Fifth-generation mobile communication system (5G) array-antenna transmitters attached to space deployable membrane structures were developed by the authors. The array-antenna mission’s main objectives are measuring the transmitters’ communication power and demonstrating the antenna’s non-flatness compensation function by beam-forming technology in Low Earth Orbit. Thermal design of the transmitters is critical for the mission’s success. Thus, this study demonstrates the process of designing Multi-Layer Insulation (MLI) to protect the 5G array-antenna transmitters from the harsh space environment. The design process includes thermal analysis, in-house fabrication of the MLI, and the thermal equilibrium test for correlation. The analysis reveals that the temperature of the radio-frequency integrated circuit in the transmitters can remain within the allowable temperature range by appropriately selecting the beaming period and satellite attitudes.

Rendezvous docking is a key technique for space activities and missions, including in-orbit service and planetary exploration missions. One of the planned missions of the HTV-X, successor to the H-II Transfer Vehicle (HTV), is a demonstration of an automatic docking system. These docking systems need a high level of reliability and safety. However, it is difficult to comprehensively evaluate and verify the systems using only ground tests due to the inability to reproduce the actual operating conditions. Therefore, an efficient and reasonable model-based development method has been constructed to evaluate feasibility and safety in this study.

In case of a disaster happening, one of the critical problems is the lack of robust communication systems capabilities for the people under the disaster. This paper proposes the portable or reconfigurable wide area network with specified low-power radio station equipment via multiple small flying objects constellations to achieve the data relay communication system. The unmanned small flying vehicles, such as drones or multicopters with specified low-power radio transmitters provide responsiveness. The small satellite with high sensitivity receiver and high-speed transmitter achieves wide-area communication, and robustness for on-ground disasters. The system concept and design policies are evaluated by rough numerical studies with realistic hardware constraints. The results show the feasibility of the proposed concept with the specific case study.

In this study, we proposed a training method and developed a training apparatus that can maintain antigravity muscles under microgravity conditions, aiming at the application to long-duration stays in space, including exploration of other planets. The training method was focused on the action of antigravity muscles. The device was designed to reproduce an unstable posture, and to make the subject use his/her muscles to stabilize the posture. In this paper, we propose an antigravity muscle training method, develop a prototype machine to realize the proposed method, and conduct posture maintenance experiments on the whole body using the prototype machine. The target movements were the maintenance of forward and backward leaning postures using the device, and the EMG potentials of each muscle were measured during the experimental movements. As a comparison, we measured the EMG potentials of each muscle during the experimental movement while the subject was standing and maintaining a posture tilted at a similar angle. The results showed that the trends of EMG changes in each muscle were similar between the experimental and comparison movements. The results showed that the prototype was able to provide the same load to the antigravity muscles as that of gravity.

In this study, we developed an atomistic interface model for a composite of processed diglycidyl ether of bisphenol A (DGEBA) molecule and carbon nanotubes (CNTs) with point defects. We investigated the interfacial, mechanical, and electronic properties of the model. We found that strong covalent bonds are formed at the interface between CNT and DGEBA without decreasing the stiffness of the CNT. The Young's modulus of CNT with a point defect (without DGEBA) is 845.49 GPa, which is 5.46% lower than that of defect-free CNT (894.32 GPa). On the other hand, the Young's modulus of the CNT/DGEBA composites is 895.20 GPa, which is close to that of defect-free CNTs, indicating that Young's modulus is reduced by defects but recovered by the termination of the defects. These results suggest that the interfacial and mechanical properties of nanocomposites can be effectively improved by controlling the microscopic structures, such as defects.

In a previous study, we proposed a method for attitude motion estimation from SLR data using a genetic algorithm (GA). While it is a very effective method in that it requires no prior information, it has the disadvantage of inefficient local solution search. Therefore, we propose a new estimation method using another global optimization method, particle swarm optimization (PSO). In this paper, we performed numerical simulations with both the PSO and the GA for the same cases as in the previous study, and compared the obtained results. As a result, followings are revealed: (1) Good solutions were obtained by the PSO as well as the GA even if observations are polluted by noise and bias and the rotational speed is slow. (2) The PSO tends to find solutions closer to the true value than the GA if there is no bias in the observation times. (3) It is preferable to use the PSO in the problem setting assumed in the paper. We also describe a preprocessing to perform the analysis using actual SLR data.

We have studied an antenna system using a smart reconfigurable sub-reflector for a high-resolution radio astronomy mission for a balloon-borne Very Long Baseline Interferometry (VLBI) mission. The antenna system consists of the camera image sensor system to capture the surface shape degradation of the primary reflector, the smart sub-reflector system to install the actuators and the displacement magnifying mechanisms to compensate for the optical path length error to recover the required antenna gain. The original strategy to achieve the stringent requirements was to adopt a high-precision image measurement method, which requires much more computation time. However, the strategy sacrifices the antenna operation time as the most important task. In order to deal with the contradictory situation, this study considers a resilient operation planning of the smart antenna system under multiple uncertainties. The system-theoretic process analysis (STPA) is adopted to re-model the smart antenna system from the resilient operation point of view. Then, the resilient operation model considering several uncertain factors as hazards is investigated.

