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1. Heliocentric Distance Dependence of Zodiacal Light Observed by Hayabusa2#

Author

Tsumura, Kohji, Matsuura, Shuji, Sano, Kei, Iwata, Takahiro, Yano, Hajime, Kitazato, Kohei, Takimoto, Kohji, Yamada, Manabu, Morota, Tomokatsu, Kouyama, Toru, Hayakawa, Masahiko, Yokota, Yasuhiro, Tatsumi, Eri, Matsuoka, Moe, Sakatani, Naoya, Honda, Rie, Kameda, Shingo, Suzuki, Hidehiko, Cho, Yuichiro, Yoshioka, Kazuo, Ogawa, Kazunori, Shirai, Kei, Sawada, Hirotaka, and Sugita, Seiji

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Zodiacal light (ZL) is sunlight scattered by interplanetary dust particles (IDPs) at optical wavelengths. The spatial distribution of IDPs in the Solar System may hold an important key to understanding the evolution of the Solar System and material transportation within it. The number density of IDPs can be expressed as $n(r) \sim r^{-\alpha}$, and the exponent $\alpha \sim 1.3$ was obtained by previous observations from interplanetary space by Helios 1/2 and Pioneer 10/11 in the 1970s and 1980s. However, no direct measurements of $\alpha$ based on ZL observations from interplanetary space outside Earth's orbit have been performed since then. Here, we introduce initial results for the radial profile of the ZL at optical wavelengths observed over the range 0.76-1.06 au by ONC-T aboard the Hayabusa2# mission in 2021-2022. The ZL brightness we obtained is well reproduced by a model brightness, although there is a small excess of the observed ZL brightness over the model brightness at around 0.9 au. The radial power-law index we obtained is $\alpha = 1.30 \pm 0.08$, which is consistent with previous results based on ZL observations. The dominant source of uncertainty arises from the uncertainty in estimating the diffuse Galactic light (DGL)., Comment: 22 pages, 19 figures, 4 tables, accepted for publication by Earth, Planets and Space

Published
2023
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2. Characterization of the MASCOT landing area by Hayabusa2

Author

Schröder, Stefan, Sakatani, Naoya, Honda, Rie, Tatsumi, Eri, Yokota, Yasuhiro, Domingue, Deborah, Cho, Yuichiro, Kameda, Shingo, Kitazato, Kohei, Kouyama, Toru, Matsuoka, Moe, Miura, Akira, Morota, Tomokatsu, Okada, Tatsuaki, Sawada, Hirotaka, Senshu, Hiroki, Shimaki, Yuri, Sugita, Seiji, Tanaka, Satoshi, Yabuta, Hikaru, Yamada, Manabu, Grott, Matthias, Hamm, Maximilian, Ho, Tra-Mi, Jaumann, Ralf, Mottola, Stefano, Otto, Katharina, Schmitz, Nicole, and Scholten, Frank

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Context. After landing on C-type asteroid Ryugu, MASCOT imaged brightly colored, submillimeter-sized inclusions in a small rock. Hayabusa2 successfully returned a sample of small particles from the surface of Ryugu, but none of these appear to harbor such inclusions. The samples are considered representative of Ryugu. Aims. To understand the apparent discrepancy between MASCOT observations and Ryugu samples, we assess whether the MASCOT landing site, and the rock by implication, is perhaps atypical for Ryugu. Methods. We analyzed observations of the MASCOT landing area acquired by three instruments on board Hayabusa2: a camera (ONC), a near-infrared spectrometer (NIRS3), and a thermal infrared imager (TIR). We compared the landing area properties thus retrieved with those of the average Ryugu surface. Results. We selected several areas and landforms in the landing area for analysis: a small crater, a collection of smooth rocks, and the landing site itself. The crater is relatively blue and the rocks are relatively red. The spectral and thermophysical properties of the landing site are very close to those of the average Ryugu surface. The spectral properties of the MASCOT rock are probably close to average, but its thermal inertia may be somewhat higher. Conclusions. The MASCOT rock can also be considered representative of Ryugu. Some of the submillimeter-sized particles in the returned samples stand out because of their atypical spectral properties. Such particles may be present as inclusions in the MASCOT rock.

Published
2022
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3. The spatial distribution of impact craters on Ryugu

Author

Hirata, Naoyuki, Morota, Tomokatsu, Cho, Yuichiro, Kanamaru, Masanori, Watanabe, Sei-ichiro, Sugita, Seiji, Hirata, Naru, Yamamoto, Yukio, Noguchi, Rina, Shimaki, Yuri, Tatsumi, Eri, Yoshioka, Kazuo, Sawada, Hirotaka, Yokota, Yasuhiro, Sakatani, Naoya, Hayakawa, Masahiko, Matsuoka, Moe, Honda, Rie, Kameda, Shingo, Yamada, Mamabu, Kouyama, Toru, Suzuki, Hidehiko, Honda, Chikatoshi, Ogawa, Kazunori, Tsuda, Yuichi, Yoshikawa, Makoto, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Nakazawa, Satoru, Kikuchi, Shota, Yamaguchi, Tomohiro, Ogawa, Naoko, Ono, Go, Mimasu, Yuya, Yoshikawa, Kent, Takahashi, Tadateru, Takei, Yuto, Fujii, Atsushi, Takeuchi, Hiroshi, Okada, Tatsuaki, Shirai, Kei, and Iijima, Yu-ichi

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Asteroid 162173 Ryugu has numerous craters. The initial measurement of impact craters on Ryugu, by Sugita et al. (2019), is based on Hayabusa2 ONC images obtained during the first month after the arrival of Hayabusa2 in June 2018. Utilizing new images taken until February 2019, we constructed a global impact crater catalogue of Ryugu, which includes all craters larger than 20 m in diameter on the surface of Ryugu. As a result, we identified 77 craters on the surface of Ryugu. Ryugu shows variation in crater density which cannot be explained by the randomness of cratering; there are more craters at lower latitudes and fewer at higher latitudes, and fewer craters in the western bulge (160 E - 290 E) than in the region around the meridian (300 E - 30 E). This variation implies a complicated geologic history for Ryugu. It seems that the longitudinal variation in crater density simply indicates variation in the crater ages; the cratered terrain around the meridian seems to be geologically old while the western bulge is relatively young. The latitudinal variation in crater density suggests that the equatorial ridge of Ryugu is a geologically old structure; however, this could be alternatively explained by a collision with many fission fragments during a short rotational period of Ryugu in the past., Comment: 18 pages 3 figures

Published
2022
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4. Resurfacing processes constrained by crater distribution on Ryugu

Author

Takaki, Naofumi, Cho, Yuichiro, Morota, Tomokatsu, Tatsumi, Eri, Honda, Rie, Kameda, Shingo, Yokota, Yasuhiro, Sakatani, Naoya, Kouyama, Toru, Hayakawa, Masahiko, Matsuoka, Moe, Yamada, Manabu, Honda, Chikatoshi, Suzuki, Hidehiko, Yoshioka, Kazuo, Ogawa, Kazunori, Sawada, Hirotaka, Michel, Patrick, and Sugita, Seiji

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Understanding the geological modification processes on asteroids can provide information concerning their surface history. Images of small asteroids from spacecraft show a depletion in terms of smaller craters. Seismic shaking was considered to be responsible for crater erasure and the main driver modifying the geology of asteroids via regolith convection or the Brazil nut effect. However, a recent artificial impact experiment on the asteroid Ryugu by the Japanese Hayabusa2 mission revealed minimal seismic activity. To investigate whether a seismic shaking model can reproduce the observed crater record, the crater distribution on Ryugu was analyzed using crater production functions under cohesionless conditions. Crater retention ages were estimated as a function of crater diameter for Ryugu, Itokawa, Eros, and Bennu using the crater size-frequency distribution and crater production function estimated for those asteroids. We found that the power-law indices "a" are inconsistent with diffusion processes (e.g., seismic shaking, a=2). This result suggests that seismic shaking models based on diffusion equations cannot explain the crater distribution on small asteroids. Alternative processes include surface flows, possibly at the origin of geomorphological and spectral features of Ryugu. We demonstrate that the vertical mixing of material at depths shallower than 1 m occurs over 10^3-10^5 yr by cratering and obliteration. The young surface age of Ryugu is consistent with the slow space weathering that results from cratering, as suggested in previous studies. The timescale (10^4-10^6 yr) required for resurfacing at depths of 2-4 m can be compared with the cosmic-ray exposure ages of returned samples to constrain the distribution of impactors that collide with Ryugu., Comment: 30 pages, 9 figures, 2 tables. Submitted to Icarus

