As number of microsatellites continues to increase every year, the demand for propulsion system is also expanding. As continuing to develop propulsion systems for microsatellites, chemical propulsion systems using low toxic propellants, commonly referred as green propellants, are emerging. This research team has been conducting research and development of a chemical propulsion system using 60wt% hydrogen peroxide (60wt%H₂O₂), which is relatively easy to handle, for microsatellites, called Microsatellite-Friendly Multi-Purpose propulsion system (MFMP-PROP). This paper reports the results of the fundamental evaluation of the performance of a valve injector that has been diverted from automotive/motorcycle to a space propulsion system to achieve an inexpensive and highly reliable propulsion system. The thruster was confirmed to operate as both mono- and bi-propellant mode, and its performance was evaluated.

This paper presents the development of a Functional Resonance Analysis Method (FRAM) network model to analyze the launch operations of various chemical rockets. This FRAM-based approach offers a systemic perspective for optimizing launch operations and for mitigating risks in complex aerospace systems. Functions that are necessary for the launch process, including stage assembly, electrical system tests, and countdown operations, were identified. Moreover, their mutual relations were defined. The resulting model represents high-risk and frequently used functions effectively, thereby providing insights into system performance variation and potential resonance effects. However, the analysis highlighted the need to incorporate additional functions related to ground safety and cyber incident management to enhance model completeness. Future improvements will be made to address these gaps to strengthen the model’s applicability. Additionally, this study demonstrated the necessity of exploring methods to improve launch system resilience, with specific examination of integrating a learning function to mitigate variation and to enhance operational robustness. An investigation into the effects of this learning function on network resilience is also planned.

The growing demand for Ka-band communications led Resolution 169 (WRC-19) to allocate additional frequencies to Earth Stations in Motion (ESIM) and establish technical requirements for their coexistence with terrestrial systems. To safeguard terrestrial services, Resolution 169 specifies per-aircraft limits on the permissible power flux density (PFD). Accurate estimation of the PFD at terrestrial base stations requires consideration of attenuation caused by the aircraft fuselage. This study evaluates the fuselage’s effect by comparing measured radiation patterns of an active electronically scanned array (AESA) antenna with equivalent isotropically radiated power (EIRP) values derived from the PFD limits set in Resolution 169. The fuselage reduces backlobe levels by up to 15.3 dB at 29.75 GHz, improving compliance with Resolution 169.

Given the recent rapid increase in the number of space objects, including space debris, in outer space, today, the establishment of proper governance for space activities in Earth's orbit has become a common agenda for all space-faring nations. For the time being, many countries, including the private sector, have been engaging in various efforts to establish national or regional Space Situational Awareness (SSA) capabilities as a foundational infrastructure to tackle Space Traffic Management (STM) and space debris issues. Now, we are facing the question: What kind of framework should we establish to achieve international cooperation and coordination among these SSA activities and systems? This paper conducts a preliminary study on the possible options and policy implications for considering the international cooperative framework for SSA by analyzing the features of existing international frameworks for global Earth observation and global navigation satellite system (GNSS). Based on the analysis, it is found that the preferences of leading actors, the flexible nature, and the participation of the private sector are important points for the future consideration of the framework.

In distributed space systems such as formation flying and constellations, relative orbit control is an essential technology. Thrusters are often used for this purpose; however, in low Earth orbit, aerodynamic forces can also be utilized. Unlike thruster-based control, aerodynamic control does not consume propellant, so the mission lifetime is free from propellant limitations. However, it cannot, in principle, increase orbital altitude, and the additional installation of aerodynamic control devices is instead expected to accelerate orbital decay. This paper investigates whether thruster-based control or aerodynamic control is more advantageous for relative orbit control from the perspective of mission lifetime. For thruster-based control, the operational duration is estimated through simulations assuming a flight-proven thruster suitable for small s atellites. For aerodynamic control, orbital decay is simulated for satellite con-figurations equipped with aerodynamic control paddles, and the feasible mission duration is estimated. These analyses are conducted across multiple classes of satellites to compare their mission lifetimes. As a result, the aerodynamic control paddle area and the scale of the relative orbit that make aerodynamic control advantageous over thruster-based control in terms of mission lifetime were clarified.

Small balloons provide an effective means of conducting in situ observations in the stratosphere. However, payload recovery has been challenging due to their passive and wind-dependent flight during both the ascent and descent phases. In this study, a parafoil-controlled payload module was developed to improve the recoverability of such payloads. The payload module consists of a parafoil with a 2.25 m wingspan and a control unit. To evaluate its performance, a balloon release experiment was conducted. The payload module was carried by a small balloon to an altitude of 4,522 m, where it was separated. After separation, the module glided under remote control. The mission was successfully concluded with a successful recovery in the designated sea area, establishing the feasibility of guided descent and demonstrating the potential for reliable payload retrieval. This manual control experiment serves as a proof of concept for future autonomous guidance systems, thereby expanding the technological scope of small-balloon missions.