cases, almost 10 magnitudes better than that achievable in space in the next decade. With a suite of spectroscopic and imaging instrumentation covering the optical and near-infrared (IR) bands, GSMT will be crucial for detailed follow-up investigations of discoveries from existing and planned facilities, including the James Webb Space Telescope (JWST) and the Atacama Large Millimeter Array (ALMA).

The promise of the next decade lies also in the capability of building a telescope to conduct systematic, repeated surveys of the entire available sky to depths unobtainable before now. Combining repeated survey images will provide composite wide-field images extending more than 10-fold fainter. Readily available synoptic data will revolutionize investigations of transient phenomena, directly addressing the key discovery area of time-domain astronomy, as well as being invaluable in surveys of regular and irregular variable sources, both galactic and extragalactic. At the same time, the combined images will provide a multi-waveband, homogeneous, wide-field imaging data set of unparalleled sensitivity that can be used to address a wide range of high-impact scientific issues. As the 48-inch Schmidt Telescope did with respect to the 200-inch Palomar Observatory, so also will LSST play a fundamental role in detecting the most fascinating astronomical targets for follow-up observations with GSMT.

Having considered proposals from the research community for new large facilities, the panel’s conclusions with respect to large projects are as follows:

  • The science cases for a 25- to 30-m Giant Segmented Mirror Telescope and for the proposed Large Synoptic Survey Telescope are even stronger today than they were a decade ago.

  • Based on the relative overall scientific merits of GSMT and LSST, the panel ranks GSMT higher scientifically than LSST, given the sensitivity and resolution of GSMT.

  • Both GSMT and LSST are technologically ready to enter their construction phases in the first half of the 2010-2020 decade.

  • The LSST project is in an advanced state and ready for immediate entry into the National Science Foundation’s (NSF’s) Major Research Equipment and Facilities Construction (MREFC) line for the support of construction. In addition, the role of the Department of Energy (DOE) in the fabrication of the LSST camera system is well defined and ready for adoption.

  • LSST has complementary strengths in areal coverage and temporal sensitivity, with its own distinct discovery potential. Indeed, GSMT is unlikely to achieve its full scientific potential without the synoptic surveys of LSST. Consequently, LSST plays a crucial role in the panel’s overall strategy.

  • GSMT is a versatile observatory that will push back today’s limits in imaging and spectroscopy to open up new possibilities for the most important scientific problems identified in the Astro2010 survey. This exceptionally broad and powerful



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