June 11, 1998
Vol. 17, No. 18

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    Gathering 'first light'

    Graduate student helps construct camera essential to Sloan Digital Sky Survey

    By Catherine Behan
    News Office

    It is one of the most sophisticated

    and expensive cameras in the

    world, built to help researchers attempt the most ambitious mapping of the universe: the Sloan Digital Sky Survey. Helping construct the camera is 26-year-old Connie Rockosi, a University graduate student -- and one of the most knowledgeable scientists in the world in electronic imaging.

    "In science, there's a special kind of person who creates the instruments that make our measurements possible," said Michael Turner, Professor and Chairman of Astronomy & Astrophysics and scientific spokesman for the survey. "Without them, science doesn't happen. Connie is one of the best."

    The Sloan Digital Sky Survey will systematically map one quarter of the entire universe -- a much larger section than previous attempts -- producing a detailed image of it and determining the positions and absolute brightness of more than 100 million celestial objects. It will also record the distances to 100,000 quasars and 1 million galaxies.

    "We're trying to find out how the world works -- how the universe was formed," Rockosi said. "The survey is a great piece of detective work."

    Many graduate students have assisted on the project, but Rockosi, a graduate student in Astronomy & Astrophysics with an undergraduate degree in electrical engineering, has had a more prominent role than most because she is a key member of the camera's construction team. She will present the first image of the sky taken with the camera at the American Astronomical Association meeting in San Diego June 7-11.

    "Connie was chosen to present the 'first light' paper at the meeting because everything she's done on the project has been spectacular," said Don York, Professor in Astronomy & Astrophysics. The camera Rockosi has been working on is valued at $6 million, and at that price, York said, "we only want the best people working on it. Connie is a first-class scientist and we couldn't ask for a better person."

    Scientists and engineers from eight institutions are collaborating at Apache Point Observatory in New Mexico to produce the new and unprecedented map of the sky. The cutting-edge camera will record the images digitally and provide extensive data for researchers around the world. The camera has more pixels than the human eye and will collect almost 100 percent of the light the telescope focuses on -- compared to the less than 1 percent collected by photographic plates used in the past.

    Rockosi first became acquainted with the Sloan Digital Sky Survey while an electrical engineering major at Princeton University. As part of a junior-year paper and senior thesis project, she searched for a topic that combined her interests in electrical engineering and astronomy. A friend recommended she talk to Jim Gunn, astronomy professor at Princeton and a project scientist in the Sloan Survey.

    The conversation marked the start of her involvement with the survey. After graduating from Princeton in 1993, she decided to pursue graduate work in astronomy, choosing to attend the University of Chicago largely because it was a key player in the Sloan project.

    At Chicago, her work on the Sloan Survey camera has allowed her to continue combining electrical engineering and astronomy. The complex camera, which is about one meter in diameter, includes 54 silicon electronic light sensors called charge-coupled devices, or CCDs. Photons striking the CCDs are converted to electrons, which allows the image to be digitized and recorded on tape. Each night of observing will produce enough data to fill a dozen tapes.

    Rockosi, who hopes to become an academic researcher in astronomy after earning her Ph.D., will be one of the first scientists to utilize information gathered in the Sloan Survey. She will use the survey data to study the colors of stars and what they say about the age of the universe and how it developed. "After helping build this instrument, it will be a thrill to use the data it collects," Rockosi said.

    In the meantime, Rockosi has been in demand for her expertise. In addition to helping the build the Sloan Survey camera, she also helped build the high-resolution spectrograph to be used on the 3.5-meter general-purpose telescope at Apache Point Observatory, which is used by University scientists.

    "We've been doing hand-to-hand combat for her time," Turner said. "When Connie gets out of school, the world will be knocking at her door because these big cameras have changed astronomy in a fundamental way. Connie is one of a handful of scientists who can build and use these cameras."

    The Sloan Survey collaboration includes scientists from the University of Chicago, Fermilab National Accelerator Laboratory, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, Princeton University, the United States Naval Observatory and the University of Washington.