(Proposal ID) S13A-089 (PI) Terai, Tsuyoshi (Proposal Title) Water-Ice Crystallinity on Trans-Neptunian Objects (Abstract) The presence of crystalline H_2O ice is a useful tool to study the thermal evolution of trans-neptunian objects (TNOs). Crystalline H_2O ice shows a deep absorption at 1.66 mu m in the reflectance spectrum. Near-infrared spectroscopy even with VLT and Keck telescope could hardly obtain sufficient data to detect this feature in TNOs smaller than 1000 km in diameter. We propose narrow-band photometry to measure the abundance of crystalline H_2O ice on TNOs and Centaurs. A newly opened narrow-band filter NB1657 is suitable to evaluate the depth of the 1.66-mu m absorption. The relationships of H_2O-ice crystallinity with size and orbit provide evidences of the heating mechanism for crystallization. This observation provides a breakthrough to investigate the surface properties and thermal evolutions of TNOs.