Hayabusa2
is a sample return mission of JAXA launched on 3 December 2014.
Hayabusa2
is the successor of
Hayabusa
, which returned samples from the asteroid Itokawa to the Earth. Although the design ...of
Hayabusa2
follows that of
Hayabusa
, the former is equipped with some new components. The small carry-on impactor (SCI) is one of those components. The SCI is a compact kinetic impactor designed to remove the asteroid surface regolith locally and create an artificial crater. One of the most important scientific objectives of
Hayabusa2
is to investigate the chemical and physical properties of the internal materials and structures of the target body, asteroid Ryugu.
Hayabusa2
will attempt to observe the resultant crater with some scientific instruments and to get samples from around the crater. High kinetic energy is required to create a meaningful crater, however, the impact system design needs to fit within strict constraints. Complicated functions, such as a guidance and control system, are not permitted. A special type of shaped charge is used for the acceleration of the impactor of the SCI in order to make system simpler. Using this explosion technique makes it possible to accelerate the impactor very quickly and to hit the asteroid without a guidance system. However, the impact operation will be complicated because the explosive is very powerful and it scatters high-speed debris at the detonation. This paper describes an overview of the SCI system, the results of the development testing and an outline of the impact experiment of the
Hayabusa2
mission.
JAXA launched the world's first deep space solar sail demonstration spacecraft “IKAROS” on May 21, 2010. IKAROS was injected to an Earth–Venus trajectory to demonstrate several key technologies for ...solar sail utilizing the deep space flight environment. IKAROS succeeded in deploying a 20
m-span solar sail on June 9, and is now flying towards the Venus with the assist of solar photon acceleration. This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS.
► JAXA launched the world's first deep space solar sail demonstration spacecraft “IKAROS” on May 21, 2010. ► IKAROS was injected to an Earth–Venus trajectory to demonstrate several key technologies for solar sail utilizing the deep space flight environment. ► IKAROS succeeded in deploying a 20
m-span solar sail on June 9, and is now flying towards the Venus with the assist of solar photon propulsion. ► This paper describes the mission design, system design, solar sail deployment operation and current flight status of IKAROS.
The Small Carry-on Impactor (SCI) equipped on
Hayabusa2
was developed to produce an artificial impact crater on the primitive Near-Earth Asteroid (NEA) 162173 Ryugu (Ryugu) in order to explore the ...asteroid subsurface material unaffected by space weathering and thermal alteration by solar radiation. An exposed fresh surface by the impactor and/or the ejecta deposit excavated from the crater will be observed by remote sensing instruments, and a subsurface fresh sample of the asteroid will be collected there. The SCI impact experiment will be observed by a Deployable CAMera 3-D (DCAM3-D) at a distance of ∼1 km from the impact point, and the time evolution of the ejecta curtain will be observed by this camera to confirm the impact point on the asteroid surface. As a result of the observation of the ejecta curtain by DCAM3-D and the crater morphology by onboard cameras, the subsurface structure and the physical properties of the constituting materials will be derived from crater scaling laws. Moreover, the SCI experiment on Ryugu gives us a precious opportunity to clarify effects of microgravity on the cratering process and to validate numerical simulations and models of the cratering process.
A projectile accelerated by the Hayabusa2 Small Carry-on Impactor successfully produced an artificial impact crater with a final apparent diameter of 14.5 ± 0.8 m on the surface of the near-Earth ...asteroid 162173 Ryugu on April 5, 2019. At the time of cratering, Deployable Camera 3 took clear time-lapse images of the ejecta curtain, an assemblage of ejected particles forming a curtain-like structure emerging from the crater. Focusing on the optical depth of the ejecta curtain and comparing it with a theoretical model, we infer the size of the ejecta particles. As a result, the typical size of the ejecta particles is estimated to be several centimeters to decimeters, although it slightly depends on the assumed size distribution. Since the ejecta particles are expected to come from a depth down to ~1 m, our result suggests that the subsurface layer of Ryugu is composed of relatively small particles compared to the uppermost layer on which we observe many meter-sized boulders. Our result also suggests a deficit of particles of less than ~1 mm in the subsurface layer. These findings will play a key role in revealing the formation and surface evolution process of Ryugu and other small Solar System bodies.
Iron (Fe) nano-polycrystalline metal obtained by sintering reduced iron nanoparticles from iron oxide was applied to an axial flux generator. When the thickness of the core material is 1/10, it has ...the same ability of the power generation as when Fe bulk is used as the core. We can also reduce the iron loss (hysteresis loss and eddy current loss), which enables the construction of thin and axial flux generators with light weight. We investigated the magnetization property of the core inductor at the direct current and found that Fe nanoparticles were produced from iron oxide particles by high voltage pulse or laser ablation in liquids. Core inductors with these materials were fabricated. It has been clarified from measurements of the core inductor magnetization that the relative permeability of the sintered Fe nanopolycrystalline was one million.
ABSTRACT
The JAXA Hayabusa2 mission accomplished the formation of an artificial crater on the asteroid Ryugu. The aim of this work is to analyse the area surrounding the artificial crater and reveal ...spectral variability compared to the same region before the crater formation, to mineralogically and physically characterize the subsurface exposed material. The crater’s investigation focused on the analysis of two regions corresponding to the inner part of crater (the pit and the crater wall/floor), two areas related to ejecta deposited close to the crater, two areas of ejecta moved far from the crater, and two external areas. Each area was investigated both before and after the crater formation, by the study of the photometrically corrected spectral parameters: the 1.9 $\mu$m reflectance, the near-infrared spectral slope, and the depth of the bands at 2.7 and 2.8 $\mu$m. The subsurface material of the post-crater areas shows deeper absorption bands, a decrease in reflectance, and a reddening in spectral slope with respect to the surface material of pre-crater areas. The subsurface regolith could have experienced a lower OH devolatilization due to space weathering and/or could be composed of finer dark grains than the surface layer. The ejecta reached distances of $\sim $20 m from the impact point, mainly moving in the northern direction; nevertheless, a few ejecta also reached the south-eastern part of crater.
