OKEANOS - A Solar Power Sail Mission to a Jupiter Trojan Asteroid and Its Updated Science Mission Proposal

The OKEANOS (Oversize Kite-craft for Exploration and AstroNautics in the Outer Solar system) is a mission under study to rendezvous with and land on a Jupiter Trojan asteroid [1]. It is primarily an engineering mission to demonstrate advanced technologies to explore the outer solar system with a small to medium sized spacecraft and limited cost, but also to conduct key science for understanding the origin and evolution of the solar system and life by performing in-depth scientific measurements. The concept is complementary to the Lucy mission [2], multi-flybys to six Jupiter Trojans, that was selected as a NASA Discovery class mission, aiming at understanding of variation and diversity of Jupiter Trojans. The OKEANOS is jointly studied between engineers and scientists both from Japan and Europe [3]. The OKEANOS is one of two candidates for the next medium class space science mission in Japan, waiting for the final selection. The scientific objectives, the latest science mission scenarios and the strawman payloads are described here.