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Currently, several polar explorations of the Moon are planned, because it has been suggested that water ice might be present in the lunar polar region based on remote sensing observation of the lunar surface using a neutron spectrometer and visible to infrared spectrometer. However, the precise amount and state of the water ice are still unknown. At the Japan Aerospace Exploration Agency (JAXA), we are also studying exploration of the lunar surface for resources, especially cold-trapped volatile such as water ice using a rover. Volatile materials are expected to be useful for future human activity on the Moon and there is strong interest in the origin and concentration mechanism of the water ice. Additionally, the polar regions are among the best candidates for long-term activity because of their long sunlight duration. To realize the mission, we are currently developing various technologies peculiar to exploration of lunar polar regions. This paper details the present status of the Japanese Lunar Polar Exploration Mission.

In geostationary Earth observation satellite system with high-resolution optical system under conceptual study phase developed by Japan Aerospace Exploration Agency (JAXA), one of its main products for users is a video with one fps captured by the telescope and the optical sensor; however, there have been few examples of satellite video with high-rate fps, especially in geostationary satellite. A satellite video has instability of the video sequences caused by an undesired disturbance of the satellite. In this study, we propose the video stabilization method corresponding to various satellite imagery characteristics, using feature point matching and bundle adjustment with eliminating outliers by using RANdom SAmple Consensus (RANSAC). Moreover, we adopt a polynomial approximation to smooth global motions of all video frames. We demonstrate the video stabilization using the experimental video captured by the helicopter. Moreover, the performance test result shows that the proposed method can stabilize the satellite video less than one pixel accuracy. In addition, we discuss various issues specific to a satellite imagery, for example, moving cloud.

This paper presents the results of a conceptual study of an Earth observation system. The new system represents a technical breakthrough in larger telescope aperture, which is necessary to improve spatial resolution. The system makes it possible to improve temporal resolution while maintaining a practical spatial resolution. The observation system was designed to have a latency of 30 minutes from the observation request until data delivery. The mission study emphasized the system's need to immediately assess the situation when a natural disaster occurs and thus reduce human suffering. Due to the required spatial resolution, the optical system needed to have a 3.6 m aperture. A synthetic aperture optical sensor with a segmented primary mirror was investigated and adopted. The segmented-mirror optical system was the most technically challenging and was investigated using a full-scale one-segment prototype to evaluate the feasibility and identify technical risks. This paper presents the tentative design of the sensor and satellite system and reports on the technical demonstration and the proposed geostationary observation system.

Accepted: 2013-07-23, 資料番号: SA1004508000

資料番号: SA1004691000

While analyzing membrane dynamic characteristics, Multi Particle Method (MPM) has several advantages than Finite Element Method (FEM). This paper presents the influence of spring allocation on the analytical value of flexural vibration using MPM. Two MPM models, one is using parallelogram element and the other is using rectangular element, and FEM model as a reference are used for comparison of the accuracy evaluations. Flexural vibration phenomenon is selected for the comparison of the eigenvalue analysis under applying a shear force upon rectangular membrane. Analytical accuracies of the eigenvalue of the membrane flexural vibration are found to be very much dependent on the shear force value and the spring allocation of the analytical model of MPM.

Accepted: 2011-02-19, 資料番号: SA1003628000

Solar Power Sail Demonstrator ”IKAROS”, which is a spin-type solar power sail, has been successful in a technology demonstration in space. During the period of the operation, the stretched shape of IKAROS was expected to be a flat shape. But the pictures taken by the monitor cameras revealed that the sail became an unexpected shape because of a curving of the thin-film solar cells. It was also confirmed that “windmill behavior” which constantly reduces the spin rate. In this study, it is suggested that the control method of the windmill torque with the shape control evens in the range of curving of thin-film solar cells. For instance, a twist angle is given to each petal by changing the tether arrangement of the main body in order to control the direction of the windmill torque. This method is expected to save the large fuel to fix the windmill torque under a severe weight request. In addition, the validity of the control method is evaluated by a FEM analysis which is specialized to the thin-film analysis.

