The National Institute of Polar Research (NIPR) is leading a six year prioritized project of the Antarctic research observations since 2010. One of the sub-projects is entitled ‘the global environmental change revealed through the... more
The National Institute of Polar Research (NIPR) is leading a six year prioritized project of the Antarctic research observations since 2010. One of the sub-projects is entitled ‘the global environmental change revealed through the Antarctic middle and upper atmosphere’. As a part of the sub-project, a Rayleigh/Raman lidar (RR lidar) was installed at Syowa, Antarctica (69S, 39E) in January, 2011. The operation has been conducted since February 2011 and the RR lidar has kept measuring temperature profiles continuously between approximately 10 and 80 km for almost 3 years. In order to extend the height coverage to include mesosphere and lower thermosphere region, a new resonance scattering lidar system with tunable wavelengths is developed at NIPR in Tachikawa (35.7N, 139.4E). The lidar transmitter is based on injection-seeded, pulsed alexandrite laser for 768-788 nm (fundamental wavelengths) and a secondharmonic generation (SHG) unit for 384-394 nm (second harmonic wavelengths). The l...
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Reliability assessment is concerned with the analysis of devices and systems whose individual components are prone to fail. This analysis documents the process and results of reliability determination of the JEM-EUSO PhotoMultiplier Tube... more
Reliability assessment is concerned with the analysis of devices and systems whose individual components are prone to fail. This analysis documents the process and results of reliability determination of the JEM-EUSO PhotoMultiplier Tube (PMT) component under the Total Ionizing Dose (TIDs). In terms of TIDs, the PMTs that may fail due to this type of radiation is of the order of 246 PMT from a total amount of 4932 PMT, which cover the focal surface of the telescope. This means a reliability of around 95%. However, the calculations show that the reliability of the ”failing components”, the remaining 5% of the PMTs, is around 80% in five years of operation of the JEM-EUSO Space Mission. Therefore, it can be concluded that around 99% of the PMT’s in terms of TIDs will complete their operation without failure, ensuring the success of the mission as far as radiation TIDs is concerned.
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JEM-EUSO is a Fresnel-optics refractive telescope devoted to the observation of Extreme Energy Cosmic Ray (EECR) showers in the Earth's atmosphere. The observation principle is the detection of fluorescence light emitted by particles... more
JEM-EUSO is a Fresnel-optics refractive telescope devoted to the observation of Extreme Energy Cosmic Ray (EECR) showers in the Earth's atmosphere. The observation principle is the detection of fluorescence light emitted by particles showering in the atmosphere. This instrument will be placed on board the International Space Station (ISS) from the JEM exposed facility. Its goal is the study of the sources of EECR and the determination of the origin and nature of these particles with high precision, thanks to the increase in statistics due to the larger exposure. Key words; cosmic rays, International space station. The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) of ISS is the first mission1 that will study from space Extreme-Energy Cosmic Rays (EECR). JEM-EUSO will observe Extensive Air Showers (EAS) produced by EECRs traversing the Earth's atmosphere from above. For each event, the detector will make accurate measurements of the energy, ar...
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The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) on board the International Space Station (ISS) is the first space-based mission worldwide in the field of Ultra High-Energy Cosmic Rays (UHECR). For UHECR... more
The Extreme Universe Space Observatory on the Japanese Experiment Module (JEM-EUSO) on board the International Space Station (ISS) is the first space-based mission worldwide in the field of Ultra High-Energy Cosmic Rays (UHECR). For UHECR experiments, the atmosphere is not only the showering calorimeter for the primary cosmic rays, it is an essential part of the readout system, as well. Moreover, the atmosphere must be calibrated and has to be considered as input for the analysis of the fluorescence signals. Therefore, the JEM-EUSO Space Observatory is implementing an Atmospheric Monitoring System (AMS) that will include an IR-Camera and a LIDAR. The AMS Infrared Camera is an infrared, wide FoV, imaging system designed to provide the cloud coverage along the JEM-EUSO track and the cloud top height to properly achieve the UHECR reconstruction in cloudy conditions. In this paper, an updated preliminary design status, the results from the calibration tests of the first prototype, the simulation of the instrument, and preliminary cloud top height retrieval algorithms are presented.
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... Another important characteristic of these sources is their potential to be X-ray burst sources. At least five of them, namely 4U 1636-53, 4U 1728 -33, 4U 1735-44, 4U 1820-30 (located in NGC 6624), and 4U 1837 +04 (Ser X-1) emit X-ray... more
... Another important characteristic of these sources is their potential to be X-ray burst sources. At least five of them, namely 4U 1636-53, 4U 1728 -33, 4U 1735-44, 4U 1820-30 (located in NGC 6624), and 4U 1837 +04 (Ser X-1) emit X-ray bursts (Lewin and Joss 1981). ...
