The information on this page was published in the past, thus it may be different from the current status.
To check the date of issuance, please refer to the following URL for the list of interviews, or for the list of special articles.
Asteroid 1999JU3 (in the yellow circle in the center of the image), imaged by the infrared astronomical satellite AKARI
The answer is that 1999JU3 is a C-type asteroid. Asteroids are grouped into different types according to their spectral characteristics, and many can be classified as Type C or Type S. The main ingredient of C-type asteroids is carbon-based materials, and about 75% of all asteroids are thought to belong to this type. In contrast, the main ingredient of S-type asteroids is silicon, and 20% of all asteroids are estimated to be this type. HAYABUSA’s asteroid, Itokawa, is an S-type. It is essential to understand these two types if you wish to understand asteroids in general.
Many S-types are in the asteroid belt located between the orbits of Mars and Jupiter, and some of them approach close to Earth. On the other hand, C-types are situated outside the asteroid belt, and few of these asteroids have orbits that get close to Earth. 1999JU3 is an exception - it approaches close enough to Earth’s orbit for a small spacecraft such as HAYABUSA-2 to make a round trip there.
HAYABUSA was originally a technology demonstration spacecraft - its primary goal was to establish new technologies. HAYABUSA-2, on the other hand, will focus on both technology and science, so the selection of the asteroid is crucial. Since an S-type asteroid was chosen last time, we decided on a C-type for Hayabusa-2. We’ve been preparing for the mission by conducting ground-based observation of 1999JU3. I can’t wait for the day when we can finally see it up close.
Asteroid explorer HAYABUSA-2 and MINERVA (courtesy: Akihiro Ikeshita)
HAYABUSA was primarily a technology demonstrator, and was a very challenging mission. Some technologies were successful and some failed. But, basically, many technologies that were tried out with HAYABUSA will be passed on to HAYABUSA-2.
First among those are the ion engines. Despite the fact that HAYABUSA’s ion engines degraded over time and did not perform optimally, it achieved the world’s first planetary round trip. We would like to advance electric propulsion technology further, and build ion engines with a longer lifespan.
Next is the navigation and guidance technology. This technology is used for touchdown - for the spacecraft to land on the surface of the asteroid, and ascend again after collecting samples. HAYABUSA’s fuel leak problem is suspected to have occurred because the touchdown was not performed properly. False landing must not happen again next time, and to ensure this, we are creating new methods of operation, navigation and guidance.
We are also planning a new attempt at MINERVA. MINERVA was a planetary exploration rover - Japan’s first - that was part of the HAYABUSA mission, but unfortunately it failed to land on Itokawa and drifted into space. This time, we want to make sure it succeeds.
In addition, we are planning to improve the attitude control, the antennae, and the sample-collection method. But most functions will be basically the same as HAYABUSA’s. The goal of HAYABUSA-2 is to perfect the technology developed for HAYABUSA, in order to perform a flawless planetary round trip.