Substantial facility investments include LIGO and IceCube, which may yield astronomical discoveries this decade.

The NSF-AST-supported radio observatories have been judged as world-leading, on the basis of both their technical performance and the desire of radio astronomers worldwide to use them. Radio telescopes operated by the National Radio Astronomy Observatory (NRAO) include the Expanded Very Large Array (EVLA), the Green Bank Telescope (GBT), and the Very Long Baseline Array (VLBA); the National Astronomy and Ionosphere Center (NAIC) operates Arecibo observatories. These centimeter-wavelength facilities provide the highest-resolution and largest-collecting-area instruments in the world. Following the recommendations of the 2006 NSF-AST senior review,⁶ funding for Arecibo ($8 million per year) and for NRAO’s VLBA, both still unique facilities, is being ramped down to optimize the program and to release funds for operating new facilities. The soon-to-be-commissioned (in 2013) $1 billion Atacama Large Millimeter/submillimeter Array (ALMA) is an international collaboration involving partners in North America, Europe, and East Asia, with Chile as the host country (Figure 6.4). In addition to these nationally managed facilities, NSF-AST funds operations and development at the university-based CARMA, ATA, and CSO ($8 million per year combined through the URO program), and NSF-OPP funds SPT ($2.5 million per year), which together at