Stargazers: Charlottesville scientists are helping build the most powerful telescope in history

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Joe Greenberg working on the prototype of the computer that will be able to image the black hole at the center of our galaxy. Photo: John Robinson Joe Greenberg working on the prototype of the computer that will be able to image the black hole at the center of our galaxy. Photo: John Robinson

The President of Chile is running about an hour late. Not surprising, perhaps, considering the dedication ceremony he’s attending is being held 25 miles from the small tourist town of San Pedro de Atacama, up a long and desolate road, in a support facility nestled at 9,000′ in the high desert of the Chilean Andes. Assembled dignitaries, politicians, scientists, and press mill about a large, white tent, planted improbably on the dusty soil of a site that’s important because of its lack of water. Crystal clear high-altitude sunlight diffuses through the sides of the tent, illuminating dark suits, professional smiles, and rows of white-sheathed folding chairs.

Some of that light enters the lens of a video camera. The lens focuses it onto a CCD chip, which pulses out a discrete raster of image data 30 times every second to a computer workstation and from there to an Internet server. The server dissects the data into packets, which it sends skittering out onto the Web. Around the globe, hundreds of other Internet routers requesting the feed pull it together, buffer it, and serve it up as streaming video.

In a small auditorium in Charlottesville, a projector jacked into a laptop casts the images onto a screen. Sixty or so people gathered in that auditorium are doing the same thing as their colleagues 5,000 miles away—smiling, chatting, and waiting. They are all employees of the National Radio Astronomy Observatory (NRAO)—scientists, engineers, technicians, and support staff. They are here to watch, from a continent away, the inauguration of ALMA—the Atacama Large Millimeter/sub-millimeter Array—the most powerful telescope on earth. They are, despite the delay, in a celebratory mood. And they should be, because they helped to build it.

When it is completed, ALMA will feature 66 of the most sensitive radio receivers ever made, placed at 16,500' in the Chilean Andes. Photo: ALMA (ESO/NAOJ/NRAO), C. Padilla
When it is completed, ALMA will feature 66 of the most sensitive radio receivers ever made, placed at 16,500′ in the Chilean Andes. Photo: ALMA (ESO/NAOJ/NRAO), C. Padilla

Twenty-plus years in the making, ALMA cost $1.3 billion. On March 13, it was officially put into service. When all of its components are in place in the coming year, it will sport 50 39′ state-of-the-art radio antennas, as well as an additional 16 smaller antennas which greatly increase its sensitivity. Each of the larger antennas is the size of a modest house, and can be moved around the vast Chajnantor plateau, a 16,500′-high portion of the Atacama desert, into configurations as large as 11 miles across, allowing astronomers to adjust the size of the slice of sky that the telescope can take in. ALMA will be able to see things farther away, fainter, and in vastly greater detail than we have ever been able to see before. Our view of the universe is about to take an exponential leap.

Like almost all big science in an age of fiscal constraint, ALMA was built by a consortium of countries. But NRAO here in Charlottesville houses its North American headquarters. The people here helped select the site in Chile. They developed the telescope’s specs and its mission. They helped create many of the super-cooled, supersensitive radio receivers that are its ears. And they designed and built, in a little low-slung building off of Ivy Road, the supercomputer capable of 17 quadrillion operations per second that is its brain. This is ALMA’s story, told in snapshots of a few of the hundreds who helped make it happen.

Climbing the ladder

“It’s been a very long haul,” said Paul Vanden Bout, who would know as well as anyone. As Director of NRAO through most of the years of ALMA’s development, Vanden Bout signed the agreements and nurtured the international relationships that made ALMA possible. He also wasn’t above a bit of tramping in the mountains if it meant finding a home for the telescope.

