The Japanese space probe Hayabusa was launched in May, 2003 and returned to the Earth in June, 2010 after traveling six billion kilometers in seven years to the asteroid Itokawa. The probe accomplished the mission, such as acceleration by an ion engine, landing on the asteroid, and collecting the samples. The sensation in space is different from one on the Earth. Although the thrust of the ion engine is almost the same as lifting one cent coin, the ion engine continued to operate for nine months and could accelerate the probe to +0.5 km/sec. In addition, an Earth swing-by was performed to further accelerate it to +4 km/sec. In order to hover 20 km above the asteroid, it was required to reduce its velocity to about 1.5 cm/sec. If you jump on the asteroid where the gravity is extremely low, you may move into the space. We would like to applaud the wisdom and enthusiasm of those who have overcome many problems and have not given up the return of the probe.
