For CubeSats, power balance design is important for their physical size limitation of electrical power subsystems (EPS) including solar array paddles (SAP) and batteries (BAT). Efficient analysis within short development periods, a characteristic of CubeSats, is also necessary. To address these challenges, we developed an integrated software platform that enables efficient power balance analysis, accommodating changing analysis settings during design stages and operation scenarios. However, the setting parameters such as component power consumption measured in a ground test have uncertainties due to differences ing round testing and integration configurations. The platform model also has its errors with reality for simplification of platform calculations. Therefore, it is essential to compare the analysis results with on-orbit measurements and utilize the findings to improve the platform’s ability to simulate real operation conditions. In this paper, we present a case study of the 6U satellite SPHERE-1 EYE, where we evaluated the power balance for BAT charging and mission scenarios using the platform. Conservative margins were set considering uncertainties in power consumption and BAT internal resistance. By comparing the results with on-orbit measurements, we assess the feasibility of the designed scenarios and discuss the utilization and potential improvements of the power analysis platform.

In this paper, differences in the characteristics of the flow field at Mach 2 of a rectangular intake at a 5-degree sideslip angle were investigated, depending on the exit nozzle opening ratio. The investigations were conducted by wind tunnel tests under the same conditions with those of the numerical analysis to study the distribution of static pressure and Mach number, as well as the shock wave structure. When the intake is given a sideslip angle, the compression and expansion wave are generated from the side wall tips. This effect made the static pressure distribution asymmetric, especially when the NOR　(Nozzle Opening Ratio; dimensionless quantity representing engine nozzle opening area) was small. The left-right asymmetry of the Mach number increased with decreasing NOR, and the expansion area was subsonic throughout, while a supersonic region existed near the throat in the compression area. For the external shock wave structure, the detached shock wave generated from the tip of the expanding sidewall became stronger as the NOR decreased. The flow rate in the intake also varied with NOR, with a smaller NOR resulting in extremely low air flow in the expansion area.

In order to obtain a trajectory with minimum fuel consumption, we have to solve an ℓ¹-optimal control problem. In the authors’ previous study, the ℓ¹-optimal Newton method has been proposed to solve this problem, but it deals with only a toy example. In this paper, we use the ℓ¹-optimal Newton method to design a more practical trajectory for spacecraft. Specifically, we design a transfer orbit from a low Earth orbit to a low lunar orbit with minimum fuel consumption in the Bicircular Restricted Four-Body Problem of the Earth, the Moon, the Sun, and the spacecraft. In the ℓ¹-optimal Newton method, it is necessary to estimate an appropriate initial solution, and we use the genetic algorithm to estimate it in this paper. In the numerical example, we confirm that a sparse control input can be obtained using the proposed method and that the obtained trajectory consumes less fuel than that obtained using the conventional method.

The rising quantity of debris in Earth orbit could trigger Kessler Syndrome, an uncontrolled growth in the number of debris objects. Laser ablation could be one part of a holistic solution for the orbital debris problem for removing <1 cm diameter debris. In ablative laser orbital debris removal, a remote laser vaporizes or delivers impulse to remove targeted objects from orbit. This experimental study seeks to collect data to assess whether laser ablation can impart sufficient impulse to effectively remove orbital debris. Materials representing a significant fraction of the overall debris mass were chosen as targets including aluminium, copper, nickel, phenolic, steel, and titanium. A ~100 microsecond duration pulsed Nd:YAG laser beam was focused to ablate these targets in a vacuum chamber at ~10^-2 Pa. The threshold fluence for ablation was measured for each material. Imparted impulse was measured for each shot to calculate momentum coupling coefficient. Optical profilometry was used to calculate removed mass and thereby construct specific impulse and mass per energy. The data are used to assess achievable delta-v for a corresponding range of debris particle masses and to document propulsion parameters for a set of debris analogous materials to support future work in laser orbital debris removal. The range of delta-v implied by the results supports the idea that removal of some size classes of Earth orbital debris particles using laser orbital debris removal could be viable. Technical challenges remain in delivering high fluence to orbit to remove debris.

Hot fire tests including flame radiation and acoustic measurements were performed in a single-element rocket combustor with large optical access (255x38 mm) for sub- and supercritical injection conditions. Three test campaigns were conducted with the propellant combination of liquid oxygen and hydrogen (LOX/H₂), liquid oxygen and compressednatural-gas (LOX/CNG), as well as liquid oxygen and liquefied natural gas (LOX/LNG) at conditions relevant for mainand upper-stage rocket engines. High-speed imaging of the flame in blue radiation wavelengths (capturing CH* when natural gas was the fuel) was conducted. For the analysis of the flame-acoustic interaction, these measurements are related with the interpolated acoustic pressure distribution in the chamber.While three load points (LPs) feature high-amplitude, self-sustaining oscillations of the longitudinal acoustic resonance modes, one LP is intermittently unstable and two LPs are stable. Three different regions of interest (ROIs) were used to calculate flame transfer functions (FTFs) from the 2D imaging data, each increasing successively in their extent. While the phase difference between the radiation intensity and acoustic pressure is consistent for all three ROIs, the gain values differ. The largest ROI including the complete extent of the optically accessible region provided gain values qualitatively most consistent with expected distributions.

