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Xu, X.*; Odaira, Takumi*; Xu, S.*; Hirata, Kenji*; Omori, Toshihiro*; Ueki, Kosuke*; Ueda, Kyosuke*; Narushima, Takayuki*; Nagasako, Makoto*; Kainuma, Ryosuke*; et al.
Advanced Materials & Processes, 180(7), p.35 - 37, 2022/10
Odaira, Takumi*; Xu, S.*; Hirata, Kenji*; Xu, X.*; Omori, Toshihiro*; Ueki, Kosuke*; Ueda, Kyosuke*; Narushima, Takayuki*; Nagasako, Makoto*; Harjo, S.; et al.
Advanced Materials, 34(27), p.2202305_1 - 2202305_11, 2022/07
Times Cited Count：12 Percentile：87.73(Chemistry, Multidisciplinary)Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.
Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03
Times Cited Count：43 Percentile：96.93(Astronomy & Astrophysics)Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 
C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.
Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.
Science, 364(6437), p.272 - 275, 2019/04
Times Cited Count：259 Percentile：99.73(Multidisciplinary Sciences)The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.
Iwata, Takahiro*; Kitazato, Kohei*; Abe, Masanao*; Otake, Makiko*; Arai, Takehiko*; Arai, Tomoko*; Hirata, Naru*; Hiroi, Takahiro*; Honda, Chikatoshi*; Imae, Naoya*; et al.
Space Science Reviews, 208(1-4), p.317 - 337, 2017/07
Times Cited Count：54 Percentile：71.62(Astronomy & Astrophysics)NIRS3: The Near Infrared Spectrometer is installed on the Hayabusa2 spacecraft to observe the target C-type asteroid 162173 Ryugu at near infrared wavelengths of 1.8 to 3.2 micrometer. It aims to obtain reflectance spectra in order to detect absorption bands of hydrated and hydroxide minerals in the 3 micrometer-band. We adopted a linear-image sensor with indium arsenide (InAs) photo diodes and a cooling system with a passive radiator to achieve an optics temperature of 188 K, which enables to retaining sufficient sensitivity and noise level in the 3 micrometer wavelength region. We conducted ground performance tests for the NIRS3 flight model (FM) to confirm its baseline specifications. The results imply that the properties such as the signal-to-noise ratio (SNR) conform to scientific requirements to determine the degree of aqueous alteration, such as CM or CI chondrite, and the stage of thermal metamorphism on the asteroid surface.
ionsNakajima, Kaoru*; Nagano, Kengo*; Suzuki, Motofumi*; Narumi, Kazumasa; Saito, Yuichi; Hirata, Koichi*; Kimura, Kenji*
Applied Physics Letters, 104(11), p.114103_1 - 114103_4, 2014/03
Times Cited Count：6 Percentile：26.85(Physics, Applied)
Mn
Si/Ge(111) heteroepitaxial interfacesNoguchi, Masaya*; Hirata, Tomoaki*; Kawakubo, Yuki*; Narumi, Kazumasa; Sakai, Seiji; Maeda, Yoshihito
Physica Status Solidi (C), 10(12), p.1732 - 1734, 2013/12
Times Cited Count：0 Percentile：0.01(Nanoscience & Nanotechnology)
(Mn
Fe)Si(111) epitaxially grown on Ge(111)Kawakubo, Yuki*; Noguchi, Masaya*; Hirata, Tomoaki*; Narumi, Kazumasa; Sakai, Seiji; Yamada, Shinya*; Hamaya, Kohei*; Miyao, Masanobu*; Maeda, Yoshihito
Physica Status Solidi (C), 10(12), p.1828 - 1831, 2013/12
Times Cited Count：0 Percentile：0.01(Nanoscience & Nanotechnology)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 314, p.39 - 42, 2013/11
Times Cited Count：4 Percentile：33.02(Instruments & Instrumentation) ions through micro- and nano-capillariesTsuchida, Hidetsugu*; Majima, Takuya*; Tomita, Shigeo*; Sasa, Kimikazu*; Narumi, Kazumasa; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Hirata, Koichi*; Shibata, Hiromi*; et al.
Nuclear Instruments and Methods in Physics Research B, 315, p.336 - 340, 2013/11
Times Cited Count：3 Percentile：26.71(Instruments & Instrumentation)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa; Kamiya, Tomihiro
JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 165, 2013/01
ion impactsHirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki*; Narumi, Kazumasa; Kamiya, Tomihiro
JAEA-Review 2011-043, JAEA Takasaki Annual Report 2010, P. 156, 2012/01
impactsHirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa
Applied Physics Express, 4(11), p.116202_1 - 116202_3, 2011/11
Times Cited Count：8 Percentile：34.67(Physics, Applied)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki*; Narumi, Kazumasa
Review of Scientific Instruments, 82(3), p.033101_1 - 033101_5, 2011/03
Times Cited Count：10 Percentile：44.79(Instruments & Instrumentation)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Takahashi, Yasuyuki; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 268(19), p.2930 - 2932, 2010/10
Times Cited Count：3 Percentile：28.83(Instruments & Instrumentation) ion impactHirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Adachi, Masahiro*; Yamada, Keisuke; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 266(10), p.2450 - 2452, 2008/05
Times Cited Count：13 Percentile：64.63(Instruments & Instrumentation)Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Narumi, Kazumasa
Applied Physics Express, 1(4), p.047002_1 - 047002_3, 2008/04
Times Cited Count：4 Percentile：18.78(Physics, Applied)Hayashi, Takumi; Konishi, Satoshi; Ohira, Shigeru; Nakamura, Hirofumi; Inoue, Masahiko*; Watanabe, Tetsuo*; Hirata, Kazuhiro*; Naruse, Yuji; Okuno, Kenji; Barnes, J. W.*; et al.
JAERI-M 93-094, 54 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Konishi, Satoshi; Nakamura, Hirofumi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Barnes, J. W.*; W.Harbin*; Anderson, J. L.*; et al.
JAERI-M 93-084, 32 Pages, 1993/03
no abstracts in English
Hayashi, Takumi; Nakamura, Hirofumi; Konishi, Satoshi; Inoue, Masahiko*; Hirata, Kazuhiro*; Okuno, Kenji; Naruse, Yuji; Anderson, J. L.*; Sherman, R. H.*; Willms, R. S.*; et al.
JAERI-M 93-083, 54 Pages, 1993/03
no abstracts in English
