論文 - 趙 孟佑
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Photoelectron current measurement in low earth orbit using a lean satellite, horyu-iv 査読有り 国際誌
Ewang E., Miyahara A., Khan A., Toyoda K., Cho M.
International Review of Aerospace Engineering 10 ( 3 ) 140 - 153 2017年01月
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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
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Microwave Breast Phantom Measurement System with Compact Side Slotted Directional Antenna 査読有り 国際誌
Islam M., Mahmud M., Misran N., Takada J., Cho M.
IEEE Access 5 5321 - 5330 2017年01月
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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）
© 2013 IEEE. In this paper, a new, complete, and comprehensive breast phantom measurement system is presented. A side slotted vivaldi antenna is used for breast phantom measurement. The radiating fins are modified by etching six side slots to enhance the electrical length and produce stronger directive radiation with higher gain. This approach reduces the lower operating frequency and increases the gain and efficiency without compromising the size of the antenna. The overall size of the antenna is 8.8 ( {L} ) ×7.5 ( {W} ) cm {{ {2}}} or approximately 0.4λ × 0.5λ at the first resonant frequency of 1.79 GHz. The results show that the antenna has a fractional bandwidth of approximately 127% from 1.54 to 7 GHz for return loss less than 10 dB with a directional radiation pattern. The average gain of the proposed prototype is 8.5 dBi, and the radiation efficiency is approximately 92% on average over the operating bandwidth. The fidelity factor for face to face is 0.98, and that for side by side is 0.4479, which proves the directionality and lower distortion of the signal. The prototype is successfully simulated, fabricated, and analyzed. The radiating fins of the proposed prototype are optimized to achieve the desired properties for breast phantom measurement. The antenna is used as the transceiver in a breast phantom measurement system to detect unwanted tumor cells inside the breast. An automated electromechanical imaging system with the necessary data post processing makes it an easy and suitable tool for microwave imaging to detect breast tumors.
DOI： 10.1109/ACCESS.2017.2690671
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EM absorption reduction in wireless mobile antenna using printed paper-based metamaterial 査読有り 国際誌
Alam T., Islam M., Kibria S., Cho M., Faruque M.
Applied Physics A: Materials Science and Processing 123 ( 1 ) 2017年01月
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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）
© 2016, Springer-Verlag Berlin Heidelberg. This paper presents a printed negative index metamaterial for electromagnetic (EM) absorption reduction in portable wireless antenna. The perceptible novelty exhibited in this paper is that EM absorption reduction toward the human head with paper-based metamaterial attachment. This research has been performed using human head phantom integrated in the commercially available CST Microwave Studio software package. The EM absorption has been reduced by 13.2 and 6% at 900 and 1800 MHz, respectively.
DOI： 10.1007/s00339-016-0631-5
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Five-year results of the world's first graduate-school-level space engineering fellowship program conducted between the UN and a university - called the PNST program 査読有り 国際誌
Maeda G., Cho M.
Proceedings of the International Astronautical Congress, IAC 17 11169 - 11173 2017年01月
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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 International Astronautical Federation IAF. All rights reserved. September 2017 will mark a major milestone in the “Post-graduate study on Nano-Satellite Technologies (PNST)” fellowship program conducted jointly by the United Nations and Kyushu Institute of Technology (Kyutech) in Japan. In September, the final batch of PNST fellows - four Phd-seeking students and two master-degree-seeking students - arrive at the Tobata Campus of Kyutech to begin their studies of nano-satellite technologies with a strong emphasis on “hands-on” training - using state-of-the-art spacecraft test facilities. They become part of Kyutech's ongoing Space Engineering International Course (SEIC), which is the only English-based, graduate-level, space engineering program in Japan. There are over fifty international and Japanese students enrolled in SEIC. Since the start of the PNST program in 2013, twenty-seven international students have enrolled in it at Kyutech. To date, under PNST, seven students have obtained doctoral degrees and four students have obtained master degrees. In this paper, we explain how outstanding engineering fellows are selected from scores of non-space-faring nations - a pool of tens of millions of young persons. We explain what we set out to do with this UN-academia collaboration in space engineering, and what we have achieved with it.
