The Sloan Digital Sky Survey data acquisition system, and early results

The Sloan Digital Sky Survey will systematically map one-quarter of the sky, producing detailed images in five color bands and determining the positions and absolute brightnesses of more than 100 million celestial objects. It will also measure the redshifts of a million selected galaxies and of 100,000 quasars, yielding a three-dimensional map of the Universe through a volume one hundred times larger than that explored to date. The SDSS collaboration is currently in the process of commissioning the 2.5-meter survey telescope. We describe the data acquisition system used to record the survey data. This system consists of twelve single board computers and their associated interfaces to the camera and spectrograph CCD electronics, to tape drives, and to online video displays, distributed among several VME crates. A central UNIX computer connected to the VME crates via a vertical bus adapter coordinates the system and provides the interface to telescope operations. We briefly discuss results from the observing runs to date and plans for the archiving and distribution of data