Published
2021
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5. Image registration for multi-band images taken by ONC-T onboard Hayabusa2

Author

Kouyama, Toru, Tatsumi, Eri, Honda, Chikatoshi, Honda, Rie, Morota, Tomokatsu, Yokota, Yasuhiro, Kameda, Shingo, Yamada, Manabu, Suzuki, Hidehiko, Sakatani, Naoya, Hayakawa, Masahiko, Cho, Yuichiro, Matsuoka, Moe, Yoshioka, Kazuo, Sawada, Hirotaka, and Sugita, Seiji

Subjects
Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Hayabusa2, a Japanese sample-return mission to a C-type asteroid, arrived at its target 162173 Ryugu in June 2018. The optical navigation cameras (ONC-T, ONC-W1, ONC-W2) successfully obtained numerous images of Ryugu. ONC-T is a telescopic framing camera with a charge-coupled device (CCD), has seven filter bands in ultraviolet, visible and near infrared wavelength ranges, and were used to map the spectral distribution of the Ryugu surface. Since the locations of a target seen in ONC-T images are slightly different among different wavelength images in one multi-band observation sequence due to changes in spacecraft positions and attitudes during the filter-changing sequence, one of the image processing issues is image co-registration among images for different wavelength bands. To quickly complete the image co-registration to meet a limited mission schedule, we combined conventional image co-registration techniques with several improvements based on previous planetary missions. The results of our analysis using actual ONC-T images indicate that image co-registration can reach accuracy on the order of 0.1 pixels, which is sufficient for many spectral mapping applications for Ryugu analyses., Comment: Hayabusa2, ONC-T, Multi-band imaging, Image co-registration, Cross correlation

Published
2021

6. High-Resolution Observations of Bright Boulders on Asteroid Ryugu: 1. Size Frequency Distribution and Morphology

Author

Sugimoto, Chiho, Tatsumi, Eri, Cho, Yuichiro, Morota, Tomokatsu, Honda, Rie, Kameda, Shingo, Yokota, Yosuhiro, Yumoto, Koki, Aoki, Minami, DellaGiustina, Daniella N., Michikami, Tatsuhiro, Hiroi, Takahiro, Domingue, Deborah L., Michel, Patrick, Schröder, Stefan E., Nakamura, Tomoki, Yamada, Manabu, Sakatani, Naoya, Kouyama, Toru, Honda, Chikatoshi, Hayakawa, Masahiko, Matsuoka, Moe, Suzuki, Hidehiko, Yoshioka, Kazuo, Ogawa, Kazunori, Sawada, Hirotaka, Arakawa, Masahiko, Saiki, Takanao, Imamura, Hiroshi, Takagi, Yasuhiko, Yano, Hajime, Shirai, Kei, Okamoto, Chisato, Tsuda, Yuichi, Nakazawa, Satoru, Iijima, Yuichi, and Sugita, Seiji

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

The near-Earth asteroid (162173) Ryugu displays a Cb-type average spectrum and a very low average normal albedo of 0.04. Although the majority of boulders on Ryugu have reflectance spectra and albedo similar to the Ryugu average, a small fraction of boulders exhibit anomalously high albedo and distinctively different spectra. A previous study (Tatsumi et al., 2021) based on the 2.7-km observations and a series of low-altitude (down to 68 m) descent observations conducted prior to the first touchdown have shown that the spectra of these anomalous boulders can be classified into two distinct groups corresponding to S and C type asteroids. The former originate most likely from an impactor that collided with Ryugu's parent body, whereas the latter may be from portions of Ryugu's parent body that experienced a different temperature history than experienced by the majority of boulder materials. In this study, we analyzed images captured after the first touchdown to determine the quantitative properties of these bright boulders on Ryugu. We measured the sizes of more than a thousand bright boulders and characterized the morphologic properties of the largest ones. Analyses revealed many properties of bright boulders important for the evolution of Ryugu and its parent body. The size-frequency distributions of S- and C-type bright boulders follow power laws. We obtained the ratios of the total volume and surface area of S-type bright boulders to those of average dark boulders on the Ryugu surface. Also, many of the bright boulders are embedded in a larger substrate boulder, suggesting that they have experienced mixing and conglomeration with darker fragments on the parent body, rather than gently landing on Ryugu during or after its formation by reaccumulation. This is consistent with the hypothesis that S-type bright boulders were likely mixed during and/or before a catastrophic disruption., Comment: 19 pages, 11 figures, 3 Tables, published in Icarus, 369, 15 November, 2021, 114529

Published
2021
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7. High-Resolution Observations of Bright Boulders on Asteroid Ryugu: 2. Spectral Properties

Author

Sugimoto, Chiho, Tatsumi, Eri, Cho, Yuichiro, Morota, Tomokatsu, Honda, Rie, Kameda, Shingo, Yokota, Yosuhiro, Yumoto, Koki, Aoki, Minami, DellaGiustina, Daniella N., Michikami, Tatsuhiro, Hiroi, Takahiro, Domingue, Deborah L., Michel, Patrick, Schröder, Stefan, Nakamura, Tomoki, Yamada, Manabu, Sakatani, Naoya, Kouyama, Toru, Honda, Chikatoshi, Hayakawa, Masahiko, Matsuoka, Moe, Suzuki, Hidehiko, Yoshioka, Kazuo, Ogawa, Kazunori, Sawada, Hirotaka, Arakawa, Masahiko, Saiki, Takanao, Imamura, Hiroshi, Takagi, Yasuhiko, Yano, Hajime, Shirai, Kei, Okamoto, Chisato, Tsuda, Yuichi, Nakazawa, Satoru, Iijima, Yuichi, and Sugita, Seiji

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Many small boulders with reflectance values higher than 1.5 times the average reflectance have been found on the near-Earth asteroid 162173 Ryugu. Based on their visible wavelength spectral differences, Tatsumi et al. (2021) defined two bright boulder classes: C-type and S-type. These two classifications of bright boulders have different size distributions and spectral trends. In this study, we measured the spectra of 79 bright boulders and investigated their detailed spectral properties. Analyses obtained a number of important results. First, S-type bright boulders on Ryugu have spectra that are similar to those found for two different ordinary chondrites with different initial spectra that have been experimentally space weathered the same way. This suggests that there may be two populations of S-type bright boulders on Ryugu, perhaps originating from two different impactors that hit its parent body. Second, the model space-weathering ages of meter-size S-type bright boulders, based on spectral change rates derived in previous experimentally irradiated ordinary chondrites, are 0.1-1 Myr, which is consistent with the crater retention age (

Published
2021
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8. Simultaneous geometric calibration and orbit-attitude determination of Hayabusa2’s deployable camera (DCAM3)

Author

Kikuchi, Shota, Shirai, Kei, Ishibashi, Ko, Wada, Koji, Yokota, Yasuhiro, Honda, Rie, Kadono, Toshihiko, Shimaki, Yuri, Sakatani, Naoya, Ogawa, Kazunori, Sawada, Hirotaka, Saiki, Takanao, Mimasu, Yuya, Takei, Yuto, Sugita, Seiji, Kouyama, Toru, Hirata, Naru, Nakazawa, Satoru, Yoshikawa, Makoto, Tanaka, Satoshi, Watanabe, Sei-ichiro, Tsuda, Yuichi, and Arakawa, Masahiko

Published
2024
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9. The Comet Interceptor Mission

