The Japanese space agency JAXA has launched its first mission to Venus. The Akatsuki craft, which means “dawn” in Japanese, took off at 21.58 GMT yesterday from the Tanegashima Space Center on the island of Kagoshima, south-west of mainland Japan. Akatsuki will study the planet’s violent atmosphere and could confirm if there are active volcanoes on its surface.
Known as the Earth’s “sister planet” due to its similar mass and size, Venus orbits closer to the Earth than any other planet in our solar system. However, Venus’s climate is very different from Earth’s. Its atmosphere contains mostly carbon dioxide and is a sultry 460 °C, with the high temperatures believed to be due to a “runaway greenhouse effect”. And while Venus rotates at around 6.5 km per hour, its atmosphere rotates at a violent 360 km per hour.
Weighing 500 kg and costing around $220m, Akatsuki will operate for the next four and a half years and has five onboard cameras. Two of these instruments operate in the near-infrared regime and will study the planet’s surface and the motion of clouds, as well as the size of particles that make up the clouds. A long-wave infrared camera, meanwhile, will measure the temperature at the “cloud top”, which lies around 65 km from the planet’s surface.
The final two cameras are an ultraviolet imager to measure sulphur dioxide at the cloud top and a lightning and airglow camera, which will capture lightning flashes that have never been observed on the planet before.
Akatsuki will join the European Space Agency’s Venus Express satellite, which launched in 2005 and has been orbiting the planet since 2006. “Akatsuki will be in position to give new information on cloud formation and its dedicated camera will hopefully be able to detect lightning in the optical,” says Håkan Svedhem, project scientist for Venus Express. “We have plans of doing many different types of joint observations between the two spacecraft.”
Some of these could include, for example, the two craft making the same observation of a lightning storm – Akatuski in the optical and Venus Express in the electromagnetic regime – as well as the two being able to track super-rotating clouds over a much longer timescale with Venus Express taking over when Akatsuki disappears behind the horizon.
Also being launched with Akatsuki is JAXA’s Interplanetary Kite-craft Accelerated by Radiation Of the Sun (IKAROS), which will test the possibility of using the Sun’s rays for propulsion. The 14 m wide square solar power sail, only 7.5 µm thick, is built from thin-film solar cells and a material called polymide. The mission will be the first spacecraft to use both solar-power generation via its onboard solar cells and propulsion from the force on its sail of the Sun’s rays.
