吉川 真

This paper reports the results of an analysis of the Mars impact probability for the Hayabusa-2 spacecraft to comply with the COSPAR planetary protection requirements. Since Hayabusa-2 is equipped with an ion engine system and its trajectory accommodates the non-ballistic trajectory, effective analysis methods are introduced. The results show that the Mars impact probability is sufficiently low for the Hayabusa-2 mission to fully comply with the COSPAR planetary protection requirements. (C) 2015 COSPAR. Published by Elsevier Ltd. All rights reserved.

Mitigation of hazardous Near Earth Objects (NEOs) has been discussed for the past few decades. The well-known Tunguska event occurred in Russia about 100 years ago, and the Chelyabinsk impact in 2013 reminded mankind that the threats of NEO impacts still exists on Earth. Although such harmful NEO impacts are relatively rare, those impacts have potential to bring severe damage to our society, and for the worst case scenario, destroy our civilization. The first international conference on the NEO hazard mitigation was convened in the United Nations in 1995, and the UN has established two organizations: International Asteroid Warning Network (IAWN) and Space Mission Planning Advisory Group (SMPAG) in 2013. The objective of this study is to propose a space-based NEO detection and impact warning system using an Artificial Equilibrium Point (AEP). In the natural equilibrium points such as Lagrange points, three kinds of forces are balanced i.e., the gravitational forces by the primary and secondary bodies and centrifugal force. The AEP, on the other hand, is literary, "artificial" equilibrium point where the residual acceleration is cancelled by low-thrust. Especially on 1 au circular orbit around the Sun, the AEP can be realized by very small acceleration, which enables to locate the space-telescope at an arbitrary fixed point relative to the Earth. Through some cases of numerical simulation, this paper presents the detectability of the virtual impactors estimated based on the debiased NEO distribution model developed by Bottke et al.

After the successful launch on the world first spacecraft, Sputnik 1 by the former Soviet Union in 1957, 58 years has passed. In 1960, Pioneer 5 of the United States escaped the Earth's gravity at the first time, and since then many interplanetary explorers had set to sail interplanetary. However, even in the present day, interplanetary voyages are not still easy. First, interplanetary missions require large amounts of delta-V, and second, the opportunity to get to the destination opens only every synodic period with the destination celestial body. For example, the synodic period with Mars is about 2 years, which means the opportunity to get to Mars opens every 2 years. For such circumstances, this paper proposes a new type of low-thrust orbit design method, "Interplanetary Parking Method" that realizes "anytime" launch of deep-space explorers. The proposed interplanetary parking method enables to make an Earth return orbit with an arbitrary time-of-flight connecting to the minimum energy transfer orbit to a destination. While the time-of-flight of the transfer orbit is fixed, the Earth return orbit with the arbitrary time-of-flight virtually eliminates the severe launch window constraint in interplanetary missions. As application of the proposed method, the paper demonstrates dual launch trajectory design of explorers to different destinations i.e., Mars and Venus. The proposed method will widen the scope of opportunity for interplanetary missions.

The Japan Aerospace Exploration Agency launched an asteroid sample return spacecraft "Hayabusa2" on December 3, 2014 by the Japanese H2A launch vehicle. Following the successful return back of Hayabusa from the asteroid 25143 Itokawa, Hayabusa2 aims at the round trip mission to the asteroid 162173 Ryugu. Ryugu is a near-Earth C-type asteroid, which is believed to contain organic and hydrated minerals. Thus it is expected that its successful sample return may provide fundamental information regarding the origin and evolution of terrestrial planets as well as the origin of water and organics delivered to the Earth. The spacecraft is equipped with four 10mN-class ion engines that provide a total delta-V of approximately 2km/s, which enables to realize the round-trip journey between the asteroid and the Earth. Some enabling technologies include the sample collection mechanism, optical navigation cameras, reentry capsule, four asteroid surface rovers and the impactor. The impactor is a kinetic impact device to create a 2m-class crater on the surface of the asteroid, enabling us to observe/collect not only the surface but also the sub-surface of the asteroid. Hayabusa2 is heavier than former Hayabusa by 100kg and has increased reliability and drastically more science capability as a sample-return spacecraft. Hayabusa2 will reach Ryugu in the middle of 2018 and perform an asteroid proximity operation for 1.5 years. Three touch downs for sample collection and one crater generation by a high-speed kinetic impact are planned during the asteroid proximity operation. The sample is to be brought back to the Earth by a re-entry capsule in December 2020. Hayabusa2 successfully conducted the Earth gravity assist (EGA) operation on December 3, 2015, passing above Hawaii islands at the altitude of 3090km, and increasing the interplanetary flight velocity by 1.6km/s. After the EGA, the spacecraft is planned to actuate the ion engine in March 2016 for the powered-cruise operation toward Ryugu rendezvous in 2018. This paper shows a brief introduction to the mission objective and spacecraft design, and then describes the first two year operation including launch, Earth gravity assist and ion engine-powered cruise operation. Finally the paper also provides a future operation plan for the asteroid proximity operation.

