From the NASA planetary program overview:
- NASA's planetary program has suffered a 50% budget reduction since 2005. This necessitates a complete replan of priorities. [Editor's notes: before this budget decline, an outer planets flagship mission could have been easily afforded]
- Launch vehicle costs are increasing rapidly, which is eroding budget purchasing power
- Current budgets would afford a new Discovery mission about every 3 years and a new New Frontiers mission about every 5 years
From the Mars program overview
- A joint NASA/ESA group will propose a joint exploration program for Mars, but the Decadal Survey will have the final say.
From the JPL concept maturity presentation:
- To avoid major cost overruns, 10-15% of the total mission cost needs to be spent upfront defining the mission. Missions that don't do this investment tend to suffer major cost overruns (See the presentation, which has a fascinating chart plotting this.)