Research for Surface Structure on Asteroids

1.利用多平天文台（1998-99）和冈山天文台HBS（2000-01）的多通道偏振器对主带小行星进行了光偏振观测。观测到偏振的相位角依赖性，以及偏振和亮度沿着小行星自转的时间变化。结果，发现该小行星在9月和6月3日存在表面不均匀的椭圆分布。实验室测量的光散射的风化物类材料已经完成。对于多种不同的样品材料，推导出了散射光强度和偏振度与类风化物样品颗粒物理性质的关系.将继续进行实验室测量，特别是偏振测量，并将完成不同类风化物材料的数据库。这些结果将用于分析MUSES-C取样返回小行星使命中预期的现场数据。

1. Photopolarimetric observations of main belt asteroids by using the multi-channel polarizer in Dodaira Observatory(1998-99) and HBS in Okayama Astronomical Observatory(2000-01) have been done. A phase angle dependence of polarization, as well as a time variation of polarization and brightness along the rotation of asteroid, are observed. As a result, the existence of surface inhomogeneous albedo distribution on the asteroid has been found for 9 Metis and 3 Juno.2. Laboratory measurements of light scattering by regolith-like materials have been performed. A dependence of scattered light intensity and polarization on the physical properties of regolith-like sample grains is derived for many different kind of sample materials.3. Laboratory measurements, especially polarization measurements, will be continued, and the data base of different regolith-like materials will be completed. The results will be applied to analyse the in-situ data expected in MUSES-C sample return mission to the asteroid.