Asteroid Phaethon is the target of DESTINY+ mission (Demonstration and Experiment of Space Technology for INterplanetary voYage with Phaethon fLyby and dUst Science). DESTINY+ will conduct in-situ analyses of chemical and physical properties of cosmic dust during the interplanetary cruising and high-speed fly-by observation of Phaethon. Phaethon is the parent body of Geminid meteor shower, delivering massive dust to the Earth every December through the Geminids dust stream. Phaethon orbits the sun with a highly elliptical orbit, and comes as close as one tenth of the Earth-Sun distance from the Sun, where the surface temperature reaches around 700oC. Upon the closest approach to the Sun, Phaethon ejects dust and is thus called “active asteroid”. Phaethon is about 6 km in diameter and among the largest asteroids approaching to the Earth. Ground-based observation shows that Phaethon is a top-shaped asteroid, similar to asteroid Ryugu of Hayabusa2 mission and asteroid Bennu of OSIRIS-REx mission. The reflectance spectra of Phaethon indicate that the surface composition is rich in carbon and organic materials, as well as those of Ryugu and Bennu.
