The challenges facing successful implementation of the exploration vision are formidable, ... ranging from budgetary to the noise-signal ratio of competing priorities facing the political system.

NASA cannot succeed alone in pursuing the exploration vision. It's a breathtakingly full dance card.

Over the past year there has been significant yardage gained for the Vision for Space Exploration. The credibility of the agency has gone up tremendously. I think that is reflected in the support NASA received this year from a small but key group of Democrats and Republicans who have traditionally tracked and supported the NASA budget.

Any misstep in human spaceflight could spell a very long hiatus in human-driven exploration in the US.

These are fault lines that have been in the NASA program for decades and it's one of the big challenges for Griffin and his team to ensure we have appropriate robustness in the science and aeronautics programs while at same time meeting very significant program and budget challenges for shuttle, station and the CEV programs.

It is burdened with old and aging infrastructure, frayed at the edges, costly, some times unreliable, ... ...any misstep in human spaceflight could spell a very long hiatus in human driven exploration spaceflight in the U.S. So this underscores the need to realize that NASA cannot succeed alone in pursuing the exploration vision.