Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

P (Space and Planetary Sciences ) » P-PS Planetary Sciences

[P-PS03] Solar System Small Bodies: A New Frontier Arising Hayabusa 2, OSIRIS-REx and Other Projects

Tue. May 28, 2019 1:45 PM - 3:15 PM A01 (TOKYO BAY MAKUHARI HALL)

convener:Masateru Ishiguro(Department of Physics and Astronomy, Seoul National University), Taishi Nakamoto(Tokyo Institute of Technology), Masanao Abe(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency), Olivier S Barnouin(Johns Hopkins University Applied Physics Laboratory), Chairperson:Olivier Barnouin(Johns Hopkins University Applied Physics Laboratory)

2:15 PM - 2:30 PM

[PPS03-09] Preliminary report on global distribution visible spectra of asteroid Ryugu based on clustering

*Rie Honda1, Yasuhiro Yokota1,2, Eri Tatsumi3, Antonella Barucci12, Davide Perna13, Moe Matsuoka2, Deborah Domingue14, Tomokatsu Morota4, Shingo Kameda5, Toru Kouyama15, Hidehiko Suzuki6, Manabu Yamada10, Naoya Sakatani2, Chikatoshi Honda7, Lucille LeCorre14, Masahiko Hayakawa2, Kazuo Yoshioka3, Yuichiro Cho3, Yukio Yamamoto2, Naru Hirata7, Naoyuki Hirata8, Tomoki Nakamura9, Takahiro Hiroi11, Hirotaka Sawada2, Yuki Fujii1, Seiji Sugita3, Ryo Hayashi1 (1.Kochi University, 2.ISAS/JAXA, 3.University of Tokyo, 4.Nagoya University, 5.Rikkyo University, 6.Meiji University, 7.Aizu University, 8.Kobe University, 9.Tohoku University, 10.Chiba Institute of Technology, 11.Brown University, 12.Paris Observatory, 13.INAF, 14.Planetary Science Institute, 15.National Institute of Advanced Industrial Science and Technology)

Keywords:asteroid, Ryugu, visible, Hayabusa2, spectra, clustering

Preliminary result of global distribution of visible spectra of asteroid Ryugu derived from multi-band images obtained by ONC-T onboard Hayabuasa 2 is presented.
The ONC-T is a telescopic charge-coupled-device (CCD) camera with a 6.27° × 6.27° field of view (FOV) , having a 1024 pixels x 1024 pixels sensor and seven narrow band filters ranging from 395nm and 950nm and one wide-band filter. Images obtained by ONC-T are spatially aligned and converted into seven-band visible spectra (reflectance factor).

The spectra are clustered, and the obtained cluster id are shown on the global map. As the method of clustering, k-means++, x-means, gaussian mixture model via EM are tested for synthetized data and x-means is selected since this method is stable to obtain a suitable number of components.

The obtained spectra are divided into seven to nine groups depending the slope of the spectra. Flat spectrum group is distributed around the equatorial ridge, the redder and darker groups are in the southern hemisphere and the relatively bright and bluer spectra are observed at the polar region, in particular at Otohime Saxum. The distribution of these spectra groups appears to indicate the surface history such as space weathering and erosion and the supply from different sources.