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2010年12月12日 (日)


--The Asahi Shimbun, Dec. 10
EDITORIAL: Failure of Akatsuki probe

Venus, which is about the same size as Earth, is also called its twin. Repeatedly in the past, however, the planet named after the goddess of love and beauty had coldly rejected U.S. and Soviet space probes. This time, too, the goddess turned its back on a messenger from Japan.

The Japan Aerospace Exploration Agency's space probe Akatsuki failed to enter an orbit around Venus.

Akatsuki's mission was to seek the real face of Venus, which has turned into a blazing hell with the greenhouse effect caused by carbon dioxide getting out of control.

Earlier this year, after a journey of tribulations, the space probe Hayabusa returned to Earth with dust samples from the asteroid Itokawa. Akatsuki had also been launched amid big expectations.

The result is really regrettable.

Original plans called for the probe to reverse its engine thrust, brake suddenly and enter Venus' sphere of gravitation, but the reverse thrust stopped midway. According to researchers, the ceramic engine nozzle developed with domestic technology may have broken. But first, it is important to thoroughly look into the cause of the failure.

Akatsuki passed by Venus and entered an orbit to travel around the sun in about six months. Six years from now, it will once again come close to Venus. When it does, JAXA plans to try to put it into orbit again. Depending on the condition of the engine and other equipment, chances of success may not be great, but we urge the agency to make every effort.

The Mars probe Nozomi, which was launched in 1998, also could not be put into an orbit around the red planet because of trouble in the fuel system and other equipment. With Akatsuki's failure, Japan's planet probes have failed two straight times.

The gravity of the Itokawa asteroid where Hayabusa landed is weak, and the probe was able to approach it repeatedly. However, engine maneuvering to enter the gravitational sphere of a large planet with great gravitational force like Venus cannot be repeated. It is difficult because it is a one-shot deal.

The history of Japan's planetary probes is short. It can even be described as immature. It is important to thoroughly study and learn from the failure this time and put it to use for future projects.

JAXA remade flight plans for Nozomi, which had little remaining fuel, to reach Mars four years later. The experience was useful in enabling Hayabusa to return to Earth three years behind schedule. This is a good precedent.

It is important to take a long view to support challenges in space, a realm that remains largely unknown.

The recent discovery of a bacterium in the United States that eats arsenic defied our common sense of biology. We don't know what kinds of living matter live where. Looking for the presence of life in space is a major purpose of planetary probes.

But the undertaking is also very costly. Countries are launching space probes commensurate with their interests and technological capability. More researchers from around the world are taking part in joint projects. For example, as far as Venus is concerned, Japan and Europe are supposedly the leading players. Plans for Japan and Europe to cooperate and launch one space probe each to Mercury are also progressing.

Also in order for Japan to live up to its international responsibility, it should clarify the problems to enhance trust and take off toward the next faraway journey into space.


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