Tokyo, October 11 — The Japan Aerospace Exploration Agency (JAXA) has announced the scientific objectives for its proposed OPENS-0 (Outer Planet Explorer for Neptune and Saturn-0) mission, a small spacecraft concept designed to conduct flyby observations of Saturn. According to JAXA’s presentation at the 2023 International Astronautical Congress held in Baku, Azerbaijan, the mission aims to investigate Saturn’s upper atmospheric composition, thermal structure, and dynamics, as well as characterize its magnetosphere and interactions with the solar wind.
The mission would carry a suite of lightweight instruments, including a neutral mass spectrometer, a Langmuir probe, and a magnetometer, to measure ionospheric plasma properties and magnetic field variations during a series of close flybys. JAXA scientists stated that OPENS-0 would build on data from the Cassini-Huygens mission, which concluded its 13-year exploration of Saturn in September 2017, by focusing on unexplored regions such as the polar auroral zones and high-latitude atmospheric jets.
The spacecraft is envisioned to launch as a secondary payload on a future H3 rocket, JAXA’s next-generation launch vehicle, which completed its first successful flight in February 2024 after two prior test failures in 2022 and 2023. OPENS-0 would have a launch mass of approximately 180 kilograms and a mission duration of up to five years, including a cruise phase to Saturn via a Venus-Earth-Earth gravity assist trajectory.
The mission remains in the conceptual study phase and has not yet been approved for funding or development under JAXA’s competitive small mission program, which selects candidates based on scientific merit, technical feasibility, and cost-effectiveness. JAXA emphasized that OPENS-0 aligns with Japan’s long-term space exploration goals outlined in its 2021 Basic Plan on Space Policy, which prioritizes outer solar system exploration through international collaboration and innovative small-scale missions.
No specific budget figure for OPENS-0 has been publicly disclosed by JAXA, and the agency noted that final instrument selection and spacecraft design would depend on the outcome of ongoing feasibility studies expected to conclude by late 2025.
