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Features May 2007: Volume 4, Number 2

Journey to the Beginning of Time
By Susan Brown

UC San Diego's new telescope, situated in Chile's Atacama Desert, 16,000 feet above sea level, is peering into the beginnings of the universe.

“These precious photons from the big bang have been traveling for 13.7 billion years,” says Keating. “We don’t want them to get absorbed in some water molecule.” Consequently, the team sited the telescope high in Chile’s Atacama desert.


The Telescope is outfitted with antennas that funnel microwave light to sensitive detectors. These measure the direction of the vibration of incoming photons.

At over 17,000 feet, the telescope rests above much of Earth’s atmosphere, making the site, … one of the highest astronomical observatories in the world.

The observatory in Chile’s Atacama desert is located at an elevation of 17,000 feet. The sky is cobalt blue and the air so thin that scientists have to breathe from supplemental oxygen tanks. It was from that otherworldly place that astronomers from UC San Diego sent a message at the beginning of 2012. Their telescope, designed to peer back to the beginning of time, had seen “first light.”

It’s a moment of truth for any astronomical instrument, when operators focus on familiar celestial objects to test its sensing ability. For this telescope and these scientists, the event also marks the beginning of a project to study traces of the universe’s earliest light. The team plans to capture some of the first light to escape the opaque fog of plasma that filled the universe in its initial moments.

“The photons originated in the big bang itself, so at time equals zero,” says Brian Keating, a physics professor who leads the project at UCSD. Cosmologists think these ancient photons carry physical evidence of an event that occurred just a fraction of a second later, called inflation.

Their calculations predict a rapid, exponential expansion of the universe, a billionth of a billionth of a billionth of a billionth of a second after the big bang. This sudden, violent event would have rippled the fabric of space, leaving an imprint on the primordial light.

Since then, as the universe has continued to expand and light waves within it stretched as well. Distended in wavelengths too long to see, this original light now falls in a part of the spectrum called microwaves, and it has cooled from billions of degrees to a little less than 3 degrees above absolute zero. Called the cosmic microwave background, its faint glow suffuses the sky, day and night.

At sea level that weak signal would be lost—absorbed by Earth’s damp atmosphere just like moist food absorbs energy in a microwave oven.

“These precious photons from the big bang have been traveling for 13.7 billion years,” says Keating. “We don’t want them to get absorbed in some water molecule.” Consequently, the team sited the telescope high in Chile’s Atacama desert.


HIGH-LEVEL CONSTRUCTION: Members of Professor Brian Keating's research team made final adjustments as construction workers used cranes to lift the telescope's mirrors, booms and base into place.

“The Atacama is the driest desert on earth. There are no plants and no clouds,” says Stephanie Moyerman, a graduate research student in Keating’s group who helped to set up the telescope late last year. “You get out of the truck and think ‘ah, it’s really nice up here.’ And then five minutes later you’re freezing.”

In September, roads from the coast finally cleared after one of the snowiest winters in decades. A convoy of trucks, with the telescope strapped to the beds in four pieces, was able to climb from the port of Antofagasta and cross to the lee side of the coastal range. Their destination was Cerro Toco, a peak in Chile’s Chajnantor Scientific Reserve, the site of many astronomical observatories.

On arrival, construction workers used cranes to lift the telescope’s mirrors, booms and base into place. The delicate detectors were shipped by air, accompanied by the astronomers. Then this international team of collaborators got to work pulling cables through conduits and installing receivers and sensors. Finally, they installed a star camera that allows operators to precisely aim the telescope toward specific regions of the sky.

Although astronomers are used to less-than-perfect living conditions in their normally isolated, high-altitude perches, the Atacama was challenging.

“There was no heat. There was no power. We were still getting the generators up and running, so we had to run everything off one tiny gas-powered generator,” Moyerman says. “But it was really fun. When you’re up there, you just have to figure everything out on the fly, on your own.”

