佐伯 孝尚

The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu’s shape, mass, and geomorphology. Ryugu has an oblate ‘spinning top’ shape with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 g cm^–3, indicates a high porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu’s shape may have been produced if it once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identify a suitable sample collection site on the equatorial ridge.

The near-Earth carbonaceous asteroid 162173 Ryugu is thought to have been produced from a parent body that contained water ice and organic molecules. The Hayabusa2 spacecraft has obtained global multi-color images of Ryugu. Geomorphological features present include a circum-equatorial ridge, east/west dichotomy, high boulder abundances across the entire surface, and impact craters. Age estimates from the craters indicate a resurfacing age of <inline-formula><m:math xmlns:m="http://www.w3.org/1998/Math/MathML" overflow="scroll"><m:mrow><m:mo>≲</m:mo><m:msup><m:mrow><m:mn>10</m:mn></m:mrow><m:mn>6</m:mn></m:msup></m:mrow></m:math></inline-formula> years for the top 1-meter layer. Ryugu is among the darkest known bodies in the Solar System. The high abundance and spectral properties of boulders are consistent with moderately dehydrated materials, analogous to thermally metamorphosed meteorites found on Earth. The general uniformity in color across Ryugu’s surface supports partial dehydration due to internal heating of the asteroid’s parent body.

© 2018 IAA The Japan Aerospace Exploration Agency launched the asteroid sample return spacecraft “Hayabusa2” on December 3, 2014. Hayabusa2 will reach the C-type asteroid 162173 Ryugu in 2018, and return back to the Earth in 2020. Sample collections from three sites, four surface rovers deployment and a 4 MJ-class kinetic impact crater forming are planned in the 1.5 years of the asteroid-proximity operation. The mission objective of Hayabusa2 has three aspects, science, engineering and exploration, all of which would be expanded by the successful round-trip journey. The objectives and technologies used in this mission is not a direct solution for the future planetary defense, but should contribute to this field by increasing general asteroid knowledge and enhancing human capabilities of small body-surface access/roving/sampling/impacting. This paper describes the outline of the Hayabusa2 mission, overviews the kinetic impact technology as an example of planetary defense-related technologies and the current flight status after the two and a half years of the interplanetary cruise.

Hayabusa2 mission is the ongoing JAXA's sample and return mission to Ryugu asteroid. In late 2018, Ryugu was in superior solar conjunction. Therefore, the Hayabusa2 spacecraft experienced communication blackouts while leaving its hovering position of 20 km from Ryugu. In this article, the design of a safe conjunction trajectory is given in the Hill frame and then verified in the full-body. Two Trajectory Correction Manoeuvres (TCMs) are scheduled before and after the deep conjunction. A linear covariance analysis is shown together with the results of the Monte Carlo analysis to compute the stochastic Delta V at TCMs. Pre/Post-flight operation data are also compared.

© 2019, Univelt Inc. All rights reserved. Hayabusa2 mission is the ongoing JAXA’s sample and return mission to Ryugu asteroid. In late 2018, Ryugu was in superior solar conjunction. Therefore, the Hayabusa2 spacecraft experienced communication blackouts while leaving its hovering position of 20 km from Ryugu. In this article, the design of a safe conjunction trajectory is given in the Hill frame and then verified in the full-body. Two Trajectory Correction Manoeuvres (TCMs) are scheduled before and after the deep conjunction. A linear covariance analysis is shown together with the results of the Monte Carlo analysis to compute the stochastic ΔV at TCMs. Pre-/Post-flight operation data are also compared.

An optical navigation method for autonomous landing on asteroids using asteroid shape model is presented. Vertices of the shape model are tracked in the sequential images obtained by a monocular camera. The proposed method does not need the process of landmark detection or mapping. The pose of the spacecraft is estimated using particle filter, considering the dynamics around the asteroid. The performance of the developed navigation method is evaluated via numerical simulation; it is based on the touchdown rehearsal operation in Hayabusa2 Mission to show the effectiveness of the proposed method against actual asteroid exploration missions.

© 2018 IAA This paper presents the robust planning of the Hayabusa2-Ryugu proximity operation and landing site selection process considering unknown asteroid environment and the spacecraft constraints. The proximity operation scenario is described together with the relationship between the selection process and the in-situ observation. The mission constraints are summarized for the possible asteroid environment, including the rotation state, thermal condition and gravity.

