船瀬 龍

Infrared sensor system is a major concern for inter-planetary missions in order to investigate the nature and the formation processes of planets and asteroids. Since it takes long time for the communication of inter-planetary probes, automatic and autonomous functions are essential for provisioning observation sequence including the setup procedures of peripheral equipment. Robotics technology which has been adopted on HAYABUSA2 asteroid probe provides functions for setting up onboard equipment, sensor signal calibration, and post signal processing. HAYABUSA2 was launched successfully in 2014 for the exploration of C class near-Earth asteroid 162173 (1999JU3). An optical navigation camera with telephoto lens (ONC-T), a thermal-infrared imager (TIR), and a near infrared spectrometer (NIRS3) have been developed for the observation of geology, thermo-physical properties, and organic or hydrated materials on the asteroid. ONC-T and TIR are used for those scientific purposes as well as assessment of landing site selection and safe descent operation onto the asteroid surface for sample acquisition. NIRS3 is used to characterize the mineralogy of the asteroid surface by observing the 3-micron band, where the particular diagnostic absorption features due to hydrated minerals appear.Modifications were required in order to apply robotics technology for the probe due to the difference of operation on satellites from robot operation environment. The major difference is time line consideration, because the standardized robotics operation software development system is based on event driven framework. The consistency between the framework of time line and event driven scheme was established for the automatic and autonomous operation for HAYABUSA2.

PROCYON (PRoximate Object Close flyby with Optical Navigation) is a 50kg-class micro-spacecraft developed by the University of Tokyo and the Japan Aerospace Exploration Agency (JAXA), to be launched in an Earth resonant trajectory at the end of 2014 as a secondary payload with Hayabusa 2 mission. The mission objective is to demonstrate low cost and applicability of a micro-spacecraft bus technology for deep space exploration and proximity flyby to asteroids performing optical navigation. This paper introduces the spacecraft and mission design for PROCYON, as well as, the operation strategy mainly for the deep-space cruising period

PROCYONは,超小型衛星による小惑星フライバイ探査ミッションを目的として,はやぶさ2のピギーバック搭載機会である2014年12月の打ち上げを目指している.超小型衛星による深宇宙探査ミッションは,大型衛星とは異なる信頼性基準,コストのバランスによって成立させる必要がある.特に搭載重量や発生電力の制約条件は大きく,従来の宇宙用通信コンポーネントの設計概念を大きく変えて積極的な民生部品の活用と小型軽量化に最適な技術の導入が不可欠である.本稿では,PROCYON通信系構成,並びに,各コンポーネントの詳細を紹介する.

In order to achieve high precision GNSS (Global Navigation Satellite Systems) positioning, accurate modeling of the disturbance forces acting on GNSS satellites, including Japanese QZS-1 (Quasi-Zenith Satellite-1), is essential to minimize the contribution of the satellite orbit and clock errors. This study focuses on the development of analytical non-conservative force models for QZS-1 precise orbit determination, especially solar radiation pressure (SRP) and thermal re-radiation pressure (TRP) forces. In order to evaluate the performance of the proposed analytical model, the acceleration profile obtained by the traditional empirical SRP model was used as a reference. Results showed that TRP was major error sources and should be modeled separately from SRP. A ray tracing study also showed that the shadow effect of the large L-band antenna cover of the QZS-1 was not negligible and should be treated properly in the SRP calculation.

Onboard signal processing system for infrared sensors has been developed for HAYABUSA2 for the exploration of C class near-Earth asteroid 162173 (1999JU3), which is planned to be launched in 2014. An optical navigation camera with telephoto lens (ONC-T), a thermal-infrared imager (TIR), and a near infrared spectrometer (NIRS3) have been developed for the observation of geology, thermo-physical properties, and organic or hydrated materials on the asteroid. ONC-T and TIR are used for those scientific purposes as well as assessment of landing site selection and safe descent operation onto the asteroid surface for sample acquisition. NIRS3 is used to characterize the mineralogy of the asteroid surface by observing the 3-micron band, where the particular diagnostic absorption features due to hydrated minerals appear.Since the processing cycle of these sensors are independent, data processing, formatting and recording are processed in parallel. In order to provide the functions within the resource limitation of deep space mission, automatic packet routing function is realized in one chip router with SpaceWire standard. Thanks to the SpaceWire upper layer protocol (remote memory access protocol: RMAP), the variable length file system operation function can be delegated to the data recorder from the CPU module of the digital electronics of the sensor system. In consequence the infrared spectrometer data from NIRS3 is recorded in parallel with the infrared image sensors. High speed image compression algorithm is also developed for both lossless and lossy image compression in order to eliminate additional hardware resource while maintaining the JPEG2000 equivalent image quality.