Currently, human feces on the International Space Station is incinerated in the atmosphere. Because feces contain a large amount of organic matter in addition to water, the reuse of feces would require an increased amount of renewable resources. However, conventional space toilets are not designed for reusing feces. One of the reasons for this is that it is difficult to transport an intermittent supply like feces. Therefore, in this study, influenced by the peristaltic movement of the intestinal tract of living organisms, we developed a device that can transport feces at low energy consumption. The device consists of multiple pump units driven by low air pressure. By applying air pressure to each unit in turn, the pumps are controlled to close and release, which reproduces the peristaltic motion for transfer. Furthermore, the transfer rate is improved by combining the air inflow with the transfer channel and water addition.

Hall thruster is considered the key propulsion technology for a variety of spacecraft including Earth-orbiting satellites, space transportation systems, and space exploration. To acquire medium-power Hall thruster technology, a 6-kW-class Hall thruster system is under development at Japan Aerospace Exploration Agency (JAXA), which is the first Japanese Hall thruster to be tested onboard the Engineering Test Satellite-9 (ETS-9). Onboard ETS-9, a limited flight experiment of the Japanese Hall thruster subsystem will be conducted along with four main flight-proven foreign Hall thrusters as the bus system. Prototype model thrusters as well as an engineering model power processing unit are devoted to qualification tests. The qualification tests are in progress including an endurance test and system compatibility tests. In 2024, an end-to-end verification of the flight model thruster subsystem with the whole satellite system is planned for preparing the flight that is currently scheduled in FY2025.

Space Solar Power Systems (SSPSs) are renewable-energy systems that provide a continuous power supply. However, the efficiency of electric-power generation of SSPSs in the research phase needs to be improved. We investigated waste-heat recovery for a ground site of SSPSs to improve this efficiency. One type of SSPSs collects solar energy and converts it into electromagnetic wave in space then transmits it to a ground site on Earth. Most proposed ground sites for SSPSs are spread over several kilometers and receive 1–2 GW. The transmission frequency from space has been considered to be 2.45, 5.8, and 10 GHz, and the size of the ground site differs for each. The conversion efficiency of receiving power at the ground site is assumed to be approximately 70–90%. Therefore, the rest of the energy becomes waste heat. We investigated the wasteheat recovery for a ground site in terms of the frequencies and size of the transmitting antenna and ground site. The cooling system for the ground site is an air-cooling system, and the usable energy of waste heat as a heat source was estimated to be up to 48%.

We proposed a pointing control technology for large support structures to meet demands for higher precision and larger size in the development of space observation equipment. A Stewart platform was adopted for the structure. As the linear actuator, we used a highly reliable artificial thermal expansion. To reduce heat transfer to structural members other than the actuator, we adopted an elastic hinge using an invar alloy called LEX-ZERO. The Stewart platform used in this study consists of six linear actuators and top/bottom plates which are connected by the elastic hinges. As a basic experiment, we conducted an experiment on the thermal insulation performance of elastic hinges. As a result of the experiment, about 97% of the heat flow from the artificial thermal expansion actuator could be cut off by elastic hinges. Then, 6 degrees of freedom control experiments were performed using the Stewart platform. As a result, it was possible to perform pointing control with excellent accuracy of within 1 μm in translational displacement and 2 arcseconds in rotational displacement.

On-orbit identification has more stringent technical constraints than on-ground identification due to the operational environment. In particular, the amount of energy consumption is severely limited. This study proposes a novel identification method that does not consume a lot of energy and does not use input sequence information. The proposed method adopts piezoelectric semi-active control to excite a structural vibration and a covariance-driven stochastic subspace identification (SSI-COV) method. The piezoelectric semiactive control temporarily converts mechanical energy into electrical energy and then excites structural vibration using the temporarily converted electrical energy. Therefore, this is an energy-saving excitation method. Since the SSI-COV method identifies the structural model under the assumption that the input sequence is white noise, it identifies the structural model without any input information. We proposed a semi-active input generation method such that the properties of the semi-active input will be equivalent to those of the white noise. We validated the proposed method through numerical simulations and experiments. To explore the feasibility of the proposed method, this study employs a simple two-degree-of-freedom structure instead of a complex continuum structure. The proposed method identified the modal parameters of the structure and consumed only 68 mJ.

The University of Tokyo and Arkedge Space Inc. are now developing 6U CubeSat named ONGLAISAT in collaboration with TASA (ex-NSPO), whose main mission is Earth remote sensing. This satellite uses S-band for telemetry and command communication by 10-100 kbps and 4 kbps for each link, and X-band for mission data transfer at high speed by 36 Mbps at maximum. Moreover, it has a Store & Forward (S&F) system for one of the missions. In this paper, we summarize the communication system of ONGLAISAT which consists of the S-band, X-band, and S&F components. In particular, we discuss the benefit of installing the S&F devices as a (compact) back-up TT&C system for a CubeSat.

