The Centaur LOX/LH2 cryogenic stage has been used as an upper-stage for most of the deep space missions because of its high ISP. Now with the advent of Lunar and Mars initiatives, Centaur-like vehicles are being considered for trans-Lunar, Earth-return, and Mars missions with quiescent coast durations lasting from a month, up to one year. This paper reviews the results of a funded study by NASA/KSC NAS10-00-060 done by Lockheed Martin Space Systems titled: Advanced Cryogenic Evolutionary Stage (ACES). This study is an assessment of the Centaur integrated with new technologies in an effort to accommodate these longer duration missions. Study specifics include: avionics, environmental effects, attitude controls, active/passive thermal controls, passive thermal Vacuum Insulation Panel applications, advanced MLI, sun-shield, RL10 engine (cold-soak, restart and long duration effects), and operations.