森 治

Copyright © 2018 by the International Astronautical Federation (IAF). All rights reserved. The solar power sail mission OKEANOS, planned to be launched in 2026, aims for sample return from a Jovian Trojan asteroid. In this mission, propagation delay (100min) is longer than that of Hayabusa2 (60min). Moreover, it is difficult to get sufficient information to make a success of the image-based navigation used in the previous mission. Another GNC method is required under the condition. This paper proposes an image-based on-board GNC method.

© 2018 Univelt Inc. All rights reserved. Attitude dynamics and control of spinning solar sails are investigated considering the flexibility of sail membranes. Attitude maneuver of solar sails is, in many cases, performed using thrusters. In most studies, the attitude motion is analyzed assuming that the spacecraft is a rigid disk. However, the sail membrane deforms during attitude maneuver due to flexibility. This may cause coupled vibration between the spacecraft main body and sail membrane. This study presents an analysis model of spinning solar sail attitude dynamics considering sail deformation, based on modal analysis.

The 28th Workshop on JAXA Astrodynamics and Flight Mechanics 2018 (July 30-31, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

The 28th Workshop on JAXA Astrodynamics and Flight Mechanics 2018 (July 30-31, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

The 28th Workshop on JAXA Astrodynamics and Flight Mechanics 2018 (July 30-31, 2018. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (JAXA)(ISAS)), Sagamihara, Kanagawa Japan

© 2018 Univelt Inc. All rights reserved. It is generally known that attitude of spacecraft having angular momentum on the spin axis moves like a vortex due to the influence of solar radiation pressure. Taking advantage of this motion, this paper proposes attitude control methods using biased (pseudo) equilibrium point. Slight change of the equilibrium point leads to stabilization of the motion. As the merit, only constant input achieves this proposed method. The purpose of this study is to verify the usefulness of the control method by performing numerical analysis on the stability of attitude motion.

© 2018 Univelt Inc. All rights reserved. Solar power sail technique was demonstrated in the IKAROS mission. However, unexpected phenomena were confirmed. The membrane surface of IKAROS has deformed to a shape that was not flat. In the shape change of the film surface, it is known that the whole membrane surface changes greatly like an umbrella shape or a saddle shape depending on the warping direction of the thin film solar cell. Objection of this study is to clarify mechanism of influence on solar radiation pressure torque due to warp of membrane device and its solution method. Therefore, the shape of the overall membrane surface is clarified by using a simple FEM model and the SRP torque with respect to the shape is calculated, and the mechanism of the overall shape change in warpage and its influence is clarified. As a result, the influence on SRP is related to membrane surface stiffness and warped direction and it was found that it is best that the membrane is warped in the radial direction and its outermost stiffness is high.

© 2018 Univelt Inc. All rights reserved. In recent years, a large space film structure having a thickness of several micro and a shape of several to several tens of meters attracts attention, and various storing methods have been studied. Considering the thickness of the film surface at the time of winding before launching, there is a problem that circumferential difference occurs inside and outside of the folded film surface. In order to solve this problem, a method of solving the difference between the inner and outer circumference by predicting the inner / outer circumferential difference arising from the film surface and the thickness of the device and managing the phase has been proposed. On the other hand, the point that the target value for adjusting the phase is unknown and empirical was pointed out, and as a result of adjusting the phase, the wave-like slack that occurred caused the unevenness of the film thickness in the circumferential direction. In this research, we derive target value of phase management analytically, compare with experiment, and verify.

© 2018 IEEE. Microwave components, prototypes of 4×4 transmitting active integrated antenna array(AIAA) and 2×2 receiving array with direction of arrival function operating at the X-band were demonstrated in this paper. For the components of the satellite on-board tracking system, a wideband and high gain low noise amplifier (LNA) as well as the compact planar antenna were fabricated using thin substrates. High isolation between the transmitting signal and the receiving signal was achieved for the good satellite tracking system. Good agreement on measured antenna patterns with the theoretical ones was obtained.

