.2514/1.A34798

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

An electrostatic discharge can cause a flashover discharge propagating on a solar array paddle. The flashover electron current flows from a solar cell (cathode) to coverglasses charged positively with respect to the cells. The return current flows from solar array circuits into spacecraft power unit via power cables. This is caused by blocking diodes connected on the positive side of solar array circuit. In the end, the flashover current passes through a bus capacitance inside the spacecraft. The amount charge of flashover current can increase the voltage in the bus capacitance. In this paper, the voltage rising due to flashover current is considered with the combination of flashover current and bus capacitance value.

DOI： 10.2514/6.2020-2011

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

As a charging method in ground experiments, an electron beam is often used to simulate high energy particles. In addition to this, a charging method using ultraviolet has been devised because charging by sunlight also occur in the space environment. Accordingly, ultraviolet were used for the discharge threshold measurement experiment of the solar cell, but the large difference of the threshold voltage was seen in two charging methods. The purpose of this research is to find out the cause of this large difference and to apply ultraviolet to charging and discharge experiment of space solar cell. We assumed that the charging potential of the cover glass edge of the solar cell was different in two charging methods and it caused the difference of the discharge threshold voltage. Therefore, we measured the surface potential focusing on the cover glass edge. In the experiment, a sample simulating the structure of the space solar cell was prepared and irradiated with ultraviolet or electron beam until the potential of the cover glass surface did not change overall. The surface potential of the cover glass edge at this time was measured with a contactless surface electrometer, and the results by two charging methods were compared. As a result, it was found that the surface potential at the cover glass edge was different in two charging methods. On the other hand, it was also found that measurement accuracy was low. We devised measurement method using Pockels effect which can measure potential directly or plan to improve measurement accuracy by improving sample because higher measurement accuracy is required to clarify the difference in charging.

DOI： 10.2514/6.2020-2012

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Interaction with the solar wind and UV/X-ray irradiation can cause the lunar dust to be electrostatically charged and mobilized all around the Moon, and light scattering by this dust cloud can be observed over the lunar terminator. This phenomenon, which has also been called the lunar horizon glow (LHG), still remains unexplained. The LHG observations using conventional lunar probes have limited observation opportunities and do not cover varying space weather conditions in cislunar environment such as strong upstream plasma flow and micrometeoroid flux that could enhance the lunar dust presence in the exosphere. The nanosatellite “HORYU-6” specialized in LHG observations will be put into lunar orbit to detect the light scattering above the lunar terminator. The proposed payload will perform multi-spectral imaging to monitor the lunar horizon several minutes before orbital sunrise or after orbital sunset for light scattering analysis. We show that we can obtain scientific results of lunar and planetary exploration using CubeSat at low cost and in a short period of time, and contribute to the development of lunar and planetary exploration in the future. The spacecraft will be developed jointly with universities in Singapore, the United States and Italy under the supervision of Kyushu Institute of Technology, with the aim of launching the SLS-2 rocket in the second half of 2022. Together with its own scientific objectives, the HORYU-6 mission will demonstrate the low thrust trajectory optimization by utilizing electric propulsion system together with other novel embedded technology demonstrations such as atomic clock, deep space navigation and communication with CubeSats.

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Pulsed electrothermal thrusters use kiloampere discharge currents for polytetrafluoroethylene (PTFE) ablation and sublimation. However, higher arc currents cause higher electromagnetic interference (EMI). A 10 J surface arc thruster (SAT), which adopts current regulating diodes (CRD), was developed that enables significant reduction in EMI. A CRD limits the discharge currents to 5 A in spite of the applied voltage. A low-melting-point sulphur propellant has been used that enables low discharge currents to efficiently ablate it and accelerate it electrothermally. In this paper, the near-term potential for elemental sulphur propellant in SAT is investigated. The advantages of sulphur with respect to PTFE are presented. First, we measured the pulse width of the main discharge. Then sulphur propellant proved superior to PTFE propellant in discharge duration. The mean pulse widths of PTFE and sulphur are 3.38 ms and 22.1 ms, respectively. Secondly, we measured the pressure rise in the vacuum chamber after each discharge. The mean pressure rises of PTFE, sulphur powder and sulphur solid are 0.43 mPa, 0.94 mPa and 1.9 mPa, respectively. Sulphur powder experienced the least intensity of discoloration in comparison with other propellants. The discharge initiator misfired frequently during PTFE ablation, but it ignited successively during sulphur ablation. Experimental results indicate sulphur is a suitable propellant for surface discharge propulsion, and for low arc currents is superior to PTFE.

Scopus

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

HORYU-IV is a 30 cm cubic satellite with an approximate mass of 11 kg. The satellite was successfully launched by a JAXA H-IIA rocket to an orbit of 575 km altitude with a 31° inclination on February 17, 2016. HORYU-IV's main mission is to capture an electrostatic discharge (ESD) current waveform by an onboard oscilloscope and capture its image by a camera triggered by the oscilloscope. HORYU-IV captured various ESD current waveforms and images in space. Ground-based experiments were carried out to compare the waveforms between the flight results and the ground results. The results of ground-based experiments, compared with the flight results, had lower peak currents and longer durations. This result does not match past ground-based experiments showing that ESD current has lower peaks and longer durations when ambient pressure is lower. Also, the relationship between ESD occurrence location and ESD current waveforms was found through ground-based experiment.

DOI： 10.2514/1.A34497

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019 IAA AOBA VELOX-IV is a 2U-sized CubeSat that has been developed by the Kyushu Institute of Technology and Nanyang Technological University for the technological demonstration of a future lunar mission. Decades ago, Surveyor and Apollo programs reported light scattering observations on the horizon of the Moon; however, only a limited number of investigations were performed after the Apollo program to observe the lunar horizon glow (LHG). It is still unknown what conditions produce the light glow on the horizon of the Moon. The lunar mission of the AOBA VELOX project is planning to send CubeSats to the Moon and to capture images of the LHG on the lunar orbit while determining the conditions that can support light scattering above the lunar horizon. Before the satellites go into the lunar orbit, the necessary technologies must first be confirmed in Earth orbit. AOBA VELOX-IV was launched to low earth orbit via a JAXA Epsilon rocket in 18th January 2019. This paper explains the LHG mission first, and presents an overview of AOBA VELOX-IV, its payloads, technical issues, and the flight model.

