It's the third in a series. Planet-A, "Suiseu" studied Halley's comet. Planet-B, "Nozomi" visited Mars. Looks like there's a Planet-D (PDF link) planned for visiting Venus, too.


An ISAS mission in development is known by a series and a letter. After successful launch, it gets a name, based on suggestions from its developers. One I worked on, ASTRO-E, unsuccessfully launched, was rebuilt as ASTRO-E2. Once successfully launched, it was named "Suzaku", after a mythical bird that is reborn in some stories.

Only top voted, non community-wiki answers of a minimum length are eligible