Satellite projects bring together people from around the world. Cultural diversity can act as a catalyst for new technologies, yet multicultural teams are also vulnerable to cultural misunderstandings. These may negatively impact outcomes in a “Tower of Babel”-type scenario, especially in small and short-duration satellite projects. Members have limited time and resources to get to know each other before engaging in highly interdependent collaboration. The Culture Map, an analytical framework developed by Erin Meyer, is widely used to facilitate global teamwork in the corporate sphere. To the authors' knowledge, it has not yet been applied to small space-related projects. This paper presents one case study. The Culture Map is applied to a six-month university satellite design project, SEIMEI, comprising members from several countries. It is used in an interactive workshop among the team, after project completion. The workshop provides an accessible interface with relevant concepts in cross-cultural communication, for members of a small space project with a skillset concentrated in STEM. The objective of the analysis is to assess whether instances of smooth and non-smooth collaboration can be traced to cultural mechanisms, and whether outcomes can be enhanced via an understanding of such effects. The workshop focuses on building awareness of other cultures and individual perceptions, as a starting point for increasing the competence to deal with cultural differences. Lessons learnt are summarized, on the usefulness of The Culture Map for effective teamworking in small, culturally diverse space projects.

Since the adoption of the Sustainable Development Goals (SDGs) at the United Nations in 2015, JAXA has been contributing to the Goals through various activities. In March 2022, JAXA established the basic policy on SDGs in order to make its contribution in an even more organizational and strategic manner. This paper outlines JAXA’s major activities contributing to the SDGs and introduces the main contents of the basic policy on SDGs, including vision, mission statement, and prioritized areas for contribution. It also touches upon the background of the establishment of the basic policy and the way forward.

We studied the effect of using Adaptive Coding and Modulation (ACM) on the data rate of a system that communicates between a high throughput satellite in geostationary orbit and the ground. We assumed two cases: OFDMA (Orthogonal Frequency Division Multiple Access) communication system and the environment under the resource control for frequency bandwidth and transmission power between beams. Rain attenuation was calculated from AMeDAS rainfall data to show the effect of ACM on actual rainfall changes. The modulation scheme and coding rate used those of DVB-S2 and DVB-S2X. The proposed method determines the allocation ratio of communication resources (transmission power and bandwidth) using the user's traffic demand information acquired from another channel and shows the effect of this method on the data rate when combined with ACM by comparing it with the case where communication resources are equally allocated to users.

In the present study a dedicated plasma probe was designed to enhance the understanding of the physical separation of objects during re-entry and their radiative response. The plasma probe was exposed to an air plasma inside the plasma wind tunnel facility PWK4 of the Institute of Space Systems (IRS) of the University of Stuttgart. The chosen plasma condition corresponds to the thermochemical environment of a typical break-up altitude of a low earth orbit entry trajectory. The radiative response during the exposure of the plasma probe to the air plasma flow was observed via spatially and temporally resolved optical emissions spectroscopy. The spatially resolved emissions of the atomic oxygen triplet at 777.34 nm prove to be an excellent indicator for the study of shock layer thickness and location. Additionally, a significant increase in the spectral radiance of N2⁺ bands of the first negative system was observed at the merging point of two shock layers in between the opened plasma probe. Thus, it was concluded that a significant change in radiative markers related to a low-level break-up or break-off event could be the increased radiation of ionized molecular species of the surrounding air plasma.

To investigate material behavior during Venusian aerobraking, a ground test facility is required that provides relatively low convective heat fluxes in combination with significant atomic oxygen fluxes. This study investigates the application of a PHLUX-type catalytic plasma probe to characterize such an environment in an inductively driven plasma wind tunnel. Using material specific properties regarding heterogeneous catalysis of oxygen recombination, the atomic oxygen flux in a highly dissociated plasma flow can be determined. For this study, copper and silicon carbide samples are utilized in the plasma probe. To determine the incident heat flux in the fringe of the plasma plume, the sample temperature is measured with both thermocouples and a thermal imaging camera. In the plasma wind tunnel PWK3 at the Institute of Space Systems (IRS) of the University of Stuttgart, atomic oxygen fluxes ranging from 1.0 × 10¹⁸ cm⁻² s⁻¹ to 1.5 × 10¹⁸ cm⁻² s⁻¹ are determined under convective heat fluxes up to 6.0kWm⁻². A brief overview of the application of PHLUX sensors as flight instrumentation for atmospheric entry studies is given with an outlook to future in-situmeasurements during the early re-entry stage of the SOURCE CubeSat.

Rotating spoke, an example of azimuthal plasma instability, has been pointed out as one of the causes of anomalous electron transport in hall thruster plasmas. The high-speed camera images showed only ionization oscillations at an applied magnetic field of 15 mT, which is the dominant region for anomalous electron transport. Therefore, an axial-azimuthal 2D3V Full-PIC-DSMC analysis was performed. The analysis shows that during ionization, rotating spoke with mode number 32 occurs in the entire thruster circumference, while it does not occur during non-ionization. The axial transport of electrons under ionization oscillation was found to be dominated by mobility and E_θ×Br drift near the anode during ionization. In addition, the electron transport with E_θ×Br drift exist up to the axial wake.

