Surveys are of fundamental importance to astronomy. They produce data sets which are large, easy to use, of high quality, and can support entire fields of research for decades. The Sloan Digital Sky Survey (SDSS) can fairly be considered to belong in this category. It has already had a major impact on large scale structure and cosmology, and has in addition produced forefront research in areas as diverse as Galactic structure, stellar populations, galaxy properties, and small solar system objects. This award supports a three and one half year extension program to use the SDSS machinery (the hardware, software, infrastructure and data bases) to continue to produce survey data focused on three main questions: the enhancement of the SDSS legacy data archive and its power to quantify the large-scale distribution of galaxies via increased area coverage and much improved photometric calibration; a major attack on the kinematics and structure of the Galaxy's stellar populations aimed at unraveling its formation history; and a search for supernovae in the redshift range sensitive to the onset of cosmological acceleration.
SDSS has efficiently and promptly produced a vast, easy-to-use public archive of extremely high quality data which has been used by astronomers nation- and world-wide to carry out a plethora of forefront, influential research. The availability of such data supports non-traditional modes of carrying out research and levels the playing field by bringing state-of-the-art data products to all. The SDSS data archive has applications across most astronomical disciplines and across the Federal agencies which support them. SDSS hardware and software technology influence the continuing development of scientific capabilities: existing major facilities, multi-wavelength archives, and the planning for and development of new facilities such as the Large Synoptic Survey Telescope, LSST. SDSS data support other astronomical facilities, both space- and ground-based: they provide accurate calibration and the raw material for target lists. Large surveys also have sociological impact, including the pioneering of new modes of scientific collaboration, the development of education at all levels from high school through senior scientists, the transfer of results and data to public education efforts in the media and at museums, and the mentoring and development of young scientists. ***
