講演情報
[PPS03-P24]Disk-Resolved Photometry Analysis of the Asteroid Ryugu Images Obtained by Hayabusa2 Visible Camera ONC
*横田 康弘1,2、本田 理恵1、巽 瑛理3、Domingue Deborah4、Schroeder Stefanus5、松岡 萌2、杉田 精司3、諸田 智克6、亀田 真吾7、神山 徹8、鈴木 秀彦9、山田 学10、坂谷 尚哉2、本田 親寿11、早川 雅彦2、吉岡 和夫3、長 勇一郎3、澤田 弘崇2 (1.高知大学、2.宇宙航空研究開発機構 宇宙科学研究所、3.東京大学、4.Planetary Science Institute、5.DLR、6.名古屋大学、7.立教大学、8.産総研、9.明治大学、10.千葉工業大学、11.会津大学)
キーワード：
小惑星、測光、リュウグウ、はやぶさ2
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.
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.