This paper reports the result of a study for super low altitude satellite. The altitude of this satellite's orbit is lower than ever. The altitude of a conventional earth observing satellite is generally around from 600km to 900km. The lowest altitude of earth observing satellite launched in Japan was 350km; the Tropical Rainfall Measuring Mission (TRMM). By comparison, the satellite reported in this paper is much lower than that and it is planned to orbit below 200km. Furthermore, the duration of the flight planned is more than two years. Any satellite in the world has not achieved to keep such a low altitude that long term. The satellite in such a low orbit drops quickly because of the strong air drag. Our satellite will cancel the air drag effect by ion engine thrust. To realize this idea, a drag-free system will be applied. This usually leads a complicated and expensive satellite system. We, however, succeeded in finding a robust control law for a simple system even under the unpredictable change of air drag. When the altitude of the satellite is lowered successfully, the spatial resolution of an optical sensor can be highly improved. If a SAR is equipped with the satellite, it enables the drastic reduction of electric power consumption and the fabulous spatial resolution improvement at the same time.

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Miniaturization and high performance are always required for space equipments. But, it can be said that miniaturization and high performance are generally contradictory requirements. In this research, a fluid loop insulation and cooling system was built as a means of realizing both miniaturization and high voltage. For the working fluid of the system, fluorinated inactive liquids were used which can provide high electrical insulation and thermal conductivity. In this paper, to begin with, the electrical insulation property of the fluorinated inactive liquids was verified by an experiment. Then the dynamics model of the constructed insulation and cooling system was derived by a system identification experiment. Finally, a control law for temperature control was constructed using the estimated model and cooling performance of the system was examined by both numerical simulations and experiments.

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One of the most important phases of satellite servicing operations by a space robot is the “contact” phase. During the contact between the end-effector and grasping point, there is a risk that the target and the robot can be pushed away from each other by the contact force. Therefore, the method to control the end-effector by the impedance control so as not to deflect the target was suggested. However, all of real control systems have the control time delay. In case of the target capture operation, the time delay of the impedance control makes the impulse of the contact larger. In this paper, to verify the effect of the time delay of the impedance control, experiments with a air-floating testbed and numerical simulations are carried out.

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A Low-ballistic-coefficient atmospheric-entry technology using a flexible aeroshell is promising for a space transportation system because it can reduce the aerodynamic heating during re-entry and the terminal velocity dramatically. Its technology will lead to realize a safer, cheaper and more universal space transportation system. Our group has researched various important subjects in order to apply the flexible aeroshell to actual atmospheric-entry missions. Two topics of them are reported in this paper. First topic is a measurement of aerodynamic characteristics of the flare-type aeroshell. The relation between the Mach number and the drag coefficient of the capsule-type vehicle with the flexible and rigid flare-type aeroshell were obtained using the supersonic and transonic wind tunnel. Second topic is a development of the inflatable aeroshell. The deployment demonstration in a vacuum chamber and the structural tests of an inflatable torus tube were carried out.

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The evaporation behavior of the central droplet in droplet clusters was observed in microgravity without combustion, and the effects of the droplet spacing were examined. The solidified-fuel fiber-suspension technique was utilized for preparing the monodispersed suspended-droplet cluster (MSDC) model. Most of the experiments were conducted with the HCP (hexagonal closest packing) structure cluster models of thirteen n-eicosane droplets at the atmospheric pressure, and some were conducted with the BCC (body-centered cubic) structure cluster models of nine 1-octadecanol droplets at an elevated pressure. The droplet images suggested that critical thermodynamic state was not attained at the ambient pressure above the critical pressure of the fuel, and the results at the elevated pressure were not largely different from those at the atmospheric pressure. The whole evaporation process was unsteady and the unsteadiness was enhanced with decreasing the droplet spacing. The initial heat-up time increased monotonically with decreasing the droplet spacing. The evaporation rate defined after the initial heat-up time was almost constant or showed an increasing trend with decreasing the droplet spacing.