© 2018, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved. Hayabusa2 is a sample return mission to the C-type asteroid 162173 Ryugu. Hayabusa2 was launched by the Japan Aerospace Exploration Agency in December 2014 and will arrive at the asteroid vicinity in the summer of 2018. Hayabusa2 will explore Ryugu for 1.5 years and return to the Earth in winter 2020. The entire flight period of Hayabusa2 is divided into 4 phases; (i)EDVEGA (launch to Earth gravity assist), (ii) Transfer (Earth gravity assist to asteroid arrival), (iii) Asteroid Proximity, (iv) Return (asteroid to Earth reentry). Different operations are required in each phase. Especially in the asteroid proximity phase, there are many critical events such as low-altitude observation, touching down, rover deployment and crater forming. There are some difficult characteristics in performing these critical operations from ground; navigation and guidance in the submeter accuracy against the microgravity environment of Ryugu, 40 minutes round-trip light time due to the 3.6 billion kilometers distance between Hayabusa2 and the Earth. We have developed a ground operation system to clear the characteristics. This paper presents the ground operation systems overview for Asteroid Proximity Operation to realize high quality operation for mission success.

© 2017 The Author(s). We report results of a laser link experiment between a laser altimeter called light detection and ranging (LIDAR) aboard Hayabusa2 and ground-based satellite laser ranging stations conducted when the spacecraft was near the Earth before and after the gravity assist operation. Uplink laser pulses from a ground station were successfully detected at a distance of 6.6 million km, and the field of view direction of the receiving telescope of the LIDAR was determined in the spacecraft frame. The intensities of the received signals were measured, and the link budget from the ground to the LIDAR was confirmed. By detecting two successive pulses, the pulse intervals from the ground-based station were transferred to the LIDAR, and the clock frequency offset was thus successfully calibrated based on the pulse intervals. The laser link experiment, which includes alignment measurement of the telescopes, has proven to be an excellent method to confirm the performance of laser altimeters before they arrive at their target bodies, especially for deep space missions.[Figure not available: see fulltext.]

The Japan Aerospace Exploration Agency launched an asteroid sample return spacecraft “Hayabusa2” on December 3, 2014 by the Japanese H2A launch vehicle. Hayabusa2 aims at the round trip mission to the asteroid 162173 Ryugu. Hayabusa2 successfully conducted the Earth gravity assist on December 3, 2015, and now the spacecraft is flying toward Ryugu with the microwave discharge ion engine as the means of propulsion. As of September 2016, 1346 h of the ion engine operation has been achieved as planned. Three touch downs/sample collections, one kinetic impact/crater generation, four surface rovers deployment and many other in-situ observations are planned in the asteroid proximity phase. The operation team will perform extensive operation practice/rehearsal using a hardware-in-the-loop simulator in the year 2017 to be ready for the asteroid arrival in the summer 2018.

Hayabusa2 is a sample return mission of JAXA launched on 3 December 2014. Hayabusa2 is the successor of Hayabusa, which returned samples from the asteroid Itokawa to the Earth. Although the design of Hayabusa2 follows that of Hayabusa, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of Hayabusa2 is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu. Hayabusa2 will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the Hayabusa2 mission.

The Small Carry-on Impactor (SCI) equipped on Hayabusa2 was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ∼1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process.

© 2017, Springer Science+Business Media Dordrecht. The Hayabusa2 mission journeys to C-type near-Earth asteroid (162173) Ryugu (1999 JU3) to observe and explore the 900 m-sized object, as well as return samples collected from the surface layer. The Haybusa2 spacecraft developed by Japan Aerospace Exploration Agency (JAXA) was successfully launched on December 3, 2014 by an H-IIA launch vehicle and performed an Earth swing-by on December 3, 2015 to set it on a course toward its target Ryugu. Hayabusa2 aims at increasing our knowledge of the early history and transfer processes of the solar system through deciphering memories recorded on Ryugu, especially about the origin of water and organic materials transferred to the Earth’s region. Hayabusa2 carries four remote-sensing instruments, a telescopic optical camera with seven colors (ONC-T), a laser altimeter (LIDAR), a near-infrared spectrometer covering the 3-μm absorption band (NIRS3), and a thermal infrared imager (TIR). It also has three small rovers of MINERVA-II and a small lander MASCOT (Mobile Asteroid Surface Scout) developed by German Aerospace Center (DLR) in cooperation with French space agency CNES. MASCOT has a wide angle imager (MasCam), a 6-band thermal radiator (MARA), a 3-axis magnetometer (MasMag), and a hyperspectral infrared microscope (MicrOmega). Further, Hayabusa2 has a sampling device (SMP), and impact experiment devices which consist of a small carry-on impactor (SCI) and a deployable camera (DCAM3). The interdisciplinary research using the data from these onboard and lander’s instruments and the analyses of returned samples are the key to success of the mission.