Until they got power for the telescope’s drive motors, they pushed and pulled it from side-to-side by hand. To point it higher or lower in the sky, they used a battery-powered drill to slowly wind the gears. They did all this while bundled up against the wind and cold, inhaling air tinctured with the smell of sulfur from the region’s many volcanoes. When working, they mostly breathed through their Camelback-like packs.

“It’s tough, definitely. It can be very cold and very windy. There’s not a lot of oxygen. But I kind of enjoy that aspect, the challenge of working in a place like that,” says Dave Boettger, another research student in Keating’s group, who returned from an 80-day stretch at the observatory in December 2011. “It took me maybe a week and a half of going up every day before I felt sort of steady state. It’s never normal. I always notice the altitude.”

At over 17,000 feet, the telescope rests above much of earth’s atmosphere, making the site, called the James Ax Observatory, one of the highest astronomical observatories in the world.

“There aren’t plants at this altitude. We drive up to the site every day. But then where we live there are plants and trees and water and people,” Boettger says.

They stay at Astro-Norte, a hostel of sorts for astronomers, near San Pedro de Atacama, an old village built around an oasis. It takes three or four airplanes and at least 24 hours to get there from San Diego, depending on the route. After landing in Santiago, they fly north again to the mining town of Colama, and then drive another 60 miles southeast to San Pedro. The drive to the observatory is another hour, with an elevation gain of more than 9,000 feet.


EPIC JOURNEY: The 50,000-pound telescope was transported by sea to the port of Antofagasta in Chile, and driven in a convoy of trucks up to Cerro Toco, a peak in the Chanjnantor Scientific Reserve.

The journey to this remote desert location actually started years ago, when Keating’s team, along with their collaborators at UC Berkeley, led by Professor Adrian Lee, began to talk with engineers at General Dynamics SATCOM Technologies, in San Jose, Calif., about optimal designs for capturing microwaves.

The metal for the dish and the telescope mount were fabricated in Italy in 2009, then shipped across the Atlantic Ocean, through the Panama Canal, and up the west coast to the port of Oakland, Calif. From there, the telescope traveled by truck around the Sierra Nevada to a site called Cedar Flat in the Owens Valley for a shakedown run. To the team’s relief, it performed beautifully.

“The telescope weighs more than 50,000 pounds, yet it can slew across the sky from one side to the other in 30 seconds while accurately measuring this faint radiation,” Keating says. “With a resolution of three-and-a-half arc minutes, the full moon fills hundreds of pixels. It’s an amazing piece of machinery.”

It needs to be, as the signals they seek are subtle. The disturbances that inflation would have left in the fabric of space, called gravitational waves, would have distorted light emanating from the big bang, altering its pattern of polarization. The project, dubbed POLARBEAR, a wordplay on ‘polarization of background radiation’, aims to measure those variations, seeking the rippling pattern that theorists have predicted.

To do this, the researchers have outfitted the telescope with antennas. These funnel microwave light to sensitive detectors designed to measure the direction of the vibration of incoming photons. To measure these minute fluctuations on top of a signal so dim and cold, the element must be chilled to a fraction of a degree above absolute zero. That takes about a week.

“At these wavelengths, the atmosphere actually glows. It washes out your signal,” says Boettger, who has worked diligently to tune individual sensors to maximize their sensitivity.

Although detecting slight wavers in a ghostly signal is the most critical technical challenge for the POLARBEAR team, they’ve had to meet others as well. The air at the observatory is too thin, for example, to float the head of a conventional hard disk drive (at too high an altitude, the thin air cannot support drive heads at the proper operating height and failure results). The team therefore erected a radio tower to stream data to a base camp at lower elevation.

Observations began in April. It will take a supercomputer and years of measurements and analysis to sort out the signals. Their goal over the next two to three years is to capture enough photons from the cosmic microwave background and measure their polarization to see evidence of the gravitational waves from inflation—if they exist.

“This would be a revolutionary thing in cosmology, akin to Edwin Hubble’s detection of the expansion of the universe, the first evidence of the big bang itself,” Keating says. “It would be an amazing accomplishment.”

Susan Brown is a writer for the Division of Physical Sciences at UC San Diego.