DOI： 10.1016/j.actaastro.2019.05.046

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 1973-2012 IEEE. This marks the seventh issue of the IEEE Transactions on Plasma Science dedicated to Spacecraft Charging Technology. The theme of this issue is based on the papers presented at the 15th Spacecraft Charging Technology Conference, Kobe, Japan, in 2018. The history of spacecraft charging goes back to the first Spacecraft Charging Technology Conference, sponsored by AFRL and NASA, that was held at the U.S. Air Force Academy, Colorado Springs, CO, USA, in 1978. The 15th Spacecraft Charging Technology Conference was hosted by the Japan Aerospace Exploration Agency (JAXA) and the Graduate School of System Informatics, Kobe University. It continues a tradition of international conferences on a ~2-year cycle. This conference, as well as each previous one in the series, was a great success. The topical discussions have greatly helped in making progress in the fields of spacecraft charging, spacecraft-plasma interactions, and related areas. At the end of the 15th Conference, the assembly agreed to request publication of the proceedings of the conference in the IEEE Transactions on Plasma Science and to encourage the submission of the papers presented at the conference to the Journal.

DOI： 10.1109/TPS.2019.2925231

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2019 COSPAR The charged dust particles can be mobilized electrostatically by the repulsion between the adjacent grains and the surface electric field due to the incoming electron current and the charge accumulation within the micro-cavities. In this study, the experimental results of the initial vertical launching velocities and the maximum dust heights are compared with the estimated values for the lofted spherical dust grains by the patch surface charging equations. Silica particles with the sizes between <6 and 45 µm in radius are loaded on a graphite plate, and they are exposed to the electron beam with 450 eV energy under 4 × 10 −3 Pa vacuum chamber pressure. During the first set of the experiments, the dust samples are tested without an initial compression process and an additional horizontal electric field. Second, the dust samples are compressed by two different weights in order to increase the packing density under approximately 780.7 Pa and 3780 Pa. Finally, the dust grains are placed between the two parallel aluminum plates to apply approximately 2000 V/m and 4800 V/m horizontal electric field. A high-speed camera is used to record the transportation of the dust grains together with a microscopic telescope, and the results point out that the patch surface dust-charging model estimations are in agreement with the first experiments. On the other hand, the dust particles from the compressed samples are lofted with higher velocities than the estimations, and the number of the dust lofting observations decreases significantly, which demonstrates the importance of the micro-cavities and the increased charging requirement to overcome the contact forces. When the horizontal electric field is present, the initial vertical launching velocities are measured to be lower than the other experiments, which can be attributed to the decreased charging requirement for the dust lofting as a result of inter-particle collisions and rolling motion. According to the experimental results, the electrostatic dust transportation can be controlled not only by the ambient plasma and the solar irradiation on the airless planetary bodies, but also by the surface properties such as the contact surfaces between the dust grains, the number of the micro-cavities related to the packing density, and the presence of the horizontal electric field contributing to the external forces by other particle motions.

DOI： 10.1016/j.asr.2019.01.045

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 1973-2012 IEEE. Coverglass has been widely used to cover the solar cells of solar arrays for space power generation. Coverglass with high antireflection is widely used to protect the solar arrays from performance deterioration due to irradiation of space ultraviolet, protons, electrons, atomic oxygen (AO), and so on. Along with these, thermal cycles and/or shock may accelerate the decay synergistically affecting the threshold voltage of electrostatic discharge (ESD) on the coverglass. In order to reveal the effect of aging due to AO interaction on the ESD threshold, several coverglass samples have been exposed to low earth orbit grade AO generated by the CO 2 laser on the ground. Later, both pristine and AO-exposed coverglasses have been irradiated by energetic electrons to generate artificial arcing (ESD) under high vacuum system. Statistical analysis and Weibull distribution confirm that the threshold voltage of ESD is lower on the aged coverglass than virgin.

DOI： 10.1109/TPS.2018.2885926

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>キューブサットなどの超小型衛星はその大きさから推進機を搭載することは難しいが，搭載できればミッションの幅が大きく広がる．また，宇宙ゴミにならないように25年以内にデオービットすることもルール化された．このような背景から固体推進剤を用いた真空アーク推進機（VAT-pi2）の開発を行ってきた．陰極である導電性の固体推進剤，陽極，コンデンサおよび電源からなる真空アーク推進機はその簡単な構造から小型化できロバストである．また低地球軌道に存在するプラズマと干渉することで点火装置なしで自発放電をすることが可能である．今回VAT-pi2の軌道上での動作試験を超小型衛星「鳳龍四号」で行った．300V発電太陽電池を電源として動作させている．また放電電流を計測できるオシロスコープを搭載しており，同時に放電の様子を撮影できるカメラも搭載されている．軌道上での実験の結果，VAT-pi2の放電を確認することができた．放電波形および放電画像の取得は引き続き行っていく．</p>

DOI： 10.14822/kjsass.67.5_158

CiNii Article

CiNii Research

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記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>To protect a satellite from accidents due to spacecraft charging, Kyushu Institute of Technology (Kyutech) is developing a device called ELFs-Charm, which stands for ELectron-emitting Film for Spacecraft CHARging Mitigation. Electron emission from ELFs-Charm was already confirmed in Polar Earth Orbit in 2012 via flight experiment onboard HORYU-II. As a next step, we are considering the practical operation for spacecraft charging mitigation. The present emission level is not enough to increase the satellite potential. We focus our efforts on improving two properties, charging property and the emission threshold. The charging property is measured by how well the differential voltage between the ELFs-charm insulator surface and the satellite chassis increases. The emission threshold is measured by the differential voltage when the electron emission starts. This paper reports the laboratory experimental results to measure the two properties of various samples. The sample made of fluorin resin coating had a good combination of the charging property and the emission threshold that makes it possible to emit electron under realistic ambient electron current density in orbit.</p>