This paper describes a method of modeling general attitude dynamics of a nonspinning momentum-biased spacecraft under strong influence of solar radiation pressure. This model, called the "generalized sail dynamics model," can be applied to realistic solar sail spacecraft with nonflat surfaces and nonuniform optical reflectance. A coarse sun-pointing momentum-biased spacecraft is especially of interest, for which an approximate solution of the equations of motion is analytically derived. Stability and fundamental characteristics of momentum-biased spacecraft dynamics as well as theoretical relations with past dynamics models are discussed in detail. Furthermore, unique attitude motion predicted by the novel model is verified with flight data of the Japanese interplanetary probe, Hayabusa 2.

This paper describes a method of modeling general attitude dynamics of non spinning momentum-biased spacecraft under strong influence of solar radiation pressure (SRP). This model, called "Generalized Sail Dynamics Model", can be applied to realistic sails with non-flat surfaces that have non-uniform optical properties. A coarse Sun-pointing, momentum-biased sail spacecraft is especially focused, for which an approximate solution for the equations of motion is analytically derived. Stability and some other fundamental characteristics of momentum-biased sail spacecraft dynamics, as well as theoretical connections with the past representative sail dynamical models are discussed in detail. Furthermore, the unique behaviors predicted by the model are verified using flight data of the Japanese interplanetary probe Hayabusa2.

A new asteroid exploration spacecraft "Hayabusa2" as a follow on of "Hayabusa" was launched on 3rd of December 2014 from Tanegashima Space Center located in the south part of Japan. The planned missions of Hayabusa2 are round trip to the target asteroid "Ryugu", scientific observation of the asteroid, releasing small rover and lander to the surface of the asteroid for scientific and engineering purposes, releasing explosive called "Small Carry on Impactor" to the asteroid in order to make a crater on the surface of the asteroid and multiple times of touchdown including "pinpoint touchdown" toward the newly created crater in order to get "fresh" material underneath the surface of it. This paper show the recent result of operation in "cruising phase" such as Earth swing-by successfully conducted in December 2015. Then current status of detailed analysis for "Asteroid Proximity Phase" is provided such as the entire planning for proximity operation, global mapping and trajectory analysis for approach to the asteroid which could be essential for successful operations in this phase.

<p>DESTINY: the Demonstration and Experiment of Space Technology for Interplanetary Voyage, which is a candidate mission of Epsilon Launch Vehicle, plans to execute scientific observations using instruments with the mass of up to about 10 kg on the transfer and Halo orbit of the sun to earth Lagrangian point L1/L2 or on the fly-by orbit of near earth objects (NEO). Potential scientific objects include in-situ observation and remote sensing from these space are solar system explorations, such as, the observations of plasma and energetic particles around the terrestrial magnetosphere, inter-planetary and inter-stellar dust, and NEO. It is also considered to be useful for the pilot observations for future infrared, gamma-ray, and cosmic-ray space astronomical telescope in the deep space. Applied missions of DESTINY will be able to go to deep space with higher mass of payloads. Using the Epsilon Launch Vehicle, it will convey instruments of up to 50 kg to the space between Venus and Mars. DESTINY launched by the improved launch vehicle with the power of M-V rocket will carry payloads of up to 200 kg into the orbit of Venus and Mars. In these phases, Explorations for Venus, Mars, and multiple NEO, and astronomical observations from the deep space observatory will be realized by low cost deep space missions.</p>