This paper describes a basic characteristic of a 7/8-GHz band circular stacked patch active integrated array antenna (AIAA) unit for solar sail embedding application. The proposed AIAA unit mainly consists of a 2×2 stacked circular patch array, two low noise amplifiers (LNAs) and two power amplifiers (PAs). The array has stacked structure for dual band operation. Moreover, the stacked patch array has orthogonal feed structure for better isolation characteristics between transmitter and receiver ports. Radiation patterns and S-parameters are evaluated by 3-D electromagnetic field simulation and measurement. © 2013 IEEE.

The present study proposes ... Features (i) stiffer for ground testing, (ii) Synchronous boom-membrane deployment, (iii) Resist launch vibration, (iv) Repeatable and simpler folding pattern, ... to be written!. Copyright© (2013) by the International Astronautical Federation.

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 shortage 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. As the result of the effort for the prediction, finally we acquire IKAROS after 9 months. This paper presents that the attitude and orbit prediction technique, while IKAROS was lost in space. © 2013 2013 California Institute of Technology.

IKAROSはJAXAが開発し,世界初の深宇宙ソーラーセイル航行を成し遂げたソーラー電力セイル実証機である.IKAROSの姿勢制御の観点での特徴は,機体全体がスピンすることによるスピン剛性でセイルの形状の維持とスピン安定を同時に得ることである.14m四方,代表厚み7.5μmという大面積柔軟構造物を有する機体を安定化し,かつ十分な制御性を有する姿勢制御を実現するために種々の工夫が施された.他方で,IKAROSは開発コスト制約を非常に厳しく課されたプロジェクトであり,姿勢制御系の簡素化と開発負荷の軽減が課題であった.結果として気液平衡推進系,太陽センサのみによる姿勢決定系など,独特の姿勢制御系構成となった.また,運用面では,迅速な運用実績の反映により,太陽光圧擾乱を逆用した省燃料の姿勢制御手法を実現した.本稿では,これらの点を中心にIKAROSの姿勢制御システムについて概説する.

本報告では,H22年5月に打ち上げられたソーラー電力セイル実証機IKAROSに搭載された薄膜発電システムの軌道上実験に関して述べる.ソーラーセイルの膜面上にa-Si太陽電池を用いた薄膜太陽電池アレイを搭載し,軌道上での展開及び発電実験を行った.太陽電池アレイは8個の発電ブロックに分けて搭載し,各発電ブロック間のばらつきは少なく,製造管理,収納及び軌道上での展開の影響評価が実施できた.ただし,打ち上げ前にフレキシブルハーネスの一部が不具合を起こしており,ハーネスの構造,管理には課題がある.発電特性は,初期特性は地上検証データと近い値を示しているが,時間変化の特性は若干劣化が大きくなる傾向が得られている.発電特性の継続的取得により,惑星探査機用薄膜超軽量発電システム開発のための知見を得る.

本稿は,世界初のソーラー電力セイル実証機IKAROSが打ち上げられてからおよそ2年間という期間に実証された,ソーラーセイルの誘導・航法に関する成果をまとめたものである.世界初となるソーラーセイルの軌道上での実際の航法・誘導において,光圧加速度・光圧トルクのその類稀なる大きさから,一般的な手法だけでは評価しきれない点が少なからず存在し,そのため,IKAROSの誘導・航法技術に関しては,いくつかの工夫がなされた.ここでは,航法技術に関して,セイルによって発生する光圧加速度を精密に計測するための推定法,及び評価結果を,また,誘導技術に関しては,光圧トルクによって発生する姿勢のドリフト運動を考慮した誘導法,及びその評価結果について紹介する.また,航法技術に関連して,IKAROSに搭載されたDDOR用のトーン生成器によって得られたデータの評価結果についても紹介する.