This experimental research study tested the effect of varying ambient air pressure on the normal incidence laser propulsive performance of various flat target element samples (Al, Bi, C, Cu, In, Mg, Mo, Ni, Si, Sn, grade 2 Ti, and V) as well as several metal alloys (mild steel, 316 stainless steel, grade 5 Ti, and 93% WHA). A spherical vacuum chamber was pumped to <0.1 Pa, then an Nd:YAG laser was operated at a fixed fluence at the focus position to vaporize fresh areas of the target with single shots of laser energy. The ambient pressure was incremented between shots by partial venting of the chamber with ambient air from ~10^-2 to ~10⁵ Pa. Momentum coupling and thermal absorptance were evaluated as a function of pressure for each material at a calculated beam fluence at ~10⁴ J/cm². The results were interpreted with the assistance of open shutter DSLR photography of the ablation events at each pressure. The data are generally consistent with literature predictions and should be helpful for design of a wide range of future laser propulsion missions involving metal ablatants.

The structural characteristics of lattice structures with additional members attached to the X-lattice were investigated. The X-lattice, with unit cells comprised of beams that connect the vertices of a cube, has a low bending and high torsional stiffness. The addition of members in the X-lattice can increase the bending stiffness in a specific direction. In other words, a lattice structure that can tolerate bending deformation in a specific direction can be realized. In addition, an X-lattice with additional members with slits was developed. This lattice structure is flexible when the bending deformation is small. However, when the deformation exceeds a certain magnitude, the members come into contact with each other, which increases the stiffness of the structure. An X-lattice specimen and specimens with additional members were fabricated by a three-dimensional printer. Bending experiments were conducted to evaluate their structural characteristics. The experimental results showed that the introduction of additional members can change the stiffness in a specific direction, while the member with a slit can increase the stiffness with a given deformation.

NICT of Japan has been conducting communications research using a high-speed Ka-band internet satellite. The project includes the development and operation of a mobile earth station mounted on a van, hereafter called the vehicle earth station. The vehicle earth station is equipped with an antenna system that can automatically detect and track the satellite at a longitude of 110 degrees east. Understanding the propagation environment is key for the construction of a communications system because shadowing between satellites and earth stations affects mobile satellite communications. In this study, we conducted propagation measurements to compare the effects of shadowing due to differences in urban structures (i.e., urban, suburban, and rural areas). Furthermore, a simulation based on GIS was conducted to evaluate shadows on buildings. The results of propagation measurements and GIS simulations were compared to evaluate the effects of shadowing due to buildings and other factors (vegetation, etc.).

To evaluate the phenomena occurring in cylindrical Hall thrusters and to improve their performance, a visualized CHT with a glass discharge chamber and eight bar-shaped magnets were designed and fabricated. Through experimental evaluation, it was confirmed that the plasma produced in the discharge chamber and the plume downstream of the thruster are visible in proximity and that the estimated thruster performance is almost the same as that of the conventional CHTs, despite the visualization (thrust of 2.3 mN, specific impulse of 820 s). Further improvement of the CHT will be useful as a method for evaluating the Test Facility Effect and as a device for promoting understanding of electric propulsion systems.

This experimental study was conducted to document an underexplored parameter space in laser propulsion. The research tested 12 solid elements for potential as laser ablation propulsion propellants, including Al, Bi, C (graphite), Cu, Fe, In, Mg, Ni, Si, Sn, Ti, and V. Digital single lens reflex (DSLR) photography captured laser ablation of these materials by an Nd:YAG laser at 1064 nm wavelength and ~100 ms pulse duration. Each propellant was ablated across a range of fluences under high vacuum conditions (~10^-2 Pa) in an effort to better understand the potential of each elemental propellant for vacuum laser propulsion. Laser-imparted impulse was calculated from measurements using a piezoelectric force sensor and areal mass removal was inferred from volumetric recordings using white light optical profilometry. The qualitative photographic results and quantitative measurement data were combined to build a better context for broadly characterizing and understanding the threshold fluence for laser ablation in the microsecond regime. Ablation threshold measurements were reported for each material.

Hypersonic aircraft are attracting attention as the first stage of TSTO. Consideration of the aerodynamic performance in both hypersonic and low-speed regimes is necessary to realize such vehicles. For this purpose, a variable geometry wing may be effective. In this paper, a new concept of an aircraft with two oblique wings, placed in a symmetric manner with respect to the center line of the fuselage, is proposed to achieve high performance in both high-speed and low-speed regimes. The wings can change their swept back angles with a relatively simple mechanism: a single pivot. The expected advantage of this twin-oblique wing configuration is to cancel the asymmetric force generated by a single oblique wing because of its asymmetric arrangement and to solve aerodynamic problems of the oblique wing. The aerodynamic characteristics of this configuration in hypersonic regime were investigated via wind tunnel test and compared with performance of conventional delta wing airplanes. Due to the shock waves and their interferences, twin-oblique wing models could not provide higher L/D than delta wing models and could not cancel the side force completely. Side force was estimated to be as much as that of single-oblique wing, and rolling moment was partially suppressed. Some parts of the aircraft concept were modified to reduce this side loading.

An artificial satellite formation flight, which is a group of small satellites working together as a system, is increasingly being used because launching multiple small satellites is more cost effective than launching one large satellite. Hence, relative positioning among multiple satellites is expected to become more important. The range of using a formation flight is predicted to extend to farther areas such as lunar orbit and areocentric orbit. Global Navigation Satellite System (GNSS) signals are often used for positioning and time synchronization, but the signal intensity and position accuracy decrease in these farther areas. GNSS-free relative-distance measurement among multiple satellites is therefore needed. We propose a high accurate method (cm order) for measuring the relative distance between satellites using a radio interferometry system (GHz order) consisting of software defined radio (SDR) containing one receiver and one transmitter. The proposed method uses two frequencies to resolve the phase ambiguity in radio interferometry and uses SDR as a transponder without the need for time synchronization. Therefore, measurement accuracy reaches 0.59% at about a 6-m distance.