<p>JAXA has developed a Jovian Trojan asteroid sample return mission using a solar power sail. Jovian Trojan asteroids are among the few remaining frontiers in our solar system and may hold clues to its formation and evolution. However, visiting Jovian Trojans is much more difficult than reaching near-Earth objects because of the large amount of fuel required to reach them. Moreover, large distance from the sun makes power generation difficult. Solar power sails offer an effective way of realizing such challenging exploration. This paper outlines a solar power sail spacecraft and discusses the design of a trajectory for a sample return mission to a Jovian Trojan asteroid. The time of flight is long, but a large payload can be delivered to the asteroid by using a solar power sail. Reducing the duration of a sample return mission is difficult, but it is possible for a one-way mission. This paper presents a trajectory design for such a one-way mission.</p>

Hayabusa2 is a current sample return mission of JAXA and it was launched on 3 December 2014. Hayabusa2 is the successor of Hayabusa, however, it is equipped with some new components. Small carry-on impactor (SCI) is one of the new components of Hayabusa2. SCI is a compact kinetic impactor and in the latter half of the proximity operation phase of Hayabusa2, the impact experiment will be performed. Because SCI has no attitude and orbit control functions, its impact accuracy depends on the separation accuracy. In this study, the results of the impact accuracy analysis are shown.

Copyright © 2016 by the International Astronautical Federation (IAF). All rights reserved. This paper describes the earth swing-by operation of Hayabusa2. Hayabusa2 is a Japanese interplanetary probe launched on December 3, 2014 to visit asteroid "Ryugu". It is a sample return mission like Hayabusa, but the spectrum type of the target asteroid is different from Itokawa, Hayabusa's target body. Itokawa is S-type asteroid but Ryugu is C-type asteroid. C-type asteroids are believed to contain more organic matter and hydrated mineral. Hayabusa2 is scheduled to reach Ryugu in the middle of 2018 and will perform an asteroid proximity operation for 1.5 years. Three touch downs for collecting the asteroids sample and one 2m class-crater generation by a kinetic impact are planned during the asteroid proximity operation. The collected sample will be brought back to the Earth by the re-entry capsule in 2020. Hayabusa2 is equipped with a high-specific ion engine system to enable the round-trip mission. The ion engine system can provide larger than 2 km/s delta-V with very small amount of xenon propellant. First one year after launch is an interplanetary cruise phase called EDVEGA (Electric Delta-V Earth Gravity Assist) phase. The transfer orbit to the asteroid is connected with the EDVEGA orbit by the Earth swing-by. After the launch, several ion engine commission operations have been successfully conducted and three long-term ion engine maneuvers were also conducted to direct the spacecraft onto the Earth swing-by corridor. The last two months before the swing-by was the precise navigation / guidance phase to the Earth swing-by. During this phase, trajectory correction maneuvers by the chemical reaction control system (RCS) were conducted. As a result, Hayabusa2 successfully performed the Earth swing-by on December 3, 2015 and it is now on its target orbit to the asteroid. This paper describes how the guidance / navigation operations were conducted around the Earth swing-by. A lot of science observation were also performed during this phase. This paper also shows the result of the science observations.

イプシロンロケットは2013年9月14日に惑星分光観測衛星「ひさき」の打上げに成功し,目標とした軌道投入精度を達成し,新規に開発した誘導制御系の性能を遺憾なく発揮した.イプシロン開発では,惑星探査機「はやぶさ」を投入したM-Vロケットの誘導制御系の性能を継承しつつ新たな技術革新にチャレンジし,M-Vの機能,性能をさらに向上させた誘導制御系を実現した.最終段には信頼性の高い低コストなスラスタを用いた液体推進系の小型ポストブースタ(PBS)を開発し,新たに導入した誘導則とともに軌道投入精度を飛躍的に向上させた.フライトソフトにはM-Vで蓄積した各種シーケンスや姿勢マヌーバ機能をユーティリティ化して搭載し,科学衛星ユーザ等の多様な要望に容易に対応できる機能を実現し運用性を高めた.

ソーラー電力セイル実証機「IKAROS」の運用は,IKAROSと地上局との距離が近い場合や通信環境に余裕がある場合には,地球周回の探査機と同様な運用が可能であるが,距離が遠くなった場合や通信環境に余裕がない場合には,深宇宙航行する探査機特有の運用を行う.本稿では,この運用(IKAROSの地上局,テレメトリ/コマンド運用,ビーコン運用,後期段階運用,探索運用)について概説する.