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Changing the paradigm of developing countries space program: Lean satellite project as a pragmatic option 査読有り 国際誌
Tejumola T., Maeda G., Cho M.
Proceedings of the International Astronautical Congress, IAC 9 5707 - 5712 2017年01月
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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）
© 2017 by the International Astronautical Federation. All rights reserved. Several developing countries have made maiden steps in the establishment of space programs through some forms of cross boarder collaborative satellite development projects, launch and operations efforts. In many of these cases such effort cannot be sustained due to several constraints. New entrants from developing countries with little or no expertise in space technology have been able to access space by exploring the benefits of the explosive growth in satellite industry through the use of small satellites launched with more innovative applications. Several of the new entrants in space industry are filling several technological need gaps by employing the concept of untraditional risk taking approach to achieve low satellite mission cost and fast delivery, i.e., lean satellite. Sustaining space program effort can only be achieved by institutionalizing space program through cost effective strategic road map for human capacity development and establishment of localized space policy. This paper shall peruse the present situation of space technology in developing countries and why these strategies are not sustainable and enumerates the lean satellite project concept as a long-term sustainable space technology development concept for developing countries especially citing several case studies of such projects.
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Establishing space activities in non-space faring nations: An example of university-based strategic planning 査読有り 国際誌
Faure P., Cho M., Maeda G.
Proceedings of the International Astronautical Congress, IAC 17 11256 - 11261 2017年01月
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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 International Astronautical Federation IAF. All rights reserved. In 2015, Kyushu Institute of Technology initiated the Joint Global Multi-Nation Birds Satellite (BIRDS) project. This project has two main goals. First, non-Master or PhD degree holder young professionals from non-space faring nations participate to the design, development, testing, and operation of a 1U CubeSat, whose development costs are secured by the young professional's home institution. Second, the young professionals of BIRDS shall return to their home country and help establishing indigenous space activities. As of September 2017, young professionals from Bangladesh, Ghana, Nigeria, Thailand, Mongolia, Philippines, Malaysia, and Bhutan are being involved in BIRDS project. To help the young professionals acquiring the right tools and preparing them to successfully achieve the second goal of establishing indigenous space activities, the space strategic planning project was established in February 2017. During the project, young professionals from Bangladesh, Ghana, Mongolia, and Bhutan were invited to think about the strategy their home country should be following in the next ten years in order to achieve their country's goals in terms of space sciences, engineering, and utilization, while respecting the country needs and constraints. In this paper, the efforts undertaken by the different young professionals are reported and the guidelines for each country space strategic planning are described. From this work, the authors aim at promoting space activities development in non-space faring nations and encouraging non-space faring nations to find their right strategy to achieve sustainable indigenous space activities despite the nation's constraints.
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Toward Lean Satellites Reliability Improvement Using HORYU-IV Project as Ccase Study 査読有り 国際誌
趙 孟佑
Acta Astronautica 133 33 - 49 2017年01月
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担当区分：筆頭著者, 最終著者, 責任著者 記述言語：英語 掲載種別：研究論文（その他学術会議資料等）
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IAC-17.B4.9-GTS.5.3: BIRDS project: Development and operation summery of a cubesat constellation project 査読有り 国際誌
Monowar M., Cho M.
Proceedings of the International Astronautical Congress, IAC 10 6405 - 6411 2017年01月
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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）
The growth of CubeSats over the years has created a gateway for developing countries to venture into the development and more need driven satellite technology development. The BIRDS Project is a constellation of 5 CubeSats belonging to 5 countries and to be operated from 7 distributed ground stations all over the world. 15 students from Japan, Ghana, Mongolia, Nigeria, Bangladesh and Thailand developed these satellites at the Kyushu Institute of Technology in Japan applying innovative system Engineering methodology. The 5 identical 1U CubeSats shall execute 6 missions viz; capture homeland picture of participating countries, broadcast voice data from space to ham receivers, detection of Single Event Latch-up (SEL) in space, however because of the gravimetric and volumetric constraints of 1U CubeSat, the three other missions are: determination of precise location of satellite, atmospheric density measurement and demonstration of coordinated ground station network for CubeSats operation planned to be achieved using advantage of 7 distributed ground stations. It is a unique experience for a university to develop five identical CubeSats within a short time, 16 months. The lessons will be shared among the community and applied in future constellation system development. Presently, the satellite development is completed and awaiting launch and deployment from the International Space Station in spring 2017. This paper shall enumerate the system engineering aspect of the development of the satellites and initial operational results after the deployment.