Hayabusa is the first asteroid sample return mission in the world, and Hayabusa2 is the second one. The purposes of these missions are to study the origin and evolution of the solar system and to develop the technologies that enable round-trip mission to asteroids. In addition to these "official" purposes, we have done many activities to enhance public interests in space. One of the successful activities was an emotional representation of Hayabusa mission. Spacecraft is a machine, so it does not have emotion. However, we described the mission of Hayabusa as if Hayabusa is a human. With a help of jazz music composed by a professional musician, the story of the mission becomes very emotional one. We were able to attract attention from the people who did not have interest in space missions. Thus this was successful to popularize the space activities to the people in Japan. Another example is the observation campaign of Hayabusa2 spacecraft when it approached to the Earth to perform the Earth swing-by. In this case, people who have a certain skill for star observation enjoyed the event by themselves, so this contributed science activities of public people. At the same time, we collaborated with public observatories in Japan to observe Hayabusa2, and people who do not have telescopes also could see Hayabusa spacecraft. These two are most noteworthy examples, and other than these we have done many things, such as the naming campaign of the target asteroid, putting people's names and messages on board, talk live show, and etc. These outreach activities have contributed to make public people have interests toward space and science. As a result, public people did some their own activities voluntarily. In this paper, we summarize what we have done for outreach activities in Hayabusa and Hayabusa2, and what happened as a consequence.

On February 15th, 2013, a meteor with size of about 20m in diameter entered the Earth's atmosphere over Chelyabinsk, Russia, and exploded at an altitude of about 20 km, damaging about 4,500 buildings and injuring about 1,500 residents. This incident widely invoked an interest in hazard mitigation caused by a NEO. Motivated by such interests, this study focuses on a new concept of NEO detection and impact warning system. In this concept, a space telescope is placed at the L1 point of the Sun-Earth system to intensively observe the NEOs in-coming from the noon-side, which ground-based observatories hardly detect because of the sunlight. Throughout some cases of simulations, this paper reveals the distributions of NEO directions at detection, V-infinity vectors at the Earth impact, and the NEO orbit determination precision are evaluated.

After the successful launch on the world first spacecraft, Sputnik 1 by the former Soviet Union in 1957, 58 years has passed. In 1960, Pioneer 5 of the United States escaped the Earth's gravity at the first time, and since then many interplanetary explorers had set to sail interplanetary. However, even in the present day, interplanetary voyages are not still easy. First, interplanetary missions require large amounts of delta-V, and second, the opportunity to get to the destination opens only every synodic period with the destination celestial body. For example, the synodic period with Mars is about 2 years, which means the opportunity to get to Mars opens every 2 years. For such circumstances, this paper proposes a new type of low-thrust orbit design method, "Interplanetary Parking Method" that realizes "anytime" launch of deep-space explorers. The proposed interplanetary parking method enables to make an Earth return orbit with an arbitrary time-of-flight connecting to the minimum energy transfer orbit to a destination. While the time-of-flight of the transfer orbit is fixed, the Earth return orbit with the arbitrary time-of-flight virtually eliminates the severe launch window constraint in interplanetary missions. As application of the proposed method, the paper demonstrates dual launch trajectory design of explorers to different destinations i.e., Mars and Venus. The proposed method will widen the scope of opportunity for interplanetary missions.

The Tomo-e Gozen camera is a next-generation extremely wide-field optical camera, equipped with 84 CMOS sensors. The camera records about a 20 square-degree area at 2 Hz, providing "astronomical movie data". We have developed a prototype of the Tomo-e Gozen camera (hereafter, Tomo-e PM), to evaluate the basic design of the Tomo-e Gozen camera. Tomo-e PM, equipped with 8 CMOS sensors, can capture a 2 square-degree area at up to 2 Hz. Each CMOS sensor has about 2.6 M pixels. The data rate of Tomo-e PM is about 80 MB/s, corresponding to about 280 GB/hour. We have developed an operating system and reduction softwares to handle such a large amount of data. Tomo-e PM was mounted on 1.0-m Schmidt Telescope in Kiso Observatory at the University of Tokyo. Experimental observations were carried out in the winter of 2015 and the spring of 2016. The observations and software implementation were successfully completed. The data reduction is now in execution.

The Tomo-e Gozen is an extremely wide-field optical camera for the Kiso 1.0-m Schmidt telescope. It is capable of taking consecutive frames with a field-of-view of 20 deg(2) and a sub-second time-resolution, which are achieved by 84 chips of 2k x 1k CMOS sensor. This camera adopts unconventional designs including a lightweight structure, a non-vacuumed and naturally-air cooled system, front-side-illuminated CMOS sensors with microlens arrays, a sensor alignment along a spherical focal plane of the telescope, and massive readout electronics. To develop technical components necessary for the Tomo-e Gozen and confirm a feasibility of its basic design, we have developed a prototype-model (PM) of the Tomo-e Gozen prior to the final-model (FM). The Tomo-e PM is equipped with eight chips of the CMOS sensor arranged in a line along the RA direction, covering a sky area of 2.0 deg(2). The maximum frame rate is 2 fps. The total data production rate is 80 MByte sec(-1) at 2 fps, corresponding to approximately 3 TByte night(-1). After laboratory testing, we have successfully obtained consecutive movie data at 2 fps with the Tomo-e PM in the first commissioning run conducted in the end of 2015.

