The Sloan Digital Sky Survey, SSDS, is the most ambitious astronomical survey ever undertaken. The experiment used a 120-megapixel digital camera, a pair of spectrographs with the ability to measure spectra of more than 600 galaxies and quasars in a single observation, and a 2.5-meter telescope in New Mexico. Over two runs, it captured detailed optical images of more than a quarter of the sky and created a 3-dimensional map of about 1 million galaxies and quasars. Data collected by SDSS has given astrophysicists insights into the nature of dark energy and dark matter.
Fermilab makes the collected data available to the scientific community and general public through the Web. The Sloan Web site has gotten more than 467 million hits since 2001. In 2008, it averaged 10 million hits per month, 1.6 million of which were requests for data. More than half of the more than 2,000 published papers based on data from the survey were written by researchers not directly involved in it. Twenty-five institutions from around the world participated in SDSS. Though the experiment completed its second run, researchers continue to mine its data to address fundamental questions about the nature, origin and evolution of the galaxies.