Thanks to recent technological advancement of astronomical observatories, fainer, more distant Jupiter Trojan asteroids have been detected and studied statistically or/and physically in detail than ever while planetary migration hypotheses have made them one of the most crucial witnesses to prove or disprove such competing concepts among the solar system formation theories.
In the past two decades or so, round trip capability has been one of the strategic targets for deep space exploration of Japan and the original Hayabusa pioneered that path. The Hayabusa-2 will follow it but they are limited within the inner planetary region.
Another strategic target of Japan's exploration technology has been to go to outer planetary region, i.e., the Jovian system and beyond, without using "nuclear" energy sources. Thus the solar power sail technology has been invested and tested from high altitude balloons, sounding rockets, an earth orbiting satellite and a deep space probe (i.e., IKAROS) by aiming to Jupiter Trojans as a final destination, since early 2000's.
This lecture outlines both scientific premises and technological challenges of reaching first and then attempting a round trip exploration to Jupiter Trojans in 2020's and an even more distant target in 2030's-40's. Also potential areas of international collaboration will be discussed through a personal view of the presenter.