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In recent years, many plans have arisen for building constellations in low Earth orbit, some of which have already provided commercial services. The number of satellites that form these constellations will exceed $$10^4$$ 10 4 , and a... more
In recent years, many plans have arisen for building constellations in low Earth orbit, some of which have already provided commercial services. The number of satellites that form these constellations will exceed $$10^4$$ 10 4 , and a number of these could become space debris due to accidental failure, leading to serious problems for human activities in space. Laser ablation-induced propulsion achieved by remote irradiation from the service spacecraft has been proposed as one effective method to remove such space debris and it involves effectively generating a propulsion impulse from a laser. Because most of the high-power lasers currently utilized in space applications are Nd:YAG lasers, in this study, we evaluate the characteristics of second harmonic generation (SHG), which can be generated using nonlinear crystals. The momentum coupling coefficient may be dependent on the irradiated laser wave length which has a significant difference in the ablation process such as plasma gener...
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Newly developed high-strength reaction-sintered silicon carbide, called New-Technology Silicon Carbide (NT-SiC) is an attractive material for lightweight optical mirror with two times higher bending strength than other SiC materials. The... more
Newly developed high-strength reaction-sintered silicon carbide, called New-Technology Silicon Carbide (NT-SiC) is an attractive material for lightweight optical mirror with two times higher bending strength than other SiC materials. The material has advantages in its fabrication process. The sintering temperature is significantly lower than that of pure silicon carbide ceramics and its sintering shrinkage is smaller than one percent. These advantages will provide rapid progress to fabricate large structures. The characteristics of the material are also investigated. The polish of the test piece demonstrated that the polished surface has no pore and is suited to visible region as well as infrared without CVD SiC coating. It is concluded that NT-SiC has potential to provide large lightweight optical mirror.
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ABSTRACT New-Technology Silicon Carbide (NT-SiC) is a reaction sintered silicon carbide with very high bending strength. Two times higher bending strength than other SiC materials is important characteristics in an optical mirror for... more
ABSTRACT New-Technology Silicon Carbide (NT-SiC) is a reaction sintered silicon carbide with very high bending strength. Two times higher bending strength than other SiC materials is important characteristics in an optical mirror for space application. The space optics is to endure the launch environment such as mechanical vibration and shock as well as lightweight and good thermal stability of their figure. NT-SiC has no open pore. It provides good surface roughness for infrared and visible application, when its surface is polished without additional coatings. Additional advantages are in the fabrication process. The sintering temperature is significantly lower than that of pure silicon carbide ceramics and its sintering shrinkage is smaller than one percent. These advantages will provide rapid progress to fabricate large structures and will enable that one meter mirror will put practical use. It is concluded that NT-SiC has potential to provide large lightweight optical mirror.
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An unique midlatitude noctunal mesopause-region temperatures resulting from 25 years of Na lidar observations at Colorado State University and Utah State University reveals influences of tropospheric and/or stratospheric forcing. These... more
An unique midlatitude noctunal mesopause-region temperatures resulting from 25 years of Na lidar observations at Colorado State University and Utah State University reveals influences of tropospheric and/or stratospheric forcing. These includes signals of Mt. Pinatubo eruption and El Nino Southern Oscillation, as well as altitude-dependent (wave-like structures) responses to the 11-year and 27-day solar flux variability. Though the cause for these intriguing signals is not yet known, publications in 2015 by colleagues elsewhere have also shown similar effects in temperatures from satellite data.
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The metallic atom and ion layers, its source is considered as ablation of meteoroids coming into the atmosphere, are generally distributed mainly height range of 80-110 km or higher in the upper atmosphere. An importance of the metallic... more
The metallic atom and ion layers, its source is considered as ablation of meteoroids coming into the atmosphere, are generally distributed mainly height range of 80-110 km or higher in the upper atmosphere. An importance of the metallic ions, such as Na and Fe, is their longer chemical lifetimes, i.e. slower recombination rates, compared with major ions, such as NO and O2 . This can contribute to maintain dens electron concentration, which can influence radio propagation in the upper atmosphere, e.g., satellite communication between the ground and space. The metallic atoms, such as Na and Fe, are also important as a reservoir of the metallic ions through their chemical processes. Thus, it is socially important to investigate the metallic atom and ion layers for understanding or prediction of the radio propagation environment in the upper atmosphere.