Author

Jones, Geraint H., Snodgrass, Colin, Tubiana, Cecilia, Küppers, Michael, Kawakita, Hideyo, Lara, Luisa M., Agarwal, Jessica, André, Nicolas, Attree, Nicholas, Auster, Uli, Bagnulo, Stefano, Bannister, Michele, Beth, Arnaud, Bowles, Neil, Coates, Andrew, Colangeli, Luigi, Corral van Damme, Carlos, Da Deppo, Vania, De Keyser, Johan, Della Corte, Vincenzo, Edberg, Niklas, El-Maarry, Mohamed Ramy, Faggi, Sara, Fulle, Marco, Funase, Ryu, Galand, Marina, Goetz, Charlotte, Groussin, Olivier, Guilbert-Lepoutre, Aurélie, Henri, Pierre, Kasahara, Satoshi, Kereszturi, Akos, Kidger, Mark, Knight, Matthew, Kokotanekova, Rosita, Kolmasova, Ivana, Kossacki, Konrad, Kührt, Ekkehard, Kwon, Yuna, La Forgia, Fiorangela, Levasseur-Regourd, Anny-Chantal, Lippi, Manuela, Longobardo, Andrea, Marschall, Raphael, Morawski, Marek, Muñoz, Olga, Näsilä, Antti, Nilsson, Hans, Opitom, Cyrielle, Pajusalu, Mihkel, Pommerol, Antoine, Prech, Lubomir, Rando, Nicola, Ratti, Francesco, Rothkaehl, Hanna, Rotundi, Alessandra, Rubin, Martin, Sakatani, Naoya, Sánchez, Joan Pau, Simon Wedlund, Cyril, Stankov, Anamarija, Thomas, Nicolas, Toth, Imre, Villanueva, Geronimo, Vincent, Jean-Baptiste, Volwerk, Martin, Wurz, Peter, Wielders, Arno, Yoshioka, Kazuo, Aleksiejuk, Konrad, Alvarez, Fernando, Amoros, Carine, Aslam, Shahid, Atamaniuk, Barbara, Baran, Jędrzej, Barciński, Tomasz, Beck, Thomas, Behnke, Thomas, Berglund, Martin, Bertini, Ivano, Bieda, Marcin, Binczyk, Piotr, Busch, Martin-Diego, Cacovean, Andrei, Capria, Maria Teresa, Carr, Chris, Castro Marín, José María, Ceriotti, Matteo, Chioetto, Paolo, Chuchra-Konrad, Agata, Cocola, Lorenzo, Colin, Fabrice, Crews, Chiaki, Cripps, Victoria, Cupido, Emanuele, Dassatti, Alberto, Davidsson, Björn J. R., De Roche, Thierry, Deca, Jan, Del Togno, Simone, Dhooghe, Frederik, Donaldson Hanna, Kerri, Eriksson, Anders, Fedorov, Andrey, Fernández-Valenzuela, Estela, Ferretti, Stefano, Floriot, Johan, Frassetto, Fabio, Fredriksson, Jesper, Garnier, Philippe, Gaweł, Dorota, Génot, Vincent, Gerber, Thomas, Glassmeier, Karl-Heinz, Granvik, Mikael, Grison, Benjamin, Gunell, Herbert, Hachemi, Tedjani, Hagen, Christian, Hajra, Rajkumar, Harada, Yuki, Hasiba, Johann, Haslebacher, Nico, Herranz De La Revilla, Miguel Luis, Hestroffer, Daniel, Hewagama, Tilak, Holt, Carrie, Hviid, Stubbe, Iakubivskyi, Iaroslav, Inno, Laura, Irwin, Patrick, Ivanovski, Stavro, Jansky, Jiri, Jernej, Irmgard, Jeszenszky, Harald, Jimenéz, Jaime, Jorda, Laurent, Kama, Mihkel, Kameda, Shingo, Kelley, Michael S. P., Klepacki, Kamil, Kohout, Tomáš, Kojima, Hirotsugu, Kowalski, Tomasz, Kuwabara, Masaki, Ladno, Michal, Laky, Gunter, Lammer, Helmut, Lan, Radek, Lavraud, Benoit, Lazzarin, Monica, Le Duff, Olivier, Lee, Qiu-Mei, Lesniak, Cezary, Lewis, Zoe, Lin, Zhong-Yi, Lister, Tim, Lowry, Stephen, Magnes, Werner, Markkanen, Johannes, Martinez Navajas, Ignacio, Martins, Zita, Matsuoka, Ayako, Matyjasiak, Barbara, Mazelle, Christian, Mazzotta Epifani, Elena, Meier, Mirko, Michaelis, Harald, Micheli, Marco, Migliorini, Alessandra, Millet, Aude-Lyse, Moreno, Fernando, Mottola, Stefano, Moutounaick, Bruno, Muinonen, Karri, Müller, Daniel R., Murakami, Go, Murata, Naofumi, Myszka, Kamil, Nakajima, Shintaro, Nemeth, Zoltan, Nikolajev, Artiom, Nordera, Simone, Ohlsson, Dan, Olesk, Aire, Ottacher, Harald, Ozaki, Naoya, Oziol, Christophe, Patel, Manish, Savio Paul, Aditya, Penttilä, Antti, Pernechele, Claudio, Peterson, Joakim, Petraglio, Enrico, Piccirillo, Alice Maria, Plaschke, Ferdinand, Polak, Szymon, Postberg, Frank, Proosa, Herman, Protopapa, Silvia, Puccio, Walter, Ranvier, Sylvain, Raymond, Sean, Richter, Ingo, Rieder, Martin, Rigamonti, Roberto, Ruiz Rodriguez, Irene, Santolik, Ondrej, Sasaki, Takahiro, Schrödter, Rolf, Shirley, Katherine, Slavinskis, Andris, Sodor, Balint, Soucek, Jan, Stephenson, Peter, Stöckli, Linus, Szewczyk, Paweł, Troznai, Gabor, Uhlir, Ludek, Usami, Naoto, Valavanoglou, Aris, Vaverka, Jakub, Wang, Wei, Wang, Xiao-Dong, Wattieaux, Gaëtan, Wieser, Martin, Wolf, Sebastian, Yano, Hajime, Yoshikawa, Ichiro, Zakharov, Vladimir, Zawistowski, Tomasz, Zuppella, Paola, Rinaldi, Giovanna, and Ji, Hantao

Published
2024
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10. Space weathering acts strongly on the uppermost surface of Ryugu

Author

Matsuoka, Moe, Kagawa, Ei-ichi, Amano, Kana, Nakamura, Tomoki, Tatsumi, Eri, Osawa, Takahito, Hiroi, Takahiro, Milliken, Ralph, Domingue, Deborah, Takir, Driss, Brunetto, Rosario, Barucci, Antonella, Kitazato, Kohei, Sugita, Seiji, Fujioka, Yuri, Sasaki, Osamu, Kobayashi, Shiho, Iwata, Takahiro, Morota, Tomokatsu, Yokota, Yasuhiro, Kouyama, Toru, Honda, Rie, Kameda, Shingo, Cho, Yuichiro, Yoshioka, Kazuo, Sawada, Hirotaka, Hayakawa, Masahiko, Sakatani, Naoya, Yamada, Manabu, Suzuki, Hidehiko, Honda, Chikatoshi, Ogawa, Kazunori, Shirai, Kei, Lantz, Cateline, Rubino, Stefano, Yurimoto, Hisayoshi, Noguchi, Takaaki, Okazaki, Ryuji, Yabuta, Hikaru, Naraoka, Hiroshi, Sakamoto, Kanako, Tachibana, Shogo, Yada, Toru, Nishimura, Masahiro, Nakato, Aiko, Miyazaki, Akiko, Yogata, Kasumi, Abe, Masanao, Okada, Tatsuaki, Usui, Tomohiro, Yoshikawa, Makoto, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Nakazawa, Satoru, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2023
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12. A dehydrated space-weathered skin cloaking the hydrated interior of Ryugu

