Talk about flying close to the wind. Japan's first interplanetary spacecraft will begin its travels to Venus next week, to get the clearest ever view of massive gusts in the planet's atmosphere.
The Venus Climate Orbiter, called AKATSUKI, aims to find out why blistering winds zip around the planet at speeds of up to 400 kilometres per hour. The upper clouds can circle the planet in four days or even less, and no one knows why. The effect is called "super-rotation", because the bulk of the atmosphere is rotating much faster than the planet itself. Venus takes 243 Earth days to make one rotation.
To investigate, AKATSUKI will move roughly in sync with the winds during part of its orbit, so it can track a patch of atmosphere for about 24 hours at a stretch. Five cameras will snap the planet at different wavelengths. "By combining the images from these cameras we can develop a three-dimensional model of the Venus atmosphere," says mission scientist Takeshi Imamura. This will be the first time such measurements have been taken on a planet other than Earth, he adds.
AKATSUKI will be particularly well equipped to study slower winds that move north and south from the planet's equator, which may well play a significant role in the atmosphere's rotation. The European Space Agency's Venus Express, which is in orbit around the planet, can already see these meridional winds. "But the error bars are quite wide," says ESA's Håkan Svedhem. "We can't really tell anything about the seasonal or day-to-day variability."
Plans for joint observations using the two spacecraft are in the works.