Keywords:asteroids Itokawa, photometry, Hapke's model, opposition effect, surface roughness
JAXA’s Hayabusa Mission succeeded in returning samples from an S-type asteroid (25143). The multi-band imaging camera, AMICA, took more than 1400 images with its multi-band filters at a wide range of solar phase angles from 0 degree (i.e. opposite direction from the Sun) up to 35 degree. There is little knowledge concerning photometric properties on Itokawa, although it has been studied through ground-based observations (Lederer et al. 2008). The Hayabusa spacecraft data, however, can provide more information that are difficult to study using ground-based data, such as the opposition effect and local heterogeneities. Here we report our research about the optical properties of asteroid Itokawa using Hapke’s bidirectional reflectance. We employed two visualization tools, the Plate Renderer developed by a group at University of Aizu with the support of Dr. N. Hirata, and the Small Body Mapping Tool developed by APJ/JHU. We had an opportunity to take them attending the 8th Data Analysis Workshop held at University of Aizu in September 2015. We investigated both disk-integrated and disk-resolved photometric function of asteroid Itokawa and derived parameters for the opposition effect and macroscopic roughness. We found that the opposition effect has a narrower width than the other S-type asteroids. The macroscopic roughness parameter is broadly consistent with those of the ground-based studies, but we noticed a local heterogeneity near the sampling site. We will report our data reduction and finding through the photometric analysis.
S. M. Lederer, D. L. Domingue, J. E. Thomas-Osip, F. Villas, D. J. Osip, S. L. Leeds, and K. S. Jarvis, The 2004 Las Campanas/Lowell Observatory campaign Ⅱ. Surface properties of Hayabusa target Asteroid 25143 Itokawa inferred from Hapke modeling, Earth Planets Space, 60, 49-59.