A Japanese satellite and the world’s first space telescope dedicated to the spectroscopic study of planets in extreme ultraviolet light. Initially named SPRINT-A (short for Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere), the 350-kilogram satellite was launched on 14 September 2013 from the Uchinoura Space Center by an Epsilon rocket and renamed Hisaki after it reached orbit. The satellite’s mission is to study how solar wind strips gas from the upper atmospheres of Venus and Mars (which are unprotected by a magnetosphere), Jupiter, and Jupiter’s moon Io. In May 2016, Hisaki, in cooperation with NASA’s Chandra X-Ray Observatory, and XMM Newton, found that the acceleration necessary for Jupiter’s X-ray aurora is triggered by the solar wind. In January 2017 JAXA announced that Hisaki data show that solar wind does influence Jupiter's inner magnetosphere—a finding that contradicts a previous hypothesis.