From the Princeton Weekly Bulletin, February 24, 1997
Road map to the universe
By Kathryn Watterson
Laughter, music and not a small amount of hooting and humming can be heard in the basement of Peyton Hall, where a group of gadget-loving astrophysicists and engineers are having the time of their lives. They're beginning to build a road map to the universe that will take them farther and deeper back into time than anyone has gone before.
What they are actually building is an extraordinary camera, the size of a coffee table, and software so complex that it boggles the mind. These instruments, together with a wide-angle telescope in New Mexico and a pair of spectrographs, are going to produce a three-dimensional map of the universe over a thousand times more detailed than ever before created.
Until recently, measurements of the galaxies, which trace the structure of the universe, the filaments and voids, typically have trickled in one by one. But this project, the Sloan Digital Sky Survey (SDSS), will produce information on a much larger scale than previously possible. It will produce a digital image of the sky in five color bands and dramatically expand our vision of the deep sky. (To give an idea of the scale: whereas today scientists have measured 10,000 quasars, this survey will measure some 100,000.) The survey will gather information over a five-year period, beginning later this year, and delineate the detailed distribution of a million galaxies in space, with information on some 100 million more, giving the detailed structure of the universe and its evolution through time.
For astrophysicists, creating this survey is akin to Columbus finding a boat capable of sailing to the Americas. While the telescope, camera and software aren't going to travel, they will be the vehicles that introduce us to new territory -- and no doubt, to many surprises, including a new understanding of just how our universe was formed.
This project, which started more than five years ago, is now being carried out by a consortium of astrophysicists at several institutions (the universities of Chicago, Washington and Tokyo; Princeton and Johns Hopkins; the U.S. Naval Observatory; Fermi National Accelerator Lab; and the Institute for Advanced Study).
"Can you keep a secret?"
It began when James Gunn, Eugene Higgins Professor of Astronomy, went to what he expected to be a "deadly dull" meeting at the National Observatory. While there, he realized that digital detectors -- electronic detectors that convert photons directly into electrons and allow that information to go directly into the computer -- had finally become big enough, fast enough and efficient enough to take an image of the entire sky in five color bands, and that a single telescope could be built that would both image the sky and obtain very large numbers of redshifts.
By the time he came home 36 hours later, Gunn had already started on designs for the telescope, the fiberoptic-fed spectrographs and CCD (charge-coupled devices) cameras.
"I remember Jim coming home from this meeting on the red eye," says his wife and fellow astrophysicist Jill Knapp, professor of astrophysics. "He walked into the bedroom at six in the morning, reached into his inside jacket pocket -- just like someone trying to scalp you tickets outside the Met -- and he said, 'Can you keep a secret?' He showed me a new silicon device -- the first one -- and told me it was finally feasible to contemplate making a survey of the whole sky."
As the story goes, when Gunn told his idea to Provost Jeremiah Ostriker, then chair of the Department of Astrophysical Sciences, Ostriker said, "If you can build it, we'll raise the money for it."
Ostriker, who later became chair of the project's governing board, got in touch with an alumnus with a long-standing interest in cosmology, who jump-started the project with a major financial contribution. "It didn't seem real before he gave us that money," says Gunn. The Alfred P. Sloan Foundation and the National Science Foundation took the project the next step with major contributions.
At no time during the development of this project, however, has the team had the confidence that they'd have enough money to finish it. "There's always the worry about where the next dollar is coming from," says Gunn. "At this point we have the money to finish construction of the instrument, but we don't have enough money to finish the project. It's a little scary, but once the data start coming in, I think it will be exciting enough that we'll get funded."
Making music and art
Today, in a "clean room" in the basement of Peyton Hall, Gunn, mechanical engineer Michael Carr and astrophysicist Maki Sekiguchi from the University of Tokyo, are close to finishing the photometric/astrometric mosaic camera. Senior technical staff member Robert Lupton (sometimes referred to as "the Jim Gunn of software") is designing and constructing the codes for the software and database that will record, collect, calibrate, correct for defects and catalogue the voluminous information gathered. The rest of the Princeton team consists of Knapp, Assistant Professor Michael Strauss, Mamoru Doi of the University of Tokyo, Constance Rockosi of the University of Chicago, project manager George Pauls, research staff member Michael Richmond, technical staff members Brian Elms and Ernst de Haas, and software specialist Nancy Ellman.
"With this team, it's like music," says fellow astrophysist, Edwin Turner. "It's like a big jam session, where they're making music and art."
For everyone working on the project, the thrill of seeing their dreams of deep sky come into focus is art indeed; it's poetry in motion.
"I walk into that clean room and just look at that camera and think, 'Oh my God, it's a piece of art work." says Carr, who came to Princeton from Caltech. "We only hoped it would work. But it's going to work!"
Carr, who built cameras with Gunn that Gunn designed for the Hale and the Hubble Space Telescope, expresses what most of the scientists working on this project feel about it -- that he's worked his whole career to build this camera. "I've used all of my experiences here," Carr says. "Everything I've ever done in my entire career, plus some."
Gunn, who calls this his "last hurrah," says that while working on such an enormous, hugely expensive project has been stressful, it has also been enormous fun.
Knapp agrees. "Being in this scientific environment is just fabulous," she says. "Not a day goes by I don't respect my colleagues more and like them more. The personality of this department is beyond price. It has a lot to do with the quality of what we're doing."