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Ignition delays and temperatures of cool flame of isolated n-decane/ethanol binary-fuel droplets in hot air were experimentally measured under microgravity and normal gravity by thermocouples. The droplet diameter was about 1 mm. Ambient pressure was atmospheric pressure, and ambi ent temperature was 620 K or 660 K under microgravity and varied between 580 K and 780 K under normal gravity, where only cool flame appears for pure n-decane droplets. Mole fraction of ethanol of the binary-fuel was varied. Near the droplet were placed three hot junctions of K-type thermocouples with a diameter of 25 mm. The droplet center and the three hot junctions were arrayed in a straight line with a constant distance of 2 mm. Both under normal gravity and microgravity, ignition delay decreased with increasing ambient temperature and increased with more addition of ethanol to n-decane. Fuel composition or ambient temperature affected cool-flame temperature very little under microgravity.

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Active Thermal Control System (ATCS) is used to collect and transfer a large amount of heat in the Japanese Experiment Module (JEM) Pressurized Module, which adopts a water-based coolant. To use this system, it is important to control and maintain coolant properties on orbit. This paper presents improvements of the water-based coolant to maintain its properties, detailed examples of anomalies that have occurred in the JEM and discusses their causes in details. In this study, we evaluate the latest prescription of the coolant proposed by NASA to determine if it was effective and stable with biocide, buffer of pH and corrosion inhibition. We also found the causes and the mechanism of the anomalies regarding the coolant in the ATCS.

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It has been pointed out in particle physics that mono-energetic electrons and positrons can be produced in the annihilation of WIMP dark matter. Although the propagation through the Galaxy would broaden the line spectrum, the observed spectrum would still have the distinctive feature in the region of sub-TeV, which indicates the existence of WIMP dark matter in the Galactic halo. The recent positron fraction spectrum by the PAMELA experiment shows a significant sharp rise up to ∼100 GeV, and the electron + positron spectrum by the ATIC experiment also shows an excess in the several 100 GeV region. In order to increase greatly the amount of statistics up to higher energies, we need to observe the high-energy electrons and positrons for much longer exposure times by space utilization such as CALET on the ISS.

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We have proposed CALET (CALorimetric Electron Telescope) mission to make observations of high energy cosmic rays, electrons, gamma-rays, and nuclei, on the International Space Station (ISS). CALET mission has been approved as one of candidates for the next mission utilizing the Japanese Experiment Module (JEM). The detector of CALET consists of an imaging calorimeter (IMC) and a total absorption calorimeter (TASC). Main objective of cosmic-ray observation with CALET is to determine precise energy spectrum of electrons up to 20 TeV. As the super nova remnants (SNR) are taken to be sources of electrons, some structure caused by nearby electron sources is expected to appear in the energy spectrum over 1 TeV. Gamma-rays from 20 MeV to a few TeV can be also observed by CALET. Because a thick TASC of CALET gives high energy resolution, annihilation line of SUSY particle, which is a candidate of the dark matter, can be detected. Observation of nuclei is also possible up to 1000 TeV owing to the thick TASC. We have been going on conceptual design of CALET to clear a next judgment in one or two years to proceed to practical development for launching in 2013.

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The second flight of microgravity experiment system using a free fall capsule from a high altitude balloon was conducted in May 2007. Using a drag free control, around 10^-4G gravity conditions were obtained for 30 seconds. Results of a combustion experiment with Japanese sparker conducted inside the microgravity experimental unit were also reported.

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Boiling heat transfer enhancement is efficient for development of a cold plate used in a two-phase flow loop type thermal control system. This study deals with boiling heat transfer enhancement for a narrow channel by thermal spray coating of metal. Copper particles were coated on the heating surface by vacuum plasma spraying. Two kinds of surface were manufactured using different particle size, about 200 and 50 µm. The heat transfer performance was evaluated in saturated flow boiling experiments of HCFC123 for ranges of mass flux of 100 to 400 kg/(m²•s), inlet quality of 0 to 0.60, and heat flux of 25 to 251 kW/m². The test channel with the width of 20 mm, and heated length of 100 mm was placed horizontally. The lower side of heating area was heated by cartridge heaters through a copper block. The channel gap was set to 2 and 4 mm. As the result, the coating surface produced higher heat transfer coefficient than the smooth surface, especially, the heat transfer performance of the surface using finer particle was higher and was about 5 to 10 times higher than that of the smooth surface. While the effect of gaps on the heat transfer coefficient was a little, the critical heat flux increased with increasing the channel gap. Critical heat flux was increased a little by thermal spray coating.