Author

Noguchi, Takaaki, Matsumoto, Toru, Miyake, Akira, Igami, Yohei, Haruta, Mitsutaka, Saito, Hikaru, Hata, Satoshi, Seto, Yusuke, Miyahara, Masaaki, Tomioka, Naotaka, Ishii, Hope A., Bradley, John P., Ohtaki, Kenta K., Dobrică, Elena, Leroux, Hugues, Le Guillou, Corentin, Jacob, Damien, de la Peña, Francisco, Laforet, Sylvain, Marinova, Maya, Langenhorst, Falko, Harries, Dennis, Beck, Pierre, Phan, Thi H. V., Rebois, Rolando, Abreu, Neyda M., Gray, Jennifer, Zega, Thomas, Zanetta, Pierre-M., Thompson, Michelle S., Stroud, Rhonda, Burgess, Kate, Cymes, Brittany A., Bridges, John C., Hicks, Leon, Lee, Martin R., Daly, Luke, Bland, Phil A., Zolensky, Michael E., Frank, David R., Martinez, James, Tsuchiyama, Akira, Yasutake, Masahiro, Matsuno, Junya, Okumura, Shota, Mitsukawa, Itaru, Uesugi, Kentaro, Uesugi, Masayuki, Takeuchi, Akihisa, Sun, Mingqi, Enju, Satomi, Takigawa, Aki, Michikami, Tatsuhiro, Nakamura, Tomoki, Matsumoto, Megumi, Nakauchi, Yusuke, Abe, Masanao, Arakawa, Masahiko, Fujii, Atsushi, Hayakawa, Masahiko, Hirata, Naru, Hirata, Naoyuki, Honda, Rie, Honda, Chikatoshi, Hosoda, Satoshi, Iijima, Yu-ichi, Ikeda, Hitoshi, Ishiguro, Masateru, Ishihara, Yoshiaki, Iwata, Takahiro, Kawahara, Kousuke, Kikuchi, Shota, Kitazato, Kohei, Matsumoto, Koji, Matsuoka, Moe, Mimasu, Yuya, Miura, Akira, Morota, Tomokatsu, Nakazawa, Satoru, Namiki, Noriyuki, Noda, Hirotomo, Noguchi, Rina, Ogawa, Naoko, Ogawa, Kazunori, Okada, Tatsuaki, Okamoto, Chisato, Ono, Go, Ozaki, Masanobu, Saiki, Takanao, Sakatani, Naoya, Sawada, Hirotaka, Senshu, Hiroki, Shimaki, Yuri, Shirai, Kei, Sugita, Seiji, Takei, Yuto, Takeuchi, Hiroshi, Tanaka, Satoshi, Tatsumi, Eri, Terui, Fuyuto, Tsukizaki, Ryudo, Wada, Koji, Yamada, Manabu, Yamada, Tetsuya, Yamamoto, Yukio, Yano, Hajime, Yokota, Yasuhiro, Yoshihara, Keisuke, Yoshikawa, Makoto, Yoshikawa, Kent, Fukai, Ryohta, Furuya, Shizuho, Hatakeda, Kentaro, Hayashi, Tasuku, Hitomi, Yuya, Kumagai, Kazuya, Miyazaki, Akiko, Nakato, Aiko, Nishimura, Masahiro, Soejima, Hiromichi, Suzuki, Ayako I., Usui, Tomohiro, Yada, Toru, Yamamoto, Daiki, Yogata, Kasumi, Yoshitake, Miwa, Connolly, Jr, Harold C., Lauretta, Dante S., Yurimoto, Hisayoshi, Nagashima, Kazuhide, Kawasaki, Noriyuki, Sakamoto, Naoya, Okazaki, Ryuji, Yabuta, Hikaru, Naraoka, Hiroshi, Sakamoto, Kanako, Tachibana, Shogo, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2023
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13. The Western Bulge of 162173 Ryugu Formed as a Result of a Rotationally Driven Deformation Process

Author

Hirabayashi, Masatoshi, Tatsumi, Eri, Miyamoto, Hideaki, Komatsu, Goro, Sugita, Seiji, Watanabe, Sei-ichiro, Scheeres, Daniel J., Barnouin, Olivier S., Michel, Patrick, Honda, Chikatoshi, Michikami, Tatsuhiro, Cho, Yuichiro, Morota, Tomokatsu, Hirata, Naru, Hirata, Naoyuki, Sakatani, Naoya, Schwartz, Stephen R., Honda, Rie, Yokota, Yasuhiro, Kameda, Shingo, Suzuki, Hidehiko, Kouyama, Toru, Hayakawa, Masahiko, Matsuoka, Moe, Yoshioka, Kazuo, Ogawa, Kazunori, Sawada, Hirotaka, Yoshikawa, Makoto, and Tsuda, Yuichi

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

162173 Ryugu, the target of Hayabusa2, has a round shape with an equatorial ridge, which is known as a spinning top-shape. A strong centrifugal force is a likely contributor to Ryugu's top-shaped features. Observations by Optical Navigation Camera onboard Hayabusa2 show a unique longitudinal variation in geomorphology; the western side of this asteroid, later called the western bulge, has a smooth surface and a sharp equatorial ridge, compared to the other side. Here, we propose a structural deformation process that generated the western bulge. Applying the mission-derived shape model, we employ a finite element model technique to analyze the locations that experience structural failure within the present shape. Assuming that materials are uniformly distributed, our model shows the longitudinal variation in structurally failed regions when the spin period is shorter than ~3.75 h. Ryugu is structurally intact in the subsurface region of the western bulge while other regions are sensitive to structural failure. We infer that this variation is indicative of the deformation process that occurred in the past, and the western bulge is more relaxed structurally than the other region. Our analysis also shows that this deformation process might occur at a spin period between ~3.5 h and ~3.0 h, providing the cohesive strength ranging between ~4 Pa and ~10 Pa., Comment: 8 pages, 5 figures, published in the Astrophysical Journal Letters, 874, 1, L10

Published
2019
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14. Thermal conductivity and coordination number of compressed dust aggregates

Author

Arakawa, Sota, Tatsuuma, Misako, Sakatani, Naoya, and Nakamoto, Taishi

Subjects
Astrophysics - Earth and Planetary Astrophysics, Condensed Matter - Soft Condensed Matter
Abstract

Understanding the heat transfer mechanism within dust aggregates is of great importance for many subjects in planetary science. We calculated the coordination number and the thermal conductivity through the solid network of compressed dust aggregates. We found a simple relationship between the coordination number and the filling factor and revealed that the thermal conductivity through the solid network of aggregates is represented by a power-law function of the filling factor and the coordination number., Comment: 8 pages, 7 figures. Accepted for publication in Icarus. arXiv admin note: text overlap with arXiv:1711.06268

Published
2019
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15. A pristine record of outer Solar System materials from asteroid Ryugu’s returned sample

Author

Ito, Motoo, Tomioka, Naotaka, Uesugi, Masayuki, Yamaguchi, Akira, Shirai, Naoki, Ohigashi, Takuji, Liu, Ming-Chang, Greenwood, Richard C., Kimura, Makoto, Imae, Naoya, Uesugi, Kentaro, Nakato, Aiko, Yogata, Kasumi, Yuzawa, Hayato, Kodama, Yu, Tsuchiyama, Akira, Yasutake, Masahiro, Findlay, Ross, Franchi, Ian A., Malley, James A., McCain, Kaitlyn A., Matsuda, Nozomi, McKeegan, Kevin D., Hirahara, Kaori, Takeuchi, Akihisa, Sekimoto, Shun, Sakurai, Ikuya, Okada, Ikuo, Karouji, Yuzuru, Arakawa, Masahiko, Fujii, Atsushi, Fujimoto, Masaki, Hayakawa, Masahiko, Hirata, Naoyuki, Hirata, Naru, Honda, Rie, Honda, Chikatoshi, Hosoda, Satoshi, Iijima, Yu-ichi, Ikeda, Hitoshi, Ishiguro, Masateru, Ishihara, Yoshiaki, Iwata, Takahiro, Kawahara, Kosuke, Kikuchi, Shota, Kitazato, Kohei, Matsumoto, Koji, Matsuoka, Moe, Michikami, Tatsuhiro, Mimasu, Yuya, Miura, Akira, Mori, Osamu, Morota, Tomokatsu, Nakazawa, Satoru, Namiki, Noriyuki, Noda, Hirotomo, Noguchi, Rina, Ogawa, Naoko, Ogawa, Kazunori, Okada, Tatsuaki, Okamoto, Chisato, Ono, Go, Ozaki, Masanobu, Saiki, Takanao, Sakatani, Naoya, Sawada, Hirotaka, Senshu, Hiroki, Shimaki, Yuri, Shirai, Kei, Sugita, Seiji, Takei, Yuto, Takeuchi, Hiroshi, Tanaka, Satoshi, Tatsumi, Eri, Terui, Fuyuto, Tsukizaki, Ryudo, Wada, Koji, Yamada, Manabu, Yamada, Tetsuya, Yamamoto, Yukio, Yano, Hajime, Yokota, Yasuhiro, Yoshihara, Keisuke, Yoshikawa, Makoto, Yoshikawa, Kent, Fukai, Ryota, Furuya, Shizuho, Hatakeda, Kentaro, Hayashi, Tasuku, Hitomi, Yuya, Kumagai, Kazuya, Miyazaki, Akiko, Nishimura, Masahiro, Soejima, Hiromichi, Iwamae, Ayako, Yamamoto, Daiki, Yoshitake, Miwa, Yada, Toru, Abe, Masanao, Usui, Tomohiro, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2022
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16. Measurement of Microscopic Thermal Diffusivity Distribution for Ryugu Sample by Infrared Lock-in Periodic Heating Method

Author

Ishizaki, Takuya, Nagano, Hosei, Tanaka, Satoshi, Sakatani, Naoya, Nakamura, Tomoki, Okada, Tatsuaki, Fujita, Ryohei, Alasli, Abdulkareem, Morita, Tomoyo, Kikuiri, Mizuha, Amano, Kana, Kagawa, Eiichi, Yurimoto, Hisayoshi, Noguchi, Takaaki, Okazaki, Ryuji, Yabuta, Hikaru, Naraoka, Hiroshi, Sakamoto, Kanako, Tachibana, Shogo, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2023
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17. Updated Inflight Calibration of Hayabusa2's Optical Navigation Camera (ONC) for Scientific Observations during the Cruise Phase