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Screening of nanosatellite microprocessors using californium single-event latch-up test results 査読有り
Tomioka T., Okumura Y., Masui H., Takamiya K., Cho M.
Acta Astronautica 126 334 - 341 2016年09月
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記述言語：英語 掲載種別：研究論文（学術雑誌）
© 2016 IAA. A single-event latch-up (SEL) test using a 252 Cf radioisotope was carried out. The results were compared with those of a proton test and from observation in orbit. A radioisotope can reproduce phenomena observed in orbit that are caused by protons. Considering the inexpensive nature of the 252 Cf test, it is more suitable for nanosatellites that require low cost and fast delivery. A SEL occurrence rate of a commercial-off-the-shelf microprocessor was derived from the ground test results. The 252 Cf test provided a SEL rate approximately 1×10 6 times greater than that in orbit. This data can be used to derive the minimum SEL occurrence rate in orbit and help satellite designers to evaluate the risk of SEL and take measures if necessary.
DOI： 10.1016/j.actaastro.2016.05.004
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A university-based model for space-related capacity building in emerging countries 査読有り
Polansky J., Cho M.
Space Policy 36 19 - 23 2016年05月
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記述言語：英語 掲載種別：研究論文（学術雑誌）
© 2016 Elsevier Ltd. Since 2011 the number of satellites less than 50 kg launched annually has increased by an order of magnitude. This trend is driven in part by proliferation of small satellite and lean satellite projects worldwide. In this decade alone, over 30 new countries are expected to achieve their first satellite in space. More than ever before, emerging countries are engaging in space-related activities. However, barriers such as lack of funding and underdeveloped human resources prevent many emerging nations from initiating or sustaining space programs. Kyushu Institute of Technology (Kyutech) has played an active role in space-related capacity building and international cooperation since 2009, then partnering with the United Nations Office for Outer Space Affairs to formulate a long-term fellowship programme hosted at Kyutech. Growing out of the success of the fellowship programme, Kyutech began significantly expanding its space-related capacity building project in 2013. This paper gives an overview of Kyutech's university-based model to enhance space-related capacity building and human resource development in emerging countries worldwide, and discusses advantages and disadvantages of alternative approaches.
DOI： 10.1016/j.spacepol.2016.01.001
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Toward the improvement of lean satellites reliability through testing - The HORYU-IV (aegis) nano-satellite case study 査読有り
Faure P., Tanaka A., Cho M.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
Copyright © 2016 by Pauline Faure and Mengu Cho, Kyushu Institute of Technology. All rights reserved. What comes to your mind when small satellites are mentioned? For a part of the space community, they represent the possibility of building a satellite despite lack of resources; and hope, through successful achievement, to be recognized as a positive contributor to space science, technology, and engineering. For another part, small satellites represent the black sheep of satellites engineering in the sense that they have the highest rate of infant mortality and mission failure, and a non-functional satellite is another space debris. High rate of infant mortality and mission failure of small satellites tend to point out that ground based testing is not carried out optimally or sufficiently. Moreover, small satellites, especially micro-to pico-satellite are relatively new comers on the space scene and documentation on their development philosophy, testing strategy, and on-orbit operations is scarce. Currently, work to define an adapted testing strategy for small satellites is undergoing through the ISO on "Design Qualification and Acceptance Tests of Small Spacecraft and Units" (ISO/CD 19683). Based on this framework, HORYU-IV testing strategy was established. Experimental data show that most failures are discovered during the early stage of testing. Moreover, experimental data show the importance of interfaces verifications. Overall, a failure was detected on average every 20h of testing. HORYU-IV failures taxonomy is also presented. In addition to testing data, simulations were carried out. The plots of the number of detected defects versus time are in good correlation with the testing data. Moreover, impact of failure criticality on overall project schedule and cost was evaluated. Simulations results show that drastically increasing the initial testing time does not drastically increase reliability, but does drastically increase cost by more than 80%. Through this paper and the presented results, the authors intend to serve as a reference and help each lean satellite program developer deciding how much time should be invested in the testing phase based on a trade-off between the desired reliability after launch for a given time and reasonable project development time and cost.
