To drum up further support, Tyson and his colleagues went on the campaign trail in 2006 and 2007, giving talks at universities and at the technical centers of companies like Google—and the dollars began to trickle in. A big break came four months ago, when Tyson announced two major gifts: $20 million from the Charles Simonyi Fund for Arts and Sciences and $10 million from Microsoft founder Bill Gates.
From Vision to Reality
Even as the money situation improves, the technological challenges of building LSST are as daunting as ever, says Lawrence Livermore physicist Don Sweeney, the LSST project manager, in charge of coordinating the facility’s erection from soup to nuts. “The system will collect data hundreds of times faster than the fastest telescopes of today through an enormous field of view,” he says, “presenting technological hurdles in three big parts.”
The first is the telescope itself. Not only will it need to process wide-angle images, but it will need to do so rapidly, concentrating light efficiently enough to capture, within seconds, objects less than one-millionth the brightness of what can be seen with the naked eye. Such fast wide-field optics require a radically new design, involving three mirrors: a smaller secondary mirror near the mouth of the telescope and two highly curved mirrors, the primary and tertiary, arranged concentrically at the back end.
LSST’s three mirrors will focus light on an array of digital chips that are part of a novel type of camera—the second challenge Sweeney is charged with seeing through. The chips in a typical personal digital camera are less than an inch square and contain some 5 or 6 million pixels. LSST images, more than two feet across, will require a camera with 3.2 billion pixels and microchips far bigger than any single silicon chip ever made. The camera’s detector, still in the planning stages, will be made of large panels each containing 200 individual chips, all linked together so that their output can be combined to form individual pictures. Even the camera shutter will require special engineering: Imagine an eyelid bigger than a manhole cover, able to snap open or closed in an instant without shaking the sensitive telescope and able to withstand millions of such repeated cycles?. With all its electronic and mechanical parts, the camera will be about the size of a small SUV. “It will be, by far, the biggest camera ever built,” Sweeney says.
The flood of data this behemoth will produce would choke most computers. Pictures will stream out so quickly that, by current estimates, just one minute of observing time on LSST will generate 72 gigabytes of data, enough to fill a pack of 100 CD-ROMs. It will require new technology to transfer and store a fire-hose stream like this—the third challenge on Sweeney’s list. Fortunately, the LSST’s high demands are paralleled by rapid advances in technologies like motion picture animation, medical imaging, and broadband Web-based video, which is one reason why Silicon Valley corporations are getting involved.
Slowly the LSST is turning from dream machine into a nuts-and-bolts tool for the next great round of astronomical exploration. It is not easy to tell when a telescope crosses the divide between idea and reality, but surely the casting of its main mirror is an important milestone. That one was reached in March 2008, when technicians loaded 26 tons of borosilicate glass into a huge rotating oven located under the football stadium at the University of Arizona and turned up the heat to 2,150 degrees Fahrenheit. Members of the LSST team, donors, dignitaries, and reporters popped in for a ceremony marking the event. Then the crowds departed, leaving the scientists at the helm the task of producing, for astronomers and the public alike, what could be the most amazing movie ever made.
Galaxy cluster CL0024 as seen by Hubble
Image courtesy of NASA/ESA/M.J. LEE and H. Ford (Johns Hopkins University)
Sleuthing Dark Matter
Dark matter and related gravitational distortions in the cluster.
Image courtesy of LSST Corporation
Cosmologists say a scaffolding of dark matter holds the universe together in an invisible web. Though other telescopes have provided evidence that dark matter actually exists, LSST will be able to map it precisely by rapidly scanning the heavens for gravitational distortions that only dark matter can explain. As LSST scans the same cosmic turf again and again, it will statistically analyze the bending and arcing of light from distant heavenly bodies, making it possible to render intricate maps that may include dark-matter structures as large as 500 million light-years across. With the ability to find especially remote dark-matter distortions, LSST will help chart the evolution of the universe from its birth.
