佐伯 孝尚

This paper presents IKAROS extended missions. IKAROS entered its extended operation phase at the beginning of 2011. In the extended operation, the spin rate was decreased to observe the deformation of the sail under low centrifugal force environment. On Oct. 18, 2011, IKAROS transferred to the reverse spin to enhance the knowledge about the effect of stiffness of membrane against the solar radiation pressure. We investigated the change of the attitude motion by the reverse spin mission. At the end of 2011, IKAROS moved to hibernation mode because the Sun angle was increased. We searched for IKAROS considering the attitude and orbital motion during hibernation. On Sep. 6, 2012, we succeedcd in tracking IKAROS which came out of hibernation. A solar power sail can be a hybrid propulsion system with a solar sail by activating the ultra-high specific impulse ion engines with the power generated by thin film solar cells. This paper also introduces an advanced solar power sail mission toward Jupiter and Trojan asteroids via hybrid electric photon propulsion.©2012 by the International Astronautical Federation.

「ソーラーセイル」は,太陽光の圧力をセイルに受けて宇宙空間を航行する宇宙帆船であり,燃料なしで推進力を得ることができる.一方,「ソーラー電力セイル」は,薄膜太陽電池をセイルの一部に貼り付けて,発電も同時に行う.ソーラー電力セイルはソーラーセイルにより燃料を節約できるだけでなく,大面積の薄膜太陽電池を利用して,太陽から遠く離れた場所でも必要電力を確保できる.この電力を用いてイオンエンジンを駆動すれば,光子加速と合わせたハイブリッド推進が可能となる.JAXAではこれを踏まえてソーラー電力セイル探査機による木星圏探査計画を提案している.この計画のリスク軽減のフロントローディングとして開発されたのが,小型ソーラー電力セイル実証機「IKAROS」であり,世界で初めてソーラー電力セイルを実証することに成功した.本稿では,IKAROSのミッションおよびシステムの概要を説明し,開発・運用について紹介する.

It is well known that the thrust force of the solar sail due to the solar radiation pressure is changed by the orientation of the sail with respect to the Sun direction. Therefore, the orbit of the solar sail can be controlled by changing the attitude of the spacecraft. In this study, we consider the spinning solar power sail IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which succeeded to become the world's first flight solar sail in orbit. The IKAROS attitude, i.e. the spin-axis direction is nominally controlled by the rhumb-line control method. By utilizing the solar radiation pressure (SRP) torque, however, we are able to change the direction of the spin-axis only by controlling its spin rate. This is because the spin axis direction relates to the balance between the angular momentum of spinning and the SRP torque. Thus, we can control the solar sail's orbit by controlling the spin rate. The main objective in this study is to construct the orbit control strategy of the spinning solar sail via the spin rate control.

This paper describes a modeling of attitude dynamics of spinning solar sail spacecraft under influence of solar radiation pressure (SRP). This method is verified and actually exploited in the attitude and trajectory guidance operation of Japanese interplanetary solar sail demonstration spacecraft IKAROS. IKAROS shows a unique attitude behavior due to strong SRP effect. This paper introduces a new generalized dynamics model called Generalized Spinning Sail Model (GSSM), which clearly explains physics behind the observed phenomena with only three parameters. Precise understanding of attitude dynamics through the GSSM led to 6 months of world first interplanetary trajectory guidance of solar sail-craft toward Venus. The GSSM also contributed to realize a zero-fuel spin axis maintenance for most of the flight path before the Venus flyby. In this paper, an overview of IKAROS attitude and trajectory control operation in the cruising phase, derivation of the proposed model and its implementation to the actual IKAROS operation are shown.

This paper introduces a new attitude control system for a solar sail, which leverages solar radiation pressure. This novel system achieves completely fuel-free and oscillation-free attitude control of a flexible spinning solar sail. This system consists of thin-film-type devices that electrically control their optical parameters such as reflectivity to generate an imbalance in the solar radiation pressure applied to the edge of the sail. By using these devices, minute and continuous control torque can be applied to the sail to realize very stable and fuel-free attitude control of the large and flexible membrane. The control system was implemented as an optional attitude control system for small solar power sail demonstrator named IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun). In-orbit attitude control experiments were conducted, and the performance of the controller was successfully verified in comparison with the ground-based analytical performance estimation. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.

JAXA launched the world's first deep space solar sail demonstration spacecraft "IKAROS" on May 21, 2010. IKAROS was injected to an Earth-Venus trajectory to demonstrate several key technologies for solar sail utilizing the deep space flight environment. IKAROS succeeded in deploying a 20 m-span solar sail on June 9, and is now flying towards the Venus with the assist of solar photon acceleration. This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS. © 2011 Elsevier Ltd. All rights reserved.

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. Copyright © 2011 by Yuichi Tsuda.