© 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. As fuel-free attitude control devices for spacecraft, we introduce Liquid Crystal Devices (LCDs). LCDs consist of multiple thin layers (∼ 150 µm thick in total) including Polymer Dispersed Liquid Crystal (PDLC) and a base film that has microstructure with aluminum deposited on it. By applying voltage, reflectivity of the surface of LCDs changes as the PDLC is directed to the electric field, and applying Solar Radiation Pressure (SRP) changes accordingly. In addition, the microstructure changes the angle of reflection only when voltage is applied such that incident light is reflected on the aluminum on it. These mean that LCDs can control both the magnitude and direction of reflection electrically, and three-degree-of-freedom attitude control can be realized by multiple LCDs mounted on a single plane controlling SRP. As light is diffracted on the microstructure and optical interference occurs, and PDLC has polarization effect, reflection on LCDs is a complex phenomenon and it must be understood for the design to realize desired performance. In this paper, we introduce basic reflection principles and a manufacturing method, and confirm them by making prototypes and measuring the distribution of luminous intensity. The performance of prototypes of LCDs is estimated based on the measurement. The results indicate validity of the reflection principles and the usefulness of LCDs considering the future view as attitude control devices.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Performance of solar sails largely depends on their attitude motion. Thrust vector of a solar sail is determined by its relative attitude to the Sun. Meanwhile, there exist some requirements on its attitude, for example, to secure enough solar power and ground communication. Therefore, conventional solar sail missions have strong constraints on attitude motion. This is because conventional solar sails assume flat sail membranes to avoid some unexpected deformation. This assumption leads to the fact that the geometry of the spacecraft is limited within two dimensions. This paper introduces a mission design scheme for spinning solar sails by actively controlling the shape of the sail membranes. The active shape control extends solar sails to three-dimensional structures, and hence the two-dimensional constraints can be removed.

Copyright © (2017) by International Astronautical Federation. All rights reserved. The authors are currently developing a novel attitude control device for solar sails. The device is called Advanced Reflectivity-Control-Device (A-RCD) which can change the optical properties between diffuse reflection and obliquereflection. This device is mounted on the solar sail's membrane and can control the torque perpendicular to the membrane. The A-RCD is composed of microstructured film and polymer dispersed liquid crystal (PDLC), and these structures cause the strong diffraction when the light propagates in the device. Simulating such light propagation is indispensable to evaluate the performance by using computer calculations, which is inevitable if one tries to achieve the optimum design via parametric studies. Besides, the ability to simulate the light propagation in the A-RCD will give designers new insights into the A-RCD design. In this context, we will introduce the simulation method for the A-RCD in this paper.

The total electric power consumption of heaters in a spacecraft has to be controlled in order not to be in short. In conventional system, a server communicates with each heater and controls the total power. In this system, the time to communicate with heaters depends on the number of heaters and the time to develop a spacecraft is long. This paper proposes the autonomous distributed system which does not need a server. This system enables the control where the time to communicate does not depend on the number of heaters and the time to develop a spacecraft is short. This paper demonstrates that it is possible to control power consumption and temperature of heaters by both a simulation and an experiment. In the experiment, ZigBee, which is a wireless unit, is used to broadcast from the transmitter to the heaters.

The total electric power consumption of heaters in a spacecraft has to be controlled in order not to be in short. In conventional system, a server communicates with each heater and controls the total power. In this system, the time to communicate with heaters depends on the number of heaters and the time to develop a spacecraft is long. This paper proposes the autonomous distributed system which does not need a server. This system enables the control where the time to communicate does not depend on the number of heaters and the time to develop a spacecraft is short. This paper demonstrates that it is possible to control power consumption and temperature of heaters by both a simulation and an experiment. In the experiment, ZigBee, which is a wireless unit, is used to broadcast from the transmitter to the heaters.