Hopkins Sacrifices Telescope, Safeguards Sky-Mapping Project

Delight overtakes him.

"I thought about writing a book," Uomoto says, from his office in the Bloomberg Center for Physics and Astronomy.

After all, The Johns Hopkins University has just saved the most ambitious sky-mapping venture in history.

The problems began three years ago for his colleagues with the Sloan Digital Sky Survey, a cooperative project of seven not-for-profit research institutions in the United States and Japan, as they constructed technology for a comprehensive census of the universe. One of the two telescopes failed. At the time, no one worried because the faulty 24-inch ‘scope was the smaller of the two, used only to calibrate a more complex, more distinguished 2.5-meter wide-angle telescope, which would do the actual mapping.

"The little telescope was ignored by leading scientists in the program because, after all, it's a little telescope," said Uomoto, a research scientist who developed the spectrographic equipment for the project. "It was needed just to identify calibrator stars. What could possibly go wrong?"

By 1997, after installation at Apache Point Observatory in New Mexico, the diminutive calibrator – called an Autoscope - still did not work, and the company that built the telescope quit answering calls. Uomoto did some quick detective work, phoned astronomers in Florida and Massachusetts, who also had attempted to use small autoscopes purchased from the company, and asked a few pointed questions.

Everyone told the same story: In each instance, a telescope was partially installed and never worked.

When the manufacturer declared bankruptcy, the Sloan team decided to fix the telescope themselves. After all, a Herculean effort to map a quarter of the entire sky and determine the positions and radiance of more than 100 million celestial objects would never succeed without an effective calibrator.

"We could see that the telescope was never engineered correctly," Uomoto explained. "It was made with incorrect materials, and there was no way to imagine it performing well enough for a long enough time to be useful. But still, when you first looked at it, you thought, ‘All I have to do is wire up this encoder to make it happen.' So you wire up the encoder and realize--oh, the board on the encoder needs modifications. You fix that, and then you realize, ‘If I fix the board, the mounting plate has to move a little bit this way.' It went on and on and on and on."

Sloan dedicated one full-time person to solve the problem and another team member spent most of his time augmenting the salvage operation.

Finally, late last year, director of project development Jim Crocker, who is also a Hopkins astronomer, polled the team and asked if anyone believed the telescope would last the life of the project. No one did.

In December of '97, the team elected to, as Uomoto says, "chuck it."With less than a year before the big telescope was scheduled to gather "first light" from the observatory, Uomoto and his colleagues searched for a new instrument. The most prominent manufacturers said they could build one – in 14 months. A number of small telescopes around the world had been decommissioned and might have been useful, but none would fit inside the small observatory building in New Mexico.

"So what do you do?" he asked.

Atop the Bloomberg building sat a small telescope, a little workhorse used mostly on Friday nights when the department invited the public to drop by for stargazing. Since 1993, when Uomoto first installed it, Bloomberg's ‘scope had also survived the occasional use and abuse of students who sought its clear eye to complement their classwork. One day, Uomoto finally fished for a tape measure and went to the roof.

If he could just knock out a five-foot concrete pier and plant a wedge under the mount to make up for the difference in latitude between Baltimore and New Mexico …

It worked. "I actually thought about using this telescope on the project a few years ago," Uomoto noted. "It does so much better than the one we had out there. But I couldn't figure out the practical aspects of making the switch, and I also knew if I suggested it, I'd get the job. As it turns out, I got the job, anyway."

In July, Uomoto, a few colleagues and technicians made the sacrifice. They unbolted their precious telescope, dismantled it, and trucked the instrument off to Apache Point. A number of them, including Uomoto, traveled to New Mexico in August to begin the installation.

The Hopkins' telescope has been retrofitted recently with new optics and is being tweaked for full service sometime next month. Soon it will be positioning the big telescope on the brightest stars and galaxies in the universe, identifying millions of galaxies for compilation in a celestial catalogue that will rival the Library of Congress and improve the quality of astronomical research for years to come.

The good news is that Hopkins' old telescope is now working at Apache Point and being readied for its work for scientists who want to explore critical questions about the nature and evolution of the universe. Its title has been cleanly transferred to the Astrophysical Research Consortium, which runs the Sloan Digital Sky Survey, and ARC has purchased a new--and improved--telescope for the rooftop of the Bloomberg Center.

Of course, nothing's perfect.

"Lately we've had a little trouble with a detector cooler on the large telescope," said Uomoto, whose office is still littered with the flotsam of telescope hardware left behind by the westward move. But, then, that's another story.

RELATED LINKS: Hopkins Digital Sky Survey GroupApache Point ObservatorySloan Digital Sky Survey

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