In the early 1990s, Vanden Bout and several colleagues found themselves in the hamlet of San Pedro de Atacama, and the going was not easy: “The other NRAO person [on the trip] was Bob Brown, and he had studied the topo maps and knew that there was high ground and a road. He knew that you could drive up there, which we attempted to do in two trucks. Brown made it up to the high altitude and was very impressed with what he saw. My truck broke down. The carburetor couldn’t take the thin air.”

Unlikely as it may seem, the path that leads astronomers to Chile was, even at the time, very well worn. Because of its abundance of high elevation sites, an aggressive technology development plan, and relatively low costs for construction and manpower, Chile is dubbed by Wikipedia “the astronomy capital of the world.” Charlottesville’s connection to astronomy is just as well founded, though it requires a bit more explanation. It came about because of the invention of a farm implement.

Cyrus McCormick, from Rockbridge County, Virginia, is credited with building the first threshing machine in the 1830s. He and his brother Leander were both heirs to the manufacturing company that eventually became known as International Harvester. In 1877, Leander, who had an interest in astronomy and had maintained an affection for his home state, donated a telescope with a 26″ primary lens to the University of Virginia.

Because of the altitude, technicians need supplemental oxygen when they work on the ALMA Correlator, a supercomputer capable of 17 quadrillion operations per second. Photo: ESO/Max Alexander
Because of the altitude, technicians need supplemental oxygen when they work on the ALMA Correlator, a supercomputer capable of 17 quadrillion operations per second. Photo: ESO/Max Alexander

UVA astronomer Ed Murphy runs the public outreach program at the McCormick Observatory, where the telescope is on display and functioning to this day. “The telescope, when it was finished, was the largest in the United States, and the second largest in the world,” said Murphy from his office on McCormick Road. “It was a very big deal when it came here, and that’s really what put astronomy in Charlottesville on the map.” In the early 1900s, the Observatory embarked on an ambitious program to measure the exact distance from the earth to nearby stars. The measurements conducted here laid the groundwork, step by step, for the measurement of increasingly distant objects.

Climbing “the distance ladder,” as it is called, astronomers in the first half of the 20th century gained a staggering new view of the cosmos. It had previously been thought that the entire universe consisted of our Milky Way galaxy—a homey collection of stars and nebulae 100,000 or so light years across. But by 1950, it was becoming more or less universally understood that our galaxy was only one of hundreds of millions spread out over the unimaginably vast space of billions of light years.

The new science of radio astronomy helped astronomers develop this picture, but after WWII, the United States found itself behind in the radio game. So in the late ’50s, the National Science Foundation established a National Radio Astronomy Observatory, purchasing land in Green Bank, West Virginia, where they built a headquarters, designated a “radio quiet zone” to minimize interference, and started building telescopes. The remote location made it easier to maintain radio silence for the telescopes, but it was an out-of-the-way place to house a national science program.

By the 1960s NRAO was looking for a new headquarters—something closer to the center of power in D.C., and in better proximity to other scientists. The UVA astronomy department, then under the direction of Laurence Fredrick, was aggressively hiring research faculty and rebuilding a national reputation. When UVA offered to construct a new home for NRAO, the deal was done. By the 1970s, between NRAO and the astronomy department, Charlottesville boasted a substantial percentage of the world’s talent, experience, and brainpower in the field of astronomy.

Al Wootten was one of those drawn into the orbit. Wootten now serves as North American Project Scientist for ALMA, but at the time he was an expert who had already made a name for himself studying molecular gas clouds. He came to NRAO to get access to the kind of instruments he needed to pursue his work. “I came here in the end of 1982 to work on a 25-meter telescope, which was cancelled when I hadn’t even been here a month,” said Wootten, with a wry chuckle. “So that was a great feeling.”

He talks resolutely, matter-of-factly, but with an undercurrent of humor that hints that he understands one or two of the absurdities that underlie most things in this world. “So I thought, well, I’d better get involved in this Millimeter Array.”

  • UVa

    Great article, from an non-NRAO engineer who knows a little about this work.
    Only error I spotted is 125 Gigahertz should be 125 Megahertz.

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