A blue-ribbon National Academy of Sciences committee released its decadal survey of astronomy and astrophysics projects August 13, revealing its recommendations for 2012 to 2021. The influential report, produced by a 23-member committee and backed by nine expert panels together constituting 123 researchers, provides lawmakers and agencies such as NASA and the National Science Foundation with a guideline for which projects most deserve funding.

Topping the list of large-scale projects on the ground, unsurprisingly, was the Large Synoptic Survey Telescope (LSST), a planned 8.4-meter telescope in Chile that should generate maps of the sky with unprecedented detail. The LSST, which the report estimates would cost the U.S. $421 million over a decade, should also make a significant contribution toward identifying which asteroids in Earth's vicinity pose an impact threat.

In placing the LSST atop its priority list, the report highlighted the telescope's technical readiness and its "compelling science case and capacity to address so many of the science goals of this survey," including exploring the fundamental physical makeup of the universe by probing the nature of dark matter and dark energy.

Among the largest space-based projects, the committee recommended prioritizing the development of a spacecraft called the Wide-Field Infrared Survey Telescope, or WFIRST (not to be confused with WISE, the Wide-Field Infrared Survey Explorer). WFIRST, with an estimated price tag of $1.6 billion over 10 years, would augment the planned Joint Dark Energy Mission of NASA and the Department of Energy to include an exoplanet census.

Other initiatives earning committee approval:

* Expand the NASA Explorer program, a series of relatively low-cost spacecraft that has produced recent successes such as the aforementioned WISE and the Wilkinson Microwave Anisotropy Probe.

* Invest in a Giant Segmented Mirror Telescope, either the Giant Magellan Telescope in Chile or the Thirty Meter Telescope in Hawaii. An investment of about $300 million would buy the U.S. a 25 percent share in one of those projects.

* Fund the New Worlds Technology Development Program, which would lay the groundwork for a space mission sometime after 2020 to study potentially habitable nearby exoplanets.

A look at the previous decadal survey, from 2001, reveals that although the field of astronomy has largely hewed to the committee's recommendations, some highly rated projects remain unrealized while others have overcome low rankings to begin taking data. The top-ranked large project in 2001's report, since dubbed the James Webb Space Telescope, is under construction and may launch as early as 2014. Among moderately priced initiatives from that report, the Fermi Gamma-ray Space Telescope (then known as GLAST and ranked #2) and the Solar Dynamics Observatory (#6) have already launched, whereas others have fallen by the wayside or remain in the planning stage.

The entire report, New Worlds, New Horizons in Astronomy and Astrophysics, is available as a free PDF download at the National Academies Web site.

Concept for WFIRST spacecraft: JDEM Project, NASA/GSFC