COVER STORY: Sky’s the Limit!

Caption: A computer-generated image depicting the Hayabusa probe in outer space
Credit: COURTESY OF JAXA

Return to Sender

In June 2010, many in Japan became excited about two entirely different events. One was when Japan’s national soccer team advanced to the final sixteen in the FIFA World Cup in South Africa. The other was the return to Earth of the space probe Hayabusa after seven years in space covering six billion kilometers.

“The United States, Russia, and European countries have all sent out probes to planets in the solar system, but most of these were one-way trips. The groundbreaking aspect of the Hayabusa mission was the fact that the probe returned. To begin with, the attempt to have a probe land on an astronomical body other than the moon and take off again was the first in the world,” says Associate Professor Makoto Yoshikawa of JAXA, who supported the Hayabusa mission as the leader of an expert team calculating the orbit of the celestial body.

Launched in May 2003, Hayabusa continued to navigate in a large arc around the sun, and in September 2005 it approached the asteroid Itokawa, which is 300 million kilometers from Earth (approximately twice the distance from the sun to Earth). It successfully landed and took off twice. However, its return to Earth was truly one ordeal after another. Successive problems occurred, such as a loss of fuel in the chemical engine that controls the orbit and the attitude, interruption of communications, and the breakdown of the ion engine (see next page) for navigation.

Professor Yoshikawa says, “When the interruption of communications ran to seven weeks, I thought that was it, we’ve had it. All the more reason why, when weak signals that appeared to be from Hayabusa began to reach Earth, we couldn’t believe it at first.”

After that, Hayabusa’s propulsion was restored by assembling the remaining parts for the four-motor ion engine. Moreover, even though the space probe was severely damaged, so that the ion engine had to be used for attitude control as well, it headed for Earth. And on June 13 this year, after releasing a capsule that is expected to contain samples of the asteroid Itokawa, it plunged into Earth’s atmosphere and burnt out in the night skies of Australia.


Professor Yoshikawa is also the project leader for the successor Hayabusa 2 project. With the Hayabusa 2 probe, the problem areas that appeared with Hayabusa have been rectified, and it is planned to aim for an asteroid other than Itokawa that is believed to contain a great deal of organic matter or hydrous minerals.

Professor Yoshikawa says, “Following Hayabusa, Hayabusa 2’s mission is to return to Earth bringing back a sample of material from an asteroid. Unlike the large planets of the solar system, asteroids retain their original form. By continuing our investigations, we might find the key to unlocking the great mystery surrounding the evolution of the solar system and planets, and even the origin of life.”