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IAA study on lean satellites 査読有り
Cho M., Graziani F.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. In recent years, the explosive growth of small satellites launches raises concern over space debris, safety, radio spectrum use, and so on. Small satellites range from a 1kg CubeSat to a satellite weighing well over 100kg, but have a common characteristic of low-cost and fast-delivery. Nowadays, even commercial CubeSats have started to appear. In 2014, an activity started at ISO/TC20/SC14 to make an ISO standard that defines what is a small satellite and sets requirements for small satellites to answer those concerns and to lay down the foundation for commercial activities utilizing small satellites. Since 2015, a new work item ISO/WD/20991, "Requirements for Small Spacecraft" is being discussed at ISO. Under these circumstances, the study group 4.18, "Definition and Requirements of Small Satellites Seeking Low-Cost and Fast-Delivery", was initiated in 2014. The objectives are to examine the definitions of small satellites, identify the requirements every satellite should follow regardless of its size or development philosophy and then reflect some of the findings to the ISO draft. After a series of meetings, the final draft of the study group report has been submitted to IAA Commission 4 in March 2016. The purpose of the present paper is to provide overview of the study group findings. The definition of small satellite was discussed extensively. The major conclusion of the study group is that mass nor size is not suitable to define small satellites and they should be defined by the philosophy of design, manufacturing, mission, program management and others. The study group came to conclusion that "lean satellite" is the most suitable word to describe a satellite that utilizes untraditional risk-taking development approaches to achieve low-cost and fast-delivery with a small number of team. The smallness is merely the result of the approaches. Scaling to measure how closely a given satellite fits into the concepts of lean satellites in terms of (1) total cost, (2) delivery time, (3) simplicity, (4) risk taking, (5) risk mitigation, (6) reliability requirement, (7) mission duration, (8) launch, and (9) waste minimization has been developed in. The scaling has been tested against nearly 30 satellites all over the world. At the symposium, the contents of the study group final draft will be presented as well as the update of the ISO standards related to lean/small satellites.
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Development philosophy and flight results of arc event generator and investigation satellite HORYU-IV 査読有り
Cho M., Faure P., Tanaka A.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
Copyright 2016 by Kyushu Institute of Technology. HORYU-IV satellite is the fourth satellite in the HORYU series to be developed at Kyushu Institute of Technology and the second satellite of the series to be piggy-back launched on H-IIA. The first to be launched was HORYU-II in May 2012, which successfully demonstrated the feasibility of generating 350V in low Earth orbit. HORYU series are categorized as lean satellites. A lean satellite is a satellite that utilizes non-traditional, risk-taking development and management approaches - with the aim to provide value of some kind to the customer at low-cost and without taking much time to realize the satellite mission. HORYU series satellites are dedicated to spacecraft charging and high voltage experiments which are not always welcomed as payloads on a shared platform due to concern over disturbance caused by discharge. Lean satellites are ideal testing platforms for those risky experiments. HORYU-IV is a cubic satellite within an envelop of 450mm × 420mm × 430mm and weighs approximately 10kg. Its structure and bus are mainly inherited from HORYU-II with various improvements in functionality and reliability. Especially, many layers of power cycle reset against single event effects were implemented. HORYU-IV implements HORYU-II high voltage photovoltaic power generation technology and uses it to study 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 plans to carry 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 project started in Mary 2013 and the flight model was delivered to JAXA in January 2016. On February 17, 2016, it was successfully launched by a H-IIA rocket to an orbit of 575 km altitude with 31o inclination as a piggyback satellite. The operation strategy was to carry out the main mission as soon as possible after the launch considering the high infant mortality rate of lean satellites. After initial check of the satellite house keeping data, the main mission was executed and the preliminary result indicates the mission was successfully conducted. It is planned to operate the satellite for at least two years in orbit. At the time of symposium, overview of the satellite, especially its development philosophy as a lean satellite, will be given along with some preliminary flight results obtained during the eight months in orbit.