IKAROSとは宇宙航空研究開発機構(JAXA)が開発した小型ソーラー電力セイル実証機であり,2010年5月21日に種子島宇宙センターよりH-IIAロケット17号機によって打ち上げられた.IKAROSは将来の外惑星領域探査ミッションを想定してソーラーセイルおよびソーラー電力セイルを世界で初めて実証した.2011年以降も運用を継続し,数多くの成果をあげている.IKAROSは小規模プロジェクトのため,広報活動に関して,予算をほとんど割くことができない状況であったが,チームメンバーが創意工夫を凝らし,精力的に活動を行った.特にツィッターやブログを通して開発・運用の現場の様子をタイムリーに発信したことで多くのファンを獲得できた.また,TPSにも発信してもらったことでIKAROSの成果が世界中に知れ渡ることとなった.さらに,はやぶさ地球帰還との相乗効果もあり,日本の探査技術が大きく取り上げられる機会となった.本稿では,我々が取り組んできたIKAROSの広報・アウトリーチ活動全般について報告する.

An attitude model for a general spinning solar sail spacecraft under the influence of solar radiation pressure is presented. This model, called "Generalized Spinning Sail Model", can be applied to realistic sails with nonflat surfaces that have nonuniform optical properties. The unique behaviors predicted by the generalized spinning sail model are verified by actual operation of the Japanese spinning solar sail spacecraft IKAROS. It is shown how imperfections in the sail surface affect the attitude motion of spinning sails, and a compact mathematical model that can precisely reproduce the spin-averaged motion of the spinning sails is derived. The stability conditions and a reduced model that preserves the key characteristics of the generalized spinning sail model are also derived to reveal the unique properties of the attitude behavior of spinning sails.

A Japanese spacecraft, Hayabusa2, the successor of Hayabusa, which came back from the Asteroid Itokawa with sample materials after its 7-year-interplanetary journeys, is a current mission of Japan Aerospace Exploration Agency (JAXA) and scheduled to be launched in 2014. Although its design basically follows Hayabusa, some new components are planned to be equipped in Hayabusa2 mission. A Small Carry-on Impactor (SCI), a small explosive device, is one of the challenges that were not seen with Hayabusa. An important scientific objective of Hayabusa2 is to investigate chemical and physical properties of the internal materials and structures. SCI creates an artificial crater on the surface of the asteroid and the mother spacecraft observes the crater and tries to get sample materials. High kinetic energy is required to creating a meaningful crater. The SCI would become complicated and heavy if the traditional acceleration devices like thrusters and rocket motors are used to hit the asteroid because the acceleration distance is quite large and guidance system is necessary. In order to make the system simpler, a technology of special type of shaped charge is used for the acceleration of the impact head. By using this technology, it becomes possible to accelerate the impact head very quickly and to hit the asteroid without guidance system. However, the impact operation should be complicated because SCI uses powerful explosive and it scatters high speed debris at the detonation. This paper presents the overview of our new small carry-on impact system and the impact operation of Hayabusa2 mission. (C) 2012 IAA. Published by Elsevier Ltd. All rights reserved.

This paper describes achievements of the IKAROS project, the world's first successful interplanetary solar power sail technology demonstration mission. It was developed by the Japan Aerospace Exploration Agency (JAXA) and was launched from Tanegashima Space Center on May 21, 2010. IKAROS successfully deployed a 20 m-span sail on June 9, 2010. Since then IKAROS has performed interplanetary solar-sailing taking advantage of an Earth-Venus leg of the interplanetary trajectory. We declared the completion of the nominal mission phase in the end of December 2010 when IKAROS successfully passed by Venus with the assist of solar sailing. This paper describes the overview of the IKAROS spacecraft system, how the world's first interplanetary solar sailer has been operated and what were achieved by the end of the nominal mission phase. (c) 2012 Elsevier Ltd. All rights reserved.

In this study, we show the multiple revolution orbits design in Elliptic Restricted 3-Body Problem (ER3BP) of Sun, Earth and a particle 3-body system. For the deep-space observation, the location around L2 point is suitable because of the wide field of view to the outer space. In near future, some missions are planned to be putted into the Sun-Earth L2 point orbits. Depending on the mission requirements, the periodic orbits may not be the necessary condition. Therefore, the multiple revolution orbit closed in configuration space under arbitrary conditions are considered. Additionally, a preliminary calculation of the orbit maintenance is provided.