In this study, we propose a flexible orbit design method that enables anytime launch of a deep-space explorer. Based on the Electric Delta-V Earth Gravity Assist (EDV-EGA) scheme, (Kawaguchi, 2001, 2002) [1,2] the proposed interplanetary parking method enables the explorer to make an Earth return orbit at an arbitrary time-of-flight by connecting to the minimum energy transfer orbit to destination. While the time-of-flight of the transfer orbit is fixed, the Earth return orbit with the arbitrary time-of-flight significantly alleviates the severe launch window constraint in interplanetary missions. We offer two case examples of applications of this method. The first is the dual launch of a Mars explorer with a geostationary transfer orbit (GTO) mission payload. The second is a dual launch of Mars and Venus explorers by a single launch vehicle. In the first case, we assume that a small Mars explorer is dual launched into a GTO for a secondary payload. With this assumption, the secondary payload cannot choose a desirable launch epoch for itself because the launch window to Mars is very narrow and opens only every 2 years. Moreover, the GTO, whose orbital period is approximately 10 h, repeatedly passes through the Van Allen belt wherein the radiation level is very high. Hence, the explorer has to escape from the GTO as soon as possible. However, our proposed interplanetary parking method enables the explorer to reach the destination within the limits of a practical mass resource, regardless of the Earth departure epoch. In the second case, the explorers traveling to different destinations, i.e., Mars and Venus, are dual launched by a single launch vehicle, and they fly to each destination via an interplanetary parking orbit. Our proposed method will widen the scope of opportunity for interplanetary missions. (C) 2015 IAA. Published by Elsevier Ltd. All rights reserved.

Hayabusa was the first asteroid sample return mission. It was launched in May 2003, and arrived at the target asteroid (25143) Itokawa in September 2005. The mission enabled us to see close up a very tiny asteroid in detail for the first time. Hayabusa observed Itokawa with its scientific instruments, and attempted to collect surface material. The mission experienced several serious problems, but successfully returned to Earth in June 2010. After retrieving the capsule, we found thousands of small grains that had been captured from the asteroid. We studied Itokawa in detail with both the remote sensing data and the returned samples, which revealed a great deal of new information to shed light on its origin. In this chapter, we review the Hayabusa mission and summarize the scientific results.

"Time-Delay Integration (TDI)" readout technique has been adopted to a mosaic CCD camera equipped with four fully-depleted CCDs. Optical distortion and image deformation due to the TDI operation are discussed. The manner and advantages of the TDI method in survey observations of geosynchronous orbit objects are summarized. We propose a new TDI application method of getting short-term light curves of artificial space objects. This method of detecting a short-term variability can be applied for a variety of objects, ranging from satellites to stars. It can also be used for the light-curve observations of transient objects which might show short-term variability and of which the precise time information is needed.

We investigated the magnitude-phase relation of (162173) 1999 JU3, a target asteroid for the JAXA Hayabusa 2 sample return mission. We initially employed the International Astronomical Union's H-G formalism but found that it fits less well using a single set of parameters. To improve the inadequate fit, we employed two photometric functions: the Shevchenko and Hapke functions. With the Shevchenko function, we found that the magnitude-phase relation exhibits linear behavior in a wide phase angle range (alpha = 5 degrees-75 degrees) and shows weak nonlinear opposition brightening at alpha < 5 degrees, providing a more reliable absolute magnitude of H-V = 19.25 +/- 0.03. The phase slope (0.039 +/- 0.001 mag deg(-1)) and opposition effect amplitude (parameterized by the ratio of intensity at alpha = 0 degrees.3 to that at alpha = 5 degrees, I(0 degrees.3)/I(5 degrees) = 1.31 +/- 0.05) are consistent with those of typical C-type asteroids. We also attempted to determine the parameters for the Hapke model, which are applicable for constructing the surface reflectance map with the Hayabusa 2 onboard cameras. Although we could not constrain the full set of Hapke parameters, we obtained possible values, w = 0.041, g = -0.38, B-0 = 1.43, and h = 0.050, assuming a surface roughness parameter <(theta)over bar> = 20 degrees. By combining our photometric study with a thermal model of the asteroid, we obtained a geometric albedo of p(v) = 0.047 +/- 0.003, phase integral q = 0.32 +/- 0.03, and Bond albedo A(B) = 0.014 +/- 0.002, which are commensurate with the values for common C-type asteroids.