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New apparatus for microgravity experiments was developed in order to obtain fundamental data of single droplet evaporation and combustion of palm methyl ester (PME) for understanding PME spray combustion in internal combustion engines. n-hexadecane droplet combustion and evaporation experiments were also performed to obtain single-component fuel data. Combustion experiments were performed at atmospheric pressure and room temperature. For droplet evaporation experiments, ambient temperature and pressure were varied from 473 to 873 K and 0.10 to 4.0 MPa, respectively. Microgravity conditions were employed for evaporation experiments to prevent natural convection. Droplet diameter history of a burning PME droplet is similar to that of n-hexadecane. Droplet diameter history of an evaporating PME droplet is different from that of n-hexadecane at low ambient temperatures. In the latest stage of PME droplet evaporation, temporal evaporation constant decreases remarkably. At ambient temperatures sufficiently above the boiling temperature of PME components, droplet diameter history of PME and n-hexadecane are similar to each other. Corrected evaporation lifetime τ of PME at 873 K as a function of ambient pressure was obtained at normal and microgravity. At normal gravity, τ monotonically decreases with ambient pressure. On the other hand, at microgravity, τ increases with ambient pressure, and then decreases.

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A CIGS solar cell module without a coverglass was demonstrated by a small satellite since October 2005. A coverglass is normally used to protect the cell performance from low-energy (<3MeV) protons in space. This mission evaluates the model to assess the cell performance of CIGS solar cells, which thus far exhibited no degradation by thermal annealing effect in space. Flight data indicates that the performance has showed no degradation for about 900 days.

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For detailed study of the relationship between boiling bubble behavior and inner wall temperature during flow boiling in microtubes, a transparent heated microtube, whose inner wall was coated with a thin gold film, was employed. Boiling behavior could be observed clearly, and the inner wall temperature of the tube was measured simultaneously with direct heating of the film. Ionized water was used as a test fluid. The experimental conditions were as follows: tube diameter, 1 mm; inlet liquid subcooling, 10 K; mass velocity, 100 kg/m²s; and heat flux, up to 469 kW/m² in the open system. As a result, the frequencies of fluctuation of the inner wall temperature and flow rate were divided into four regions. In addition, the fluctuation range of flow rate increased with increasing heat flux however, this fluctuation decreased drastically for heat flux over 212 kW/m². The fluctuation of void fraction coincided with that of inner wall temperature.

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The effect of the sample width on the flame spread rate over a thin PMMA film in microgravity has been investigated by experiments and scale analysis. The oxygen level of the ambient gas is kept fixed at 30% while different diluents - N₂, Ar, He, and CO₂ - are used. The sample width is also used as a parameter, varying through 5mm, 10mm, and 20mm. When helium is used as the diluent, the conductive heat loss to the sides becomes large, and therefore, the flame is suppressed with a significant drop in the flame spread rate and flame size, especially at low oxygen level and for narrow sample widths. For other diluents, the radiative loss is the dominant factor for the suppression, and the sample width has small impact. These experimental findings can be explained with the scale analysis.

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Subcooled quasi-pool boiling of water is performed at liquid subcooling of 15K ∼ 30K for a flat heating surface of 10mm in diameter in the ultrasonic field. Microbubble emission boiling is generated at higher liquid subcooling than 25K without ultrasonic activation and the heat flux increases higher than the ordinary critical heat flux. At liquid subcooling of 20K in the ultrasonic field, microbubble emission boiling is generated and the heat flux increases as high as the case of high liquid subcooling. The ultrasonic wave accelerates the instability of bubble interface and is strongly effective for heat transfer enhancement with microbubble emission boiling at liquid subcooling of 20K in the experiments.

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One engineering experiment and two scientific experiments are scheduled by using the bare electro-dynamic tape tether on the S520 sounding rocket in 2009. Purpose of the engineering experiment is a quick deployment of tape tether stored in the box with the foldaway storage method, which is a new concept of tether deployment schemes. The design of braking control system for foldaway tape tether deployer is studied in this paper. Braking drag force is measured by experiment in vacuum condition and air, and braking drag characteristic is analyzed from these results of several kinds of experiments.