DOI： 10.2322/tastj.17.1

CiNii Article

CiNii Research

その他リンク： https://ci.nii.ac.jp/naid/130007542851

記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2018 COSPAR It has been suggested that lunar dust grains can be transported by the electrostatic forces above the lunar terminator and produce the lunar horizon glow (LHG) by forward-scattering of sunlight. In addition, the recent experiments have shown that dust grains can be lofted in the vacuum chamber due to charging within micro-cavities by absorbing the emitted secondary electrons under the electron beam current (Wang et al., 2016; Schwan et al., 2017). In this study, the required charge within micro-cavities in order to separate dust particles from the lunar surface are estimated by using the surface electric field and the forces of gravity and contact. In addition, the maximum heights for dust grains are calculated by initial vertical launching velocity from the surface and the acceleration within the electron sheath against the gravity. The following calculations are performed for the particles with 0.1, 1 and 5 μm radius, and the variation of ambient plasma conditions are studied throughout solar wind data of CME passages on 8–13 February 1997, 1–3 May 1998 and 8–12 March 2012. Current balance method is used to estimate the surface potential, electric field and Debye length to investigate how the lunar dust particles are mobilized under the various conditions. First, strong negative surface potentials can be observed during the post-shock plasma passages, and it produces stronger electrostatic forces acting on the lofted dust particles. Second, submicron-sized dust particles are launched from the surface less frequently than the larger size grains due to the charging time. The height predictions of the dust grains with 5 μm radius are similar to the LHG observations of Surveyor mission, and the results suggest that the heights of micron-sized dust grains are controlled by the initial vertical launching velocity more than the surface electric field, unlike the smaller sized particles. Finally, strong electrostatic forces are not sufficient solely to loft the dust particles to higher altitudes since a charged dust requires accelerating for a proper time and distance in the electron sheath.

DOI： 10.1016/j.asr.2018.05.027

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担当区分：筆頭著者   記述言語：英語   掲載種別：記事・総説・解説・論説等（その他）

© 2018 Wiley Periodicals, Inc. Spacecraft need high-voltage power generation for high power. However, the high voltage can cause severe discharge problem on spacecraft. This paper describes the mechanism of spacecraft charging and discharging. Mitigation methods are also mentioned.

DOI： 10.1002/eej.23077

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© 2018 by the International Astronautical Federation (IAF). All rights reserved. HORYU-IV is a 30cm cubic satellite with an approximate mass of 11kg. The satellite was successfully launched by a H-IIA rocket to an orbit of 575km altitude with 31ºinclination on February 17, 2016. Since then, HORYU-IV has been conducting various flight experiments related to spacecraft plasma interaction. HORYU-IV implements HORYU-II, the previous satellite operated from 2012 to 2017, high voltage photovoltaic power generation technology and uses it to perform research on discharge phenomena. HORYU-IV's main mission is to acquire an arc current waveform by an onboard oscilloscope and capture its image by a camera triggered by the oscilloscope. In addition, HORYU-IV carries out scientific experiments on arc mitigation high voltage solar array, plasma measurement using a double Langmuir probe, vacuum arc thruster, photoelectron current measurement and polymer material degradation. HORYU-IV captured various discharge waveforms and images in space that can be categorized into several types. Ground experiments were carried out to compare the waveforms between the flight results and the ground results. The Double Langmuir probe was operated in space and its result was compared with the computer simulation results. Photoelectron emission yield was measured for several material for the first time in orbit. The overall results obtained in the past two and a half years from the spacecraft plasma interaction experiments will be presented.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>Assessment of the worst plasma environment for spacecraft surface charging in the geosynchronous Earth orbits (GEO) is important for spacecraft designs and operations, because it could cause spacecraft anomalies due to surface charging with resultant discharging arcs. The differential charging potential of spacecraft surfaces is considered to generate the harmful discharging arcs. There was no common standard of the worst GEO plasma environment for analysis of differential surface charging to prevent and mitigate the anomalies. Therefore in order to determine a new International Organization for Standardization (ISO) document for the purpose, a round-robin simulation was performed using the NASCAP-2k and MUSCAT. We perform surface charging simulations by Spacecraft Plasma Interaction Software (SPIS) as same as the round-robin simulation and evaluate the worst GEO plasma environmental models showing the detailed results. This study will contribute to a revision of the ISO document and also apply spacecraft charging risk estimations as space weather forecast.</p>

DOI： 10.2322/tastj.16.556

CiNii Article

CiNii Research

その他リンク： https://ci.nii.ac.jp/naid/130007481369

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 1973-2012 IEEE. HORYU-IV is a nanosatellite developed to conduct experiments on electrostatic discharges (ESDs) in real space environments. Testing in space is very important to confirm ground testing results, because it is difficult to fully simulate the comprehensive environment of space on the ground, to evaluate the effects of such things as satellite movements, plasma conditions, sunlight, and chamber walls. Conventionally, occurrence counters have been used for such in-orbit experiments to find threshold voltages. However, they cannot provide detailed information for example magnitudes and the location of each ESD. We became highly aware of this limitation through our HORYU-II experience (which only had an occurrence counter) and we designed HORYU-IV in order to overcome this limited data issue. The main challenge with HORYU-IV is the carrying of standard laboratory equipment, such as oscilloscopes and event-capture cameras, which have never been successfully used in space before. Such measurement instruments, with solar array sample coupons and a high-voltage source, were launched on this satellite and have successfully provided current waveforms and images of spark of light from ESDs from space. This experimental method has been commonly used in ground-based spacecraft charging experiments, but has never been used in orbit. Hence, our satellite became the world's first operational platform equipped with an oscilloscope and event-capture camera for high-voltage experiments in space. Three different shapes of current waveforms were observed, and the arcing locations from images captured in orbit were identified. We have proved the concept of the remote laboratory in orbit. The observed discharge conditions will be replicated on the ground and the feedback will improve the ground testing methodology.

