Thermophysical Properties of C-Type Asteroid 162173 Ryugu Revealed by the Thermal Infrared Imager TIR on Hayabusa2

抄録

Thermophysical properties of the surface of asteroid 162173 Ryugu have been investigated through global, local and close-up thermal imaging from the Hayabusa2 spacecraft using the thermal infrared imager TIR, a two-dimensional thermographic camera. The set of thermal images during one rotation of asteroid allowed to map thermal inertia of the asteroid, indicating the characteristics of large boulders and rocks covering the surface. The close-up thermal images have resolved the temperature of each geologic unit and boulders one by one, indicating the variation of rocks. Advantages of using TIR are to investigate the surface physical state even from the home position, 20 km from the surface, and to track the artificial targets against the asteroid surface while they are not well seen with a visible imager at the same time.