Abstract
In HAYABUSA/XRS, X-ray CCD needs to be kept below -40 degree Celsius to achieve the energy resolution to analyze elemental composition of the asteroid surface. XRS has three different techniques cooling CCDs; 1.thermal filament between XRS and HAYABUSA, 2. Pertie cooler on CCDs, 3. passive radiation by the hood to remove the stray light. The thermometer attached on the hood is available to measure thermal emissivity from the asteroid. To construct a thermal model of Itokawa, we considered the thermal balance between XRS and other environments such as the solar flux, heat radiation of HAYABUSA and Itokawa, heat generation of inside instruments that affected the temperature observed by this thermometer. To estimate the heat generation of inside instruments we divided XRS into 26 elements and solved equations of thermal conduction between nodes. To reveal the radiation from Itokawa we constructed the thermal model considering the shape of Itokawa and tried to investigate the most suitable characteristic for the observation and compared our analysis with infrared and near infrared ground observations.