In the overall context of a solar sail mission in the vicinity of the Trojan asteroids swarm around the L4 Lagrange point, the purpose of this work is to find an optimal sequence of asteroids rendezvous that accommodates given mission constraints. A currently considered strategy to solve this problem will be presented and design choices will be outlined. A subset of the Trojan asteroids database is first extracted based on orbital elements considerations and a tree containing all the potential sequences is generated. A first set of pruning techniques is applied to the tree in order to quickly reduce the search space by several orders of magnitude. A global optimization method is then used: it combines a branch-and-bound approach and an evolutionary algorithm to find good sequence order, departure date, transfer and coasting durations. In order to enable a fast computation of potential transfer costs, the dynamics are linearized around L4 and the Delta Vs are computed analytically. Preliminary results show a drastic reduction of the search space along with a reasonable accuracy on the cost prediction. This method has been used to analyze a tour scenario starting from 588 Achilles and including three rendezvous; the final result provides a list of sequences of potential interest.

QZS-1 is the first satellite of Japanese Quasi-Zenith Satellite System (QZSS) launched in September 11, 2010. QZSS is a regional navigation satellite system, which provides the signals interoperable with GPS as well as integrity and correction information. The L-band experimental (LEX) signal broadcasted in L6 band (1278.75 MHz) contains high-precision corrections for GPS and QZSS satellite orbit and clock errors. QZS-1 is at an altitude of geo-synchronous orbit, where the solar radiation pressure (SRP) is the largest non-gravitational orbit perturbation acting on the satellite body and its solar panels. This paper describes newly proposed physics-based SRP models specially designed for the QZS-1 satellite and makes a comparison of the orbit determination accuracies with the conventional SRP models such as an empirical DBY model and a simple box-wind model. Although the orbit determination accuracy achieved by the empirical model is still much better than those obtained by the physics-based models, the newly proposed SRP models effectively reduce periodic acceleration errors from the conventional box-wing model and improve the orbit determination accuracy.

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 shortage 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. As the result of the effort for the prediction, finally we acquire IKAROS after 9 months. This paper presents that the attitude and orbit prediction technique, while IKAROS was lost in space.

Thermal infrared imager system is developed for HAYABUSA2, which is planned to be launched in 2014 and aims at sample-return from a C class near-Earth asteroid 1999JU3 considered to contain organic or hydrated materials. The system consists of a thermal-infrared imager (TIR) and a digital electronics, which is used not only for the scientific investigation of physical properties of the asteroid surface, but also for the assessment of landing site selection and safe descent operation onto the asteroid surface with in situ measurement.Since round trip communication time between the asteroid and the Earth is more than thirty minutes, onboard automatic data processing function and high speed data recording capability are provided to exploit the limited downlink capacity which is up to 32kbps.TIR adopts an uncooled bolometer with 320 x 240 effective pixels. Image operations as multiple images summation, dark image subtraction, and the compensation of dead pixels are processed onboard. A processing module is connected to sensor interfaces through SpaceWire in order to provide deterministic processing time. Data compression is also provided to reduce restriction on storage capacity and operation time, which provides the equivalent compression ratio as JPEG2000 in 1/30 processing time in average. A high speed data recorder is also connected through SpaceWire in 50Mbps in order to record TIR data in parallel with other sensor data.The modularity of SpaceWire enables to use as built devices for TIR and inherits the same design as the long-wavelength infrared imager developed for the Venus climate orbiter Akatsuki.

This paper describes design criteria for sail surface quality derived from requirements about attitude dynamics of spinning solar sail spacecraft. The method has been developed by an experience of the Japanese interplanetary solar sail mission IKAROS. The authors derived, in their previous work, a combination of a generalized spinning attitude model and a finite element model-based sail deformation analysis method to directly relate the sail surface wrinkling and the attitude disturbance via solar radiation pressure effect. Based on this work, this paper attempts to derive design criteria for the sail surface quality, which is useful for the mission analysis and the quality control in sail production. Specifically, this paper provides an acceptable deformation level as a function of scale length for given attitude stability requirements against the solar radiation pressure disturbance, which is then compared and verified by the post-flight analysis of IKAROS. © 2012 by Yuichi Tsuda.

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.

The authors had developed a propellant-free attitude control system for spinning solar sails that utilize only the solar radiation pressure and solar energy. This system implements specially developed thin-film reflectivity control devices (RCDs) that can electrically control their optical parameters such as reflectivity, and attitude control torque can be generated by switching the reflectivity of these devices synchronizing with the spin motion of the sail. In this paper, a precise attitude control torque model for the proposed system was derived considering arbitrary sail deformation. The derived torque model revealed three-axis controllability of the system, that is, the system can generate arbitrary three-dimensional attitude control torque. We further analysed the model and it was found that the switching control of RCDs can change the dynamical property' of natural spiral attitude motion observed for spinning solar sail. The proposed propellant-free attitude control system was demonstrated by the world's first solar sail demonstrator IKAROS and the on-orbit attitude control results showed the validity of the derived torque model. Copyright © (2012) by the International Astronautical Federation.

