distances to—more than 600 galaxies and quasars in a single observation. A custom-designed set of software pipelines keeps pace with the enormous data flow from the telescope.

In its first 5 years of operation, the Sloan telescope searched more than 8,000 square degrees of the northern sky—about a fifth of the entire sky—in five wavelength bands. It recorded some 217 million objects, mostly galaxies, stars, and asteroids, and measured spectra for around 675,000 of these.b

With funding from multiple sources and countries, the SDSS has followed a policy of freely releasing data annually, with separate Web sites for research users and the general public. A recent release, Data Release 7 (DR7), in November 2008, included some 16 terabytes of images and spectra. Its current phase, SDSS-II, is among the largest astronomical collaborations ever undertaken, involving more than 300 astronomers, astrophysicists, and engineers at 25 institutions around the world.

The SDSS has helped to revolutionize the interactions between a telescope, its data, and its user communities. Because the SDSS data archive is available to any astronomer, roughly half of the 2,100 refereed papers based on SDSS data have come from authors outside the project itself, and that proportion is rising. In fact, for the past 2 years, the SDSS has produced the most high-impact papers of any astronomical observatory.c At the same time, the project has extended the “reach” of those wishing to participate in frontier astronomy research or to simply enjoy the ability to “be there” as amateur aficionados. The public is offered both the raw data of SDSS and, at a “SkyServer” Web site, a range of search tools to help them use the data. Teachers are encouraged to adapt the projects for use in the classroom. SDSS data also are available through the National Virtual Observatory (http://www.us-vo.org), a collaborative effort involving universities, supercomputer centers, observatories, and data repositories.d

Even bigger projects are under development. For example, the Large Synoptic Survey Telescope (http:/www.lsst.org) that is currently being developed will generate as much data each night as a complete SDSS. As the “Living LSST Document, Version 1.0, of May 15, 2008” put it:

LSST has been conceived as a public facility: The database it will produce, and the associated object catalogs that are generated from that database, will be made available to the world’s astronomical research community and to the public at large with no proprietary period. The software which created the LSST database will be open source. LSST will be a significant milestone in the globalization of the information revolution. LSST will put terabytes of data each night into the hands of anyone who wants to explore it, and in some sense will become an Internet telescope: the ultimate network peripheral device to explore the universe, and a shared resource for all humanity.


a Alexander Szalay and Jim Gray. 2001. “The world-wide telescope.” Science 293:2037–2040.


b Robert C. Kennicutt, Jr. 2007. “Sloan at five.” Nature 450:488–489.


c J. P. Madrid and F. D. Macchetto. 2006. “High-impact astronomical observatories.” Bulletin of the American Astronomical Society 38:1286–1287.


d Alexander Szalay, Johns Hopkins University, presentation to the committee, December 10, 2008.

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