Crosslink radio occultation (RO) using multiple spacecraft is a promising method to observe the planetary atmosphere with higher spatial and temporal resolution than conventional RO measurements between a spacecraft and a ground station. In this paper, an optimal orbit configuration design method for crosslink RO is discussed. Orbit elements of two spacecraft are explored under two evaluation functions: values of observation and fuel costs for orbit injection. Then, generated Pareto optimal solutions are analyzed based on three categories classified by orbit characteristics, and we proposed an orbit design guideline to enhance observational value against fuel cost. The qualitative understandings for crosslink RO orbit design by this paper can contribute to future mission design.

Space membrane structures provide a large surface area while being lightweight and efficiently storable. Two types of deployment methods have already been demonstrated: using booms or centrifugal force. However, it is difficult to control the deployment force in high frequency, and the associated impact and vibration to the membrane structures pose risks for mission failure. This study proposes a new deployment method using electromagnetic force. This method flows electrical current on the membrane to deploy via electromagnetic force. While electromagnetic force can be manipulated by changing the electrical current, electromagnetic force is also affected by the membrane deployment behavior. Since electromagnetic force is weak, the influence of environmental forces on the deployment behavior becomes larger than in the previous methods. Thus, to achieve consistent electromagnetic force control, the deployment behavior should be understood. This study aims to reveal the possibility of deployment using the proposed method and investigate the deployment behavior in LEO with numerical simulation based on the multi-particle method. From the results, this research finds that the membrane deployment with the proposed method can be divided into three phases. Furthermore, this study reveals the relationship between the deployment behavior and electromagnetic and environmental forces in LEO.

The present paper proposes a decentralized trajectory optimization method for air traffic management including conflict resolution. The proposed method does not require an explicit exchange of tactical intent information with neighboring aircraft and infers it by estimating the objective function of the inverse optimal control problem based on observed trajectories. The method then solves a decentralized model predictive control (MPC) problem to approximately minimize the sum of the objective functions of all the concerned aircraft. Moreover, to make the calculation of the resulting non-convex MPC problem tractable, a novel convexification technique for quadratic equalities/inequalities is introduced. Through numerical simulations, the effectiveness of the proposed method is demonstrated.

Turbulence might affect aircraft operations and flight safety. In Japan, an index indicating turbulence intensity objectively and quantitatively, Eddy Dissipation Rate (EDR), is considered for introduction within 10 years. EDR is calculated from flight data and thus provides more precise information than conventional observations called PIREP reported by pilots in flight. To estimate turbulence probability, the Japan Meteorological Agency developed a turbulence index called TBindex. On the other hand, the Japan Aerospace Exploration Agency (JAXA) has been developing electronic flight bag software to assist pilots in making operational decisions using the TBindex. In this study, we evaluated the prediction accuracy of the TBindex using EDR as accurate observations. In addition, for exploring a more efficient usage of the TBindex, we investigated the relationship between TBindex and EDR using regression analysis and revealed it tends to differ among flight levels and seasons. This result shows that the software under development may be able to provide more accurate information on turbulence prediction by correcting TBindex values in accordance with the altitude and seasonal tendency and by using observations obtained during the flight in addition to TBindex.

In order to improve ion engine's performance, the neutralization performance with two field emission cathodes in an ion engine is investigated. The neutralization performance is evaluated by the potential difference between cathode and ground, using a 100μN class ion thruster developed at Kyushu University and two 50×50mm² field emission cathodes with carbon nanotube emitter. The potential difference between cathode and ground is not only determined by cathode electron supply capacity and the position of the cathodes but also foot print of the neutralizers, it would be due to the space charge limitation. That is, the potential difference between cathode and ground is improved with increase in total emission current, and that with a single field emission cathode at emission current of 6mA is -20V, on the contrary, that with two field emission cathodes is -12V.