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By the early 2000s, most solar system bodies had received at least a preliminary inspection by spacecraft, making it difficult for the US National Aeronautics and Space Administration (NASA) to decide upon the next steps in its program and to prioritize objectives. Hitherto, the agency had decided the targets for its missions based on strategic planning by its Office of Space Science. It relied on input from the scientific community, in particular from the Space Science Board of the National Research Council, part of the National Academy of Sciences. In 2001 therefore, NASA asked the National Research Council to assess the current state of US planetary exploration and recommend which missions scientists believed to be the most significant and should be attempted in the 2003-2013 period. The Council interviewed some of the top planetary scientists, not only in the US but also abroad, and produced a report which, although the first of its kind in this field, was similar to the 'decadal surveys' that NASA had previously used for its astronomy, astrophysics and solar physics programs. While the survey was underway, NASA announced the creation of a new series of medium-class planetary missions, which it decided to call New Frontiers, to complement the Discovery and flagship-class missions. Discovery missions would fly every 1.5 to 2 years, New Frontiers every 5 years on average and flagships every 10 years for comprehensive investigations of especially significant targets. Like Discovery, New Frontiers was to be a program of flights that would be selected on a competitive basis and led by principal investigators, but with budgets of up to $650 million to enable them to attempt more ambitious objectives. |
