May 18, 2010

Japan Sets Its Sights On Venus

The Japanese are about to launch a mission to Venus to study the planet's weather and to search for signs of lightning and active volcanoes, and will also deploy a number of other experiments.

The Japan Aerospace Exploration Agency (JAXA) will launch the Akatsuki probe aboard an H-IIA rocket from the Tanegashima base. The probe will take about 6 months to reach Venus's orbit. It will join a probe from the European Space Agency that arrived at the planet in 2006.

Venus is a dense planet with a carbon dioxide-rich atmosphere that traps incoming solar radiation and heats the planet to an average temperature of 860 degrees Fahrenheit. Surface pressure on Venus is nearly 90 times that on Earth.

Studying the hostile planet may help scientists better understand how a warming trend on our own planet might evolve.

"Although Venus is believed to have formed under similar conditions to Earth, it is a completely different world from our planet with extremely high temperatures due to the greenhouse effect of carbon dioxide and a super rotating atmosphere blanketed by thick clouds of sulfuric acid," explained Takeshi Imamura, Akatsuki's project scientist, to BBC News.

Instruments that operate on visible wavelengths will not be able to penetrate the thick atmosphere of Venus, so the Japanese probe will carry five cameras that are sensitive in the infrared and ultraviolet parts of the electromagnetic spectrum.

The instrument will be able to investigate the atmosphere and the clouds layer by layer. Scientists want to get a better understanding of why Venusian weather patterns move so swiftly.

"On Venus, a high-speed wind called super-rotation is blowing all over the planet, in the direction of planetary rotation, with a velocity reaching 400km (248 miles) per hour at an altitude of around 60km (37 miles) from the surface," explained Imamura.

"This wind blows 60 times faster than the planet's rotation, which is very slow (one Venusian day takes 243 Earth days)," he said.

"Akatsuki will investigate why this mysterious phenomenon occurs. Another objective is to study the formation of the thick sulfuric acid clouds that envelop Venus, and to detect lightning on the planet," Imamura added.

The probe will use infrared sensitivity to possibly find evidence of active volcanoes on the surface of Venus.

Europe's Venus probe recently found lava flows that could have been younger than 250,000 years old.

Much interest has also centered on a solar sail project called IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) that will accompany Akatsuki to Venus. The 700 pound, 6 foot-wide, disc-shaped spacecraft will deploy an ultra-thin, ultra-light membrane that sunlight falling on the structure should propel the disc out to Venus behind Akatsuki.

This "solar-sailing" technique has long been hyped as a means of moving spacecraft around the Solar System. The sail will also have solar cells to generate power.

The mission team will be watching to see if IKAROS produces a measurable acceleration, and how well its systems are able to steer the craft towards Venus.


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