Photometric Behaviour Dependent on Solar Phase Angle and Physical Characteristics of Binary Near-Earth-Asteroid (65803) 1996 GT

Photometric behavior of an asteroid is generally considered to derive from mainly changing distances from Earth and Sun, rotation causing a periodic variation of the area and/or average albedo of the visible surface, and changing solar phase angle. The goal of this study is to map out the relationships between photometric behavior and solar phase angle as accurately as possible. Furthermore we have taken near-Earth-asteroids survey of the target of the next asteroid exploratory mission (post-HAYABUSA mission) in Japan. The object observed in this study is also one of them and to reveal its physical characteristics is important purpose, too. Asteroid of (65803) 1996 GT is an near-Earth-asteroid designed as belonging to the PHA (Potentially Hazardous Asteroid) group (q = 1.013 AU, a = 1.644 AU, i = 3.4 deg (MPO 53573)) and one of the most accessible asteroids by spacecraft. The object was predicted from ephemeris to make a close pass by the Earth on November 2003, which represented the enhancement of the apparent brightness. We had observed the object using with Kiso 30-cm Telescope (K.3T) for long periods. During these observational periods the solar phase angle of 1996 GT had varied 40.0 to 2.0. In the past, there is little observation to obtain the photometry of asteroids such as solar phase angle varied remarkably by a same telescope and in a continued term, and thus these data sets are very informative. In addition, we had observed the object using with 1.05-m Kiso Schmidt Telescope at UBVRI band filters and determined the color index and the taxonomic type of this asteroid.