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Recently, the activity of the development of a small rocket in universities has been enhancing. Focusing on safety, we have been developing a small rocket engine using two liquids (LN₂ and H₂O) without combustion process. In order to improve reliability and performance of this engine, we developed the engine without a valve in a LN₂ passage. In this engine system, initial water temperature and GN₂ pressure were changed within the ranges of 100-170°C and 1.0-2.0 MPa for reducing weight of water and getting higher performance. Thrust was increased with increasing the initial water temperature because the flow rate of H₂O was decreased with increasing the water temperature. In addition, thrust was increased with decreasing the GN₂ pressure under these experimental conditions. As a result, the ratio of LN₂ and H₂O weight could be reduced from 3:4 to 1:1. The relation between the mixing chamber pressure and an initial water temperature was very important for reducing of amount of fuel.

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We are working in the development of a compact, low power water recycling device that can supply delicious drinking water which can be consumed safely and with peace of mind in order to help astronauts lead a healthy and comfortable life in space. This device uses electrolysis to decompose ammonia and organic matter, purifies the water using a reverse osmosis membrane, adds minerals to the water, and then sterilizes the water, thereby maintaining water quality. An online system for measuring TOC and harmful substances is also used to manage the water quality.

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The influence of an acoustic field on premixed flame propagation was examined by numerical simulation and experiment. The influence was evaluated from the two points of view. One is the diffusive transport and the other is convective transport. The particle oscillation by sound is considered to increase diffusivity in the acoustic field like turbulent diffusion. The thermal convection occurs when the density difference exists in the acoustic field. It is considered that flame front is deformed by this thermal convection. To analyze the diffusive and convective influence of the acoustic field, experiment and numerical simulation with strong standing wave had been made. To evaluate the influence of the thermal convection, buoyancy-induced natural convection was removed. As the result, the effect of the thermal convection is clearly observed in both experiment and numerical simulation when the sound pressure level is above 150dB. And the numerical simulation results agreed with experimental results. The burning velocity changes in the acoustic field. The effect is significant especially for a flame that propagates perpendicular to the particle oscillation.

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SCOPE is the magnetospheric explorer mission using a distributed sensing system to investigate space-time correlation of particle behaviors in the magnetotail. The mission needs an autonomous inter-satellite link system enabling commanding, data transfer, ranging, and timing control support for data sampling in unison in a distributed system. TDM/TDMA system has been proposed so as to fit to SCOPE specification. We have developed a simulator to validate our design for SCOPE and obtained successful results. As an instrument to work within a limited resources of small sized satellites like SCOPE, data link, ranging performance, timing accuracy satisfy requirements of SCOPE mission. We describe our inter-satellite link system and achievements obtained through the simulator experiments.

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The distance for quantum key distribution using optical fibers is limited to around 100 km by the transmission loss, background level in the optical fibers, and birefringence in the fibers. Free space is an ideal medium for transmitting photon-based quantum information; this is considered to be the key advantage of quantum cryptography. In fiber-based systems, there is an optical loss in the fiber of about 0.2 dB/km for a telecom wavelength of 1.5 µm. That is, after a propagation of 150 km, the transmission loss in the fiber becomes 30 dB. On the other hand, free-space transmission obeys the diffraction theory of laser light; therefore, the free-space transmission loss is inversely proportional to the square of the distance, and this transmission has an advantage at longer distances over fiber-based transmission. The final key rates for free-space and fiber-based transmission systems are compared with respect to the parameters for the dark count rate, the imperfection of the optical system, and so on. In this paper, the trade-off of free-space and fiber-based systems is presented.

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The PHEBUS (Probing of Hermean Exosphere By Ultraviolet Spectroscopy) instrument on Mercury Planetary Orbiter in the BepiColombo mission is a dual FUV-EUV spectrometer (EUV: 55-155 nm, FUV: 145-315 nm). We are now developing the compact detector system sensitive to FUV airglow emissions of the Mercury. The FUV detector is required to have high spatial resolution (512×512 pixels) so that the wavelength resolution of the PHEBUS instrument should be 2 nm at the FUV range. The FUV detector consists of a Cs₂Te photocathode, microchannel plates (MCPs), and a resistive anode encoder. In a position-sensitive system with a resistive anode encoder, the spatial resolution is determined by the signal-to-noise ratios at the anode terminals. Therefore, a high and stable electron gain of MCPs allows the position determination of each photoelectron event with high spatial resolution. We studied a method for achieving a high and stable electron gain. We fabricated a test model of the FUV detector incorporating a clamped pair of MCPs (V-stack) followed by a gap and a clamped triplet of MCPs (Z-stack) in cascade. We investigated the effect of the negative inter-stack potential on the PHD and the spatial resolution by means of calculation and experiments. As a result, the negative inter-stack potential made the electron gain more stable and the spatial resolution higher by ∼14%. In this paper we report the specific performance of the test model of the FUV detector.