DOI： 10.1109/TPS.2017.2688725

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 1973-2012 IEEE. In 2012, the high-voltage technology demonstration satellite HORYU-II which is a nanosatellite (30 cm 3 , 7 kg) was launched into polar earth orbit. It is known that high-voltage power generation above 200 V in low earth orbit induces discharging. The main mission of HORYU-II was to achieve high-voltage (more than 300 V) generation without discharge in space orbit, and it was successful. After the initial operation, HORYU-II malfunctioned due to the single event latch-up, and could not continue mission operation. On December 22, 2014, HORYU-II was revived and restarted mission operations until HORYU-II malfunctioned again (March 18, 2015). We performed three types of missions that were high-voltage generation modes, nominal TJ array discharge experiment modes, and film TJ array discharge experiment modes. Even if the satellite spent two years in orbit, HORYU-II could still generate around 350 V and the discharge rate on a nominal TJ array showed little change.

DOI： 10.1109/TPS.2017.2705726

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© Springer International Publishing AG 2017. Coverglasses are used to protect solar cells from damages caused by space environment irradiation. Damage to coverglasses from space irradiation, the electrostatic discharge and even the breakdown related to surface charging of coverglass are among the main reasons for malfunctioning of solar cells in space missions. This paper using dielectric temperature spectroscopy investigated the typical solar cell coverglasses that were exposed in ground-based simulators to space environments, such as thermal cycling, proton-beam irradiation, electronbeam irradiation, ultraviolet irradiation and their synergistic irradiation. The dielectric properties of coverglasses were measured using a broadband dielectric spectrometer with the frequency range from 0.1 Hz to 1 MHz at temperatures ranging from -140 to 120 ˚ C. It was found that the dielectric constants of five kinds of irradiated coverglasses increase to different degrees at different temperatures compared with the virgin coverglass. And irradiation has little effect on the dielectric loss, DC conductivity and DC conductivity activation energy of coverglasses.

DOI： 10.1007/978-3-319-19309-0_12

Scopus

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2017 Praise Worthy Prize S.r.l.-All rights reserved. This study presents the development and implementation of a photoelectron current measurement system on-board HORYU-IV satellite to take on-orbit measurements from conductive and insulator surfaces. The measurement system aims at providing critical information on photoelectron yield of materials widely used onboard spacecraft. HORYU-IV is the fourth satellites of the HORYU series developed at Kyushu Institute of Technology and it was piggy-back launched on-board H-IIA F30 rocket at an altitude of 575 km on February 17, 2016 (JST). The measurement system mainly consists of current-voltage amplifier circuits for AU, Kapton ® and black Kapton ® samples with gains of 1x, 3x and 1x amplification, respectively. In this article, the analysis of the on-orbit results is presented. The on-orbit results show that a photoelectron current of 2.9nA and 3.1nA was measured from black Kapton® sample at respective elevations of 70.7° and 71.1°. These results respectively correspond to a current density of 14.0μA/m 2 and 18.0μA/m 2 at 71.1°. This study also presents various ground-based tests results performed to verify and validate the effectiveness of the photoelectron current measurement system developed for space applications.

DOI： 10.15866/irease.v10i3.12394

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A33622

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. The lunar horizon glow (LHG) was first spotted in 1966 and 1968 by onboard cameras on Surveyor spacecraft after the sunset from the western horizon, and Apollo astronauts reported that they had seen the horizon glow. Surveyor missions observed lunar horizon in different distances, angles and time periods (from 0.5 to 2.5 hours after local sunset). Even though the horizon glow was highly visible in the Apollo 15 sunset, Apollo 16 showed no traces of the horizon glow. Therefore, it is highly varying phenomenon. Aoba VELOX-IV is a technology demonstration 2U CubeSat platform for LHG imaging in a future lunar mission. Nanyang Technological University (NTU Singapore) is collaborating with Kyushu Institute of Technology (Kyutech), to build Aoba VELOX-IV, which will be launched by Japan's national agency, the Japan Aerospace Exploration Agency (JAXA) in 2018. In this paper, the requirements of the LHG imaging system will be presented as well as hardware design, operation modes, sensitivity, power consumption and software. The camera options are limited due to power, volume and mass constraints. In addition, communication constraints for a lunar mission limit these options further. The horizon must be observed from the night side due to the physical mechanism of the LHG, and the visible light range must be selected as focus in order to provide evidence for Apollo observations. Also, this operation may require horizon detection to have a right perspective to capture the forward scattered light of the LHG, which is directly related to attitude determination and control subsystem. AOCS will rotate the camera to observe the horizon during the local sunset or sunrise.

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

<p>This paper will describe the development of the Vacuum Arc thruster (VAT) for micro and nano satellites with the main purposes of: attitude control, maintaining orbit-satellite deorbiting. Firstly, this VAT thruster is integrated on-board student microsatellite Horyu-IV, which was developed at the Kyushu Institute of Technology (KIT), Japan. The satellite will be launched in the fiscal year 2015 by H2A rocket. This paper describes the principles of VAT as a direct drive from High Voltage Solar Array (HVSA). Expected performance of this vacuum arc thruster with passive ignition (space plasma condition) was measured. We propose a method for improving the thruster efficiency. Results show that the impulse bit was of the μNs order, and the thrust–56 nN– and efficiency– 2.5%–were calculated. Moreover, it was found that the impulse bit changes with the applied voltage. A new CFRP material was developed and used as a cathode for the purpose of improving efficiency. Discharge characteristics of current and the arc rate are presented. Measurements of impulse bit were also done for the VAT in configuration with two different propellants (commercial and new CFRP) and with a permanent magnet of 300 mT.</p>

DOI： 10.2322/tastj.14.Pb_91

CiNii Article

CiNii Research

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）

衛星に搭載される太陽電池パネルで発生する放電に関する地上試験の方法について紹介する.実験は大きく2つに分かれる.1つ目は放電がどの程度の乖離電圧で発生するのかを調べる実験であり,2つ目は初期放電によって誘起される持続放電に関する実験である.この章では上記2種類の実験の手法,回路について概説する.

