Asteroid explorer "Hayabusa" arrived at the small asteroid "Itokawa" whose size is only about 500m and showed us the mysterious world. Hayabusa made it possible for us to see exact nature of a very small asteroid approaching to the earth.
JAXA is now considering a mission named "Hayabusa-2". This is a mission to retrieve samples of surface from an asteroid to the earth. This is a similar mission to Hayabusa's one, However, target asteroid is different from Hayabusa's. The Asteroid Itokawa explored by Hayabusa is rock-rich S-type one. Hayabusa-2 will visit a C-type asteroid. C-type asteroids are also rock quality but it is thought that their rocks contain much more organic matters and water. Hayabusa-2 will challenge very interesting objectives: what are original organic matters and water existed in the solar system?, how are they related to life and ocean water? Also, Hayabusa-2 will challenge new technologies as well as improving the technologies of Hayabusa.
An asteroid currently considered as a target of Hayabusa-2 is temporally called 1999 JU3. This has not been named yet. Observation of spectrum of sunlight reflected by the asteroid shows that it has features of C-type. That is exactly suitable for Hayabusa-2.
Asteroid 1999 JU3 has a similar orbit as that of Itokawa and it is in the orbit that occasionally comes close to the earth orbit. Past observations show that, the size is approximately 920m and relatively it looks like a sphere. The rotation period is approximately 7.6 hours. The albedo on the surface is tiny, estimated about 0.06.
Like Hayabusa, Hayabusa-2 will use an ion engine to access the destination asteroid. Hayabusa-2's spacecraft is almost same as Hayabusa's one, but, we will improve the problem identified at Hayabusa and aggressively adopt new technology. And Hayabusa-2 will observe and collect the sample, based on the C type of Asteroid
Best timing to launch to the asteroid for this sample return mission is 2014. Hayabusa-2 is supposed to reach the asteroid in the middle of 2018, stay there about one and half years, depart from the asteroid to return to the earth at the end of 2019, and come back to the earth at the end of 2020.
It is considered to mount "Crackup installation" on Hayabusa-2 that Hayabusa didn't have. It will be separated above 1999 JU3 and explodes there after Hayabusa-2 hides behind the asteroid. Then an impactor of approximately 2 kg hits the surface of the asteroid and it will make a crater of several meters in diameter. After that, it tries to collect materials inside of the crater. In other words, Hayabusa-2 will collect materials of underground not only the ones on the surface. By doing that, we try to collect less altered materials.
Information about Hayabusa-2
Website of Hayabusa-2 Pre-project Team