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.

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.

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.

This paper summarizes the guidance, navigation and control of the world&#039;s first solar power sail IKAROS. During the 1.5 years of its interplanetary flight, IKAROS has carried out the guidance, navigation and control experiments using the large solar radiation force generated by its 200 m2 solar sail. Since solar radiation pressure is the main controllable force for a solar sail, its modeling is the key factor for a successful guidance. A precise solar radiation pressure modeling for this spinning solar sail has been performed in order to support the navigation and guidance using the large membrane. Due to the complexity of the sail surface and shape, the refinement of the SRP model is done after the deployment in space with radiometric measurements. This solar sail navigation is also supported by the precise delta-DOR (Differential One-way Range) measurements. These in-flight demonstrations with IKAROS enable the future deep space exploration with solar sailing technique.

The Japan Aerospace Exploration Agency (JAXA) makes the world's first solar power sail craft IKAROS demonstration of photon propulsion and thin film solar power generation during its interplanetary cruise. The spacecraft deploys and spans a membrane of 20 meters in diameter using the spin centrifugal force. It also deploys thin film solar cells on the membrane, in order to evaluate its thermal control property and anti-radiation performance in the real operational field. The spacecraft weighs approximately 310kg, launched together with the agency's Venus Climate Orbiter, AKATSUKI on May 21, 2010. This paper presents the summary of development and operation of IKAROS.

The three-dimensional reaction wheel (3DRW) is a three-axis free rotor reaction wheel, which can achieve a compact and high integrity attitude control systems. In the system we propose, a spherical rotor is levitated without mechanical contact by gas bearings and rotated by the torque generated by magnetic fields. To realize the precise control of the rotor, it is important to understand the characteristics of spherical gas bearings such as pressure distribution, load capacity, stiffness and flow rate. Some previous works clarified them but few researches are there relating the use of gas bearings in the space. What is required for the space gas bearing is having the minimum robust characteristic against various small disturbances. It is more appropriate to adopt small-light air compressor which can provide the minimum air pressure and flow than big-heavy powerful one. In this study, the authors have developed a spherical gas bearing with a circular slot restrictor and analyzed its performance by experiments and numerical calculations. The result shows that this type of bearing can generate necessary floating force with low supply pressure and low flow rate, and that leaves the possibility to realize 3DRW system operated by a compact pump such as piezoelectric type.

In this paper, the attitude dynamics of IKAROS, which is spinning solar sail, are presented. The first mode model of out-of-plane sail deformation (FMM) and multi-particle model (MPM) are introduced to analyze the oscillatory motion of the spinning solar sail. Three oscillation modes are derived from the FMM. They are caused by the nutation motion of the main body, as well as the nutation motion and the out-of-plane oscillation of the sail. The precise attitude motion after sail deployment and reorientation using thrusters is calculated using the MPM considering thruster plume. The IKAROS flight data of the nutation angular velocities of the main body after sail deployment or reorientation using thrusters are nearly equal to the analytical data found using the FMM and MPM.

This paper shows the attitude operation results of Japanese interplanetary solar sail demonstration spacecraft IKAROS. IKAROS was launched on 21 May 2010(JST) aboard an H-IIA rocket, together with the AKATSUKI Venus climate orbiter. As IKAROS is the secondary payload, the development cost and period were restricted and the onboard attitude system is very simple. This paper introduces the attitude determination and control system. And as IKAROS is spin type spacecraft and it has the large membrane, the attitude control is not easy and it is very important to determine the long-term attitude plan in advance. This paper also shows the outline of the IKAROS attitude operation plan and its operation results.

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.

This paper describes an attitude determination strategy for spinner spacecraft based on the Sun and the Earth angles. This method realizes a complete spin vector determination using only one sun sensor. Thus this method is suitable for low cost, resource-limited spacecraft with a moderate attitude determination accuracy requirement. The method has been developed for and is actually used in IKAROS, which is a Japanese interplanetary solar sail demonstration mission. This paper introduces theoretical backgrounds of Sun-Earth based attitude determination and shows how the actual implementation was done in the IKAROS mission. Then the attitude determination performance achieved during the actual operation is evaluated.