Results from Hisaki and prospects for LAPYUTA observations of the Jupiter System

Remote sensing with ultraviolet wavelength (UV) are one of powerful probes to uncover dynamic behaviors of the planetary environment. The Hisaki satellite was an earth orbiting extreme ultraviolet (EUV) spectroscope dedicated for observing solar system planets. Thanks to its long-term monitoring capability, Hisaki had carried out unprecedented continuous observation of Io plasma torus, Jovian aurora, and Mars and Venus upper atmospheres from 2013 to 2023. One of notable phenomena observed by Hisaki is significant enhancements of neutral gas from presumed activation of volcanic activity on Io. Hisaki revealed, for the first time, that not only the plasma source, but transport, heating, and loss processes of magnetospheric plasma were influenced by the variation in the neutral source input.After the end of the Hisaki mission, we have proposed the next UV space telescope, LAPYUTA (Life-environmentology, Astronomy, and PlanetarY Ultraviolet Telescope Assembly). One of goals of this mission is dynamics of our solar system planets and moons as the most quantifiable archetypes of extraterrestrial habitable environments in the universe. LAPYUTA will not only provide a UV monitoring platform like Hisaki but also have a high spatial resolution and high sensitivity to uncover stability of Io’s atmosphere, water plumes that gushes from the subsurface ocean of icy moons, and spatio-temporal aspects of Jupiter's giant UV aurora. Primary goal of the LAPYUTA mission other than the Jovian system includes atmospheric evolution of Venus and Mars, characterization of exoplanet atmosphere, galaxy formation, and time-domain astronomy.