CiNii Article

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記述言語：英語   掲載種別：研究論文（学術雑誌）

© 2015 IEEE. HORYU-4 is a 12-kg satellite currently under development at the Kyushu Institute of Technology. Its main mission is to perform an in-orbit high-voltage technology demonstration to evaluate state-of-the-art arc mitigation technologies in real space environments. The main objective is to perform a similar experiment as those on the ground for the validation of existing test methods. The obtained data (arc current waveforms, in particular) will be utilized to evaluate testing methods, as the waveforms on the ground must have some resemblance to those in space. To perform such an experiment in orbit, we have outfitted this satellite with typical laboratory equipment, such as oscilloscopes and video cameras and a high-voltage source (i.e., Sphelar solar cells, also used on HORYU-2). In fact, this satellite is a miniaturized in-orbit laboratory for high-voltage experiments. An oscilloscope and video camera have been designed and developed using commercial off-the-shelf components that provide sufficient measurement capabilities with a limited size and power range.

DOI： 10.1109/TPS.2015.2453330

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TDEI.2015.7076823

Scopus

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A33007

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A32829

Scopus

記述言語：日本語   掲載種別：記事・総説・解説・論説等（その他）

2014年度の電気・情報関係学会九州支部連合大会が鹿児島大学で開催され，同じ鹿児島県にある内之浦宇宙空間観測所を見学会で訪れた。ここでは1962年以来多くのロケッ

DOI： 10.1541/ieejjournal.135.243

CiNii Article

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

記述言語：英語   掲載種別：研究論文（学術雑誌）

CiNii Article

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1016/j.vacuum.2014.01.030

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A32736

Scopus

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

Satellite is greatly affected by the space environment and one of these effects is satellite charging. A passive electron emitter has been developed for satellite charging mitigation. In 2012, emission of electron from this emitter has been confirmed by a high voltage technology demonstration satellite, 'Horyu-II', made by Kyushu Institute of Technology. However, due to insufficient data and longer time resolution, repeated emission has yet to be confirmed. In order to have more data in the shorter time resolution, this emitter has been mounted on a small satellite, named 'Hodoyoshi-3' and 'Hodoyoshi-4' made by Tokyo University, passing through the aurora zone, similar to 'Horyu-II'. Functioning of this emitter and related circuitry for measuring emission current and surface potential on the flight model (FM) of 'Hodoyoshi-4', ground operation has been confirmed. Sampling rate of emission current measurement of 'Horyu-2' was 4 minutes, whereas for 'Hodoyoshi-4' it is one second only. Therefore, we expect much better and reliable information.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A32559

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2013.2288699

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2013.2280287

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2013.2288575

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2013.2276439

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.A32370

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2013.2290251

Scopus

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記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

© Springer-Verlag Berlin Heidelberg 2013. Since material surfaces on the outside of spacecraft are exposed directly to the space environment, material having high tolerance to atomic oxygen, ultraviolet rays and radiation are preferred for long time spacecraft operation. In order to examine the influence of atomic oxygen (AO) on space grade materials, an atomic oxygen simulation chamber was developed. A system was developed that generates AO using a laser detonation method. A CO 2 gas laser (5 J) irradiates the oxygen gas in a vacuum chamber (2 MPa) to dissociate the molecular oxygen into atomic. The velocity of AO can be controlled based on the timing between the laser and the gas pulse valve that injects oxygen gas into the chamber. The AO velocity generated by this system is measured using a QMASS (Quadruple Mass Spectrometer) and found to be 8 km/s. It was necessary to measure the AO flux distribution in the chamber at the location where the material samples are exposed to AO. The AO flux distribution was evaluated by measuring the mass gain on a QCM (QuartzCrystal Micro-balance) coated with a silver film upon exposure to the AO.

DOI： 10.1007/978-3-642-30229-9_56

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2012.2216053

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2012.2187074

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2011.2176754

Scopus

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

A testing method for evaluating the robustness of insulation films against sustained arcs on solar array panels was developed. Metal electrodes were used to simulate solar cells. The gap length between electrodes was controlled. In this paper, five samples with various insulator thicknesses were tested with the testing method. The robustness of the insulation films was evaluated. © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.1109/TPS.2011.2173954

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

DOI： 10.2514/1.50735

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）

Electrostatic discharge tests were performed on large solar array panels under the simulated plasma environments of a geostationary orbit and a low Earth orbit to investigate the propagation length and velocity of flashover plasma. To investigate the propagation length, the neutralized current on the strings was also examined. The neutralized charge value due to flashover plasma was found to decrease with distance. Propagation length was limited under both the geostationary orbit environment and the low-Earth-orbit environment. Visual investigation of the velocity of flashover plasma clarified that velocity decreases with time. The initial velocity of flashover plasma measured was several tens of km=s, regardless of orbital environment conditions. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

DOI： 10.2514/1.50907

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Flashover discharge on the solar array is an issue of spacecraft charging, because the discharge potentially causes the catastrophic failure of a satellite. The discharge experiment on solar array has been carried out to investigate the propagation area of flash-over discharge. During the flash-over discharge, neutralization current flows on the solar array strings. The charge of neutralization current was calculated to investigate the relationship between the charge and the distance from the cathode spot The experiment result in the maximum propagation area of flash-over plasma is 3m in simulated geostationary orbit. © 2010 The Institute of Electrical Engineers of Japan.