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Aoba Velox-IV attitude and orbit control system design for a LEO mission applicable to a future lunar mission 査読有り
Cordova-Alarcon J., Örger N., Kim S., Soon L., Cho M.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. Aoba VELOX-IV is a 2U-Cubesat which will serve as a platform for technology validation towards a future lunar mission for the observation of lunar horizon glow (LHG). 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. Even though the horizon glow was highly visible in the Apollo 15 sunset, Apollo 16 showed no traces of the horizon glow, proving that it is a highly varying phenomenon. 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. Though its AOCS scheme is designed to meet the requirements for a low-Earth-orbit (LEO) mission, it can be directly applicable to a lunar mission. This paper is dedicated to the description of the design and analysis of a AOCS to meet these requirements. Because of dimension restrictions, the satellite attitude is two-axis controlled. The hardware of AOCS consists on Sun sensors, gyroscope, reaction wheels and pulsed plasma thrusters (PPT). Satellite position, velocity and time will be determined by a ground station and the satellite will propagate them until the next revisit. Based on PPT thrusters, the AOCS will desaturate RW during attitude control maneuvers for the pointing towards Earth horizon in such a way that the satellite can observe sunrise and sunset. In eclipse phase, the satellite is required to know its attitude by means of Kalman filtering to observe the sunrise. The geometry configuration of PPT will allow the extension of the satellite mission lifetime while desaturation of RW and while the satellite is visible to the ground station.
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Birds project: An innovative way to educate post-graduate students from developing countries 査読有り
Maeda G., Cho M.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. With help of the United Nation's "Post-graduate study on Nano-Satellite Technologies (PNST)", Kyushu Institute of Technology (Kyutech) has an unusually large number of space engineering graduate students from developing countries (currently 33 such students from 19 countries). All PNST fellows and all self-funded overseas students are enrolled in our "Space Engineering International Course (SEIC)", which has a strong emphasis on hands-on training. We believe the best way to master satellite technology is to design, build, launch, and operate, a real satellite, within given time constraints - in Japan the standard duration for a masters degree is two years. We wish to describe one hands-on international project of SEIC, which in October of 2016 will be past the halfway point. The BIRDS Project started in October of 2015 with 15 students - 3 Japanese and 12 from developing countries. None have designed a spacecraft before. They represent five nations, and the goal is for the students of each nation to build a 1U cubesat for their nation - of which four are non-space faring nations. The students hammer out the design themselves, and then each cubesat is built to that common design using commercially available parts. Hence, when in LEO, the five cubesats will form the first constellation of 1U cubesats designed, built, and flown, by university students. Launch (to the ISS) is set for second quarter of 2017. The schedule is exceedingly ambitious. The project has six missions: (1) capture images of their homelands, (2) broadcast songs to ham radio stations of their homelands (using the onboard "Digi Singer" device), (3) determine precise satellite location by examining the time lag of signals received at several ground stations (because there is no room for GPS in BIRDS cubesat), (4) measure atmospheric density based on the aforementioned precise location information, (5) demonstrate the feasibility of a ground station network based on university facilities in developing nations, and (6) investigate single-event latch-up's by carefully assessing onboard resets. When students go through all of the above, it becomes a uniquely intensive and extensive space technology learning experience. Of course, each student is assigned specific roles (e.g., mechanical design of the cubesat frame or design of the camera system). However, in the end, each will have participated in the entire process from design to in-orbit operation.
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Aoba Velox-IV camera system design for lunar horizon glow imaging in a future lunar mission 査読有り
Örger N., Cordova-Alarcon J., Toyoda K., Soon L., Cho M.
