PLANET-C is JAXA’s third planetary explorer succeeding the Suisei (PLANET-A), which observed Halley’s Comet, and the Nozomi (PLANET-B), which could not complete its mission to reach Mars. PLANET-C will be launched in 2010 and travel around the sun to reach Venus within the same year, then it will enter the Venusian orbit. The results JAXA achieved from the interplanetary navigation by the Hayabusa (MUSES-C) will be utilized in this project.

PLANET-C will research the Venusian atmosphere, which is covered by thick clouds. It carries five cameras including ultraviolet and optical devices and even infrared cameras. Each of them will capture images of the clouds at different altitudes. The infrared cameras will look through the top layer of the clouds to see the lower atmosphere. Using these cameras, PLANET-C will take one photo every two hours at various wavelengths. When these photos are combined, we will be able to see the cloud distribution in three dimensions. If you put all the data together and look at it like a movie, you can understand the motions of the clouds in each layer. By accumulating data and processing it statistically, we can research what kind of force is needed to physically move the Venusian atmosphere.

Venus was previously a forgotten planet as a planetary exploration destination. Currently, the U.S. is mainly putting its efforts into Martian exploration and the U.S.S.R., which used to send many explorers to Venus, has been disbanded. Nevertheless, European countries were encouraged by the PLANET-C project and planned their own explorer called the Venus Express, which was successfully launched within an extremely short developing period. The Venus Express reached Venus in April 2006 and is currently sending back data to the Earth.