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）

LEOPARD (Light intensity Experiment with On-orbit Positioning and satellite Ranging Demonstration) is a 3-unit (3U) research CubeSat with various mission objectives such as light-scattering observation over the horizon with a multispectral camera, onboard processing of Earth-origin one-way radio ranging signal (OPERA), single event latch-up (SEL) detection, solar panel deployment demonstration with shape memory alloy (SMA), and measurement of magnetic field independent components of stray and natural fields. The solar panel deployment mechanism utilizes shape memory alloy with a heater to ensure controlled panel deployment. In this paper, the structural design of the LEOPARD CubeSat is presented in addition to the assembly and integration procedures. Furthermore, structural analysis is presented from modal analysis to static load analysis, and the simulation of stress distributions and validation of structural integrity have been performed with finite element analysis. Vibration testing is also conducted to evaluate the system level response to mechanical excitations during launch, ensuring robustness against dynamic loads. LEOPARD used a slot-type design for subsystem integration that has been used in our previous satellites, and the novelty of the structure design comes from the deployment mechanism and method. Finally, the LEOPARD flight model is under testing, and the operation is expected to begin in the second half of 2025.

DOI： 10.52202/078379-0039

Kyutacar

Scopus

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記述言語：英語   掲載種別：研究論文（研究会，シンポジウム資料等）

We describe scientific o bjective a nd p roject s tatus o f a n a stronomical 6 U C ubeSat m ission V ERTECS (Visible Extragalactic background RadiaTion Exploration by CubeSat). The scientific g oal o f V ERTECS i s t o reveal the star-formation history along the evolution of the universe by measuring the extragalactic background light (EBL) in the visible wavelength. Earlier observations have shown that the near-infrared EBL is several times brighter than integrated light of individual galaxies. As candidates for the excess light, first-generation s tars in the early universe or low-redshift intra-halo light have been proposed. Since these objects are expected to show different e mission s pectra i n v isible w avelengths, m ulti-color v isible o bservations a re c rucial t o r eveal t he origin of the excess light. Since detection sensitivity of the EBL depends on the product of the telescope aperture and the field o f v iew, i t i s p ossible t o o bserve i t w ith a s mall b ut w ide-field te lescope sy stem th at ca n be mounted on the limited volume of CubeSat. In VERTECS mission, we develop a 6U CubeSat equipped with a 3U-sized telescope optimized for observation of the visible EBL. The bus system composed of onboard computer, electric power system, communication subsystem, and structure is based on heritage of series of CubeSats developed at Kyushu Institute of Technology in combination with high-precision attitude control subsystem and deployable solar array paddle required for the mission. The VERTECS mission was selected for JAXA-Small Satellite Rush Program (JAXA-SMASH Program), a new program that encourages universities, private companies and JAXA to collaborate to realize small satellite missions utilizing commercial small launch opportunities, and to diversify transportation services in Japan. We started the satellite development in December 2022 and plan to launch the satellite in FY2025.

DOI： 10.1117/12.3014708

Kyutacar

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）

The design of the attitude determination and control system (ADCS) of CubeSats plays a crucial role in the success of their missions. ADCS design is a challenging task for CubeSats with commercial-off-the-shelf, low-cost, and small-size equipment due to limited resources. In this paper, the proposed ADCS design of the LEOPARD satellite is presented. The LEOPARD is a 3U cubesat developed by the Kyushu Institute of Technology and its main missions are to perform technology demonstration for an on-orbit positioning system and observe the horizon for light-intensity experiment. The light-intensity experiment requires 8 degree attitude control accuracy to realize its mission. The ADCS of LEOPARD is equipped with two three-axis gyroscopes, two three-axis magnetometers, six coarse sun sensors, a three-axis magnetorquer, and a y-axis reaction wheel. The attitude determination part consists of a coarse attitude determination algorithm that is to be used to initialize the attitude information and an extended Kalman filter as a main attitude estimation technique that makes use of all the sensors. As a backup solution, a gyroless extended Kalman filter is designed in case of gyro failure. An estimation algorithm is designed to determine the residual magnetic moment. The attitude control algorithms provide the satellite detumbling using the B-dot control algorithm and target-pointing PD-type control algorithms. The estimated residual magnetic moment is also compensated by the feedforward control approach. The simulations show that the attitude and angular velocity could be estimated in the Sun phase as well as in eclipse using gyroscope measurements in addition to the magnetometer and sun sensor. Nadir pointing and Sun pointing modes can be realized using solely magnetic actuation within the requirements for communication and Sun acquisition. Horizon detection algorithm with Sun pointing is achieved for scientific missions in sunrise and sunset phases by using a reaction wheel in addition to magnetorquers.