Proceedings of the International Astronautical Congress, IAC 2016年01月
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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）
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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Vacuum Arc Thruster Development and Testing for Micro and Nano Satellites
AHEIEVA Kateryna, TOYODA Kazuhiro, CHO Mengu
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 14 ( 30 ) Pb_91 - Pb_97 2016年01月
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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>
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Finite Element Analysis of Vibration Amplification Distribution in Lean Satellites
BATSUREN Amgalanbat, HATAMURA Toru, MASUI Hirokazu, CHO Mengu
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 14 ( 30 ) Pf_51 - Pf_60 2016年01月
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記述言語：英語 掲載種別：研究論文（学術雑誌）
<p>This paper presents a part of the basic research for establishing the unit Qualification Test (QT) conditions within the framework of an international project to make ISO standard, namely, "Space Systems—Design Qualification and Acceptance Tests for Small-Scale Satellites and Units Requiring Low Costs and Fast Delivery". A laboratory test is conducted to study how vibration acceleration is distributed in a satellite body, so as to define the unit QT random vibration test level. The range of natural frequency and the amplification of acceleration are identified through statistical analysis of the test results. Finite element analysis is carried out to extend the findings to other structural types of micro/nanosatellites. Three structural types are analyzed, i.e., Yojo han, T-type and Pi-type. Based on the results, a unit QT vibration level that provides the minimum reliability assurance for use in space is proposed.</p>
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Development of Low Cost Double Probe Plasma Measurement System for a Lean Satellite HORYU-IV
TEJUMOLA Taiwo R., TANAKA Atomu, KHAN Arifur, HORYU-IV Project Team, CHO Mengu
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 14 ( 30 ) Pr_39 - Pr_46 2016年01月
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記述言語：英語 掲載種別：研究論文（学術雑誌）
<p>A lean satellite is equivalent to a small/micro/nano/pico satellite that utilizes untraditional risk-taking development approaches to achieve low-cost and fast-delivery. Lean satellites have demonstrated great ability to be used for the study of space plasma and Earth's ionosphere which has helped in the prediction of many astrophysical phenomena and forecasting of geophysical changes on ground. Several methods have been employed in the measurement of space plasma parameters over the years using the Langmuir Probe. These methods employed different techniques using single probes or double probes. Single probe requires a well-defined reference which is difficult in small spacecraft. Moreover, high current flow in the saturation mode may destroy the probe and on-board circuitry. A low cost double Langmuir probe made of gold with its measurement circuit has been designed and tested inside RF generated Argon plasma in the pressure of 1.4×10<sup>-2 </sup>Pa that confirms the electron density from 10<sup>10</sup> to 10<sup>12 </sup>m<sup>-3</sup>. Important design considerations such as operability of the designed system in low earth orbit grade plasma, mitigation of probe contamination and sputtering of the electrode surface were analysed in the paper to ensure that the developed system can provide high fidelity plasma measurement data throughout the life span of HORYU-IV (Arc Event Generator and Investigator Satellite) which is a 13 kg, 40 cm cubic lean satellite under development at the Kyushu Institute of Technology.</p>
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Design and Testing of Electrical Power Subsystem of a Lean Satellite, HORYU-IV
EDRIES Mohamed Yahia, TANAKA Atomu, HORYU-IV Team, CHO Mengu
TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN 14 ( 30 ) Pf_7 - Pf_16 2016年01月
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記述言語：英語 掲載種別：研究論文（学術雑誌）
HORYU-IV is a lean satellite weighing 10 kg or less designed at the Kyushu Institute of Technology. It is planned to be launched with the ASTRO-H in FY2015 as a piggyback on an H-IIA rocket. The main mission of HORYU-IV is to acquire on-orbit data of discharge phenomena occurring on high-voltage solar arrays. An electrical power subsystem (EPS) is one of the HORYU-IV bus subsystems. The function of the EPS is to provide uninterrupted power to all subsystems during the satellites lifetime. High reliability, high efficiency and simplicity are the main requirements to be considered in the design of an EPS. Generally, an EPS consists of solar arrays, rechargeable batteries, and a power control and distribution unit (PCDU). A peak power tracking topology is preferred to extract the maximum power generated by the solar arrays. The extra energy is stored in nickel-metal hydride batteries. The simple design and usage of available commercial-off-the-shelf components are the main features of the PCDU which controls the battery charging and load voltage regulation. Functional tests under different operating conditions were carried out on the designed EPS to qualify its performance. The aim of this paper is to explain the design of the EPS, and to present and analyze the test results.