The Taiki Aerospace Research Field in Hokkaido, Japan, is a crucial hub for the Japan Aerospace Exploration Agency’s scientific balloon operations, with three telemetry antennas playing a pivotal role in supporting these operations. The antennas can measure the balloon’s position and receive telemetry data. In contrast, GPS receivers carried in the balloon’s payload are the primary means of obtaining the balloon’s position via telemetry data. The antenna pointing direction obtained using electric-field-strength tracking provides essential backup for GPS balloon positioning since it does not require receiving and demodulating telemetry data. Our study has identified significant errors in the direction of the antenna pointing when analyzing GPS data via telemetry. For instance, previous balloon operations revealed systematic errors of approximately 0.4 degrees in azimuth, corresponding to a position error of 0.7 km at a distance of 100 km. We developed an automatic system to track satellite signals and correct pointing errors to address this inaccuracy. Traditional error prediction models proved challenging since the antenna-pointing error has a complex dependence on the pointing direction. Our study uniquely demonstrated that calibration models—such as Radial Basis Function interpolation and neural networks—combined with satellite tracking data can reduce the pointing error during balloon tracking for the first time. When applied to balloon-flight data, these models significantly reduced the systematic errors in both azimuthal and elevation angles, marking a novel advancement in balloon tracking systems.

ISAS/JAXA has been conducting research and development on the reusable sounding rocket with air-breathing engines called New Sounding Rocket. Its propulsion system is Air Turbo Rocket for Innovative Unmanned Mission (ATRIUM) engine, which combines an air-turbo engine and a rocket engine. A three-dimensional supersonic inlet for the rocket was designed for Mach 2.0 based on a Busemann inlet. The flow field and the performance of the designed inlet were investigated at the design and off-design points by conducting wind tunnel tests and CFD simulations. At the design point with a freestream Mach number of 2.0, a shock wave formed near the inlet entrance induced flow separation and reduced the inlet performance. Compared to the theoretical values in the critical state, the mass capture ratio and the total pressure recovery were reduced by about 0.2 and up to 0.41, respectively. As for the off-design characteristics, at Mach number of 1.5, the mass capture ratio was significantly reduced due to larger spillage flow by the shock wave formed near the entrance of the inlet. At Mach number of 2.5, the total pressure recovery became smaller because the total pressure loss due to the terminal shock wave was larger than that at the design point. It was concluded that the flow path of the designed inlet would need to be modified to improve its performance, considering the influence of the boundary layer.

In recent years, the number of CubeSat launches has increased, with significant advancements in attitude control accuracy. However, due to limited development time and human resources, CubeSat projects are often launched with insufficient reliable attitude determination and control algorithms. To enhance reliability in CubeSat development with limited resources, cost-effective, reusable Software-In-the-Loop Simulator (SILS) and Hardware-In-the-Loop Simulator (HILS) environments are necessary. Traditionally, ground testing environments have been tailored to specific missions, making them difficult to reuse and often inaccessible to external users. By developing an open-source SILS and HILS environment, this research addresses these limitations, promoting broader applicability. Using these reusable environments, we present simulation results for a 1U AOCS (Attitude and Orbit Control System) module developed in collaboration with the University of Tokyo, Seiren, and JAXA. Furthermore, we discuss the attitude control results of the 6U satellite SPHERE-1 EYE, equipped with this module, confirming the successful performance of the algorithms during on-orbit operations. We plan to integrate our AOCS module into ONGLAISAT (ONboard Globe-Looking And Imaging Satellite), with a scheduled launch in 2024. We explore potential advancements in our ground testing environments for future missions.

The University of Tokyo has been developing two 6U CubeSats. One satellite is named “SPHERE-1 EYE” in collaboration with Sony Group Corporation and JAXA launched on January 3rd, 2023, whose main mission is to let users operate the satellite to take their original photos or videos. The other is “ONGLAISAT” collaborating with ArkEdge Space Inc. and TASA, whose main mission is to perform the Earth remote sensing, which was released from the International Space Station (ISS) on December 9th, 2024. Those two satellites use S-band for telemetry and command communication, and X-band for mission data downlink at high speed. Additionally, they have an LPWA transceiver to perform a Store & Forward (S&F) mission. While each of these transmitters and receivers has its unique role, they have the potential to work as a redundant system to supplement a specific functionality. In this paper, we explain the installed communication modules, discuss the application of the redundant system for 6U CubeSat, and show the results of the on-orbit demonstration.