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To improve the post mission disposal (PMD) rate of the satellites and provide future active debris removal (ADR), SKY Perfect JSAT Corporation has begun designing a brand-new end-of-life (EOL) deorbit service satellite to remove... more
To improve the post mission disposal (PMD) rate of the satellites and provide future active debris removal (ADR), SKY Perfect JSAT Corporation has begun designing a brand-new end-of-life (EOL) deorbit service satellite to remove nonfunctional satellite targets from orbit. The Corporation aims to launch a demonstration satellite in 2024 and begin service in 2026, in collaboration with RIKEN and other partners. A service satellite with a laser system (less than 50 W of output power) emits a focused laser beam to the target to cause laser ablation. The orbit and attitude (including rotational status) of the target can be changed sufficiently by the reaction force of the plasma/gas ejected from the target surface. In this paper, the results of a conceptual study and several advantages of the laser ablation method over conventional active methods for the removal of nonfunctional satellites are described.
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An impulse measurement system based on a simple pendulum is newly developed. The system has a resolution of 10−7 Ns for ablation events induced by a single laser at a pulse rate of 2 Hz or less. For ablation events at 10 Hz and above, the... more
An impulse measurement system based on a simple pendulum is newly developed. The system has a resolution of 10−7 Ns for ablation events induced by a single laser at a pulse rate of 2 Hz or less. For ablation events at 10 Hz and above, the system can record the impulse as an average force. The impulse generated by a Nd:YAG pulse laser irradiating a 7075 aluminum alloy is investigated in vacuum. The impulse arises at 3 J/cm2 and the momentum coupling factor, C m , plateaus at approximately 20 μNs/J over a range of 5 to 50 J/cm2 without producing a plasma shielding effect. C m is characterized by only fluence independent of pulse width in the range of 10 to 20 ns. This result indicates that it should be feasible to deorbit a 150 kg abandoned satellite at an altitude of 1200 km using a chaser satellite equipped with a 100 W laser.
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We have been developing a diode pumped Nd:YAG laser with 12 mJ output energy for a LIDAR system which is used on a sample return mission of a near-Earth asteroid. The laser was required to display both optical performance for the LIDAR... more
We have been developing a diode pumped Nd:YAG laser with 12 mJ output energy for a LIDAR system which is used on a sample return mission of a near-Earth asteroid. The laser was required to display both optical performance for the LIDAR and the durability and resistance of a spaceborne component. We succeeded by applying such techniques as laser design,
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ABSTRACT Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because of high stiffness, low density, low coefficient of thermal expansion, high thermal conductivity and thermal stability. Newly... more
ABSTRACT Silicon carbide (SiC) is the most advantageous as the material of various telescope mirrors, because of high stiffness, low density, low coefficient of thermal expansion, high thermal conductivity and thermal stability. Newly developed high-strength reaction-sintered silicon carbide (NTSIC), which has two times higher strength than sintered SiC, is one of the most promising candidates for lightweight optical mirror substrate, because of fully dense, lightweight, small sintering shrinkage (+/-1 %), good shape capability and low processing temperature. In this study, 650mm in diameter mirror substrate of NTSIC was developed for space telescope applications. Three developed points describe below. The first point was to realize the lightweight to thin the thickness of green bodies. Ribs down to 3mm thickness can be obtained by strengthen the green body. The second point was to enlarge the mirror size. 650mm in diameter of mirror substrate can be fabricated with enlarging the diameter in order. The final point was to realize the homogeneity of mirror substrate. Some properties, such as density, bending strength, coefficient of thermal expansion, Young's modulus, Poisson's ratio, fracture toughness, were measured by the test pieces cutting from the fabricated mirror substrates.
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ABSTRACT New-Technology Silicon Carbide (NTSIC(R)) is a reaction sintered silicon carbide with very high bending strength. Two times higher bending strength than other SiC materials is important characteristics in an optical mirror for... more
ABSTRACT New-Technology Silicon Carbide (NTSIC(R)) is a reaction sintered silicon carbide with very high bending strength. Two times higher bending strength than other SiC materials is important characteristics in an optical mirror for space application. The space optics is to endure the launch environment such as mechanical vibration and shock as well as lightweight and good thermal stability of their figure. NTSIC has no open pore. It provides good surface roughness for infrared and visible application, when its surface is polished without additional coatings. Additional advantages are in the fabrication process. The sintering temperature is significantly lower than that of a sintered silicon carbide ceramics and its sintering shrinkage is less than one percent. These advantages will provide rapid progress to fabricate large structures. Both reaction bonding method and brazing are studied in order to larger application for larger telescope. It is concluded that NTSIC has potential to provide large lightweight optical mirror.