Japan Geoscience Union Meeting 2019

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[E] Poster

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

Wed. May 29, 2019 3:30 PM - 5:00 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

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)

[PPS03-P24] Disk-Resolved Photometry Analysis of the Asteroid Ryugu Images Obtained by Hayabusa2 Visible Camera ONC

*yokota yasuhiro1,2, Rie Honda1, ERI TATSUMI3, Deborah Domingue4, Stefanus E. Schroeder5, Moe Matsuoka2, Seiji Sugita3, Tomokatsu Morota6, Shingo Kameda7, Toru Kouyama8, Hidehiko Suzuki9, Manabu Yamada10, Naoya Sakatani2, Chikatoshi Honda11, Masahiko Hayakawa2, Kazuo Yoshioka3, Yuichiro Cho3, Hirotaka Sawada2 (1.Kochi University, 2.ISAS/JAXA, 3.Univ. of Tokyo, 4.Planetary Science Institute, 5.DLR, 6.Nagoya Univ., 7.Rikkyo Univ., 8.AIST, 9.Meiji Univ., 10.Chiba Institute od Technology, 11.Aizu Univ.)

Keywords:Asteroid, Photometry, Ryugu, Hayabusa2

Since June 2018, the Optical Navigation Camera (ONC) onboard Hayabusa2, has observed the C-type asteroid 162173 Ryugu at a distance below 20 km. ONC-T and ONC-W1 are used for surface imaging operations, and their images allow us to investigate the disk-resolved photometric properties of the surface. A narrow-angle camera ONC-T has 7 broad-band filters ranging in wavelength from 0.39–0.95 μm. ONC-W1 is a wide-angle (> 65°) pan-chromatic camera mainly used for optical navigation during cruise and low-altitude (< 20km) operations. We are proceeding the analysis of both dataset, ONC-T and ONC-W1.

Since Hayabusa2’s position is nominally fixed on the line connecting Ryugu and the Earth, the available solar phase angle range by ONC-T changes seasonally with the orbits of Earth and Ryugu around the sun. Therefore, we are collecting a large number of ONC-T images over a long period of time to cover a wide phase angle range.

ONC-W1 data has a strong point that it covers a wide phase angle range within a single frame during the descent operations, because of its wide field of view. One of our current challenges is deriving a precise viewing geometries (incidence angle, emission angle, and phase angle) at each pixel. Additionally, comparison of the absolute brightness value (radiance factor) with ONC-T is an ongoing issue.