The accuracy of thermal analysis is important when conducting satellite thermal design, and it is greatly affected by the accuracy of the thermal model. Thermal models have many parameters, such as thermal conductance and surface optical properties. For conventional medium and large satellites, these parameters are generally calibrated based on thermal vacuum test results. After that, thermal analysis is performed using the thermal model under multiple conditions to guarantee that the temperature of each component is kept within the allowable temperature range with appropriate margins. This process was used for the thermal design of the two 6U CubeSats, SPHERE-1 EYE and ONGLAISAT, both of which share a common bus system. However, nanosatellites have different characteristics from medium and large satellites, such as stronger thermal coupling between components due to their small size. We evaluated the accuracy of these two nanosatellite thermal models by comparing on-orbit temperature data with analytical predictions, and we verified that the conventional thermal design process is also effective for nanosatellites. Our findings indicate that these thermal models, calibrated from thermal vacuum test data, could predict on-orbit temperatures to within 5 degrees Celsius for most components. Additionally, comparing the analytical and on-orbit temperatures for SPHERE-1 EYE revealed that there was little temperature margin on the high-temperature side of the AOBC. To address this, we implemented an additional heat path, which is discussed in detail.

Understanding plasma detachment in a magnetic thrust chamber for laser fusion rocket is an important issue for thrust generation. Many previous studies have demonstrated that the cross-field transport of electrons is driven by electric field fluctuations. However, the relationship between electron detachment and electric field fluctuations in laser fusion rockets remains unclear. In this study, the plasma behavior in the magnetic thrust chamber was investigated using a full particle-in-cell simulation code. By comparing the velocity increments caused by electric and magnetic fields, it was revealed that electric field fluctuations contribute to electron detachment. A fast Fourier transformation was conducted in two regions; high-intensity electric field was observed to identify the instabilities of electric field. The dispersion relations of the electric field fluctuations show two types of features with an intensity of ∼10^7‐8V/m: parabolic and linear, which qualitatively agree with the dispersion relations of the several plasma waves, including Langmuir, ion acoustic, Alfven, and magneto acoustic waves.

This paper presents in-orbit operation of 6U CubeSat “OMOTENASHI” which aimed to be the world’s smallest moon lander. The CubeSat was launched aboard NASA’s SLS Artemis-1 rocket on 16 Nov. 2022. However, due to an anomaly, it lost power during the first contact pass. At the time of writing, efforts are ongoing to detect an RF signal from OMOTENASHI. This paper provides an overview of the mission, spacecraft configuration, the cause of the anomaly, and details of the ongoing recovery operation.

Disaster mitigation essentially requires the use and analysis of geospatial information appropriate to the special characteristics of the areas. The basis of disaster mitigation requires recognizing the inherent characteristics of the archipelago that cause disaster risk, and utilizing and analyzing geospatial information appropriate to the particular characteristics of the region.This study focuses on the Chubu and Kanto regions, mainly the Greater Tokyo Area. We used satellite images, geological maps, and other sources to select structurally weak areas (blocks of topographical contours such oceanic undersea troughs, river channel, and lineaments) that could be natural disaster predispositions as “teaching patterns” to search for areas with similar characteristics. 1)We have experimentally created a triangular fractal(topographical contour) regional characteristic map, based on the multi-directional action of the conflicting plates, which forms a belt-shaped structural and geological zone around the accretionary complex. In the process, we found a) areas with similar topographical contours are not necessarily in sync with the geological type, but are distributed in a parallel and periodic manner, and b) the metropolitan area is located and developed on unstable ground on the edge of the fractal. 2) Social disaster predispositions are spread over natural disaster predispositions. Predispositions were integrated and taken into consideration, for example, heavy rainfall caused by recent environmental changes. The areas affected by expected earthquakes, such as the Nankai Trough earthquake, were also included in the assumptions. a) In addition to areas of existing concern, these are areas of urban land cover change that are prone to liquefaction. b) It was found that there is concern about areas with high population and social infrastructure along the old riverbed that runs along the tectonic line. 3) We examined how our approach, based on the geospatial information and its analysis, could be useful for disaster mitigation measures.

Dammam is the largest city of the Eastern Province in Saudi Arabia with a population of 1.25 million as of 2020. The area was originally a fishing hamlet. The area's transformation began with the discovery of oil in 1938. The Kingdom of Saudi Arabia, today, is integrating network infrastructure and industrial facilities with the natural environmental conservation policies. The plans include town greening for sound living and public architectures for citizens. This study is a survey of land use pattern change and greening in the area during last 10 years from 2013 to 2022 by Landsat-8 imageries, while considering the long-term development process as a background.

The wake of two co-rotating vortex generators (VGs) was investigated using particle image velocimetry in a low-speed wind tunnel. The model had a rectangular shape with an aspect ratio of 4. The height was 20 mm, which was determined to be equal to the local boundary layer thickness at the model position. The spacing between the two VGs was varied (40, 70, 80, or 120 mm). The angle of each VG was set to 20 degrees. Two cross sections downstream of the VGs (160 and 724.8 mm downstream of the trailing edge, denoted as the near and far fields, respectively) were used for the particle image velocimetry measurement. It was found that two separate vortices were emitted from each VG in the near field, even for a small VG spacing (e.g., 40 mm). These vortices eventually merged into a single vortex in the far field due to the interaction between them. Under this interaction, the vortices are attenuated more rapidly compared to that produced by a single VG, for which there is no interaction between the vortices.