This paper provides a unique data set representing the taxonomic type of near-Earth asteroids (NEAs) accessible by available spacecraft. The research on NEAs has entered upon a new phase, thanks to sample-return space explorations together with state-of-the-art large ground-based telescopes. We made observations of 13 asteroids with the Subaru, GEMINI-North, GEMINI-South, and Okayama 188cm telescopes. Twelve of them have low delta-v orbits with the potential to be investigated by manned/unmanned spacecraft. Also, ten subkilometer-sized bodies are included among them, and are one of remarkable characteristics in terms of their evolutionary scenario. We have found that eleven asteroids are classified as S-complex, and one asteroid as the V-type. Most S-complex asteroids (eight out of eleven, similar to 70%) have spectra similar to subgroups of Q- or Sq-type, suggesting that these objects are less matured by space weathering. We discuss the dominance of S-complex asteroids based on previous research.

The Planetary Material Sample Curation Facility of JAXA (PMSCF/JAXA) was established in Sagamihara, Kanagawa, Japan, to curate planetary material samples returned from space in conditions of minimum terrestrial contaminants. The performances for the curation of Hayabusa-returned samples had been checked with a series of comprehensive tests and rehearsals. After the Hayabusa spacecraft had accomplished a round-trip flight to asteroid 25143 Itokawa and returned its reentry capsule to the Earth in June 2010, the reentry capsule was brought back to the PMSCF/JAXA and was put to a series of processes to extract recovered samples from Itokawa. The particles recovered from the sample catcher were analyzed by electron microscope, given their ID, grouped into four categories, and preserved in dimples on quartz slide glasses. Some fraction of them has been distributed for initial analyses at NASA, and will be distributed for international announcement of opportunity (AO), but a certain fraction of them will be preserved in vacuum for future analyses.

Hayabusa2 is an asteroid exploration mission to return surface samples of a near-Earth C-type asteroid (162173) 1999 JU . Because asteroids are the evolved remnants of planetesimals that were the building blocks of planets, detailed observation by a spacecraft and analysis of the returned samples will provide direct evidence regarding planet formation and the dynamic evolution of the solar system. Moreover, C-type asteroids are expected to preserve the most pristine materials in the solar system, a mixture of minerals, ice, and organic matter that interact with each other. Space missions are the only way to obtain such pristine materials with geologic context and without terrestrial contamination. Hayabusa2 will launch off in 2014, arrive at 1999 JU in mid-2018, and fully investigate and sample the asteroid at three different locations during its 18-month stay. The concept and design of the Hayabusa2 sampler are basically the same as that on-board Hayabusa, and impact sampling with a 5-g Ta bullet will be made at three locations of the asteroid. The sample container has three separate chambers inside to store samples obtained at different locations separately. The spacecraft will return to Earth with samples in December 2020. Returned samples will be investigated by state-of-the-art analytical techniques in 2020 to understand the evolutionary history of the solar system from 4.56 Gyr ago to the present by combining results from laboratory examinations of the returned samples with remote-sensing datasets and comparing all results of observations of meteorites, interplanetary dust particles, and future returned samples. 3 3

Hayabusa2 is an asteroid sample return mission. It is the follow-on mission of Hayabusa, which was the first spacecraft in the world that brought back the surface material of an asteroid to the earth. Hayabusa2 is now almost ready to launch in 2014. The target asteroid of Hayabusa2 is (162173) 1999 JU3, which is a C-type asteroid. The scientific purpose is to study not only the formation and evolution of the solar system but also the organic matter and water, which existed in the early stage of the solar system. Since we have the experiences and heritages of Hayabusa, we modified the spacecraft in a lot of parts. Thus the spacecraft becomes much more robust and reliable with some new technological challenges. After the launch in 2014, it will arrive at the asteroid in the summer of 2018, stay there for one and half years, and it will come back to the earth at the end of 2020.

A hybrid estimation technique was applied to determine the solar radiation pressure (SRP) force acting on the solar sail spacecraft Interplanetary Kite-craft Accelerated by Radiation of the Sun (IKAROS). To evaluate the SRP force, only tracking data obtained during coast arcs are used. The orbit determination and SRP parameters estimation is implemented using batch weighted least squares. The observables are X/X band two-way Doppler and range measurements. The actually encountered solar radiation pressure acceleration of the IKAROS spacecraft is found to amount to only 88% of the value of the prelaunch simulations. Furthermore, the hybrid technique improves the accuracy of the solar radiation pressure acceleration estimation almost by a factor of five. These results underline the importance of applying a hybrid evaluation of not only the solar radiation pressure force but also the torque for navigation of a solar sail spacecraft.

The Japan Aerospace Exploration Agency is currently developing the second asteroid sample return mission, designated as Hayabusa 2. Following the successful return of Hayabusa from the asteroid "Itokawa", Hayabusa 2 is designed as a round-trip mission to the asteroid "1999 JU3". The 1999 JU3 is a C-type asteroid, which is believed to contain organic matter and hydrated minerals. Thus, it is expected that successful sample collection will provide additional knowledge on the origin and evolution of the planets and, in particular, the origin of water and organic matter. The current mission scenario will enable the spacecraft to reach 1999 JU3 in the middle of 2018 and perform an asteroid proximity operation for 1.5 years. Three touch downs for sampling and one 2-m-class crater generation by means of a high-speed impact operation are planned during the asteroid proximity operation. The samples are to be brought back to the Earth by a re-entry capsule. The present paper describes the system design of Hayabusa 2, some key technical challenges of the mission, and the development status. (C) 2013 IAA. Published by Elsevier Ltd. All rights reserved.