This paper presents an autonomous navigation system that uses optical inter-satellite communication technology. Autonomous navigation systems improve robustness by predicting global navigation satellite system (GNSS) orbits and clock offsets on board and providing navigation messages to enable a satellite positioning service to continue operating even when ground stations are unavailable. This paper reports the results of our feasibility study on a suitable target value of signal-in-space user-range-error (SIS-URE), an index that indicates errors in satellite positioning systems caused by unforeseen circumstances.

The S-520 Japanese sounding rocket has recently begun to be utilized as a Flying Test Bed (FTB) for investigating Flight Test Models (FTMs). The FTM contains fuel and avionics and thus requires a Ground Air-Conditioning System (GACS). The GACS has two roles. One is to maintain the inert gas atmosphere inside the FTM, which prevents combustion in case of fuel leak. The other is to keep the inside of the FTM at a temperature suitable for its avionics by supplying cold gas. The GACS was developed for the S-520-RD1 sounding rocket, which is used in supersonic combustion flight testing. The GACS consists of five sections: a gas source, heat exchanger, flow path switching system, rotation arm, and vacuum connector. The GACS was successfully operated throughout S-520-RD1 launch schedule. FTM Internal atmosphere kept perfectly inert and met avionics cooling requirement. The vacuum connector was correctly separated from the FTM by remote vacuum breaking and the motion of the rotation arm during the vacuum connector separation phase just before launch. In short, the operation was completed successfully.

In this study, we have fabricated ionic liquid electrospray thrusters to prevent ionic liquid leakage and provide high current density. A double-emitter structure with a needle protruding from the capillary emitter, where the ionic liquid was intended to be held by the needle, was proposed. The fabrication process employs a fabrication technique of a field emitter array, and a newly designed process to reduce the distance between emitters was used to improve emitter density. As a result of the fabrication, the needle was successfully formed in the emitter electrode, and it was found that emitter density could be improved by changing the deposition conditions of multiple SiO₂ layers.

KOSEN-1, the first artificial satellite developed by 10 National Institutes of Technology (KOSEN), was launched in November 2021. KOSEN-1 is a 2U size (20×10×10cm) CubeSat orbiting in a low orbit at an altitude of about 575km. In order to extending the operating time of KOSEN-1, a propulsion system for increasing altitude is necessary. In the present study, we designed and manufactured a compact Pulsed Plasma Thruster (PPT) that operates with a power of several Watts. We performed an experiment for demonstration of PPT in vacuum chamber. As a result, we showed that the ignition voltage at which the main discharge of 1.4 kV occurs stably repeatedly is around 10 kV and observed the generation of plasma in the PPT. The velocity of PPT plasma of 19 km/s was measured by TOF method. The PPT plasma temperature and density were measured 3.04 eV and 2.81×10²¹ m^-3 by Double Probes respectively. At the main discharge voltage of the PPT of 1.4kV, the impulse bit measured using the target method was 65 µNs.

When a sample return capsule re-enters the Earth's atmosphere, a strong shock wave is generated in front of the capsule and it receives severe aerodynamic heating. An ablation method is one of the thermal protection methods to protect the capsule from this heating. In the future, capsules are expected to become larger and re-entry speeds are expected to increase. Therefore, the capsule will be exposed to more significant aerodynamic heating. In this experiment, lightweight porouscarbon materials with controllable density and porosity and resin-impregnated porous-carbon materials were fabricated, and heating experiments using air plasma freejets were conducted. Spectroscopic measurements were made at the tip of test piece and around the tip of that emitted light during the experiments. The change in the apparent temperature value of the test-piece surface due to pyrolysis gas generation and the chemical species of the pyrolysis gases generated were investigated. Based on the spectroscopic results, the apparent temperatures of the test-piece surface of porous-carbon materials and resinimpregnated porous-carbon materials were estimated to be about 2,500 K and 1,600 K, respectively. The chemical species of the pyrolysis gases generated by heating were C₂ Swan band systems.

Space weathering is the process to change the optical properties of surface particulate materials of airless silicate bodies such as asteroids, the Moon and Mercury. The three typical changes are reddening (increase in spectral slope), darkening (overall darkening), and attenuation of the absorption bands in the reflectance spectrum. These changes are thought to be caused by formation of nanophase iron particles in amorphous rim of surface mineral grains. Responsible processes are micrometeorite impacts, solar wind and cosmic ray irradiation, and irradiation of ultraviolet light from the sun. So far various experiments of pulse laser irradiation simulating high velocity dust impacts and ion irradiation simulating solar wind irradiation have been carried out, but only a preliminary work has been done for ultraviolet light irradiation. We conducted a space weathering simulation experiment by irradiation of ultraviolet light on olivine and pyroxene (enstatite) pellet samples. Visible reflectance of olivine and enstatite decreases by 40% and 20%, respectively. Such spectral decrease may be saturated, without altering spectra of longer infrared wavelength. We measured ESR (Electron Spin Resonance) on UV irradiated samples, but no related signals were detected, suggesting lack of nanophase iron particles. Pulsed laser irradiation should overprint the change by UV irradiation: more darkening from visible and NIR range. Our results suggest that on space weathering of asteroid surface solar UV is the main cause for the first 1-10 yr, then solar wind irradiation until 1 Myr, and space weathering by micrometeorite impacts afterwards.