In this paper we present a feasibility study of solar sail artificial equilibrium solutions close to an asteroid. This research is part of the in-progress effort by J AX A to design a mid-size solar power sail to rendezvous with Jupiter and its trojan asteroids. The idea of maintaining a stationary position only using solar radiation pressure is attractive, but several practical restrictions must be considered for use in a real mission. We describe the equilibrium solution surfaces in 3-dimensional space for various asteroid sizes, while keeping the baseline acceleration of the sail constant. These solutions are found in the context of Hill's problem with a point-like asteroid in a circular orbit. Different sail reflectivity indices are tested and the corresponding equilibrium solutions are shown. Finally, we present preliminary estimates of the time and At required to move from a solar sail equilibrium to a traditional hovering position powered by impulsive or ion thrusters. Copyright© (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.

本稿では,小型ソーラー電力セイル実証機IKAROSのセイル展開方式として採用した,遠心力展開方式について, JAXAにて著者らが行ってきた研究開発を概説する. IKAROSは世界に先駆けてJAXAが実施したソーラー電力セイル技術の宇宙技術実証であり,宇宙機全体のスピンによる遠心力を利用してセイルの展開・展張をするという独特な方式を採用している.著者らは,軽量かつスケーラブルなセイル展開システムとして遠心力展開方式を採用し,研究開発を行ってきた.本活動は, 2002年にJAXA内に発足したソーラーセイルワーキンググループが中心となり,全国の多数の大学研究機関とともに行ってきたものである.最終的な目標はφ50m級のソーラー電力セイルを実現することにあり,φ20m級のセイルを搭載したIKAROSはその最終段階の宇宙技術実証試験と位置付けられたものである.ここでは,本研究開発活動の主要な柱である遠心力展開技術について紹介し, IKAROSプロジェクト発足以前に著者らが行ってきた主要な試験プロセスと数値シミュレーション技術について概説する.

本稿は,世界初のソーラー電力セイルであるIKAROS(Interplanetary Kite-craft Accelerated by Radiation Of the Sun)のソーラーセイル膜面の構成,その製作法,そして実際の製作の流れについて述べたものである.IKAROSのソーラーセイル膜面は,2種類のポリイミドによるベースフィルム上に,薄膜太陽電池や液晶デバイスをはじめとする各種デバイスを搭載する構造となっている.差し渡し20mの大きさを持つIKAROSのソーラーセイル膜面は,多数の試作モデルの製作を通じて確立した製作法により,ハンドメイドで製作された.その後,IKAROSは2010年5月21日に打ち上げられ,続く2010年6月9日に軌道上でソーラーセイル膜面の展開を完了した.展開後に撮影されたカメラの画像から,ソーラーセイル膜面は亀裂が発生することなく完全に展開できていること,ソーラーセイル膜面を構成する各構成要素が所定の機能を果たしていることなどが確認されている.また,その後の運用により,IKAROSのメインミッションの他に,各種デバイスの経年劣化に関するデータも取得できている.

A fuel-free attitude control system for a spinning solar sail which utilizes solar radiation pressure was developed. This system consists of thin-film devices attached to the sail that electrically control their optical parameters such as reflectivity, and the attitude control torque is generated by switching their optical parameters synchronizing with spin motion. Attitude control torque model for a sail of arbitrary shape and deformation was derived. The control system was implemented for Japanese interplanetary solar sail demonstration spacecraft IKAROS and the on-orbit attitude control performance was evaluated.

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 method of evaluating sail quality utilizing in-flight attitude behavior of spinning solar sailer IKAROS. Since the successful deployment of the sail, IKAROS has received SRP which strongly affects both translational and rotational motion of the spacecraft. The authors have derived the "Generalized Spinning Sail Model (GSSM)" to reproduce observed unique attitude behavior of IKAROS. Following the previous work, this paper attempts to relate the GSSM with sail quality such as sail shape and flatness. An optical FEM model is constructed to evaluate the precise SRP effect on the spacecraft, and some candidates of deformed sail shape is reproduced which is consistent with the observed attitude motion. We also conclude by the in-flight attitude behavior that the surface roughness of the IKAROS sail is 0.33% at minimum.