講演情報
[PPS03-17]Disk-resolved photometric properties of local regions on asteroid 25143 Itokawa
*平田 成1,2、北里 宏平1,2、巽 瑛理3、佐藤 広幸4、菊地 紘4、石黒 正晃5 (1.会津大学コンピュータ理工学部、2.会津大学宇宙情報科学研究センター、3.カナリア天文物理学研究所、4.宇宙航空研究開発機構月惑星探査データ解析グループ、5.ソウル大学物理天文学科)
キーワード：
はやぶさ、イトカワ、光散乱特性、小惑星
Asteroid Itokawa shows a wide variety of terrains; rough and smooth terrains, exposure of less space weathered materials on steep slope regions. Disk-resolved photometry gives an opportunity to investigate local photometric properties of these interesting sites. We developed a pixel-oriented DB system of images taken by AMICA onboard Hayabusa, which stores not only images, but also individual pixel values of the images with observation conditions such as incidence, emission, and phase angles taken from the geometry backplanes. It enable us to make photometric modeling using pixel values and observation geometries throughout all available images. Here we present the DB design and preliminary results on estimation of the Hapke photometric parameters of terrains on Itokawa.
Three local regions, a rough terrain, a smooth terrain and a steep slope region are selected as target for the parameter estimation, and the global data is also used to check consistency to the disk-integrated parameters by a previous work (Tatsumi+2018). For global analysis, pixel data are sampled with a 1:100 ratio from the entire pixel data collection in the DB.
Disk-resolved global parameters are consistent with the disk-integrated ones, except a smaller roughness parameter theta. Rough terrain, major terrain on Itokawa, fall into the parameter range similar to global ones. Smooth terrain is characterized with a smaller single scattering albedo w than global/rough terrain. Roughness parameter theta is smaller than rough terrain, may reflect its smooth topographic appearance. Preliminary result on the steep slope region shows a similar single scattering albedo w, despite its bright appearance suggesting exposures of fresh materials, and other parameters are also close to those of rough terrain, except a smaller roughness parameter theta.
Three local regions, a rough terrain, a smooth terrain and a steep slope region are selected as target for the parameter estimation, and the global data is also used to check consistency to the disk-integrated parameters by a previous work (Tatsumi+2018). For global analysis, pixel data are sampled with a 1:100 ratio from the entire pixel data collection in the DB.
Disk-resolved global parameters are consistent with the disk-integrated ones, except a smaller roughness parameter theta. Rough terrain, major terrain on Itokawa, fall into the parameter range similar to global ones. Smooth terrain is characterized with a smaller single scattering albedo w than global/rough terrain. Roughness parameter theta is smaller than rough terrain, may reflect its smooth topographic appearance. Preliminary result on the steep slope region shows a similar single scattering albedo w, despite its bright appearance suggesting exposures of fresh materials, and other parameters are also close to those of rough terrain, except a smaller roughness parameter theta.