This paper discusses the deformation properties of the solar sail IKAROS membrane to identify the possible causes of the phenomena observed by the flight data: mechanics of higher out-of-plane stiffness of the IKAROS membrane. Two possible causes are hypothesized in this paper; the bending stiffness increased by the curvature of thin-film solar cells, and the deformation mode changed by the curvature. Although the second moment of area of the sail membrane is calculated by the natural vibration analyses, the effects of the bending stiffness increased by the curvature on the out-of-plane displacement is small. The effects of the deformation mode on the out-of-plane displacement is examined by geometrically calculating the relationships between the sensitivity of the margin in a circumferential length to the displacement. The results indicate that the sensitivity becomes small as the curvature becomes large. Thus, the high out-of-plane stiffness of the IKAROS membrane can be induced by the increased bending stiffness and by the changed deformation mode due to the curvature of the solar cells.

This paper identifies the possible causes of two phenomena observed in the membrane of the solar sail IKAROS: its nonflat shape and high out-of-plane stiffness. IKAROS’ flight data showed that the sail was significantly nonflat. In addition, the out-of-plane deformation of the membrane was smaller than that predicted preflight by numerical simulations, which indicates higher out-of-plane stiffness than expected. This study hypothesized that the initial deformation of the membrane could have been induced by the curvatures of the thin film solar cells and the reflection control devices attached on the sail. The effects of the curvatures on the sail shape were examined through geometrically nonlinear finite element analyses of a 1/4 IKAROS membrane with shell elements. The analysis results indicated that the on-orbit IKAROS membrane could be nonflat owing to the propagation of wrinkles throughout the membrane induced by the curvature of the thinfilm components. Furthermore, the out-of-plane deformation of the sail under solar pressure became very small when the entire sail was wrinkled, which explains IKAROS’ on-orbit phenomena.

The world’s first solar sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) which is operated by Japan Aerospace Exploration Agency (JAXA) lost communication with the ground station due to the power short-age on December 24, 2011. In order to acquire IKAROS again after the power comes back, we immediately initiated to predict the attitude and orbit for the spacecraft.

In the post operational phase of spin type solar sail “IKAROS”, a slow-spin operation and a reverse-spin operation were conducted to acquire basic knowledge of mechanics of sail membrane. The flight data indicates that the sail membrane kept its shape against the solar radiation pressure even with low centrifugal force.

The Japan Aerospace Exploration Agency (JAXA) makes the world’s first solar power sail demonstration of photon propulsion and thin film solar power generation during its interplanetary cruise by IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). It deployed and spans a membrane of 20 m in diameter taking the advantage of the spin centrifugal force. It accelerates and controls the orbit using solar radiation pressure successfully. This is the first actual solar sail flying an interplanetary voyage. This paper presents the summary of development and operation of IKAROS.

Hiraku Sakamoto∗, Shogo Kadonishi, Yasutaka Satou, Hiroshi Furuya, Tokyo Institute of Technology, Tokyo 152-8552, Japan Yoji Shirasawa, Nobukatsu Okuizumi, Osamu Mori, Hirotaka Sawada, Japan Aerospace Exploration Agency, Kanagawa 252-5210, Japan Jun Matsumoto, University of Tokyo, Tokyo 113-8656, Japan M. C. Natori, Waseda University, Tokyo 169-8555, Japan Yasuyuki Miyazaki Nihon University, Chiba 274-8501, Japan and Masaaki Okuma Tokyo Institute of Technology, Tokyo 152-8552, Japan

ecently, a variety of solar sail spacecrafts using thin large membranes have been developed in US, Europe and Japan. In Japan, centrifugally deployed solar sails have been mainly investigated 1 . A solar power sail demonstration spacecraft “IKAROS” was developed by Japan Aerospace Exploration Agency and was launched on May 21th, 2010 by H-IIA launch vehicle. 2,3 Figure 1 shows an overview of “IKAROS” in space. The square solar sail with 20 meters in diagonal and 7.5 micrometers in thickness was successfully deployed by centrifugal force using no extendable booms. The sail consists of four trapezoidal petals which were folded up into strips and rolled up around the spacecraft in stowed configuration. The deployment of the membrane consists of two stages. In the first stage, the strips are quasistatically reeled out. In the second stage, the strips are dynamically unfurled. Since on-ground dynamic deployment experiments of the large membrane are impossible, small-scale experiments and numerical simulations are necessary to predict the deployment dynamics. In this paper, a deployment experiment of a smallscale square membrane similar to “IKAROS” is conducted in a vacuum chamber and corresponding numerical simulations are performed by employing a spring-mass system model. The deployment behavior is discussed and the results of the experiment and simulations are compared to examine the validity of the simulations.

