In recent years, the design and performance of solar array paddles have become vital due to the increasing complexity of space missions. These paddles supply essential power for satellite operations, requiring high power generation capacity. Performance is evaluated using specific power (W/kg) and economic efficiency (W/$). To meet these demands, a new paddle structure incorporating concave-curved thin-film solar cells with STEM structures and cables has been proposed. This design enhances power generation through multiple sunlight reflections using mirrors, reduces solar cell attachment area, and maintains roll-up storability for economic efficiency. Traditional studies focused on two-dimensional sunlight incidence, but this research explores a three-dimensional approach, analyzing light behavior in detail using Monte Carlo ray tracing simulations. This method models numerous sunlight rays, accounting for interactions like reflection, refraction, and absorption. The simulation results were verified against Thermal Desktop software, which also uses Monte Carlo methods. However, parameter optimization remains a challenge. This study demonstrates the potential to meet future satellite power demands by incorporating three-dimensional light interaction characteristics. Future efforts will focus on improving simulation accuracy and optimizing design parameters to further enhance power generation efficiency.

Research is being conducted on nonlinear dynamic vibration absorbers (NDVAs) to suppress vibrations over a broader frequency range compared to traditional dynamic vibration absorbers (DVAs). Typical nonlinear springs can be categorized into two types: hardening springs and softening springs. In this study, we consider springs with cubic nonlinearity stiffness. The coefficient of the cubic term in the restoring force-displacement characteristic of nonlinear springs is defined as the strength of the nonlinearity. The vibration transmissibility of an NDVA with hardening spring decreases in the high-frequency range, while that of an NDVA with softening spring decreases in the low-frequency range. Using an approximate solution to the equations of motion for NDVAs discussed in previous studies, we investigate the phenomena occurring when the vibration transmissibility of the NDVA. Our investigation focused on the derivative of the primary system's amplitude with respect to the strength of the nonlinearity in the range of valid frequency. As a result, it was found that this derivative is negative within the range of nonlinear spring characteristics where the vibration does not diverge, except that the strength of the nonlinearity is large in hardening type NDVA. This indicates that as the strength of the nonlinearity increases, the vibration transmissibility of the NDVA decreases in the high-frequency range for the hardening type and in the low-frequency range for the softening type. Although this derivative is not negative in hardening type occasionally, this value is so small that the nonlinear characteristic is not sensitive to the vibration transmissibility on such situation.

Spacecraft are exposed to severe environments unlike those on Earth, including mechanical stresses such as vibration, acoustics, and shock during launch. In orbit, the vacuum necessitates meticulous thermal management, and challenges like damage from atomic oxygen, ultraviolet radiation, and cosmic rays are significant. The recent surge in lunar and planetary exploration adds demands for spacecraft to endure landing vibrations, adapt to different atmospheric conditions, and handle thermal and dust environments on planetary surfaces. While analytical methods like simulations are increasingly applied, verification still heavily relies on testing with actual engineering and flight models. Japan's space development is at a new turning point amid intensified global competition. Enhanced domestic support and investment have enabled private companies and universities to undertake large-scale spacecraft R&D, accelerating progress at an unprecedented pace. However, this rapid growth raises concerns about shortages in testing facilities and personnel, potentially hindering R&D and diminishing Japan's competitiveness. This paper reviews the current state of spacecraft environmental testing and examines the challenges in the context of Japan's expanding space activities.

In satellite-to-ground station communication, factors such as atmospheric effects, Doppler shifts, and interference from other signal sources make it challenging to evaluate the practicality of satellite transmission power and modulation schemes through ground testing alone. In this study, we replicated these challenging communication impairments using a simulator developed with GNU Radio and software-defined radios. We measured and compared the signal levels from the simulator and the actual signals from the satellite, demonstrating the validity of the simulated elements.

Furthermore, the simulator aims to support parameter selection for LoRa modulation to be used in the "Ten-Koh 3" microsatellite currently under development by the Okuyama Laboratory at Nihon University. For this purpose, we are working to implement functionality that outputs LoRa-modulated signals.

Nihon University and the University of Shizuoka are jointly developing the W6U (366 x 227.3 x 100 mm) nano-satellite ”PRELUDE”. PRELUDE aims at early prediction of earthquakes by elucidating the physical mechanism of electromagnetic phenomena (ionospheric electron density variations).This paper examines the thermal design of PRELUDE that satisfies the allowable temperature range of onboard equipment in all thermal environments that the satellite system may be subjected to during mission operations, taking into account the limited power and structural resources unique to CubeSat. In order to confirm that the design is satisfied, thermal mathematical models were constructed for both nodal analysis and Thermal Desktop, and the thermal design was evaluated under several conditions.

A safety review must be completed before a satellite can be launched. In the worst case, the dummy mass is launched instead of the satellite, or the launching schedule is postponed. However, it is difficult for academic satellite developers to ensure that their satellite systems meet safety review requirements because they are students without enough skills to understand the relationship between them. This research aims to clarify the connections between safety review requirements and CubeSat systems by visualizing the interrelationships. It introduces the Design Structure Matrix (DSM) to solve this issue. DSM can represent connections in matrix form, clarify the relationships between elements, and enhance user understanding. Moreover, this research focuses on the safety requirements for ISS release and the BIRDS satellite system as the subject of analysis. From this DSM, it was clear that the electrical power supply system is the most related to the requirements from the safety review. Also, the mission payload's material and circuit design can be included as standard or unique hazards. This presentation shows the relationship between safety requirements and CubeSat systems using the DSM and proposes a method to enhance comprehension of safety review details.

This paper newly introduces a gold-plated version of Zirconium Copper metal mesh for deployable reflector for X band. Based on the manufacturing technology of metal mesh for Ka band, a prototype of gold-plated Zirconium Copper metal mesh was evaluated. As a result, the mesh had electrical performance of reflection loss that is less than 0.5dB at X band and a mechanical performance of over 10% elongation.

This paper describes a feasibility study conducted on applying a reflector-based digital beam forming (DBF) synthetic aperture radar (SAR) to small X-band SAR satellites. The study assumes to use 3.6 m diameter deployable reflectors and DBF units (DBFU). Fan-fold deployable reflectors, which are researched and developed to apply for Ka-band geostationary communications satellites, are employed for this study. The DBFU is designed with a central frequency of 9.8 GHz and a band width of 1,200 MHz. With a reflector diameter of 3.6 m, an antenna tower capable of accommodating a 2 m-long stowed reflector was necessary. Based on this configuration, a structural mass of under 50 kg and the first natural frequency at 20.5 Hz were accomplished. An 8-channel DBF unit (DBFU) with a 1,200 MHz bandwidth was designed using FPGA technology, and it was confirmed that the required processing speed for DBF operations could be achieved. For the reflector, by setting facet sizes for 9.6 GHz, 1.6 mmRMS surface accuracy was achieved. Based on these results, the feasibility of a reflector-based DBF SAR system for a small X-band SAR satellite was confirmed.

JAXA has been researching the on-orbit assembly methods for large, lightweight space structures to realize a 30-meter-square planar antenna. The DEployable LIGHtweight planar antenna Technology demonstration (DELIGHT) mission is scheduled to demonstrate this novel assembly method in orbit. It will deploy two columns of four serially connected panels, each with a unique deployment and assembly mechanism. This presentation outlines the assembly technology and the design of the lightweight planar antenna. We also present the current development status of the proto-flight model of the DELIGHT system with a focus on deployment testing.