Johns Hopkins Magazine -- November 1997
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NOVEMBER 1997
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Taming the Terabyte
Collaborating to Map the Universe

The telescope for the Sloan Digital Sky Survey, at Apache Point, New Mexico, will include two spectrographs that will record the light coming from celestial objects across a wide range of the electromagnetic spectrum. Instead of photographic plates, it will contain charge-coupled devices (CCDs), the electronic light sensors used in video cameras. Each star and galaxy will be represented by roughly 1,000 pixels, but the sky will be viewed through five different color filters, so there will be five measurements per pixel. This all translates into a lot of data: a grand total of about 40 terabytes of raw data, collected during the five-year project, says Hopkins astronomer Alexander Szalay, Sloan's archive director. The images will be digitized, recorded on tapes, and transferred to Fermilab, outside Chicago. Collaborating astronomers will then access the raw data through vBNS, analyze it, and whittle down the results, saving the distinct objects and tossing the rest. The finalized archive will contain 1 terabyte, says Szalay, and will be placed on compact discs (or a future technology) for public use within two years.
--MH
Photo by Mike Ciesielski

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