DOI： 10.1541/ieejfms.130.793

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

An electrostatic discharge test performed on a solar array panel is one of the important tests carried out before spacecraft launch to ensure spacecraft reliability in orbit. In this study, the effects of secondary arcs on the solar array, which can cause catastrophic accidents, are considered. The sustained-arc threshold of multijunction and silicon solar arrays was investigated to establish the design guidelines for ensuring the safety of satellite solar arrays. In this experimental study, the string voltage, string current, gap length, and solar-cell type were selected as test parameters. Gap lengths were 0.5, 0.8, 1.0, and 2.0 mm. For 0.5 and 0.8mmof gap length, a permanent sustained arc occurred under the condition of 1.5 A of string current for 50, 70, 90, and 110 V of string voltage. Furthermore, temporary sustained-arc duration exponentially increased with increasing string current. Temporary sustained-arc duration longer than 1 ms can serve as a practical alarm for the imminent permanent sustained-arc inception. © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

DOI： 10.2514/1.49571

Scopus

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担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）

2005年04月  -  2005年04月

主要論文集（会議）

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

記述言語：英語   掲載種別：研究論文（学術雑誌）

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

担当区分：筆頭著者   記述言語：英語   掲載種別：研究論文（学術雑誌）

開催期間： 2013年12月01日   記述言語：英語  

In this paper, a pulsed scanning method for the total electron emission yield measurement of insulating materials is proposed. A total electron detector with big hollow space and insulating spacer, and a pulsed yield scanning measurement system is recommended. This method can avoid influence from the charged surface of the insulating material. Using the system, the total secondary electron emission yields of several typical polymers, such as, PA, PS, PI, PTFE, HDPE, PC, PMMA, PEEK, PET, UHMW-PE, have been reported, as induced by a 30 microsecond pulse of primary electrons with ∼ 20 nA incident beam current and energies up to 2500 eV. © 2013 IEEE.

開催期間： 2013年08月19日   記述言語：英語  

Vacuum arc thruster is very light and small for installed nano-satellite, and it operates without igniter. The thruster takes use of discharging in triple (insulator, conductor and vacuum) junction. The vacuum arc discharge releases the metal vapor, which can result in producing thrust. This research investigated on basic performance of vacuum arc thruster and EM development. © 2013 by the American Institute of Aeronautics and Astronautics, Inc.

開催期間： 2013年08月19日   記述言語：英語  

The High Voltage Technology Demonstration Satellite named HORYU-II is a nano-satellite (30cm cubic shape, 7kg) successfully developed by students at Kyushu Institute of Technology. The main purpose of this satellite is orbital demonstration of the feasibility the forthcoming space high voltage technologies. The International Space Station (ISS) generates the highest voltage, 160V, among all of the current active space systems. HORYU-II aims at being the world's first satellite to generate a voltage of 300V by using solar array, which is significantly higher voltage than the one generated on board the ISS. However, due to the generation of the high voltage, Electrostatic Discharges (ESDs) are more likely to occur. Therefore, HORYU-II also aims at performing a demonstration of ESD mitigation technology. HORYU-II was launched by a H-2A rocket on May 18, 2012. HORYU-II is functioning normally and data from orbit have recently been recorded and data analysis is under way. Results of the analysis will be presented in detail at the conference. © 2013 by Kyushu Institute of Technology.

開催期間： 2013年01月01日   記述言語：英語  

Repeated low power, or primary arcing, may adversely affect the performance of space solar cells. The cumulative effects of primary arcing on common solar cell performance parameters has been the subject of numerous ground studies in simulated plasma environments. The Primary Arc effects on Solar Cells At LEO (PASCAL) flight experiment is presently active aboard in the International Space Station (ISS) and characterizing such effects in-orbit for numerous state-of-the-art space solar cells with initial results presented herein. © 2013 IEEE.

開催期間： 2013年01月01日   記述言語：英語  

Recently, the trend of spacecraft designers has led to the tendency of making larger and multifunctional satellites. In order to achieve the growing demands, the development of a large satellite bus is indispensable. However, electrical discharge accidents have increasingly come to occur on the solar arrays due to the higher bus voltage of any satellite. An electrical discharge on the solar array not only decreases the generating power but also can even halt operation of the satellite entirely. During electrical discharges, various arcing are possible, among which sustained arc is the most detrimental to the satellite. At present, grouting (adhesive is buried between solar cells to which high voltage is applied) is practiced as a mitigation method of sustained arc. However, this method has several disadvantages. Therefore, the development of a new mitigation method is requested. In this paper, we report the effect of mitigation method for sustained arc on solar array, by inserting capacitor and inductor into sustained arc circuit. It is confirmed that sustained arcs were oscillated by the capacitor (i.e. several hundred nF). Therefore, if the oscillation is sufficiently big, sustained arcs can be mitigated. In addition, this paper discusses a relation between flashover current and secondary arc. From the experimental results, when flashover is short, arc current to vibrate and it is suppressed. When flashover is long, arc current can't cut and it isn't suppressed. But, by increasing the capacitance of the capacitor, it was possible to accommodate long flashover discharge. Copyright ©2013 by the International Astronautical Federation.