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）

This paper focuses on the analysis of the magnetic field measurements observed by the nanosatellite KITSUNE, focusing on the calibration methods used during the development and operations of the satellite. KITSUNE is a 6U CubeSat developed at Kyushu Institute of Technology, Japan, and deployed to orbit on 24th March 2022. It is equipped with an active 3-axis attitude control system consisting of reaction wheels, magnetorquers, an Inertial Measurement Unit (IMU), an external magnetometer, and six coarse sun sensors. Typically, the magnetometers used in CubeSats missions are attached to the satellite body. Hence, the magnetometers can give unexpected results due to scaling factors, offsets, and non-orthogonality errors. The non-orthogonality errors are defined as angular deviations from the orthogonal three-axis. The genetic algorithm is being used in this study to calibrate the on-orbit magnetometer data. As a study case, the on-orbit magnetic field data collected by this magnetometer was used to demonstrate the performance of the proposed genetic algorithm to calibrate the magnetometer on the ground. The Fortran language is used to develop the genetic algorithm to calibrate the magnetometer data. The genetic algorithm uses a weight function to find the best match for the unknowns. A relationship between the reference magnetic field, the measured magnetic field by the magnetometer, offsets, and scaling factors, is used as the weight function of this study. The magnetometer data from the International Geomagnetic Reference Field (IGRF) is used as the reference magnetic field in the weight function. The results of the implemented genetic algorithm for the calibration of KITSUNE magnetometer show that the observed error in the measured magnetic field can be reduced by this method.

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記述言語：英語   掲載種別：研究論文（学術雑誌）

Featured Application: The presented innovative design concept significantly impacts the development of nanosatellites such as CubeSats, particularly for mass production missions that demand high efficiency and fast delivery. With the recent increase in CubeSats’ ability to undertake complex and advanced missions, they are being considered for missions such as constellations, which demand high development efficiency. From a satellite interface perspective, productivity can be maximized by implementing a flexible modular structural platform that promotes easy reconfigurability during the integration and testing phase. Thus, the structural design of a CubeSat plays a crucial role in facilitating the satellite integration process. In most cases, the mechanical interface implemented between the primary load-supporting structure and internal satellite subassemblies affects the speed and efficiency of satellite integration by adding or reducing complexity. Most CubeSat structural designs use stacking techniques to mount PCBs onto the primary structure using stacking rods/screws. As a result, the internal subsystems are interconnected. This conventional interface method is observed to increase the number of structural parts, while increasing complexity during integration. In this study, flexible 3U and 1U CubeSat platforms are developed, based on the slot concept. This innovative mounting design provides a simple method of mounting PCBs into the slots. The concept is evaluated and verified for its feasibility for mass production applications. Count and complexity analysis is carried to evaluate the proposed design against the conventional type of structural interface methods. The assessment reveals that this new concept demonstrates a significant improvement in the efficiency of the mass production process.

DOI： 10.3390/app12189087

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）

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

CiNii Article

CiNii Research

その他リンク： https://kyutech.repo.nii.ac.jp/records/7082

記述言語：英語   掲載種別：研究論文（学術雑誌）

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

Scopus

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記述言語：英語   掲載種別：研究論文（研究会，シンポジウム資料等）

CiNii Article

CiNii Research

その他リンク： http://id.ndl.go.jp/bib/027611004

担当区分：筆頭著者   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）

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.

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）

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.

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（国際会議プロシーディングス）

Due to mission requirements, fault detection and isolation protocols or budget restrictions, a satellite is required to use most reliable attitude determination hardware, such as magnetometers and sun sensors, in order to keep 3-axis attitude information available during its complete orbit. However, satellites experiencing sun-eclipse phases, sun sensors become no operational. In this paper, we propose an attitude determination system which provide 3-axis attitude information in both sun and eclipse phases, considering vector observations acquired from sun and magnetic measurements. To compensate the unavailability of sun sensors during eclipse phase, two variations of innovation processes merged into the Extended Kalman Filters are proposed. In order to keep the accuracy of attitude estimation process during eclipse mode, angular rates must be accurately estimated during sun phase. To solve this issue, rough angular rate information is calculated based on previous attitude information calculated by Gauss-Newton method, which fuse magnetic and sun sensor data. Numerical simulation results show the performance of the proposed attitude determination system, considering the use of vector measurement hardware with different precision degree.

DOI： 10.1007/978-3-319-09858-6_8

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（国際会議プロシーディングス）

The Extended Kalman Filter (EKF) has been the workhorse of real time attitude estimation problems, for several years now. However, an essential and unsolved issue in the practical implementation of the EKF is the selection of the process and measurement noise covariance matrices. In this article, we evaluate experimentally an estimation algorithm that solves a gyro free quaternion formulation of Wahba's problem. This algorithm is based on an EKF and a least squares algorithm sensor fusion procedure. In particular, we address the tuning issues of the covariance matrices in the EKF and the stop criteria and the initial condition in the sensor fusion procedure. Unfortunately, our experimental results show that the algorithm fine tuning is not an easy task and our best results, by the time being, rely on gyroscopic measurements.

DOI： 10.1109/ICEEE.2009.5393442

Scopus

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