The Near-Earth Asteroid 162173 Ryugu (1999 JU3) was investigated by the JAXA Hayabusa2 mission from June 2018 to November 2019. The data acquired by NIRS3 spectrometer revealed a dark surface with a ...positive near-infrared spectral slope. In this work we investigated the spectral slope variations across the Ryugu surface, providing information about physical/chemical properties of the surface.
We analysed the calibrated, thermally and photometrically corrected NIRS3 data, and we evaluated the spectral slope between 1.9 μm and 2.5 μm, whose values extend from 0.11 to 0.28 and the mean value corresponds to 0.163±0.022. Starting from the mean value of slope and moving in step of 1 standard deviation (0.022), we defined 9 “slope families”, the Low-Red-Slope families (LR1, LR2 and LR3) and the High-Red-Sloped families (HR1, HR2, HR3, HR4, HR5, HR6). The mean values of some spectral parameters were estimated for each family, such as the reflectance factor at 1.9 μm, the spectral slope, the depth of bands at 2.7 μm and at 2.8 μm. A progressive spectral reddening, darkening and weakening/narrowing of OH bands is observed moving from the LR families to the HR families.
We concluded that the spectral variability observed among families is the result of the thermal metamorphism experienced by Ryugu after the catastrophic disruption of its parent body and space weathering processes that occurred on airless bodies as Ryugu, such as impact cratering and solar wind irradiation. As a consequence, the HR1, LR1, LR2 and LR3 families, corresponding to equatorial ridge and crater rims, are the less altered regions on Ryugu surface, which experienced the minor alteration and OH devolatilization; the HR2, HR3, HR4, HR5 families, coincident with floors and walls of impact craters, are the most altered areas, result of the three processes occurring on Ryugu. The strong reddening of the HR6 family (coincident with Ejima Saxum) is likely due to the fine-sized material covering the large boulder.
We adopted a single-mode, single-wavelength volume holographic grating (VHG) wavelength-stabilized wavelength laser diode (LD) as a pumping LD for an end-pumped microchip Nd:YAG and Nd:YVO4 lasers we ...developed during CW and pulse operations. Higher optical-optical and slope efficiencies during CW operation have been obtained than when using a VHG LD experimentally. Output laser power is insensitive to the temperature of the LD when using a wavelength-stabilized LD and can remain stable and almost constant until the temperature of LD increases up to 40°C. The improved optical-optical conversion efficiency of 58% for the Nd:YVO4 laser has been obtained and calculated the output laser power during CW operation and compared it with the experimental results. We found that the output laser power of the Nd:YVO4 laser using the VHG wavelength-stabilized LD was more than twice as high as that using an LD without VHG. When the ambient temperature increases, the difference in output laser power should be large. In the future, a low-cost end-pumped microchip laser that does not require a temperature control should be developed.
An output peak power of over 1kW for a Nd/Cr3+:YAG ceramic multi-amplifier system with white-light pumping was obtained. A four-stage active-mirror amplifier system was adapted for obtaining kW laser ...peak power. Output spectrum of pumping light used was close to that of solar light. Enhancement of saturated output laser power at high temperatures was observed owing to the phonon-assisted cross-relaxation effect. An output laser peak power of 1.6kW were achieved at a ceramic disk temperature of 100°C. The evaluated optical-optical conversion efficiency for volume of ceramics through which laser passed was 63% for the maximum output laser peak power of 1.6kW. The laser system will be applicable to solar-pumped lasers with high optical-optical conversion efficiency.
•An output peak power of over 1kW for a Nd/Cr3+:YAG ceramic multi-stage active-amplifier system with white-light pumping was obtained. The output spectrum of pumping light used was close to that of solar light.•Enhancement of saturated output laser power at high temperatures was observed owing to the phonon-assisted cross-relaxation effect. An output laser peak power of 1.6kW were achieved at a ceramic disk temperature of 100°C withoptical-optical conversion efficiency for volume of ceramicsthrough which laser passed was 63%.•The laser system will be applicable to solar-pumped lasers.
Ceramic is promising for use as a solid-laser material pumped with solar or lamp light. We developed a Cr3+ ion doped Nd : YAG ceramic laser that converts white light into near-infrared laser light ...more efficiently. Investigation of its optical properties has revealed that large gain can be realized with excitation power that is one order of magnitude less than that in the case of Nd : YAG. Ce3+ ion doping also makes it possible to utilize the excitation light components with wavelengths of 350 nm or less, preventing generation of color centers. A rod-type Ce3+/Cr3+/Nd : YAG ceramic pumped by white light such as solar light or flash lamp light was developed. Fluorescence lifetime of ceramic was measured. Laser oscillations at free running mode were observed. Also, numerical calculation for output laser power and gain at lasing threshold was performed. Fluorescence lifetime increased as temperature rose, which was observed in Cr/Nd : YAG ceramic. This increase suggests the existence of a cross-relaxation effect. Maximum output laser energy of 73 mJ with the peak power of 330 W was obtained. Obtained output laser energy was around twice more than that in case of Cr3+/Nd : YAG ceramic with the same Nd and Cr ion concentration.
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