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 study aims to establish a flexible orbit design method which enables "any-time" launch of a deep-space explorer. In this study, it is assumed that a 500 kg deep-space explorer attached with a 300 kg small kick stage, designated as Earth Escape Stage, EES, is dual launched into a Geostationary Transfer Orbit, GTO, together with a primary payload, whereupon the EES is initiated at perigee to inject the deep-space explorer into an orbit whose orbital energy, C3, is almost zero. Then the on-board Ion Engine System, IES, accelerates the explorer through the Electric Delta-V Earth Gravity Assist, EDVEGA , scheme to increase the Earth relative velocity at the Earth reencounter point, which enables the explorer to inject into a transfer orbit to a deep-space destination after the Earth swing-by. In this assumption, the secondary payload i.e. the explorer cannot choose the "desired" launch epoch for itself, which is critical for deep-space missions. As a solution to this problem, this study suggests a flexible orbit design method utilizing a concept of "interplanetary parking orbit", which drastically alleviates the launch window constraints. The suggested method will open the door for deep-space mission designers to use dual launch opportunities of geostationary missions. 1,2

The Japanese asteroid explorer Hayabusa-2 will be launched in the mid-2010s to return samples from C-type near-Earth asteroid 1999JU3. During the rendezvous phase (i.e. proximity operation phase), we will conduct scientific observations to estimate physical parameters (e.g. gravity field, shape, pole direction, spin-rate, ephemeris) of the target body, which are crucial not only for its scientific investigation but also for spacecraft navigation. In particular, the mass is essential to perform a stable touchdown sequence to collect samples from the asteroids surface. We will attempt to estimate the gravity field of the target body using Earth-based radiometric tracking measurements (2-way Doppler and range) and spacecraft-based measurements (information from optical navigation cameras and laser altimeter) using a global parameter estimation technique. As the first step for gravity field estimation, we performed a simulation study on mass estimation under simple configuration and evaluated the relation between the quality and quantity of measurements and the accuracies of the estimation results. Subsequently, the detectability of the low degree and order gravity field coefficients was also studied. We will also present a method for ephemeris improvement of 1999JU3 using spacecraft relative position data and radiometric tracking measurements. © 2013 2013 California Institute of Technology.

The Japanese asteroid explorer Hayabusa-2 will be launched in the mid-2010s to return samples from C-type near-Earth asteroid 1999JU3. During the rendezvous phase (i.e. proximity operation phase), we will conduct scientific observations to estimate physical parameters (e.g. gravity field, shape, pole direction, spin-rate, ephemeris) of the target body, which are crucial not only for its scientific investigation but also for spacecraft navigation. In particular, the mass is essential to perform a stable touchdown sequence to collect samples from the asteroids surface. We will attempt to estimate the gravity field of the target body using Earth-based radiometric tracking measurements (2-way Doppler and range) and spacecraft-based measurements (information from optical navigation cameras and laser altimeter) using a global parameter estimation technique. As the first step for gravity field estimation, we performed a simulation study on mass estimation under simple configuration and evaluated the relation between the quality and quantity of measurements and the accuracies of the estimation results. Subsequently, the detectability of the low degree and order gravity field coefficients was also studied. We will also present a method for ephemeris improvement of 1999JU3 using spacecraft relative position data and radiometric tracking measurements.

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.

This paper describes a newly designed wide-band optical filter. It is optimized for deep imaging of small solar-system bodies. The new filter, which we denote as Wi, is designed to reduce contamination by light pollution from street lamps, especially strong mercury and sodium emission lines. It is also useful for reducing unwanted scattered moonlight. Compared with the use of a commercially available long-wave cut wide-band filter, the signal-to-noise ratios in the detection of asteroids are improved by about 6% by using the Wi filter.

Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 μm, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-μm-sized craters but also a large number of sub-μm- to several-μm-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-μm-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

Microparticles recovered from the Asteroid 25143 Itokawa surface by the Hayabusa mission have been examined for the occurrence of soluble organic compounds. After five individual particles (∼50 to 100 μm in diameter) were rinsed with organic solvents on a diamond plate, two extracts were hydrolyzed with hydrochloric acid for amino acid analysis (AAA), and three extracts were combined for time of flight-secondary ion mass spectrometry (ToF-SIMS) to look for other organic compounds, including polycyclic aromatic hydrocarbons. The organic compounds detected by both methods have the same concentrations as those in blank levels, indicating that indigenous organic compounds are not found in this study. Based on the sensitivities of AAA and ToF-SIMS with the reference sample analyses, the concentrations of indigenous organics in the samples are below part-per-million (ppm), if present. Copyright © 2012 by The Geochemical Society of Japan.