Hirokata Sawada Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Osamu Mori 2 Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Nobukatsu Okuizumi Japan Aerospace Exploration Agency, Kanagawa, 252-5210, JAPAN Yoji Shirasawa University of Tokyo, Tokyo, JAPAN Yasuyuki Miyazaki Nihon University, Chiba, 274-8501, JAPAN Michihiro Natori Waseda University, Tokyo, 169-8555, JAPAN Saburo Matunaga Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiroshi Furuya Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN Hiraku Sakamoto Tokyo Institute of Technology, Tokyo, 152-8552, JAPAN

The Solar Sail “IKAROS” (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) , which is the first solar sail on orbit, consists of 20m diagonal length square membrane made of 7.5μm thickness polyimide film. The sail membrane is deployed by centrifugal force due to spinning motion of the spacecraft. The wrapping fold is applied to realize stable deployment property. The manufacturing process of the large membrane with the folding techniques are described in detail.

IKAROS is the Japanese deep-space solar sail technology demonstration mission launched in 2010. IKAROS is a spinner spacecraft with the 20m-span solar sail kept extended by the centrifugal force. During its solar sailing flight from Earth to Venus, IKAROS showed a unique attitude behavior due to solar radiation pressure attracted on the sail. This paper proposes a generalized model of spinning sail-craft, which clearly explains the attitude behavior observed in IKAROS. Then it is shown that this behavior has a clear dependency on the sail shape and the optical property distributions on the sail. We show the estimation results of the on-orbit sail shape using this new model.

The small solar power sail demonstrator Ikaros successfully deployed its sail by a nominal sequence, which consists of two stages. However, in case of anomaly of the deployment mechanism, a one-step dynamic deployment of the sail might be employed as a contingency plan. This paper proposes a spin-up control scheme that enables the one-step deployment of Ikaros’s sail, and evaluates the controlled responses using a numerical multi-particle model.

1 Post-doctoral Researcher, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 2 Assistant Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 3 Professor, Department of Aerospace Engineering, 7-24-1 Narashinodai, Funabashi, Chiba, Japan. 4 Assistant Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 5 Graduate Student, Department of Aeronautics and Astronautics, 4-1-1 Kitakaname, Hiratsuka, Kanagawa, Japan. 6 Assistant Professor, Institute of Space and Astronautical Science, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 7 Post-doctoral Fellow, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 8 Associate Professor, Department of Built Environment, 4259-G3-6, Nagatsuta, Midori-ku, Yokohama, Japan. 9 Associate Professor, Department of Mechanical and Aerospace Engineering, 2-12-1 Ookayama, Meguro-ku, Tokyo, Japan. 10 Visiting Professor, Faculty of Science and Engineering, 55S-608, 3-4-1 Okubo, Shinjyuku, Tokyo, Japan. 11 Professor, JAXA Space Exploration Center, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa, Japan. 52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference 19th 4 7 April 2011, Denver, Colorado AIAA 2011-1890

This study aims at finding structural parameters as well as control laws that enable spin-stabilized spacecraft to deploy large membranes or cable-webs in a single step. If the structures/controllers are not properly designed, the deployed elements may re-wrap around the hub after deployment, which may cause entanglement; in addition, the nutation dynamics of the system may become unacceptably large during/after the deployment. In order to develop a reliable strategy for single-step deployment, this study carries out a series of three-dimensional transient analyses of spin deployment, using a simple analytical model that allows for the nutation dynamics of the spacecraft. The analytical model consists of a rigid body and four cables with tip masses. The analysis results lead to the proposal of the structural/controller-design criteria. Finally, the applicability of the proposed design criteria is evaluated using a more practical solar sail model, in which membranes are modeled as mass-spring networks.

