One startling realization that's come from NASA's explorations of the satellites of Jupiter and Saturn is that the so-called “habitable zone” around our Sun may not be restricted to Earth's vicinity. The Galileo mission found conditions that might support life on two Jovian moons-Europa & Callisto. This raises the possibility of habitable zones elsewhere near the outer planets.
Consideration of human missions beyond Mars, likely to occur sometime beyond the year 2040, exceeds the horizon of even the most advanced planning activities within NASA. During the next 25 to 30 years, robotic spacecraft are envisioned to explore several moons of outer planets, especially Europa and Titan. Since Callisto lies well outside Jupiter's radiation belt, and there is evidence of water ice there is a compelling rationale to send human explorers to that Jovian moon.
Human exploration of Callisto would most certainly require breakthroughs in the technologies of propulsion and power; in situ resource utilization, radiation protection; artificial gravity; vehicle reliability, and extreme autonomy. Well-planned, robust precursor mission(s) will be required to not only demonstrate such breakthroughs, but to also establish supporting infrastructure at Callisto to enable safe and efficient human operations on its surface.
This paper delineates an efficient and effective potential precursor mission architecture for making critical science measurements, and establishing sufficient infrastructure to facilitate human landing on Callisto. For orbiting, landing, and exploring the Callisto surface, the study addresses the problem of determining the tradeoff space in terms of hardware choices: monolithic, a large number of small, dexterous robotic, and their judicious combinations.