Hisaki

Hisaki is an ultraviolet spectrograph mission aimed at the planets of our own solar system, not distant stars. It observes extreme-ultraviolet emissions from the thin outer atmospheres of Venus, Mars, and Jupiter, including Jupiter's aurora and the plasma torus created by Jupiter's volcanic moon Io. These emissions are invisible from Earth's surface because our atmosphere blocks ultraviolet light.

It launched on September 14, 2013, on the very first flight of Japan's Epsilon rocket (the Epsilon-1 mission) from the Uchinoura Space Center in Kagoshima. The launch was a key milestone for the Epsilon, which was developed to lower the cost of small-satellite launches. The spacecraft was also designated SPRINT-A.

The name comes from Hisaki Point, a headland near the Uchinoura Space Center in Kagoshima, continuing JAXA's practice of naming small science missions after local landmarks near the launch site. Hisaki was JAXA's first space science satellite dedicated to planetary remote sensing in extreme ultraviolet. The SPRINT-A designation stands for its original mission name.

The mission was designed for roughly a one-year prime lifetime, but it operated well beyond that, continuing observations of Jupiter and other targets into the late 2010s and reportedly beyond. Such long extensions are common for small JAXA science satellites that remain healthy. It has contributed long-duration monitoring of the Io plasma torus that quick flybys cannot provide.