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In the very long baseline interferometry (VLBI) radio sources mission of selenological and engineering explorer, the differential phase delay between the Rstar and Vstar sub-satellites is obtained by using the multifrequency VLBI method during the switching VLBI observation period. The cycle ambiguity is successfully determined and the differential phase delay is estimated within an error of 7 picoseconds. The RMS error is somewhat larger than that for the case of same-beam VLBI because fluctuations of propagation delays whose periods are shorter than the switching interval cannot be canceled out between Rstar and Vstar. However, the differential phase delay during the switching VLBI period is sufficiently accurate and, together with Doppler and range measurements, can be a useful means for precisely determining satellite orbits and precisely estimating the lunar gravity field.

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In this paper, the estimation method of impact probability for Near-Earth Objects (NEOs) is investigated. The impact probability of NEOs has been calculated by a linear target plane analysis and a Monte-Carlo method. Since the collisions of NEOs with the Earth are quite sensitive problems, the calculations have to be confirmed by everal methods. A linear target plane analysis cannot be applied if the position uncertainty is too large since the uncertainty ellipsoid is not a good assumption in this case. A Monte-Carlo method can be used for a large position uncertainty, but the computational cost is high. The limitation of using a linear target plane analysis is investigated using the Monte-Carlo method for the close approach of 99942 Apophis (2004 MN4). The relation between impact probability and observation accuracy is investigated by analyzing the close approach of 2007WD5.

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As a new sampling technique, a “Harpoon & Penetrator” method by a tethered sampler is planned instead of “Touch and Go” method for the next sample return project of small celestial bodies explorations. This paper reports about the results of micro gravity experiments by using parabolic flights of the airplane in order to analyze 3-dimensional dynamic behavior of the tethered rigid body. Objectives of the experiments are demonstration of feasibility of the present sampling method and observation of dynamic characteristics in micro gravitational environments. The extraction / catching experiments and the launch / deployment experiments are explained in this paper. These results contribute to the feasibility study of the tethered sampler and will help to understand the characteristics and to make trade off of the tethered sampling methods.

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The tether sampling method is a new minor-body sampling method proposed by the authors. It consists of three phases; 1) shooting a corer to penetrate the surface of a minor-body, 2) pulling up the corer with tether using a reel mechanism, 3) recovering the corer into a storage box. In this paper, the recovery phase is focused on, and its feasibility under micro-gravity is examined using parabolic flights. The experimental setup and parameters are described in this paper, and the experimental results indicate that the retrieval phase in tethered sampling method is feasible to work under micro-gravity.

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On September 14, 2007, Selenological and Engineering Explorer (SELENE), which is a Japanese lunar polar orbiter, was launched. SELENE carries the optical instrument, which is referred to as the Lunar Imager / SpectroMeter (LISM). The LISM is composed of three sensors. One of sensors of the LISM is the Terrain Camera (TC). TC is used to produce Digital Terrain Model (DTM) from stereo observation of lunar surface. In this work, the lunar surface bidirectional reflectance is investigated from images acquired by the TC. The Radiance Ratio (RR) of surface-reflected solar radiance measured from two view angles is obtained. The estimation of lunar surface roughness using images of the TC is discussed. As a result, it is found that the moon surface is not based on Lambert's law.

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The high precision gamma-ray spectrometer (GRS) is carried on the first Japan's large-scaled lunar explorer, SELENE (KAGUYA), successfully launched by the H-IIA rocket on Sep. 14, 2007. The GRS consists of a large Ge crystal as a main detector and massive bismuth germanate crystals and a plastic scintillator as anticoincidence detectors. The Ge detector is cooled and kept below 90K by a Stirling cryocooler. After a series of initial health check of the GRS, it started a regular observation on December 21, 2007. Energy spectra of gamma rays are obtained with a good energy resolution over the lunar surface. Energy spectra including many peaks of major elements and trace elements on the lunar surface have been measured by the GRS. The GRS identified individual gamma-ray lines emitted from the lunar surface and provided the global intensity maps of naturally radioactive elements. Here, we review an in-flight performance of the GRS and the initial results observed during the period from Dec. 21, 2007 to Feb. 17, 2008.