Author

Tatsumi, Eri, Kouyama, Toru, Suzuki, Hidehiko, Yamada, Manabu, Sakatani, Naoya, Kameda, Shingo, Yokota, Yasuhiro, Honda, Rie, Morota, Tomokatsu, Moroi, Keiichi, Tanabe, Naoya, Kamiyoshihara, Hiroaki, Ishida, Marika, Yoshioka, Kazuo, Sato, Hiroyuki, Honda, Chikatoshi, Hayakawa, Masahiko, Kitazato, Kohei, Sawada, Hirotaka, and Sugita, Seiji

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

The Optical Navigation Camera (ONC-T, ONC-W1, ONC-W2) onboard Hayabusa2 are also being used for scientific observations of the mission target, C-complex asteroid 162173 Ryugu. Science observations and analyses require rigorous instrument calibration. In order to meet this requirement, we have conducted extensive inflight observations during the 3.5 years of cruise after the launch of Hayabusa2 on 3 December 2014. In addition to the first inflight calibrations by Suzuki et al. (2018), we conducted an additional series of calibrations, including read-out smear, electronic-interference noise, bias, dark current, hot pixels, sensitivity, linearity, flat-field, and stray light measurements for the ONC. Moreover, the calibrations, especially flat-fields and sensitivities, of ONC-W1 and -W2 are updated for the analysis of the low-altitude (i.e., high-resolution) observations, such as the gravity measurement, touchdowns, and the descents for MASCOT and MINERVA-II payload releases. The radiometric calibration for ONC-T is also updated in this study based on star and Moon observations. Our updated inflight sensitivity measurements suggest the accuracy of the absolute radiometric calibration contains less than 1.8% error for the ul-, b-, v-, Na-, w-, and x-bands based on star calibration observations and ~5% for the p-band based on lunar calibration observations. The radiance spectra of the Moon, Jupiter, and Saturn from the ONC-T show good agreement with the spacecraft-based observations of the Moon from SP/SELENE and WAC/LROC and with ground-based telescopic observations for Jupiter and Saturn., Comment: Submitted to Icarus

Published
2018
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18. Asteroid Ryugu Before the Hayabusa2 Encounter

Author

Wada, Koji, Grott, Matthias, Michel, Patrick, Walsh, Kevin J., Barucci, Antonella M., Biele, Jens, Blum, Jürgen, Ernst, Carolyn M., Grundmann, Jan T., Gundlach, Bastian, Hagermann, Axel, Hamm, Maximilian, Jutzi, Martin, Kim, Myung-Jin, Kührt, Ekkehard, Corre, Lucille Le, Libourel, Guy, Lichtenheldt, Roy, Maturilli, Alessandro, Messenger, Scott R., Michikami, Tatsuhiro, Miyamoto, Hideaki, Mottola, Stefano, Nakamura, Akiko M., Müller, Thomas, Nittler, Larry R., Ogawa, Kazunori, Okada, Tatsuaki, Palomba, Ernesto, Sakatani, Naoya, Schröder, Stefan, Senshu, Hiroki, Takir, Driss, and Zolensky, Michael E.

Subjects
Astrophysics - Earth and Planetary Astrophysics
Abstract

Asteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that Ryugu is a C-type near-Earth asteroid with a diameter of less than 1 km, but the knowledge of its detailed properties is still very limited. This paper summarizes our best understanding of the physical and dynamical properties of Ryugu based on remote sensing and theoretical modeling. This information is used to construct a design reference model of the asteroid that is used for formulation of mission operations plans in advance of asteroid arrival. Particular attention is given to the surface properties of Ryugu that are relevant to sample acquisition. This reference model helps readers to appropriately interpret the data that will be directly obtained by Hayabusa2 and promotes scientific studies not only for Ryugu itself and other small bodies but also for the Solar System evolution that small bodies shed light on., Comment: 62 pages, 10 figures, 8 tables. Submitted to Space Science Reviews, on 6 April 2018

Published
2018

19. Site selection for the Hayabusa2 artificial cratering and subsurface material sampling on Ryugu

Author

Kikuchi, Shota, Watanabe, Sei-ichiro, Wada, Koji, Saiki, Takanao, Yabuta, Hikaru, Sugita, Seiji, Abe, Masanao, Arakawa, Masahiko, Cho, Yuichiro, Hayakawa, Masahiko, Hirata, Naoyuki, Hirata, Naru, Honda, Chikatoshi, Honda, Rie, Ishibashi, Ko, Ishihara, Yoshiaki, Iwata, Takahiro, Kadono, Toshihiko, Kameda, Shingo, Kitazato, Kohei, Kouyama, Toru, Matsumoto, Koji, Matsuoka, Moe, Michikami, Tatsuhiro, Mimasu, Yuya, Miura, Akira, Morota, Tomokatsu, Nakamura, Tomoki, Nakazawa, Satoru, Namiki, Noriyuki, Noguchi, Rina, Ogawa, Kazunori, Ogawa, Naoko, Okada, Tatsuaki, Ono, Go, Sakatani, Naoya, Sawada, Hirotaka, Senshu, Hiroki, Shimaki, Yuri, Shirai, Kei, Tachibana, Shogo, Takei, Yuto, Tanaka, Satoshi, Tatsumi, Eri, Terui, Fuyuto, Yamada, Manabu, Yamamoto, Yukio, Yokota, Yasuhiro, Yoshikawa, Kent, Yoshikawa, Makoto, and Tsuda, Yuichi

Published
2022
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20. Three-axial shape distributions of pebbles, cobbles and boulders smaller than a few meters on asteroid Ryugu

Author

Michikami, Tatsuhiro, Hagermann, Axel, Morota, Tomokatsu, Yokota, Yasuhiro, Urakawa, Seitaro, Okamura, Hiroyuki, Tanabe, Naoya, Yumoto, Koki, Ebihara, Tatsuki, Cho, Yuichiro, Ernst, Carolyn M., Hayakawa, Masahiko, Hirabayashi, Masatoshi, Hirata, Naru, Honda, Chikatoshi, Honda, Rie, Kameda, Shingo, Kanamaru, Masanori, Kikuchi, Hiroshi, Kikuchi, Shota, Kouyama, Toru, Matsuoka, Moe, Miyamoto, Hideaki, Noguchi, Takaaki, Noguchi, Rina, Ogawa, Kazunori, Okada, Tatsuaki, Sakatani, Naoya, Sasaki, Sho, Sawada, Hirotaka, Sugimoto, Chiho, Suzuki, Hidehiko, Tanaka, Satoshi, Tatsumi, Eri, Tsuchiyama, Akira, Tsuda, Yuichi, Watanabe, Sei-ichiro, Yamada, Manabu, Yoshikawa, Makoto, Yoshioka, Kazuo, and Sugita, Seiji

Published
2022
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21. Resurfacing processes constrained by crater distribution on Ryugu

Author

Takaki, Naofumi, Cho, Yuichiro, Morota, Tomokatsu, Tatsumi, Eri, Honda, Rie, Kameda, Shingo, Yokota, Yasuhiro, Sakatani, Naoya, Kouyama, Toru, Hayakawa, Masahiko, Matsuoka, Moe, Yamada, Manabu, Honda, Chikatoshi, Suzuki, Hidehiko, Yoshioka, Kazuo, Ogawa, Kazunori, Sawada, Hirotaka, Michel, Patrick, and Sugita, Seiji

Published
2022
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23. Preliminary analysis of the Hayabusa2 samples returned from C-type asteroid Ryugu

