The Japan Aerospace Exploration Agency (JAXA) succeeded in putting its Akatsuki spacecraft onto orbit around Venus early this month. The spacecraft will start full-scale observations in April — the nation’s first planetary exploration. The Nozomi spacecraft launched in 1998 for the exploration of Mars failed to enter orbit around the red planet. While there are some concerns over the Akatsuki probe since it has already exceeded its design life of 4 1/2 years and will be unable to get as close to Venus as originally planned, we hope Akatsuki’s mission to observe the mysterious planet will bring fruitful results.
Akatsuki, which means dawn in Japanese, was launched in May 2010. But in December that year, JAXA failed to place the probe onto orbit around Venus after its main engine broke down. Instead of entering Venus’s orbit, it sailed toward the sun. This time, JAXA fired four of Akatsuki’s thrusters and it was eventually captured by Vensus’s gravity. The success of the second attempt itself is a great achievement in itself.
If the Akatsuki mission successfully carries out its observations of Venus, it will mark an accomplishment comparable with that of the Hayabusa probe, which was launched in 2003, landed on the near-Earth asteroid Itokawa in 2005 and returned to Earth in 2010 with a sample of material from the small celestial body, completing a journey of some 6 billion km and overcoming a series of troubles. Hayabusa 2, a successor probe to Hayabusa that is now traveling in space, is scheduled to return to Earth in late 2020 with material taken from the asteroid Ryugu.
Venus is familiar to people since it is known as the morning star and the evening star. Following the sun and the moon, it is the third-brightest celestial body — about 160 times brighter than a star of the first magnitude. It has almost the same size and mass as Earth, but the composition of its atmosphere and the speed of its atmosphere’s rotation completely differ.
Some knowledge of Venus has been accumulated since the history of modern observation of the planet is fairly long. In the 1960s, the United States and the Soviet Union started launching Venus probes. It is known that the atmosphere of Venus is mostly carbon dioxide and covered with thick clouds of sulfuric acid. A great mystery about the planet remains to be resolved, however. While the planet revolves slowly — the equatorial rotation velocity being 1.81 meters per second — its atmosphere rotates at a speed of up to 100 meters per second. Usually the rotation speed of a planet’s atmosphere slows down due to its viscosity and friction with the planet’s surface. One important task for the Akatsuki mission is to find out what causes Venus’s atmosphere to move so fast.
Another mystery about Venus has something to do with Earth’s evolution as a planet. The temperature of Venus’ surface reaches some 460 degrees Celsius due to the greenhouse effect of the carbon dioxide in its atmosphere. It is thought that in the distant past, Earth’s atmosphere also contained a large amount of carbon dioxide, but its atmospheric conditions are very different today. Finding the clues to what factors contributed to the two planets taking different paths in their evolution will also be a key task for Akatsuki.
Next spring JAXA plans to send Akatsuki onto an elliptical orbit up to 300,000 km away from Venus with an orbital period of about nine days. It will spend at least two years studying the structure of the planet’s atmosphere and the movements of its clouds with the help of five specially designed cameras that can capture three-dimensional images using a wide ultraviolet-to-infrared spectrum of rays.
The probe will engage in the observation mission from a position more remote from the planet than originally planned and there are concerns that its long exposure to heat from the sun may have damaged its equipment. We hope the mission will face no further hitches and accumulate meaningful data. There is a possibility that the mission will reveal more information about volcanic activity on Venus, which the Venus Express spacecraft of the European Space Agency (ESA) discovered before it stopped functioning a year ago.
JAXA plans to expand its space exploration activities, including a fiscal 2016 launch of a joint Mercury probe with ESA and future exploration of Mars and the moon. But Japan’s space policy in general places low priority on scientific projects. The government’s basic space program adopted in January puts an emphasis on defense-related projects, such as increasing the number of reconnaissance satellites and the development of an early warning satellite to detect missile launches. The nation’s budget for space science is much smaller than those of the U.S. and European nations. At around ¥20 billion annually, it is roughly one-twentieth the U.S. budget and less than half of what Europe spends a year.
To expand the range of Japan’s basic research in science and to pass on knowledge about outer space to future generations, the government should boost the budget on space science. Japan contributes ¥40 billion annually to the International Space Station program, but it’s questionable whether the program’s results are worth the expense. Japan should spend more resources on its own space science projects and focus on areas that can produce significant achievements. The government should also consider engaging in joint space research programs with other countries in the region in an effort to improve relations.
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