The Japan Aerospace Exploration Agency (JAXA) is studying the feasibility of using the solar power sail as a new propulsion engine for deep space exploration missions. In this paper, the sail shape and equipment layout for missions utilizing small-sized solar power sails are proposed. The two-stage deployment method of the sail is also proposed. The sail need to be deployed statically at the first stage, and two types of deployment mechanisms are introduced. On the other hand the second stage of the deployment can be performed dynamically, and the oscillating motion of the membrane is converged by tethers connecting the membrane to the main body. The deployment motions are analyzed by numerical simulations using multi-particle models in order to verify the deployment. They are compared with the results calculated by finite element method models. The numerical simulation results are discussed from the technological viewpoint of the sail deployment dynamics and mechanisms.

資料番号: SA1160297000

資料番号: SA1160216000

This study estimates the effect of creases, or plastic wrinkle lines, on the out-of-plane stiffness of solar sails. A method to simulate the crease effects using reduced-order finite-element (FE) models is proposed, and is applied to a practical solar sail architecture. A detailed crease shape is determined by a geometrically nonlinear FE analysis using a simple model first; the effect of creases is then replaced by beam elements. This method substantially reduces the computational effort required for the FE analysis of a solar sail model. The result suggests the significant impact of creases on membrane's out-of-plane stiffness when the tension level in the membrane is small., 資料番号: PA1510010000

Japan Aerospace Exploration Agency (JAXA) are planning an outer solar system exploration and sample return mission from a Jovian Trojan asteroid using a 3000 m2 solar power sail. The difficulty of this mission is a severe restriction on the weight; only 300 kg is allocated for sampling and returning to Earth. In this weight, fuel for trajectory and attitude control, sampling mechanism, re-entry capsule, and other systems required to return to the Earth are included. In this paper, a preliminary analysis of this sample return mission is conducted. Three scenarios for sampling are proposed; sampling with a 3000 m2 solar power sail, with a detachable small solar power sail using electric propulsion systems and with a small probe using chemical propulsion systems. The mission analysis shows that the most feasible configuration is to conduct the sampling with the 3000 m2 solar power sail using an extension mast., 資料番号: PA1510011000

Piecewise Straight Fold is proposed for large solar sail membranes to simultaneously realize the high packaging efficiency and the simple folding. The fold pattern is based on Spiral Fold to reduce the deviation of the fold line, which improve the packaging efficiency. In addition, the fold pattern consists of piecewise straight fold lines, which approximate the Spiral Fold line, in order to simplify the folding. A simple manufacturing process of Piecewise Straight Fold is developed based on the Z-fold membrane. The preliminary experimental results show the feasibility of the Piecewise Straight Fold and its simple manufacturing process, where the high packaging efficiency is also verified. The wrapping fold experiments for the solar power sail membrane is demonstrated by using the Piecewise Straight Fold. In the wrapping fold experiments, the applicability of the Piecewise Straight Fold to the solar power sail membrane is verified., 資料番号: PA1510012000

資料番号: SA1005043000

The small solar power sail demonstrator IKAROS was developed and launched in 2010 by JAXA and deployed its large membrane successfully. Through IKAROS's on-orbit operation, one of the most critical problems was a sail's shape imbalance during the sail deployment sequence. This paper focuses on the evaluation and consideration of the sail's imbalance through high vacuum experiments using a scale-down sail model. The experimental results obtained using the specially designed rotating mechanism and a small scale model lead to a hypothesis of the reason for the IKAROS's imbalanced deployment. The experimental results are extrapolated up to IKAROS's scale, using dimensionless analyses.

資料番号: SA1004852000

資料番号: SA1004855000

資料番号: SA1005035000

Japan Exploration Agency (JAXA) launched a powered solar sail “Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS)” on May 21, 2010. One of the primal technologies demonstrated at IKAROS is the spin-deployment of the sail whose diameter is 20 m class. After the launch, two-step deployment operation was performed and successful expansion of the sail was confirmed. This paper shows the flight data and observed dynamic motion during the deployment. At the quasi-static first stage deployment, the spin rate of main body shows little oscillation after each step and then damped quickly. The damping ratio of the spin rate after a later step of deployment is estimated by curve-fitting to be 0.0127. At the dynamic second stage deployment, the nutation motion is maintained within ±1.5 deg/s and the spin rate of main body is converged quickly about 60s after the deployment start. These flight result and observed dynamic motion during the deployment are compared with the results of numerical simulations using multi-particle model. These results show that the multi-particle model can simulate the global behavior of membrane sufficiently except the dumping motion of in-plane oscillation between the main body and the expanded membrane.