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We have developed ultra thin polyethylene film for the high altitude balloon which can float in the mesosphere. It is required that the development of thin and strong polyethylene films to reduce the weight of balloons themselves. But it was difficult to manufacture the ultra thin film under 2.8 µm in thickness by a conventional film manufacturing machine. In 2005, we developed a new machine and succeeded in manufacturing 2.5-µm-thick film. We measured its strain-stress properties at low temperature and confirmed that the film is suitable for balloons which float in the mesosphere.

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The on-board small vacuum gauge developed in this study is the quartz friction gauge, which is based on the principle that the resonance impedance of a quartz oscillator varies with the pressure of ambient gas. The gauge has a wide measuring range (10⁵-10^-2 Pa), which corresponds to the atmospheric pressure from the ground to an altitude of about 100 km. The sensor part and data processing part weigh 136 g and 210 g, respectively. In addition, the gauge can operate at a power consumption level of less than 1W. The gauge is suited for high altitude balloon experiments where the weight of on-board instruments must be kept to a minimum. The tuning-fork-shaped quartz oscillator in the gauge is widely used for wrist watches and has high resistance to vibration and shock, and thus the gauge is applicable to sounding rocket experiments that require on-board instruments with high resistance to the environment.

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This paper studies a formation of Asteroid Itokawa in 2-dimension, dividing the formation process into two steps. The first step is a collapse of parent bodies and the second step is the attachment of small fragments to the early Itokawa that is created by the first step. In the first step, the aggregation of fragments after a head-on impact of two parent bodies is investigated by utilizing the N-body problem with the spring-dumper system. The radius of each fragment and the total mass in the system are set to be 32 meters and 10 times as large as Itokawa, respectively. It is found in the first process that the collision of two parent bodies allows a formation of the early Itokawa that is made by a soft contact of two primary bodies. In the second step, 500 fragments are randomly positioned around the early Itokawa and their motions are numerically analyzed by applying the circular restricted three-body problem. It shows that the population of fragments around the early Itokawa is almost constant regardless of the Jacobi integral, the conserved value in the problem. It implies that fragments may play a role in creating the current shape of Itokawa.

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Synergistic fusion of multi-resolution remote sensing images is important to data users that require observation frequency, spatial resolution and observation wavelength. However, it requires compatibility of these data products. Top of Atmosphere (TOA) radiances of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Moderate Resolution Imaging Spectroradiometer (MODIS) are compared in the shortwave infrared (SWIR) and it is found that the sensitivity of MODIS is slightly higher and that the ASTER radiance is higher at the lower reflectance regions. ASTER suffers from stray light phenomena because of the nature of a pushbroom sensor, which stands out for SWIR. In contrast, MODIS is free from ghost phenomena in reflective bands, although existence of stray light is known in thermal bands. In this work, correction of stray light in ASTER is carried out using MODIS images with a wider swath, which makes the correction of full scene of ASTER images.

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Adaptive optical system architecture for small remote sensing satellite is proposed. Spatial Light Modulator is used for wavefront aberration compensator and phase diversity generator. Onboard signal processing method using neural network and principal component analysis is proposed to reduce computation load. The performance of proposed system is evaluated by computer simulation. High estimation accuracy for aberration parameters is shown by simulation study.

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Since the condition of space environment (the “space weather”) near the Earth is strongly influenced by the solar wind, improvement of our understanding of it is essential for minimizing adverse space weather impacts on space technologies and astronauts. Interplanetary scintillation (IPS) observations are useful to gain insight into the global properties of the solar wind, which are poorly understood by in situ measurements. We have carried out IPS observations at 327 MHz regularly using the four-station system of the Solar-Terrestrial Environment Laboratory (STEL) of the Nagoya University. The deconvolution analysis of our IPS observations has revealed the 3-dimesnional feature, solar origin and dynamical behavior of the solar wind, which are crucial information to develop the space weather prediction model.

