Japan’s unmanned space probe Hayabusa (peregrine falcon) returned from a seven-year, 6-billion-kilometer trip to the asteroid Itokawa. Although its main body burned up while re-entering Earth’s atmosphere, a capsule released from it landed in the desert near Woomera in southern Australia on the night of June 13 and was sent to Japan. The round-bottomed, pan-shaped capsule, 30 cm in diameter and 15 cm in height, may contain sand from the asteroid.
Even if Hayabusa failed to collect any material from the asteroid, its journey is a praiseworthy space saga in which a project team at the Japan Aeronautical Exploration Agency (JAXA) demonstrated its ingenuity and perseverance. Hayabusa achieved the first-ever, round-trip voyage of a spacecraft to a heavenly body other than the moon.
Hayabusa also returned from the longest voyage in space (2,592 days). The previous record of 2,534 days had been set by the Stardust mission of NASA (U.S. National Aeronautics and Space Administration). Launched in February 1999, Stardust collected cosmic dust and returned in January 2006. Despite Hayabusa’s feat, however, the fiscal 2010 budget for Hayabusa’s successor mission had been slashed. The government must immediately work out a better strategy for Japan’s space exploration program and basic science research.
Hayabusa was launched in May 2003 from Uchinoura Space Center in Kagoshima Prefecture and landed on the asteroid Itokawa twice in November 2005. The asteroid, only 550 meters long, was discovered by a Massachusetts Institute of Technology team in 1998 and named after the late Hideo Itokawa, Japan’s pioneer in rocket engineering. Itokawa’s orbit is close to those of Earth and Mars.
Japan targeted Itokawa because asteroids are records of the early stages of the solar system. Observation of them could shed light on the history of our solar system. Hayabusa’s core mission was to collect rocks and sand from Itokawa and to bring them back to Earth.
Before landing on Itokawa, Hayabusa closely observed it from a short distance and sent data to Earth. Scientists around the world praised Hayabusa’s observation results, which were featured in a top American science magazine.
Once on Itokawa, Hayabusa was to shoot two metal balls at the asteroid’s surface and collect debrits blown up by the impact. Although it is believed that Hayabusa failed to shoot the metal balls, it is possibile that sand kicked up by the probe’s landing entered the capsule.
The capsule will be opened in a vacuum chamber at JAXA’s facility in Sagamihara, Kanagawa Prefecture. Scientists say that a sand particle with a diameter of 0.1 millimeter is sufficient for scientific analysis — to identify minerals, their composition and molecular structures. If the capsule contains sand, it will take until around September to determine if it is from Itokawa.
The Hayabusa mission’s technological achievements are remarkable. It proved that use of an ion engine, which creates thrust by expelling ions, is appropriate for interplanetary voyages. Although the engine thrust is relatively weak, the spacecraft gains high speed as the engine is accelerated over a long period. Hayabusa also used an autonomous navigation system that enabled automatic landing on the asteroid by calculating the distance to the surface.
Hayabusa’s return to Earth was delayed by three years due to a series of problems. Three of its four advanced ion engines stopped working. A fuel leak rendered a chemical engine inoperative. Two of the three attitude control devices broke down. Communication was lost for some 50 days after the second landing. The JAXA team overcame the glitches using ingenuity and succeeded in leading Hayabusa back to Earth by using the last ion engine. They succeeded in freeing the heat-resistant capsule three hours before its re-entry and retrieved the capsule.
Hayabusa cost ¥12.7 billion. The education and science ministry asked for ¥1.7 billion for fiscal 2010 to develop an unmanned space probe to succeed Hayabusa, but the budget was cut to ¥30 million. The government must provide sufficient funds so that space probes can be launched at short intervals. This is indispensable for ensuring a handover of experience and knowhow accumulated in earlier missions to future generations of scientists and engineers, and to stimulate research for more meaningful achievements.
The government’s annual investment in space science is ¥20 billion — one-twentieth of the United States’ and half of Europe’s. It should rethink Japan’s participation in the International Space Station project, whose scientific achievements do not appear to have justified the ¥40 billion a year cost to Japan.
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