Time-of-flight (ToF) mass spectroscopy for electrospray thrusters was constructed to investigate the species and fraction of ions in the beam and the presence of fragmentation, where a cylindrical shield was placed just in front of the collector. The shield was expected to prevent the detection of secondary species, which were recently found to be one of the vacuum facility effects. However, the shield seemed to have almost no effects on the ToF signals because the signal did not decrease to zero, and some particles were always detected as they had been detected without the shield. To examine the cause of this signal detection, the collector current was measured under the condition that the gate electrode completely blocked the ion beam. The results implied that the electrospray ion source also emitted some neutrals. The measurement system was reconstructed to detect ions using a high-speed amplifier to avoid neutral particle detection. Then, the results showed that the electrospray thruster was operating in the pure ion mode.

Currently, the exploration of Mars using airplanes is being widely studied. In this study, transonic and low-Reynoldsnumber airfoil was investigated using direct numerical simulation to understand its flowfield and aerodynamic characteristics, including unsteady phenomena, in relation to Mars exploration. As a result, we extracted the key features governing the aerodynamic characteristics. Several additional features such as negative lift were identified. For unsteady phenomena, short- and long-period oscillations were the focus of this study. Short-period oscillations were caused by Kármán vortex shedding, which interacted with shock waves and caused weak and short-period shock oscillations. Pressure waves emanating from vortex shedding were observed to propagate both in front of and behind the shock wave. This may have been related to the mechanism of transonic buffet. Long-period oscillations, the so-called low-Reynolds-number buffet, were observed. It exhibited a strong Reynolds-number dependency and attenuated as the angle of attack (AoA) increased. Moreover, it showed differences from transonic buffet at high Reynolds number, such as the onset of oscillation and the role of shock waves in the buffet mechanism. Further investigation of the mechanism of low-Reynolds-number buffets is needed to predict and control for Mars airplanes.

Evaluation of propellant flow in the ground test facility (vacuum chamber) is important in the study of electric propulsion, and the measurement and evaluation of the dynamic pressure in the vacuum chamber have been conducted in our laboratory. For evaluating the dynamic pressure distribution of the propellant flow in a vacuum chamber, a measuring device that consists of an ionization vacuum gauge covered with a spherical shell with a single hole was designed and fabricated in this paper. Through measurement of the total pressure around the measurement point using this device, it was confirmed that the static pressure at the measurement point can be calculated from the average of the total pressure, that the dynamic pressure distribution around the measurement point can be estimated, and that the calculated average dynamic pressure is almost the same as the value detected by the conventional device. Since the influence of multiple sources of dynamic pressure can be estimated from the measured dynamic pressure distribution, this device was considered useful for propellant flow evaluation of electric propulsion systems.

We have fabricated an externally wetted emitter array with a deep-grooved structure using grayscale lithography for ionic liquid electrospray thrusters to improve the ionic liquid transport to the emitter tips and to reduce the percentage of the current intercepted by the extractor electrode, which was more than 30% with our conventional deep-grooved emitter. The experimental results of the ion emission have shown that a stable ion emission characteristic and the percentage of the current intercepted by the extractor electrode decreases by approximately one-third compared with our previous one. This decrease indicates that the emitter fabrication process using grayscale lithography optimized the deep-grooved emitter shape.

Given the importance of ensuring a sustainable food supply in space, there is a growing interest in the research of life science experiments such as plant cultivation and cell culture under microgravity conditions. In this study, we propose a new compact life science experiment device, AMAZ, which incorporates freedom of installation in the space station and an astronaut-friendly design concept. First, the fundamental design and design guidelines for the entire system and each part, including the conceptual design, are described. Unlike similar existing devices in the ISS, AMAZ employs an artificial gravity generation mechanism by a centrifuge without a turntable. In addition, the motor arrangement is designed to reduce the size of the device to 0.18 m in diameter and 0.40 m in length. Furthermore, based on these basic designs, a prototype machine using optical fabrication will be fabricated to demonstrate some of the functions, including the rotation mechanism. A prototype is manufactured utilizing stereolithography technique to validate certain functions, such as the rotation mechanism. The initial operational tests successfully demonstrate that the artificial gravity values could be changed as per the set values by controlling the number of rotations.

At Japan Aerospace Exploration Agency (JAXA), several sample return missions that use Hayabusa(HYB)-type sample return capsules (SRCs) have been proposed. Since HYB-type SRCs use spin-stabilization scheme during reentry, the determination of spin rate deceleration during reentry is important. However, roll damping effect, which may affect spin stability prerequisite, is not well-known for the capsules. In this work, we develop a numerical simulation scheme for roll damping coefficients, and investigate rarefaction effect and dependence of the coefficients on size, spin rate, and surface accommodation for the purpose of improving the reliability of attitude stability especially in rarefied flow regime. Finally, we discuss the feasibility of measurements for rarefied roll damping phenomena in a ground test facility.