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In this study, the active removal of space debris is studied from the point of view of technological feasibility. First, the actual debris distribution is analyzed to determine which debris objects should be removed considering the effectiveness in preventing collisional cascading and feasibility such as the delta-V required for rendezvous with the objects. Target regions such as sun-synchronous orbit and a 1,000km altitude, 83 degree inclination orbit are then selected and rendezvous with debris object in these regions are studied. Electrodynamic tether is promising as a highly-efficient propulsion system required for debris de-orbit in these regions. A small piggyback-launched satellite to dispose of one debris object, and a dedicated debris removal satellite which removes several debris objects from crowded regions are proposed. Precise numerical simulations of EDT are performed to evaluate the de-orbit time.

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A full particle-in-cell (PIC) plasma simulator with higher accuracy as well as reasonable performance for studying spacecraft-plasma interactions has been developed. It is applied to estimate characteristics of the onboard current monitors (CRM) for a small scientific satellite REIMEI in the polar orbit, because calibration is required for the observation data. Basic characteristics in typical plasma environments including effects of the satellite geometry are demonstrated.

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A three-dimensional electrostatic full Particle-In-Cell code has been developed to analyze spacecraft-plasma interactions quantitatively. The code is expected to achieve highly accurate computation because it has no robust algorithm. We adopted the code to evaluate the electric field measurement onboard spacecraft, especially under low-density ambient plasma environment with photoelectron emission. In this paper, first, fundamental functions for computation of the electric field were validated in Low Earth Orbit and Geosynchronous Orbit environments by comparing with the thin-sheath limit theory and the thick-sheath limit theory, respectively. Second, the floating potential of a spacecraft model with photoelectron emission in Geosynchronous Orbit was computed to examine the effects of photoelectron emission to the electric potential around the spacecraft. The dependence of the floating potential on the photoelectron temperature was shown in the simulation.

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This paper proposes a new approach to improve the calculation of the average cross-sectional area of breakup fragments, and a new technique for modeling the area-to-mass ratio distribution resulting from the new approach. This paper applies the proposed methods to the re-analysis of fragments from micro-satellite impact tests completed in late 2005. It can be concluded that the area-to-mass ratio distribution model resulting from the proposed methods fits very well with the fragments observed in the micro-satellite impact tests.

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Light-weight thin film (plate) structure is expected to play an important role in space development in the near future. Thin film solar array, large planar antenna, inflatable structure, and Solar Power Satellite (SPS) are the typical examples. We have carried out hypervelocity impact experiments on thin materials using the railgun accelerator at the Institute of Space and Astronautical Science, with the aim of clarification of the process of the plasma generation in case of the thin target. In our experiments, the velocity of the projectile is around 4.5 km/s. Copper (Cu), Aluminum (Al) and Silver (Ag) were used as the thin plate targets. Propagation of the impact-generated plasma was observed by a high-speed video camera and plasma probes. In the front side of the target, a spherical-shape plasma was observed, which propagated near the same velocity as the projectile. On the other hand, the impact-generated plasma propagating along the surface of the target was observed in the rear side. In particular, the plasma propagating along the plate surface in the rear side is practically important in the design of solar array paddle.

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Discharge mechanism in a space-used cable is needed to clarify the arc tracking formation process on the cable under different environments, against the background of the accident of ADEOS2. The experiment was performed in the vacuum chamber that simulated LEO environment. Three types of sample cables were prepared under different environments (Cut, Heat and UV). Arc tracking formation process has been studied by repetition of sustained arc (SA) inception. With the repetition of SA inception lowering of the resistance between the cables was observed. Only the arcs tracking which occurred below the resistance of about 10kΩ were studied. As a result, there was no difference observed between the cables prepared under different environments. Arc tracking formation process does not depend on the state of deterioration of cable.

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As the power level of Geostationary satellites increases, discharge phenomena on solar array are becoming serious threat to safe operation. Arcs on solar array can short-circuit the satellite circuit, decrease the satellite power, and then cause the satellite permanent failure. To prevent the failure caused by charging and arcing, it is necessary to investigate the mechanism of satellite charging and arcing phenomenon. The purpose of this paper is to investigate the occurrence condition of a secondary arc by measuring arc plasma characteristics in ground test. We measured the arc plasma temperature and identified the materials emitted using spectrometer at arbitrary time during arc occurring. We investigated the difference of secondary arcs occurrence condition during secondary arcs. From the spectroscopic measurement results, we found that it was necessary for shifting to the secondary arc that the metallic vapor same as the cathode material was emitted. In case of primary arc (PA) dimension changes, the probability of secondary arc and TSA occurrence became high. And plasma temperature was not affected by PA dimension, however the metallic vapor emission of silver was greatly affected. Thus, secondary arc occurrence greatly depends on metallic vapor emission from cathode.