Hayabusa was a JAXA sample-return mission to Itokawa navigated, in part, by JPL personnel. The spacecraft survived several near mission-ending failures at Itokawa yet returned to Earth with an asteroid regolith sample on June 13, 2010. This paper describes NASA/JPL's participation in the Hayabusa mission during the last 100 days of its mission, wherein JPL provided tracking data and orbit determination, plus verification of maneuver design and entry, descent and landing. © Copyright 2011 California Institute of Technology. Government sponsorship acknowledged.

JAXA's next asteroid investigator is now under development supposing a launch in 2014. The new mission is called HAYABUSA-2. It is a similar sample return mission to HAYABUSA, however its target asteroid is different from HAYABUSA. From the point of the scientific objective, 1999JU3 which is the asteroid with the primitive composition (C-type) is chosen as the target. HAYABUSA-2 is planned to be equipped with some new components. A small carry-on impactor (SCI) is one of the new challenges that were not seen with HAYABUSA. SCI is a small impact system for creating an artificial crater. One of the most important scientific objectives of HAYABUSA-2 is to investigate chemical and physical properties of the internal materials in order to understand the formation history of small bodies. The impact system is considered one of the most effective methods for investigating the inner structure of asteroids. We can extend our knowledge about asteroids by observing the diameter, depth and shape of the artificial crater. Additionally, the direct investigation of the inner materials of the asteroid becomes possible by sampling materials inside of the crater. This paper presents the development status of SCI and the results of its development tests. Copyright © (2012) by the International Astronautical Federation.

Context. The Hayabusa2 mission, which will be launched by JAXA in 2014, will return samples from the C-type near-Earth asteroid (162173) 1999 JU3. To better plan the mission, it is important to obtain as many physical characteristics of the asteroid as possible from ground-based observations. Moreover, these can then be calibrated with the in-situ and laboratory studies and be used to better understand other similar objects. Regarding the surface composition of the target asteroid, previous spectroscopic studies in the visible provided conflicting results for the possible presence of a deep absorption band, which is usually related to aqueous alteration processes. Aims. Our goal is to better understand the surface composition of asteroid (162173) 1999 JU3, and how it relates to the spectral differences observed by diverse authors at different epochs and telescopes. Moreover, to support the JAXA mission planning, we aim to constrain the level of aqueous alteration and thermal activity undergone by the object. Methods. The adopted methodology was to observe different regions of the surface of the asteroid that rotates around its axis. Spectroscopic observations that cover about 70% of its surface were therefore obtained at the SOAR telescope in Chile on 2012 July9-10. Results. Our results indicate that the surface of asteroid (162173) 1999 JU3 presents featureless spectra with very little variation. Conclusions. No sign of an absorption feature that could be related to aqueous alteration processes is detectable in the observed spectra. © © ESO, 2012.

"Akatsuki" mission has been launched on May 21, 2010 on an H-IIA booster from Tanegashima Space Center (TSC), Kagoshima, Japan, and arrived at Venus on December 6, 2010, without trouble, after cruising interplanetary approximately seven months. In this paper, the orbit determination result, the estimation strategy, and experiences during the period from the launch through the VOI (Venus Orbit Insertion) phase are discussed.

"Akatsuki" mission has been launched on May 21, 2010 on an H-IIA booster from Tanegashima Space Center (TSC), Kagoshima, Japan, and arrived at Venus on December 6, 2010, without trouble, after cruising interplanetary approximately seven months. In this paper, the orbit determination result, the estimation strategy, and experiences during the period from the launch through the VOI (Venus Orbit Insertion) phase are discussed.

The HAYABUSA asteroid explorer successfully released its sample capsule to Australia on 2010 June 13. Since the Earth reentry phase of sample return was critical, many backup plans for predicting the landing location were prepared. This paper considers the reentry dispersion using ground-based optical observation as a backup observation for radiometric observation. Several scenarios were calculated and compared for the reentry phase of HAYABUSA to evaluate the navigation accuracy of the ground-based observation. The optical observation doesn't require any active reaction from a spacecraft, and thus these results show that optical observations could be a steady backup strategy even if a spacecraft had some trouble. We also evaluated the landing dispersion of HAYABUSA only with optical observation.