開催期間： 2013年01月01日   記述言語：英語  

The World's largest spacecraft bus voltage is the International Space Station (ISS) with a bias voltage of 160V. We have investigated a power bus able to handle higher voltage than the ISS. Electro-static discharges (ESDs) are more likely to occur when a satellite generates power at a high voltage rather than low voltage in low Earth orbit (LEO). However, high voltage generation is essential for building large space systems. Therefore, Kyushu Institute of Technology (Kyutech) is developing a high voltage generation technology that could counteract ESDs. This could be considered as a key technology for next generation spacecraft. Nano-satellites are useful and less risky tools for technology demonstration since they are faster and less expensive to develop than large satellites. Therefore, we focused on nano-satellite development to demonstrate Kyutech's advanced high voltage generation technology. All of the on-orbit high voltage tests have been demonstrated by using a DC/DC converter to adapt the high voltage generated by the solar array. This was a World premiere as no high voltage tests had previously been performed in space using solar arrays. To demonstrate the feasibility of on-orbit high voltage generation, we developed a High Voltage Technology Demonstration Satellite named HORYU-2. The mission consisted of 300V generation without causing arcing, and contribution to the practical development of 1MW class spacecraft. On May 18, 2012, HORYU-2 was launched by the H-2A rocket number 21. HORYU-2 has been operated from Kyutech's ground station, and HORYU-2's orbit was confirmed and the mission successful. For the first time in the World, 350V have been generated on-orbit without arc creation. Using two specially designed solar arrays arcing was mitigated. Regarding the sub-missions, ELF was proven to work well on-orbit, Trek measurements are currently under investigation, the SCAMP camera successfully imaged Earth, and the debris sensor has not yet detected debris impact. During the conference, we will present all mission analysis in further detail. Copyright ©2013 by the International Astronautical Federation.

開催期間： 2012年12月01日   記述言語：英語  

High Voltage Technology Demonstration Satellite HORYU-II is a Nano-Satellite (30cm cubic shape, 7kg) being developed by the students in Kyushu Institute of Technology. One of the objectives of this satellite is orbital demonstration of forthcoming space high-voltage technologies. The satellite with the highest voltage generation in Low Earth Orbit has been ISS, generating 160V. On orbit, especially LEO, high-voltage (over about 200V) generally induces electro-static discharges (ESD). HORYU-II is aimed to demonstrate new designs of solar array that can generate power, free of ESD, by producing 300V via a specially designed solar array itself, not via a conventional DC/DC converter. If successful, HORYU-II will become the first spacecraft in the world that achieved 300V photovoltaic power generation in space. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.

開催期間： 2012年12月01日   記述言語：英語  

A cubic nano-satellite with a length of 30 cm, named HORYU-II, was developed at Kyushu Institute of Technology in Japan. HORYU-II is a demonstration satellite for high voltage technology and its two main advantages are its low cost and short time development. HORYU-II's main mission is to demonstrate the possible generation of 300V on-orbit by using spherical solar cells connected in series. This mission can be considered as the first high voltage technology demonstration in the world. To control arcing under negative 300V in space plasma, ETFE (ethylene tetra flouro ethylene) cover and semi-conductive coated solar array efficiency will be demonstrated. Along with this, charging mitigation of spacecraft by using electron emitting film, operation of commercial-off-the-shelf (COT) surface potentiometer will also be demonstrated. HORYU-II was launched by a H-IIA rocket on May 18, 2012. We have been acquiring on-orbit data and monitoring the satellite conditions. HORYU-II succeeded in generating the highest 300V photovoltaic voltage in space for the first time in the world. However, many problems were found during data collection. In this paper, the result of HORYU-II's missions is described.

開催期間： 2012年12月01日   記述言語：英語  

Space debris is a space object which is not useful and can cause accident in space. Space debris is moving with high speed with average velocity of 10km/s, which can cause damages to the spacecraft and the astronaut operating outside satellite. The method of removing the debris is demanded for our safety operation in space. In this paper, a debris removal method was proposed for small diameter less than 1mm. This method utilizes the interaction between the electrode biased in positive and space ambient plasma in LEO. The verification experiment of charging and moving debris was performed in a vacuum chamber simulating LEO plasma environment. A space potential and floating potential were also measured. A pseudo debris was charged and attracted to biased net electrode in plasma environment. Copyright © 2012 by the American Institute of Aeronautics and Astronautics, Inc.

開催期間： 2010年12月20日   記述言語：英語  

A shunt resistance on the solar cell edge which is made by an electrostatic discharge (discharge) causes the degradation of multi-junction solar cell (MJ cell). To prevent the degradation, a trench was formed along the edge of multi-junction solar cell (AD MJ cell). The degradation characterization tests were performed on state-of art MJ cell and AD MJ cell to investigate the effect of trench in plasma environment. © 2010 IEEE.

開催期間： 2010年12月20日   記述言語：英語  

Space Systems/Loral (SS/L) successfully completed electrostatic discharge (ESD) tests of Multi-junction (MJ) GaAs/Ge solar array design in geosynchronous space environment. This ESD test was based on ISO-11221, Space systems - Space solar panels -Spacecraft Charging Induced Electrostatic Discharge Test Methods. In addition to the ISO reference for the test schematic, SS/L implemented modified test circuitry to better simulate the on-orbit operational conditions of our solar array design. The ESD test circuit also included simulated solar array panel coverglass flashover. The ESD test program utilized a 25-cell coupon that had been subjected to 2,000 thermal cycles caused by earth eclipses in GEO orbit and > 12,000 thermal cycles caused by the shadow of the spacecraft antennas. Other ESD test coupons are 4-cell coupons that, after baseline ESD experiments, can later be subjected to combined space environmental exposures tests. To demonstrate design robustness, we performed ESD tests to voltages and currents that are higher than that of on-orbit solar array operational voltages and currents. This paper discusses the coverglass flashover simulation, ESD test setup, the importance of the electrical test design in simulating the on-orbit operational conditions, and the test results. © 2010 IEEE.