A calculation method to estimate the survivability of a net-like tether system is explained in this paper. An electrodynamic tether is a candidate device to decelerate orbital debris without propellant. The major problem with using a tether in space is its vulnerability against collisions by space debris. Some conceptual designs are proposed to enhance the survivability of tether, such as tape tether, multiline tether, or net-type tether. Authors formulated the survivability of multi-segmented double-line tether in the preceding study. In this study, the calculation method is extended to treat a net-type triple tether which has been developed for the EDT by JAXA. The procedure of the calculation is as follows. First, fatality rates of each element in nettype tether are calculated by integrating differential flux multiplied by cross-sectional area, then survivabilities of each tether element are obtained as a function of time. Next, considering the topology of the net, probabilities along possible severing paths are summed up, and the survivability of the whole tether is obtained. At last, a simplified method with desirable precision and faster computation time is introduced. The numerical example shows that the net tether has much higher survivability than the double tether.

The present work aims to enhance a hybrid Navier-Stokes (NS) and Direct Simulation Monte Carlo (DSMC) methodology with the possibility of computing multispecies reactive flow, enabling the simulation of plasma in multiscale continuous and rarefied flows. A particular interest is the electron density field resulting from the ionization of the flow, answering a need to predict radio communication attenuation at high altitude between rockets and ground stations. Two main hypotheses are proposed to achieve this goal. The first one is that the flow expansion is supposed to be driven by the major species, and the influence of ions and electrons is negligible. The second one is that diffusive effects are neglectable due to the supersonic speed of the flow. These hypotheses allow to post-compute the minor species along streamlines taken from the flow solution using a Lagrangian thermochemical solver rather than natively calculating them, as handling such species in a DSMC simulation is complex. This study investigates these hypotheses on a simple thruster geometry to evaluate and validate the post-computation of the plasma. The obtained widen plume is in agreement with previous study expectation of the increased jet flow expansion angle in a rarefied atmosphere.

Transportation efficiency of a reusable launch vehicle must be improved in order to realize low cost and frequent space transportation. Utilizing aerodynamic force instead of the engine thrust is effective during a return flight of a reusable vehicle. However, the feasibility of such a return flight is questionable since aerodynamic characteristics are not understood enough for a slender body in a pitching motion over a wide range of angles of attack. We investigated the surface pressure distribution of a slender body both in pitching motions and in the steady condition in a wind tunnel experiment, covering a range of angles of attack from 0° to 180°. Our results show the pitching motion has a significant influence in delaying the transition of surface pressure. From the measured surface pressure, we evaluated the variation of aerodynamic characteristics corresponding to various angular pitching velocities. We also found that, during the pitching motion, the transition in flow patterns around the body is related to the surface pressure distribution and, consequently, influences the aerodynamic characteristics.

In cable-mesh reflector antennas, the balance between mesh tension and cable tension can cause out-of-plane deformation of the mesh surface. This deformation is called pillow deformation, and it causes considerable degradation of surface accuracy. Therefore, to develop a high-precision mesh antenna, it is necessary to clarify the pillow deformation caused by the mesh-to-cable tension ratio. In this study, the mesh deformation on reflector surface was investigated. The tension balance between the cable and the mesh caused node movement and affected pillow deformation. Furthermore, the relationship between the tension ratio and the accuracy of the surface was clarified.

This study presents the overall operation concept of a multi-loop capillary heat pipe (MCHP) system. This system is developed to cool the central detectors of the balloon-borne General AntiParticle Spectrometer (GAPS). MCHP, as a gasliquid two-phase closed heat transport device, transfers heat from detectors to a radiator. The MCHP is equipped with a reservoir. By regulating the temperature of this reservoir, which dictates the system’s saturation pressure, the MCHP operation is managed. A full-scale MCHP model was developed to investigate MCHP’s time response. Analysis of MCHP operation tests revealed that one-shot heat-up of auxiliary heaters attached to the MCHP induced the boiling of fluids in the MCHP and contributed to uniformity in detector temperatures. In addition, when the radiator was colder than the detectors, the MCHP quickly adapted to changes in ambient temperature—a scenario that is expected to occur during balloon flights. Conversely, the investigation of off-nominal cases where the radiator was warmer than the detectors demonstrated that the MCHP effectively prevented the detectors from experiencing rapid warming. These experimental results support the design and operation concept of the GAPS MCHP.

A geostationary Earth observation satellite with a middle-resolution optical system can observe a particular point at any time, but image registration and geometric correction are not easy because an oblique view is required when observing the Japan area from geostationary orbit. In this paper, we propose an image registration framework including image matching with other satellite images to perform image registration with high accuracy. In the proposed framework, the most distinctive feature is to perform an inverse-ortho correction before image matching to improve matching accuracy corresponding to oblique viewing from geostationary orbit. Additionally, the framework integrates a telescope alignment estimation method to accurately obtain line-of-sight direction as an alternative registration approach. This method entails fitting observed alignment values to a change model based on thermally induced errors in the telescope, ensuring precise alignment estimation. Our simulation results demonstrate the superiority of image matching using inverse-ortho correction compared to conventional standard-ortho correction. The proposed method achieves sub-pixel matching accuracy. Furthermore, we show that an alignment value can be estimated with an order of 10^-5 degrees by applying the proposed estimation method.

