Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.3390/electronics11071163

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

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

Scopus

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1007/s42423-021-00074-5

Scopus

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A34798

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)

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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Language：English   Publishing type：Research paper (international conference proceedings)

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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Language：English   Publishing type：Research paper (international conference proceedings)

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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Language：English   Publishing type：Research paper (international conference proceedings)

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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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A34497

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2019.2925231

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.actaastro.2019.05.046

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.asr.2019.01.045

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2018.2885926

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

<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

Other Link： https://ci.nii.ac.jp/naid/130007542851

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.14822/kjsass.67.5_158

CiNii Article

CiNii Research

Other Link： https://ci.nii.ac.jp/naid/130007642572

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.asr.2018.05.027

Scopus

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Authorship：Lead author   Language：English   Publishing type：Article, review, commentary, editorial, etc. (other)

DOI： 10.1002/eej.23077

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

<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

Other Link： https://ci.nii.ac.jp/naid/130007481369

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2017.2705726

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2017.2688725

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1007/978-3-319-19309-0_12

Scopus

Other Link： https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85019752838&origin=inward

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.15866/irease.v10i3.12394

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A33622

Authorship：Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

<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

Other Link： http://ci.nii.ac.jp/naid/130005172062

Language：English   Publishing type：Research paper (other academic)

CiNii Article

Other Link： http://ci.nii.ac.jp/naid/110010016784

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2015.2453330

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TDEI.2015.7076823

Scopus

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A33007

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A32829

Scopus

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (other)

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

Other Link： http://ci.nii.ac.jp/naid/130005060632

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)

CiNii Article

Language：English   Publishing type：Research paper (scientific journal)

CiNii Article

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1016/j.vacuum.2014.01.030

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A32736

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A32559

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2013.2288699

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2013.2280287

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2013.2288575

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2013.2276439

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.A32370

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2013.2290251

Scopus

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Language：English   Publishing type：Research paper (international conference proceedings)

DOI： 10.1007/978-3-642-30229-9_56

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2012.2216053

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2012.2187074

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2011.2176754

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1109/TPS.2011.2173954

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.50735

Scopus

Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.50907

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.1541/ieejfms.130.793

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

DOI： 10.2514/1.49571

Scopus

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Language：English   Publishing type：Research paper (scientific journal)

Kyutacar

Language：English   Publishing type：Research paper (international conference proceedings)

オーランド   2009.01.05  -  2009.01.08

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オーランド   2009.01.05  -  2009.01.08

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グラスゴー   2008.09.29  -  2008.10.30

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グラスゴー   2008.09.29  -  2008.10.30

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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浜松   2008.06.01  -  2008.06.08

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東京   2008.01  -  2008.01

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アメリカ   リノ   2008.01  -  2008.01

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東京   2008.01  -  2008.01

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東京   2008.01  -  2008.01

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東京   2008.01  -  2008.01

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France   2007.06  -  2007.06

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France   2007.06  -  2007.06

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France   2007.06  -  2007.06

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France   2007.06  -  2007.06

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France   2007.06  -  2007.06

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Franc   2007.06  -  2007.06

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主要雑誌

Language：English   Publishing type：Research paper (international conference proceedings)

スペイン   2006.10  -  2006.10

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金沢   2006.09  -  2006.09

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松江   2006.09  -  2006.09

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松江   2006.09  -  2006.09

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松江   2006.09  -  2006.09

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松江   2006.09  -  2006.09

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フランス   2006.06  -  2006.06

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金沢   2006.06  -  2006.06

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金沢   2006.06  -  2006.06

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2005.04  -  2005.04

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

Language：English   Publishing type：Research paper (scientific journal)

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)

Event date： 2013.12.01   Language：English  

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.

Event date： 2013.08.19   Language：English  

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.

Event date： 2013.08.19   Language：English  

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.

Event date： 2013.01.01   Language：English  

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.

Event date： 2013.01.01   Language：English  

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.

Event date： 2013.01.01   Language：English  

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.

Event date： 2012.12.01   Language：English  

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.

Event date： 2012.12.01   Language：English  

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.

Event date： 2012.12.01   Language：English  

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.

Event date： 2010.12.20   Language：English  

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.

Event date： 2010.12.20   Language：English  

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.

Event date： 2010.12.13   Language：English  

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.

Event date： 2010.12.13   Language：English  

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.

Event date： 2010.12.13   Language：English  

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.

Event date： 2010.12.01   Language：English  

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.

Event date： 2010.12.01   Language：English  

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.

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