開催期間： 2010年12月13日   記述言語：英語  

Prevention of spacecraft charging and discharging has become increasingly important as GEO satellites employ higher bus voltage. There are numerous mitigation techniques against spacecraft charging including electron emission from the spacecraft chassis. A new electron emission device operating in completely passive manner has been developed which utilizes the field enhancement at the triple junction formed at the interface of metal and insulator exposed to space. It is named as Electron Emitting Film for Spacecraft Charging Mitigation (ELF's CHARM). Micro-etching was applied to polyimide-copper (PI-Cu) laminated film to manufacture a laboratory prototype. ELF utilizes pre-breakdown electron emission current leading to arcing at the triple junction keeping the current at the steady state. The electric field at the triple junction is macroscopically enhanced by charging of the polyimide film and microscopically by dielectric impurity on the copper surface. Theoretical rough estimate gives a current of 100 to 1,000μA. The laboratory experiment confirmed stable current emission from 10 to 100 μA from a sample of several centimeters square for 4 hours. Its robustness against ground handling and in-orbit contamination has already been demonstrated. To prepare for flight demonstration as early as 2011, the research and development have been accelerated. To ensure the endurance, recently 100 accumulated hours emission test and effect of high energy electron and proton and thermal cycling have been investigated on recently developed ELF. Post-emission of this electron emitting film confirms the durability under those harsh environments. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

開催期間： 2010年12月13日   記述言語：英語  

ESD ground testing on satellite solar array paddle is performed to mitigate catastrophic accidents. An international standard is desired to perform international satellite business smoothly. A standard has been developed in laboratory of spacecraft environment interactions. The draft has been applied. In this paper, preliminary experiments were performed to improve the testing method. Copyright © 2010 by the American Institute of Aeronautics and Astronautics, Inc.

開催期間： 2010年12月13日   記述言語：英語  

Electrostatic discharge may cause an anomaly on a solar array. Nowadays, an electrostatic discharge test on solar array panels is required to ensure the durability of the solar arrays against electrostatic discharge. To perform a realistic electrostatic discharge test, the electrostatic discharge current must be simulated accurately. As the current of the electrostatic discharge is mainly supplied by flashover discharge, it is necessary to investigate the characteristics of flashover discharge such as the propagation area and velocity of flashover plasma. We performed the electrostatic discharge test on large solar array panels in a simulated plasma environment of geostationary orbit and low earth orbit. In this paper, we discuss the propagation area and velocity of flashover plasma.

開催期間： 2010年12月01日   記述言語：英語  

As geo-stationary (GEO) satellite bus voltage increased due to the increased size of the satellites, the number of solar array failures due to spacecraft charging increased. We are developing an electron emitter that emits electrons from the conductor by using the enhanced electric field at the triple junction which occurs simultaneously while spacecraft charging. The emitter is composed of an insulator on top of cupper plate. Parts of the cupper plate are exposed through the insulator ensuring the triple junctions that are the source of electron emission. This emitter operates in a completely passive fashion. In this paper, the authors conducted the verification test of this emitter after making a measurement circuitry. This time, the surfaces of the emitters were coated with a special material to enhance the electron emission current. In the ground test, the emitters were biased to a highly negative potential with respect to a vacuum chamber ground and exposed to an electron beam. This leaded the simulation of satellite charging. Then the operation of the measurement system had been checked to confirm the emission as well as surface potential. These results permit this electron emitter to be used in actual space environment.

開催期間： 2010年12月01日   記述言語：英語  

Spacecraft surface charging can leads to arcing and a loss of electricity generation capability of solar panel or even loss of a satellite. The arcing problem may be further aggravated by the atomic oxygen (AO) exposure in Low Earth orbit, which modify the surface of materials like polyimide, Teflon, anti reflective coating, cover glass etc used on satellite surface affecting materials properties such as resistivity, secondary electron emissivity, photo electron emission which govern the charging behavior. These properties are crucial inputs parameters for spacecraft charging analysis. To study the AO exposure effect on the charging governing properties, an AO exposure facility based on laser detonation of oxygen was built which produce 8-14km atomic oxygen with higher flux than in orbit. After exposing materials to 10years equivalent AO flux at the altitude of 700-800km, surface charging properties like resistivity and secondary electron emission is being measured. Measurement of surface and volume resistivity for AO exposed samples was done for polyimide. The measurement was done using the charge storage decay method at a room temperature, which is considered most appropriate for measuring the resistivity for space application. It was found that the value of surface resistivity increases more than two fold and volume resistivity remains same. Measurement of secondary electron emission characteristics is under progress.

開催期間： 2009年03月17日 - 2009年03月19日   記述言語：日本語   開催地： 名古屋  

開催期間： 2009年03月17日 - 2009年03月19日   記述言語：日本語   開催地： 名古屋  

開催期間： 2009年01月19日 - 2009年01月20日   記述言語：日本語   開催地： 相模原  

開催期間： 2009年01月19日 - 2009年01月20日   記述言語：日本語   開催地： 相模原  

開催期間： 2008年12月18日 - 2008年12月19日   記述言語：日本語   開催地： つくば  

開催期間： 2008年11月14日   記述言語：日本語   開催地： 福岡  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年11月05日 - 2008年11月07日   記述言語：日本語   開催地： 兵庫  

開催期間： 2008年10月27日 - 2008年10月31日   記述言語：日本語   開催地： 松江  

開催期間： 2008年10月27日 - 2008年10月31日   記述言語：日本語   開催地： 松江  

開催期間： 2008年09月17日 - 2008年09月18日   記述言語：日本語   開催地： 東京  

開催期間： 2008年04月   記述言語：日本語   開催地： 福岡  

開催期間： 2008年03月   記述言語：日本語   開催地： 福岡  

開催期間： 2008年03月   記述言語：日本語   開催地： 福岡  

開催期間： 2008年03月   記述言語：日本語   開催地： 福岡  

開催期間： 2008年03月   記述言語：日本語   開催地： 福岡  

開催期間： 2008年03月   記述言語：日本語   開催地： 福岡  

開催期間： 2007年11月   記述言語：日本語   開催地： 熊本  

開催期間： 2007年11月   記述言語：日本語   開催地： 熊本  

開催期間： 2007年11月   記述言語：日本語  

開催期間： 2007年10月   記述言語：日本語   開催地： 札幌  

開催期間： 2007年10月   記述言語：日本語   開催地： 札幌  

開催期間： 2007年10月   記述言語：日本語   開催地： 札幌  

開催期間： 2007年10月   記述言語：日本語   開催地： 札幌  

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