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The number of the small satellite projects is recently dramatically increasing and there are great demands for effective project management methods for them. The goal of this paper is to propose effective project management methods for small satellite projects, which are obtained through the real-life experience of the small satellite Flying Laptop project. The project management methods implemented in this project maximize the advantages of rapid and cost-effective small satellite approaches. The management of the project is based on project breakdown structures, which are derived from a combination of several existing standards and empirical methods. These management methods use a product tree as the backbone of the management architecture. The project management activities, such as the establishment of a work breakdown structure, drawing and documentation management structures, time scheduling, and cost management is described with real-life examples. Applications of project management tools, including open source software, which play important roles in cost-effective small satellite approaches, are also summarized and examples of them are illustrated. Finally, further possibilities of effective project management with up-coming new management tools are discussed.

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The costs of transportation from the Earth to the orbit are very high. Decreasing the transportation costs should increase the launch market significantly. However, the objective of transportation costs is ambiguous and few studies have examined the relationship between transportation costs and commercial profits of businesses. On-Orbit Servicing (OOS) is a business that could profit from lower transportation costs, and we quantified the relationship between costs and profitability for this business. Real-coded Adaptive Range Genetic Algorithm optimized the OOS method. The results showed that the revenues generated by OOS would support the outlay required to decrease transportation costs.

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The paper overviews recent enlarging research and development activities of Japanese universities especially in the field of nano-satellites and hybrid rockets. Development of real satellites or rockets and actually launching them provides excellent materials for space engineering education as well as project management, which is rather difficult to teach in usual class lectures. In addition, it may lead to a new way of space development with its cheap and quick access to space. In order to support these kinds of student oriented activities, “University Space Engineering Consortium (UNISEC)” was founded in 2002, which has had large effect of further facilitating these students' space related activities. Significance and history of such activities is reviewed with focus on University of Tokyo as one example, followed by the objectives and future vision of UNISEC with some discussion how such activities will contribute to the actual space development and utilization.

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The Orbiting Carbon Observatory (OCO) and the Greenhouse Gases Observing Satellite (GOSAT) are the first two satellites designed to make global measurements of atmospheric carbon dioxide (CO₂) with the precision and sampling needed identify and monitor surface sources and sinks of this important greenhouse gas. Because the operational phases of the OCO and GOSAT missions overlap in time, there are numerous opportunities for comparing and combining the data from these two satellites to improve our understanding of the natural processes and human activities that control the atmospheric CO₂ and its variability over time. Opportunities for cross-calibration, cross-validation, and coordinated observations that are currently under consideration are summarized here.

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Greenhouse gases Observing Satellite (GOSAT) is designed and developed to globally monitor the Greenhouse gases distribution from space. This paper presents the program overview and current status of GOSAT.

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Greenhouse gases Observing SATellite (GOSAT) is a Japanese mission for monitoring greenhouse gases, such as CO₂ and CH₄, from space. The GOSAT carries a Fourier transform spectrometer and a push broom imager. On orbit, the observation data will be evaluated by onboard calibration data and implemented by ground L1 processing system. The post-launch calibration items are planned and the methods will be developed before the launch. The methods are investigated by analyzing the current MODIS data, which has similar wavelength bands to GOSAT. In this paper, we show the plans of onboard calibration, and post-launch vicarious calibration of GOSAT sensors.

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Greenhouse Gases Observing Satellite (GOSAT) is under developing to launch in 2008 fiscal year. In this paper the main feature of the satellite bus system, subsystems and the development status of the bus system are presented.

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The rocket-ramjet combined-cycle engine is studied for the next space transportation in JAXA. The engine realizes a higher effective specific impulse than that of the conventional rocket engines. Engine model combustion tests were conducted in the ejector-jet mode at a sea-level static-air condition and in the ramjet mode at a Mach 4 flight condition. Flight tests with the CAMUI hybrid rocket are planed for the ejector-jet system design technology. Aerodynamic tests and combustor tests are conducted to modify the engine design technologies. Studies on the high enthalpy flow, the light weight material and the vitiation effect on the engine performances are also conducted.

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