Discovery Missions – These Principal Investigator (PI)-led projects are complete, self-standing, and uncoupled Science Mission Directorate (SMD) investigations. The total cost to the National Aeronautics and Space Administration (NASA) for each Discovery mission has a not-to-exceed cost cap ($425M in the 2006 Announcement of Opportunity (AO)) to cover the complete mission, including spacecraft development, mission operations, data analysis, and education and public outreach.
The New Frontiers Program seeks to contain total mission cost and development time and improve performance through the use of validated new technologies, efficient management, and control of design, development and operations costs while maintaining a strong commitment to flight safety. The cost for the entire mission must be less than $700 million.
For the current Explorer 2011 decision, the proposal document states that the PI mission cost is limited to $200 million. This does not include launch; the document states that the exact launcher is not determined (to be contracted with one of several providers); only the fairing size is stated. "Large" Explorers have been so infrequent that comparison from one to the next is very difficult - the rules can change on faster timescales.