Quality control in manufacturing solar array panels is important and requires detailed inspection. The conventional inspection method evaluates the current-voltage characteristics of the arrays, but those of the individual solar cells in the arrays cannot be obtained. This paper proposes a simple inspection method for evaluating individual solar cells in an array using electroluminescence (EL). This light emission phenomenon occurs when a forward current is injected into a solar cell. Current crack detection in solar cells has used images of relative EL intensity. However, this study focused on images of absolute EL intensity. This novel method was demonstrated using the solar array panel on the proto-flight model of JAXA‘s SLIM (Smart Lander for Investigation Moon) project before and after testing. The SLIM solar panel consists of arrays of InGaP/GaAs/InGaAs triple-junction solar cells. The validity of the new method was confirmed by comparing the array's electrical properties measured by the conventional method and the sum of the cell's electrical properties derived from the absolute EL intensity.

Multi-point Earth observation missions perform multiple Earth observations at various attitudes in a short space of time. Variable shape attitude control (VSAC) has been proposed for multi-point observation missions due to its ability to enable microsatellites to realize agile large-angle attitude maneuvers. As the details of applying VSAC for multi-point observations have yet to be discussed, the authors used a specific assumed scenario of multi-point observations of landslides due to large earthquakes along the Nankai Trough. The authors used optimal control and formulated multi-point observations, and evaluated the number of points a satellite could observe and its precision using VSAC and compared this with the use of reaction wheels (RWs). In numerical simulations, VSAC succeeded in performing pointing observations for three different points during thirty seconds, and allowed the observation of more or an equal number of observation points compared to RWs.

In this paper, we propose an algorithm for a star tracker (STT) for rapid, large-angle attitude maneuvers. Recently, missions with rapid large-angle changes using small satellites have been proposed. Such missions require rapid and precise changes in attitude to the required observation direction. Generally, an STT is used for high-precision attitude determination for satellites. However, STTs have angular velocity limitations and cannot determine attitude during rapid angle changes. To estimate angular velocity and attitude during attitude changes, we propose a method to identify stars using the estimated star position and previously estimated angular velocity. Furthermore, random sample consensus (RANSAC) is used for more accurate identification. Results of numerical simulation show that we can identify stars with a probability of 98.2% and estimate angular velocities with an accuracy of about 2.00 x10^-2 [deg/s]. The attitude during an attitude change can be estimated with an error angle of 1.75 x10^-2 [deg] in each axis if there is no rotation in the roll direction.

In this study, the sequential data assimilation (SDA) methods for tension monitoring of the cable-beam structure are presented via two different approaches. In the first approach, the axial stiffness of the cable is set as a model parameter for the SDA. In this approach, the change in cable tension is monitored directly as a variation in cable stiffness, while a nonlinear sequential Bayesian filter is needed for the SDA. Although nonlinear sequential Bayesian filters can adequately handle nonlinear problems; they are often computationally expensive. In the second approach, we propose another method to circumvent nonlinearities in the estimation by setting a pseudo-temperature variation of cable as a model parameter, where the linear Kalman filter is used for the SDA. A simple cable-beam structure model with two support cables attached to a cantilever beam is given for numerical examples. The comparisons of efficiency for tension monitoring of the cable-beam structure in both approaches are indicated.

A demonstration experiment using a small satellite in a Low Earth Orbit (LEO) has been proposed to realize the space Solar Power Satellite (SPS). In this paper, we will report on the current status of two types of field experiments as part of this demonstration satellite experiment. Our first objective is to measure the characteristics of the transmitting Active Phased Array Antenna(APAA) of the SPS demonstration satellite in low earth orbit. This is divided into satellite antenna pattern measurement and tracking characteristic measurement. The two-dimensional antenna pattern is measured by the movement of the satellite by arranging multiple receiving stations in a straight line on the ground. Additionally, the tracking characteristics are measured by deploying the receiving station two-dimensionally on the ground. These patterns have distortions as a result of measurement errors. For this reason, we reconstruct the antenna pattern using the two-dimensional least-squares function and show that appropriate reconstruction is possible by selecting the optimum function. In addition, as a proposal for experiments on power transmission from satellites, we examined the effectiveness of "satellite rectenna radios" that operate unpowered radios using power from satellites.

In the frame of the project CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), DLR, JAXA and CNES develop a demonstrator for a reusable, vertical take-off, vertical landing rocket first stage. The need for reusability of launchers imposes a new set of loads and requirements to almost every part of the rocket. Former flight heritage does not cover the descent and landing phase sufficiently. This lack of information is currently part of many investigations all around the space industry. CALLISTO aims to gather flight data and technological knowledge to achieve such return missions. This paper focuses on the development of the fairing and presents the design, major FE analysis results and performed test activities to achieve a lightweight and reusable space structure. As there is no payload deployed, the fairing is connected to the vehicle for the whole flight acting as a primary structure. Analyses show, that most of the driving loads are induced at the descent phase. In particular the thermal environment during this phase is dimensioning for the CFRP sandwich structure, which is equipped with a cork TPS.