We present lightcurve observations and multiband photometry for 107P/Wilson-Harrington using five small- and medium-sized telescopes. The lightcurve has shown a periodicity of 0.2979 day (7.15 h) and 0.0993 day (2.38 h), which has a commensurability of 3:1. The physical properties of the lightcurve indicate two models: (1) 107P/Wilson-Harrington is a tumbling object with a sidereal rotation period of 0.2979 day and a precession period of 0.0993 day. The shape has a long axis mode (LAM) of L-1:L-2:L-3 = 1.0:1.0:1.6. The direction of the total rotational angular momentum is around lambda = 310 degrees, beta = -10 degrees, or lambda = 132 degrees, beta = -17 degrees. The nutation angle is approximately constant at 65 degrees. (2) 107P/Wilson-Harrington is not a tumbler. The sidereal rotation period is 0.2979 day. The shape is nearly spherical but slightly hexagonal with a short axis mode (SAM) of L-1:L-2:L-3 = 1.5:1.5:1.0. The pole orientation is around lambda = 330 degrees, beta = -27 degrees. In addition, the model includes the possibility of binary hosting. For both models, the sense of rotation is retrograde. Furthermore, multiband photometry indicates that the taxonomy class of 107P/Wilson-Harrington is C-type. No clear rotational color variations are confirmed on the surface. (C) 2011 Elsevier Inc. All rights reserved.

The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission and scanning electron microscope analyses indicate that the mineralogy and mineral chemistry of the Itokawa dust particles are identical to those of thermally metamorphosed LL chondrites, consistent with spectroscopic observations made from Earth and by the Hayabusa spacecraft. Our results directly demonstrate that ordinary chondrites, the most abundant meteorites found on Earth, come from S-type asteroids. Mineral chemistry indicates that the majority of regolith surface particles suffered long-term thermal annealing and subsequent impact shock, suggesting that Itokawa is an asteroid made of reassembled pieces of the interior portions of a once larger asteroid.

Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but oxygen isotopic compositions of asteroids themselves have not been established. We measured, using secondary ion mass spectrometry, oxygen isotopic compositions of rock particles from asteroid 25143 Itokawa returned by the Hayabusa spacecraft. Compositions of the particles are depleted in (16)O relative to terrestrial materials and indicate that Itokawa, an S-type asteroid, is one of the sources of the LL or L group of equilibrated ordinary chondrites. This is a direct oxygen-isotope link between chondrites and their parent asteroid.

Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.

Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation from cosmic rays and solar wind on its surface. Large amounts of solar helium (He), neon (Ne), and argon (Ar) trapped in various depths in the grains were observed, which can be explained by multiple implantations of solar wind particles into the grains, combined with preferential He loss caused by frictional wear of space-weathered rims on the grains. Short residence time of less than 8 million years was implied for the grains by an estimate on cosmic-ray-produced (21)Ne. Our results suggest that Itokawa is continuously losing its surface materials into space at a rate of tens of centimeters per million years. The lifetime of Itokawa should be much shorter than the age of our solar system.

IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is the world's first spacecraft to successfully demonstrate solar-sail technology in interplanetary space. The spacecraft is made of square shape of very thin membrane, whose diagonal dimension is 20m. By changing its attitude toward Sun, radiation pressure of solar photons can be used as propulsive force of the spacecraft. To determine the orbit under the continuous big influence of the nongravitational perturbative force (i.e. solar radiation pressure), Very Long Baseline Interferometry (VLBI) observation is effective because sky plane position of the spacecraft can be directly and instantaneously measured by VLBI observables without (or with less dependence on) a priori assumption for solar radiation pressure model. In order to effectively perform VLBI measurements, a signal generator of Differential One-way Range (DOR) tones, which consist of multiple tones whose spanning bandwidth is about 28MHz, was developed and installed to the spacecraft. A digital backend system for the ground stations which has maximum output performance of 4-Gbps had also developed to sample wideband DOR tones. A total number of 24 international VLBI experiments were carried out by using totally 15 antennas among 8 agencies during July and August in 2010. As a result of initial analysis, measurement accuracy of VLBI delay was confirmed to be 50 pico second level, which is 20 times improved precision compared to the JAXA's conventional deep space spacecraft such as Hayabusa and Akatsuki. © 2011 IEEE.

The Japanese asteroid explorer HAYABUSA launched in 2003 arrived at its target asteroid ITOKAWA in September, 2005. HAYABUSA has made amount of scientific discoveries and technological achievements during its stay at ITOKAWA and it came back to the Earth on June 13, 2010. Under this situation, the next asteroid exploration mission started. The spacecraft is called HAYABUSA-2. Although its design basically follows HAYABUSA, some new components are planned to be equipped in HAYABUSA-2 mission. A small carry-on impactor is one of the new challenges that were not seen with HAYABUSA. One of the most important scientific objectives of HAYABUSA-2 is to investigate chemical and physical properties of the internal materials and the internal structures in order to understand the formation history of small bodies. In order to achieve this objective, the impactor is required to remove the surface regolith and create an artificial crater on the surface of the asteroid. Ulis paper presents the overview of our small carry-on impactor system and impact operation of HAYABUSA-2 mission. And how to improve this impactor when it is applied to another small body exploration mission is also presented in this paper. Copyright ©2011 by the International Astronautical Federation. All rights reserved.