Author

Yada, Toru, Abe, Masanao, Okada, Tatsuaki, Nakato, Aiko, Yogata, Kasumi, Miyazaki, Akiko, Hatakeda, Kentaro, Kumagai, Kazuya, Nishimura, Masahiro, Hitomi, Yuya, Soejima, Hiromichi, Yoshitake, Miwa, Iwamae, Ayako, Furuya, Shizuho, Uesugi, Masayuki, Karouji, Yuzuru, Usui, Tomohiro, Hayashi, Tasuku, Yamamoto, Daiki, Fukai, Ryota, Sugita, Seiji, Cho, Yuichiro, Yumoto, Koki, Yabe, Yuna, Bibring, Jean-Pierre, Pilorget, Cedric, Hamm, Vincent, Brunetto, Rosario, Riu, Lucie, Lourit, Lionel, Loizeau, Damien, Lequertier, Guillaume, Moussi-Soffys, Aurelie, Tachibana, Shogo, Sawada, Hirotaka, Okazaki, Ryuji, Takano, Yoshinori, Sakamoto, Kanako, Miura, Yayoi N., Yano, Hajime, Ireland, Trevor R., Yamada, Tetsuya, Fujimoto, Masaki, Kitazato, Kohei, Namiki, Noriyuki, Arakawa, Masahiko, Hirata, Naru, Yurimoto, Hisayoshi, Nakamura, Tomoki, Noguchi, Takaaki, Yabuta, Hikaru, Naraoka, Hiroshi, Ito, Motoo, Nakamura, Eizo, Uesugi, Kentaro, Kobayashi, Katsura, Michikami, Tatsuhiro, Kikuchi, Hiroshi, Hirata, Naoyuki, Ishihara, Yoshiaki, Matsumoto, Koji, Noda, Hirotomo, Noguchi, Rina, Shimaki, Yuri, Shirai, Kei, Ogawa, Kazunori, Wada, Koji, Senshu, Hiroki, Yamamoto, Yukio, Morota, Tomokatsu, Honda, Rie, Honda, Chikatoshi, Yokota, Yasuhiro, Matsuoka, Moe, Sakatani, Naoya, Tatsumi, Eri, Miura, Akira, Yamada, Manabu, Fujii, Atsushi, Hirose, Chikako, Hosoda, Satoshi, Ikeda, Hitoshi, Iwata, Takahiro, Kikuchi, Shota, Mimasu, Yuya, Mori, Osamu, Ogawa, Naoko, Ono, Go, Shimada, Takanobu, Soldini, Stefania, Takahashi, Tadateru, Takei, Yuto, Takeuchi, Hiroshi, Tsukizaki, Ryudo, Yoshikawa, Kent, Terui, Fuyuto, Nakazawa, Satoru, Tanaka, Satoshi, Saiki, Takanao, Yoshikawa, Makoto, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2022
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25. Hayabusa2 pinpoint touchdown near the artificial crater on Ryugu: Trajectory design and guidance performance

Author

Kikuchi, Shota, Saiki, Takanao, Takei, Yuto, Terui, Fuyuto, Ogawa, Naoko, Mimasu, Yuya, Ono, Go, Yoshikawa, Kent, Sawada, Hirotaka, Takeuchi, Hiroshi, Ikeda, Hitoshi, Fujii, Atsushi, Sugita, Seiji, Morota, Tomokatsu, Yamada, Manabu, Honda, Rie, Yokota, Yasuhiro, Sakatani, Naoya, Kameda, Shingo, Kouyama, Toru, Hirata, Naru, Hirata, Naoyuki, Shirai, Kei, Kitazato, Kohei, Nakazawa, Satoru, Yoshikawa, Makoto, Tanaka, Satoshi, Wada, Koji, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Published
2021
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26. Development of image texture analysis technique for boulder distribution measurements: Applications to asteroids Ryugu and Itokawa

Author

Tanabe, Naoya, Cho, Yuichiro, Tatsumi, Eri, Ebihara, Tatsuki, Yumoto, Koki, Michikami, Tatsuhiro, Miyamoto, Hideaki, Morota, Tomokatsu, Honda, Chikatoshi, Michel, Patrick, Otto, Katharina, Barnouin, Olivier, Yoshioka, Kazuo, Sawada, Hirotaka, Yokota, Yasuhiro, Sakatani, Naoya, Hayakawa, Masahiro, Honda, Rie, Kameda, Shingo, Matsuoka, Moe, Yamada, Manabu, Kouyama, Toru, Suzuki, Hidehiko, Ogawa, Kazunori, and Sugita, Seiji

Published
2021
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27. Resurfacing processes on asteroid (162173) Ryugu caused by an artificial impact of Hayabusa2's Small Carry-on Impactor

Author

Honda, Rie, Arakawa, Masahiko, Shimaki, Yuri, Shirai, Kei, Yokota, Yasuhiro, Kadono, Toshihiko, Wada, Koji, Ogawa, Kazunori, Ishibashi, Ko, Sakatani, Naoya, Nakazawa, Satoru, Yasui, Minami, Morota, Tomokatsu, Kameda, Shingo, Tatsumi, Eri, Yamada, Manabu, Kouyama, Toru, Cho, Yuichiro, Matsuoka, Moe, Suzuki, Hidehiko, Honda, Chikatoshi, Hayakawa, Masahiko, Yoshioka, Kazuo, Hirata, Naru, Hirata, Naoyuki, Sawada, Hirotaka, Sugita, Seiji, Saiki, Takanao, Imamura, Hiroshi, Takagi, Yasuhiko, Yano, Hajime, Okamoto, Chisato, Tsuda, Yuichi, and Iijima, Yu-ichi

Published
2021
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28. Hayabusa2’s kinetic impact experiment

Author

Saiki, Takanao, primary, Sawada, Hirotaka, additional, Ogawa, Kazunori, additional, Mimasu, Yuya, additional, Takei, Yuto, additional, Arakawa, Masahiko, additional, Kadono, Toshihiko, additional, Wada, Koji, additional, Fujii, Atsushi, additional, Terui, Fuyuto, additional, Ogawa, Naoko, additional, Ono, Go, additional, Shirai, Kei, additional, Honda, Rie, additional, Ishibashi, Ko, additional, Sakatani, Naoya, additional, Yoshikawa, Kent, additional, Yoshikawa, Makoto, additional, Nakazawa, Satoru, additional, and Tsuda, Yuichi, additional

Published
2022
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29. Extended mission of Hayabusa2

Author

Mimasu, Yuya, primary, Kikuchi, Shota, additional, Takei, Yuto, additional, Saiki, Takanao, additional, Watanabe, Sei-ichiro, additional, Tanaka, Satoshi, additional, Hirabayashi, Masatoshi, additional, Sakatani, Naoya, additional, Kouyama, Toru, additional, Yoshikawa, Makoto, additional, Nakazawa, Satoru, additional, and Tsuda, Yuichi, additional

Published
2022
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30. Contributors

Author

Abe, Masanao, primary, Arakawa, Masahiko, additional, Bellerose, Julie, additional, Danno, Satoshi, additional, Farnocchia, Davide, additional, Fujii, Atsushi, additional, Fujita, Kazuhisa, additional, Fujita, Naoyuki, additional, Furukawa, Katsumi, additional, Goto, Daisuke, additional, Hayashi, Daisuke, additional, Hihara, Hiroki, additional, Hirabayashi, Masatoshi, additional, Hirose, Chikako, additional, Ho, Tra-Mi, additional, Honda, Rie, additional, Hosoda, Satoshi, additional, Ichikawa, Tsutomu, additional, Ikeda, Hitoshi, additional, Ishibashi, Ko, additional, Ishimaru, Takahiro, additional, Ito, Taichi, additional, Kadono, Toshihiko, additional, Kagawa, Hideshi, additional, Kameda, Shingo, additional, Kato, Takaaki, additional, Kawahara, Kosuke, additional, Kikuchi, Shota, additional, Kitazato, Kohei, additional, Kobiki, Noboru, additional, Kouyama, Toru, additional, Kushiki, Kenichi, additional, Maru, Yusuke, additional, Masuda, Tetsuya, additional, Matsuhisa, Takashi, additional, Matsuoka, Masatoshi, additional, Matsuoka, Moe, additional, Matsushima, Kota, additional, Michigami, Keisuke, additional, Mimasu, Yuya, additional, Miura, Akira, additional, Mori, Osamu, additional, Morota, Tomokatsu, additional, Moussi, Aurelie, additional, Nagata, Taiichi, additional, Nakatsuka, Junichi, additional, Nakazawa, Satoru, additional, Namiki, Noriyuki, additional, Nishiyama, Kazutaka, additional, Oda, Kenji, additional, Ogawa, Kazunori, additional, Ogawa, Naoko, additional, Ohnishi, Takafumi, additional, Okada, Tatsuaki, additional, Oki, Yusuke, additional, Ono, Go, additional, Oshima, Takeshi, additional, Saiki, Takanao, additional, Sakatani, Naoya, additional, Sano, Junpei, additional, Sawada, Hirotaka, additional, Sawai, Shujiro, additional, Shida, Maki, additional, Shimada, Daisuke, additional, Shimada, Takanobu, additional, Shirai, Kei, additional, Soldini, Stefania, additional, Sugita, Seiji, additional, Tachibana, Shogo, additional, Takami, Tsuyoshi, additional, Takei, Yuto, additional, Takeuchi, Hiroshi, additional, Tanaka, Satoshi, additional, Taniguchi, Sho, additional, Tanno, Hideyuki, additional, Tarzi, Zahi, additional, Tasker, Elizabeth, additional, Tatsumi, Eri, additional, Terui, Fuyuto, additional, Toda, Tomoaki, additional, Tsuda, Yuichi, additional, Tsukizaki, Ryudo, additional, Uo, Masashi, additional, Uramachi, Hikaru, additional, Van Wal, Stefaan, additional, Wada, Koji, additional, Watanabe, Sei-ichiro, additional, Yabuta, Hikaru, additional, Yamada, Manabu, additional, Yamada, Tetsuya, additional, Yamaguchi, Tomohiro, additional, Yasuda, Seiji, additional, Yokota, Yasuhiro, additional, Yoshikawa, Keisuke, additional, Yoshikawa, Kent, additional, Yoshikawa, Makoto, additional, and Yumoto, Koki, additional

