essential in the cycle of discovery—including technology development, theory, computation and data management, and laboratory experiments, as well as, and in particular, human resources. At the same time, the greatest strides in understanding often come from bold new projects that open the universe to new discoveries, and such projects thus drive much of the strategy of the committee’s proposed program. This program requires a balance of small, medium, and large initiatives on the ground and in space. The large and medium elements within each size category are as follows:
In Space: (Large-scale, in priority order) Wide-Field Infrared Survey Telescope (WFIRST)—an observatory designed to settle essential questions in both exoplanet and dark energy research, and which will advance topics ranging from galaxy evolution to the study of objects within our own galaxy. The Explorer Program—augmenting a program that delivers a high level of scientific return on relatively moderate investment and that provides the capability to respond rapidly to new scientific and technical breakthroughs. Laser Interferometer Space Antenna (LISA)—a low-frequency gravitational wave observatory that will open an entirely new window on the cosmos by measuring ripples in space-time caused by many new sources, including nearby white dwarf stars, and will probe the nature of black holes. International X-ray Observatory (IXO)—a powerful X-ray telescope that will transform our understanding of hot gas associated with stars and galaxies in all evolutionary stages. (Medium-scale, in rank order) New Worlds Technology Development Program—a competed program to lay the technical and scientific foundation for a future mission to study nearby Earth-like planets. Inflation Probe Technology Development Program—a competed program designed to prepare for a potential next-decade cosmic microwave-background mission to study the epoch of inflation.
On the Ground: (Large-scale, in priority order) Large Synoptic Survey Telescope (LSST)—a wide-field optical survey telescope that will transform observation of the variable universe and will address broad questions that range from indicating the nature of dark energy to determining whether there are objects that may collide with Earth. Mid-Scale Innovations Program augmentation—a competed program that will provide the capability to respond rapidly to scientific discovery and technical advances with new telescopes and instruments. Giant Segmented Mirror Telescope (GSMT)—a large optical and near-infrared telescope that will revolutionize astronomy and provide a spectroscopic complement to the James Webb Space Telescope (JWST), the Atacama Large Millimeter/submillimeter Array (ALMA), and LSST. Atmospheric Čerenkov Telescope Array (ACTA)—participation in