The Hayabusa spacecraft aiming at technology demonstration for the world's first sample and return from an extra-terrestrial object was launched by the fifth M-V rocket from Uchinoura Space Center, JAXA on May 9, 2003. It went through several troubles and hardships during totally 7 years of interplanetary flight. It successfully returned to the earth and completed the powered- flight by the ion thruster in the beginning of 2010. After successive trajectory correction maneuvers for the reentry, the mother spacecraft, Hayabusa successfully released a small sample-return capsule with asteroid Itokawa sample contained in the sample canister aboard. The capsule entered the earth atmosphere in the desert of Australia on June 13, 2010, and was successfully recovered by June 15. This paper overviews the return operation of the Hayabusa mother spacecraft and reentry flight and recovery operation of the sample return capsule. And the paper also will provide how these TCM and EDL activities were performed and some associated information regarding the Hayabusa mission.

The Hayabusa spacecraft aiming at technology demonstration for the world's first sample and return from an extra-terrestrial object was launched by the fifth M-V rocket from Uchinoura Space Center, JAXA on May 9, 2003. It went through several troubles and hardships during totally 7 years of interplanetary flight. It successfully returned to the earth and completed the powered-flight by the ion thruster in the beginning of 2010. After successive trajectory correction maneuvers for the reentry, the mother spacecraft, Hayabusa successfully released a small sample-return capsule with asteroid Itokawa sample contained in the sample canister aboard. The capsule entered the earth atmosphere in the desert of Australia on June 13, 2010, and was successfully recovered by June 15. This paper overviews the return operation of the Hayabusa mother spacecraft and reentry flight and recovery operation of the sample return capsule. And the paper also will provide how these TCM and EDL activities were performed and some associated information regarding the Hayabusa mission.

Spacecraft escape and capture trajectories from or to Halo orbits about the L1 or L2 points using impulsive maneuvers at periapsis of the manifolds for interplanetary transfers are analyzed in the restricted Hill three-body problem. This application is motivated by future proposals to place deep-space ports at the Earth and Mars L1 or L2 points. First, the feasibility of interplanetary trajectories between Earth Halo orbits and Mars Halo orbits is investigated. In this study, unstable and stable manifolds associated with the Halo orbits are used to approach the vicinity of the planet's surface, and use impulsive maneuvers at periapsis for escape and capture trajectories to and from Halo orbits. Interplanetary trajectories between Earth and Mars Halo orbits with reasonable A V and flight time are found. Next, applying these dynamics to an Earth Mars transportation system using spaceports on Earth and Mars Halo orbits, the system is evaluated in terms of the spacecraft mass of round-trip transfer. As a result, transfer between low Earth orbits and low Mars orbits via the planets' Halo orbits can reduce spacecraft wet mass compared with a direct round-trip transfer, by leaving propellant for the return.

We present the new method of detecting the asteroids quickly and automatically from a large volume of imaging data that are obtained by fully-depleted and undersampled CCD camera, by optimizing for a multi-core PC. The method detects the asteroids as faint as those detected by eyes *in much shorter time than eyes.

'Hayabusa' re-entry capsule was safely carried into the clean room of Sagamihara Planetary Sample Curation Facility in JAXA. After executing CT scanning, removal of heat shield, and surface cleaning of sample container, the sample container was enclosed into the clean chamber. After opening the sample container and residual gas sampling in the clean chamber, optical observation, sample recovery, sample separation for initial analysis is carried out. This curation work is continued with some selected member of Hayabusa Asteroidal Sample Preliminary Examination Team (HASPET) for several months. We report the 'Hayabusa' capsule recovery operation and current status of curation work for 'Hayabusa' sample.

This paper investigates the solar sail modeling and its estimation approach of solar power sail spacecraft IKAROS. Estimation of solar sail force model in space is the key factor for successful solar sail navigation because the solar sail have large uncertainty due to the flexible membrane. Since the sail wrinkles after the deployment and its surface will suffer from degradation, the solar sail force model is difficult to develop before the launch. In this paper, the spinning solar sail model is introduced considering the deformation of the sail. A practical analysis of estimating the solar sail force model from radiometric tracking data is investigated. The solar sail model estimation using the real tracking data is also demonstrated. Copyright ©2010 by the International Astronautical Federation. All rights reserved.

This paper investigates the solar sail modeling and its estimation approach of solar power sail spacecraft IKAROS. Estimation of solar sail force model in space is the key factor for successful solar sail navigation because the solar sail have large uncertainty due to the flexible membrane. Since the sail wrinkles after the deployment and its surface will suffer from degradation, the solar sail force model is difficult to develop before the launch. In this paper, a practical analysis of estimating the solar sail force model from radiometric tracking data is investigated. This is demonstrated by orbit determination including parameter estimation of generalized sail model.

This paper investigates the solar sail modeling and its estimation approach of solar power sail spacecraft IKAROS. Estimation of solar sail force model in space is the key factor for successful solar sail navigation because the solar sail have large uncertainty due to the flexible membrane. Since the sail wrinkles after the deployment and its surface will suffer from degradation, the solar sail force model is difficult to develop before the launch. In this paper, a practical analysis of estimating the solar sail force model from radiometric tracking data is investigated. This is demonstrated by orbit determination including parameter estimation of generalized sail model.