Published
2022
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37. Crater depth-to-diameter ratios on asteroid 162173 Ryugu

Author

Noguchi, Rina, Hirata, Naoyuki, Hirata, Naru, Shimaki, Yuri, Nishikawa, Naoki, Tanaka, Sayuri, Sugiyama, Takaaki, Morota, Tomokatsu, Sugita, Seiji, Cho, Yuichiro, Honda, Rie, Kameda, Shingo, Tatsumi, Eri, Yoshioka, Kazuo, Sawada, Hirotaka, Yokota, Yasuhiro, Sakatani, Naoya, Hayakawa, Masahiko, Matsuoka, Moe, Yamada, Manabu, Kouyama, Toru, Suzuki, Hidehiko, Honda, Chikatoshi, Ogawa, Kazunori, Kanamaru, Masanori, and Watanabe, Sei-ichiro

Published
2021
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38. Measurement of Microscopic Thermal Diffusivity Distribution for Ryugu Sample by Infrared Lock-in Periodic Heating Method

Author

Ishizaki, Takuya, Nagano, Hosei, Tanaka, Satoshi, Sakatani, Naoya, Nakamura, Tomoki, Okada, Tatsuaki, Fujita, Ryohei, Alasli, Abdulkareem, Morita, Tomoyo, Kikuiri, Mizuha, Amano, Kana, Kagawa, Eiichi, Yurimoto, Hisayoshi, Noguchi, Takaaki, Okazaki, Ryuji, Yabuta, Hikaru, Naraoka, Hiroshi, Sakamoto, Kanako, Tachibana, Shogo, Watanabe, Sei-ichiro, Tsuda, Yuichi, Ishizaki, Takuya, Nagano, Hosei, Tanaka, Satoshi, Sakatani, Naoya, Nakamura, Tomoki, Okada, Tatsuaki, Fujita, Ryohei, Alasli, Abdulkareem, Morita, Tomoyo, Kikuiri, Mizuha, Amano, Kana, Kagawa, Eiichi, Yurimoto, Hisayoshi, Noguchi, Takaaki, Okazaki, Ryuji, Yabuta, Hikaru, Naraoka, Hiroshi, Sakamoto, Kanako, Tachibana, Shogo, Watanabe, Sei-ichiro, and Tsuda, Yuichi

Abstract

The thermophysical properties of small Solar System bodies are essential to be determined, on which the thermal evolution of small bodies largely depends. The carbonaceous asteroid Ryugu is one of the small undifferentiated bodies formed in the early Solar System. Hayabusa2 explored the asteroid Ryugu and returned the surface samples in 2020 for detailed on-ground investigation, including measurements of thermal properties. Because the available sample amount was limited, this study developed a novel method to measure the thermal diffusivity of small and irregularly shaped samples of about 1 mm in diameter by combining lock-in thermography and periodic heating methods on the microscale. This method enables us to measure the thermal diffusivity of both flat-plate and granular shape samples by selecting the suitable detecting direction of the temperature response. Especially, when the sample has a flat-plate shape, the anisotropic distribution of the in-plane thermal diffusivity can be evaluated. This method was applied to six Ryugu samples, and the detailed anisotropic distribution of the thermal diffusivity was obtained. The measurement results showed that the samples show local thermal anisotropy caused by cracks and voids. The average thermal diffusivity among all samples was (2.8 to 5.8) × 10^−7 m2·s. Based on the density and specific heat of the samples obtained independently, the thermal effusivity was estimated to be 791 J·(s^1/2·m^2·K) to 1253 J·(s^1/2·m^2·K), which is defined as the resistance of surface temperature to the change of thermal input. The determined thermal effusivity, often called thermal inertia in planetary science, is larger than the observed value of 225 ± 45 J· (s^1/2·m^2·K) of the asteroid Ryugu's surface, obtained from the diurnal temperature change of the rotating asteroid by a thermal infrared camera onboard Hayabuas2. This difference is likely to be attributed to the difference in the analytical scale between the sample and the surfac

Published
2024

39. Thermophysical properties of the surface of asteroid 162173 Ryugu: Infrared observations and thermal inertia mapping

Author

Shimaki, Yuri, Senshu, Hiroki, Sakatani, Naoya, Okada, Tatsuaki, Fukuhara, Tetsuya, Tanaka, Satoshi, Taguchi, Makoto, Arai, Takehiko, Demura, Hirohide, Ogawa, Yoshiko, Suko, Kentaro, Sekiguchi, Tomohiko, Kouyama, Toru, Hasegawa, Sunao, Takita, Jun, Matsunaga, Tsuneo, Imamura, Takeshi, Wada, Takehiko, Kitazato, Kohei, Hirata, Naru, Hirata, Naoyuki, Noguchi, Rina, Sugita, Seiji, Kikuchi, Shota, Yamaguchi, Tomohiro, Ogawa, Naoko, Ono, Go, Mimasu, Yuya, Yoshikawa, Kent, Takahashi, Tadateru, Takei, Yuto, Fujii, Atsushi, Takeuchi, Hiroshi, Yamamoto, Yukio, Yamada, Manabu, Shirai, Kei, Iijima, Yu-ichi, Ogawa, Kazunori, Nakazawa, Satoru, Terui, Fuyuto, Saiki, Takanao, Yoshikawa, Makoto, Tsuda, Yuichi, and Watanabe, Sei-ichiro

Published
2020
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40. The spatial distribution of impact craters on Ryugu

Author

Hirata, Naoyuki, Morota, Tomokatsu, Cho, Yuichiro, Kanamaru, Masanori, Watanabe, Sei-ichiro, Sugita, Seiji, Hirata, Naru, Yamamoto, Yukio, Noguchi, Rina, Shimaki, Yuri, Tatsumi, Eri, Yoshioka, Kazuo, Sawada, Hirotaka, Yokota, Yasuhiro, Sakatani, Naoya, Hayakawa, Masahiko, Matsuoka, Moe, Honda, Rie, Kameda, Shingo, Yamada, Manabu, Kouyama, Toru, Suzuki, Hidehiko, Honda, Chikatoshi, Ogawa, Kazunori, Tsuda, Yuichi, Yoshikawa, Makoto, Saiki, Takanao, Tanaka, Satoshi, Terui, Fuyuto, Nakazawa, Satoru, Kikuchi, Shota, Yamaguchi, Tomohiro, Ogawa, Naoko, Ono, Go, Mimasu, Yuya, Yoshikawa, Kent, Takahashi, Tadateru, Takei, Yuto, Fujii, Atsushi, Takeuchi, Hiroshi, Okada, Tatsuaki, Shirai, Kei, and Iijima, Yu-ichi

Published
2020
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42. Spectrally blue hydrated parent body of asteroid (162173) Ryugu

Author

Tatsumi, Eri, Sakatani, Naoya, Riu, Lucie, Matsuoka, Moe, Honda, Rie, Morota, Tomokatsu, Kameda, Shingo, Nakamura, Tomoki, Zolensky, Michael, Brunetto, Rosario, Hiroi, Takahiro, Sasaki, Sho, Watanabe, Sei’ichiro, Tanaka, Satoshi, Takita, Jun, Pilorget, Cédric, de León, Julia, Popescu, Marcel, Rizos, Juan Luis, Licandro, Javier, Palomba, Ernesto, Domingue, Deborah, Vilas, Faith, Campins, Humberto, Cho, Yuichiro, Yoshioka, Kazuo, Sawada, Hirotaka, Yokota, Yasuhiro, Hayakawa, Masahiko, Yamada, Manabu, Kouyama, Toru, Suzuki, Hidehiko, Honda, Chikatoshi, Ogawa, Kazunori, Kitazato, Kohei, Hirata, Naru, Hirata, Naoyuki, Tsuda, Yuichi, Yoshikawa, Makoto, Saiki, Takanao, Terui, Fuyuto, Nakazawa, Satoru, Takei, Yuto, Takeuchi, Hiroshi, Yamamoto, Yukio, Okada, Tatsuaki, Shimaki, Yuri, Shirai, Kei, and Sugita, Seiji

