The report lists the missions from top to lowest priority, and excludes some efforts on the wish lists of astronomers. "This is not just a typical 'please send money' report," says William Wulf, president of the National Academy of Engineering and NRC vice chairman. "This represents tough choices" made within the astronomy community.

The study urges NASA to consider a host of mission sizes, not just the very large and the very small, which dominate the agency's planning. While the team proposes four major space-based initiatives -- that is, missions costing more than about $500 million -- it also recommends five moderate initiatives, each with an average price tag of about $300 million. One panel member says that mid-sized missions today don't win the support that the larger ones do, while smaller spacecraft are built and flown under special programs like Explorer or Discovery.

Despite the study's call for NASA to provide more opportunities for variety in mission size, NASA officials greeted the report enthusiastically; saying it largely matches the agency's plans for the next decade. The top NRC priority, for example, is the Next Generation Space Telescope, a $1 billion observatory with a mirror nearly four times the size of the current Hubble Space Telescope. That future mission already is high on NASA's to-do list. The effort will include substantial contributions from the European Space Agency and the Canadian Space Agency, and is slated for launch around 2007.

The NRC panel was made up of 15 distinguished astronomers and astrophysicists and included a number of sub-panels with more than 100 additional scientists participating. A number of outside reviewers then closely examined the results. As a result, researchers say the report has a large amount of credibility in the astronomy community. Not every mission proposed by advocates made the cut: the Space Ultraviolet Observatory, for example, is not on the list. The proposed spacecraft would study the intergalactic gas that birthed galaxies, but McKee said at a press conference today that the technology for that effort is not yet advanced enough.

Among the winners:

• Constellation-X Observatory: This $800 million spacecraft would include four X-ray telescopes to study the formation and evolution of black holes, as well as spot quasars at the edge of the visible universe. NASA should begin the project around 2005, the report states
• Terrestrial Planet Finder: A massive technological effort, this $1.7 billion mission would be the most ambitious scientific effort ever attempted by NASA. A series of spaceborne telescopes linked together would create a formidable instrument to study terrestrial-like planets around nearby stars. But first, the panel says that the Next Generation Space Telescope and the Space Interferometry Mission must be built to provide the technological foundation for the effort. Work would begin in this decade, but it would not be launched until well after 2010.
• Gamma-Ray Large Area Space Telescope: A $600 million flight to study gamma rays is the committee's top priority for a moderate-sized space mission. The second priority is the Laser Interferometer Space Antenna, which could detect gravity waves from merging supermassive black holes.
• National Virtual Observatory: The top priority among smaller missions is creation of this organization, which would provide astronomers, as well as the public, with access to vast amounts of astronomical data which is now difficult to find. This effort not only would be a blessing for astronomers, but would also provide "an unparalleled opportunity for education and discovery to the public," according to the draft version of the report released today. The remainder of the smaller missions are not ranked in order of priority, but they include a mix of efforts, ranging from an advanced cosmic-ray experiment to additional funds for astrophysical theory programs at universities.

The McKee-Taylor report called for $4.7 billion in total spending for new observatories, with about $1 billion for those on the ground and the remainder for space projects. The last long-term NRC report on astronomy, led by Princeton astronomer John Bahcall, called for $640 million for ground-based initiatives and $3.3 billion for space-based observatories.