In this paper, the attitude dynamics of IKAROS, which is spinning solar sail, is presented. Multi Particle Model (MPM) and First Mode Model of out-of-plane deformation (FMM) are introduced to analyze the out-of-plane oscillation mode of spinning solar sail. Considering the thruster configuration of IKAROS, the force on main body and membrane by thruster plume as well as reaction force by thruster are integrated into MPM. The attitude motion after sail deployment or reorientation using thrusters can be analyzed by MPM numerical simulations precisely. The out-of-plane oscillation of IKAROS is governed by three modes derived from FMM. FMM is simple and valid for the design of attitude controller. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

This paper describes a method of modeling attitude dynamics of spinning solar sail spacecraft under influence of solar radiation pressure (SRP). This method is verified and actually exploited in the operation of Japanese interplanetary solar sail demonstration spacecraft IKAROS. MAROS shows a unique attitude behavior due to strong SRP effect. This paper shows a new attitude model of spinning sail, which is verified by flight data of MAROS. It is also shown that the model proposed in this paper has a direct relation with the Generalized Sail Model.

The instruments and actuators in the attitude control system of small spacecraft are restricted in weight and space, and need to be reduced in weight and size. The rhumb line control strategy is one of the most popular schemes in reorientation of spin-stabilized spacecraft, since it requires only a spin sun sensor and a single axis reaction control system. By being combined with active nutation control, rhumb line control can reorient the spin axis of the spacecraft to any direction. To verify the control strategy, we manufactured an attitude controller and demonstration experiments were conducted using a motion table at ISAS/JAXA. This paper reviews the configuration of the controller and the outlines of the experiments, and evaluates the control performance. The same type of controller was installed in the Solar Sail Subpayload Satellite (SSSAT) launched in September 2006. An attitude control experiment in orbit was not conducted because of trouble with the satellite, but new control logic for the SSSAT was implemented for the attitude controller. This paper also reviews the control logic of the SSSAT.

Miniature space GPS receivers have been developed by means of automobile-navigation technology. We expanded the frequency sweep range in order to cover large Doppler shift on orbit. We tested the performance in low earth orbits by means of a GPS simulator. The range error caused by the receiver is measured to be 0.9m in RMS. The receiver is tolerant for 20krad radiation. Receiver was on-boarded on INDEX (“REIMEI”) satellite, which was launched in 2005. Cold start positioning is confirmed repeatedly to finish within 30min on orbit. The short term random error of GPS positioning is as large as 1.5m for PDDP = 2.7 on orbit. The range error due to the receiver is 0.5m RMS from the flight data. These results on orbit are consistent with the simulation results by means of a GPS simulator. This miniature space GPS receiver is promising as an inexpensive space GPS receiver in commercial market.

In recent years, there has been impending interest in the formation flying with many satellites. Multiple satellite system enhances the missions' flexibility with less total mass and cost, and realize some missions that were impossible with a single satellite. At the Institute of Space and Astronautical Science (ISAS/JAXA), the plasma and magnetic field observation missions with several satellites is under investigation. The mission under consideration is designated as SCOPE(GEOTAIL-II). The observation area of the SCOPE mission is twenty or thirty earth radii away from the center of the earth where the geomagnetic field has interaction with the energetic particles from the sun. Therefore its orbit becomes highly elliptic. In the observation area, the formation of plural satellites is requested to constitute a polygon that assures the high spatial resolution observation. This study show the orbital design method for the SCOPE mission. The frozen property that maintains high spatial resolution near the apogee is found feasible for elliptic orbit. Numerical examples are presented with practical illustrations.

多くのフォーメーションフライトミッションでは衛星群は適切な相対位置関係を維持することが求められる．現在衛星フォーメーションフライトに関する相対航法，誘導制御に関する研究が盛んに行われている．しかしながら，それらの研究の多くは，複数衛星をある幾何的な配置に誘導，維持するための燃料消費を前提とした積極的な制御に関する研究である．本来は燃料消費を抑制しミッション寿命の長期化を図るという意味でも，制御をすることなく衛星間の相対位置を受動的に，または自動的に維持したいという要求があるのだが，そのような研究はかなり稀である．また，過去のフォーメーションフライト関連の論文は慣性系での運動を扱ったものや，軌道運動を考慮したとしても円軌道周りの線形化された簡単なHillの方程式を扱ったものがほとんどである．しかし，実際の衛星ミッションは円軌道のみとは限らず，むしろ楕円軌道が必要とされるものも多い．そこで本研究は，楕円軌道上で軌道制御を積極的に行うことなく衛星群の相対位置関係を維持する軌道の設計法について扱った．軌道設計の際の解は解析的に得られ，結果は相対位置関係をよく保つものであり有意であることが分かった．