Published
2021
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43. Design of telescopic nadir imager for geomorphology (TENGOO) and observation of surface reflectance by optical chromatic imager (OROCHI) for the Martian Moons Exploration (MMX)

Author

Kameda, Shingo, Ozaki, Masanobu, Enya, Keigo, Fuse, Ryota, Kouyama, Toru, Sakatani, Naoya, Suzuki, Hidehiko, Osada, Naoya, Kato, Hiroki, Miyamoto, Hideaki, Yamazaki, Atsushi, Nakamura, Tomoki, Okamoto, Takaya, Ishimaru, Takahiro, Hong, Peng, Ishibashi, Ko, Takashima, Takeshi, Ishigami, Ryoya, Kuo, Cheng-Ling, Abe, Shinsuke, Goda, Yuya, Murao, Hajime, Fujishima, Saori, Aoyama, Tsubasa, Hagiwara, Keiji, Mizumoto, Satoko, Tanaka, Noriko, Murakami, Kousuke, Matsumoto, Miho, Tanaka, Kenji, and Sakuta, Hironobu

Published
2021
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45. Alignment determination of the Hayabusa2 laser altimeter (LIDAR)

Author

Noda, Hirotomo, Senshu, Hiroki, Matsumoto, Koji, Namiki, Noriyuki, Mizuno, Takahide, Sugita, Seiji, Abe, Shinsuke, Araki, Hiroshi, Asari, Kazuyoshi, Cho, Yuichiro, Fujii, Atsushi, Hayakawa, Masahiko, Higuchi, Arika, Hirata, Naoyuki, Hirata, Naru, Honda, Chikatoshi, Honda, Rie, Ishihara, Yoshiaki, Kameda, Shingo, Kikuchi, Shota, Kouyama, Toru, Matsuoka, Moe, Mimasu, Yuya, Morota, Tomokatsu, Nakazawa, Satoru, Ogawa, Kazunori, Ogawa, Naoko, Ono, Go, Oshigami, Shoko, Saiki, Takanao, Sakatani, Naoya, Sasaki, Sho, Sawada, Hirotaka, Shizugami, Makoto, Suzuki, Hidehiko, Takahashi, Tadateru, Takei, Yuto, Tanaka, Satoshi, Tatsumi, Eri, Terui, Fuyuto, Tsuda, Yuichi, Tsuruta, Seiitsu, Watanabe, Sei-ichiro, Yamada, Manabu, Yamada, Ryuhei, Yamaguchi, Tomohiro, Yamamoto, Keiko, Yokota, Yasuhiro, Yoshida, Fumi, Yoshikawa, Kent, Yoshikawa, Makoto, and Yoshioka, Kazuo

Published
2021
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46. Surface environment of Phobos and Phobos simulant UTPS

Author

Miyamoto, Hideaki, Niihara, Takafumi, Wada, Koji, Ogawa, Kazunori, Senshu, Hiroki, Michel, Patrick, Kikuchi, Hiroshi, Hemmi, Ryodo, Nakamura, Tomoki, Nakamura, Akiko M., Hirata, Naoyuki, Sasaki, Sho, Asphaug, Erik, Britt, Daniel T., Abell, Paul A., Ballouz, Ronald-Louis, Banouin, Olivier S., Baresi, Nicola, Barucci, Maria A., Biele, Jens, Grott, Matthias, Hino, Hideitsu, Hong, Peng K., Imada, Takane, Kameda, Shingo, Kobayashi, Makito, Libourel, Guy, Mogi, Katsuro, Murdoch, Naomi, Nishio, Yuki, Okamoto, Shogo, Ota, Yuichiro, Otsuki, Masatsugu, Otto, Katharina A., Sakatani, Naoya, Shimizu, Yuta, Takemura, Tomohiro, Terada, Naoki, Tsukamoto, Masafumi, Usui, Tomohiro, and Willner, Konrad

Published
2021
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47. Highly porous nature of a primitive asteroid revealed by thermal imaging

Author

Okada, Tatsuaki, Fukuhara, Tetsuya, Tanaka, Satoshi, Taguchi, Makoto, Arai, Takehiko, Senshu, Hiroki, and Sakatani, Naoya

Subjects
Asteroids -- Thermal properties -- Natural history -- Observations, Porosity -- Observations, Carbonaceous rocks -- Thermal properties -- Natural history -- Observations, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Carbonaceous (C-type) asteroids.sup.1 are relics of the early Solar System that have preserved primitive materials since their formation approximately 4.6 billion years ago. They are probably analogues of carbonaceous chondrites.sup.2,3 and are essential for understanding planetary formation processes. However, their physical properties remain poorly known because carbonaceous chondrite meteoroids tend not to survive entry to Earth's atmosphere. Here we report on global one-rotation thermographic images of the C-type asteroid 162173 Ryugu, taken by the thermal infrared imager (TIR).sup.4 onboard the spacecraft Hayabusa2.sup.5, indicating that the asteroid's boulders and their surroundings have similar temperatures, with a derived thermal inertia of about 300 J m.sup.-2 s.sup.-0.5 K.sup.-1 (300 tiu). Contrary to predictions that the surface consists of regolith and dense boulders, this low thermal inertia suggests that the boulders are more porous than typical carbonaceous chondrites.sup.6 and that their surroundings are covered with porous fragments more than 10 centimetres in diameter. Close-up thermal images confirm the presence of such porous fragments and the flat diurnal temperature profiles suggest a strong surface roughness effect.sup.7,8. We also observed in the close-up thermal images boulders that are colder during the day, with thermal inertia exceeding 600 tiu, corresponding to dense boulders similar to typical carbonaceous chondrites.sup.6. These results constrain the formation history of Ryugu: the asteroid must be a rubble pile formed from impact fragments of a parent body with microporosity.sup.9 of approximately 30 to 50 per cent that experienced a low degree of consolidation. The dense boulders might have originated from the consolidated innermost region or they may have an exogenic origin. This high-porosity asteroid may link cosmic fluffy dust to dense celestial bodies.sup.10. Thermal imaging data obtained from the spacecraft Hayabusa2 reveal that the carbonaceous asteroid 162173 Ryugu is an object of unusually high porosity., Author(s): Tatsuaki Okada [sup.1] [sup.2] , Tetsuya Fukuhara [sup.3] , Satoshi Tanaka [sup.1] [sup.4] [sup.5] , Makoto Taguchi [sup.3] , Takehiko Arai [sup.6] , Hiroki Senshu [sup.7] , Naoya Sakatani [...]

Published
2020
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49. Boulder size and shape distributions on asteroid Ryugu

Author

Michikami, Tatsuhiro, Honda, Chikatoshi, Miyamoto, Hideaki, Hirabayashi, Masatoshi, Hagermann, Axel, Irie, Terunori, Nomura, Keita, Ernst, Carolyn M., Kawamura, Masaki, Sugimoto, Kiichi, Tatsumi, Eri, Morota, Tomokatsu, Hirata, Naru, Noguchi, Takaaki, Cho, Yuichiro, Kameda, Shingo, Kouyama, Toru, Yokota, Yasuhiro, Noguchi, Rina, Hayakawa, Masahiko, Hirata, Naoyuki, Honda, Rie, Matsuoka, Moe, Sakatani, Naoya, Suzuki, Hidehiko, Yamada, Manabu, Yoshioka, Kazuo, Sawada, Hirotaka, Hemmi, Ryodo, Kikuchi, Hiroshi, Ogawa, Kazunori, Watanabe, Sei-ichiro, Tanaka, Satoshi, Yoshikawa, Makoto, Tsuda, Yuichi, and Sugita, Seiji

Published
2019
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50. Updated inflight calibration of Hayabusa2's optical navigation camera (ONC) for scientific observations during the cruise phase

Author

Tatsumi, Eri, Kouyama, Toru, Suzuki, Hidehiko, Yamada, Manabu, Sakatani, Naoya, Kameda, Shingo, Yokota, Yasuhiro, Honda, Rie, Morota, Tomokatsu, Moroi, Keiichi, Tanabe, Naoya, Kamiyoshihara, Hiroaki, Ishida, Marika, Yoshioka, Kazuo, Sato, Hiroyuki, Honda, Chikatoshi, Hayakawa, Masahiko, Kitazato, Kohei, Sawada, Hirotaka, and Sugita, Seiji

Published
2019
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