Sharing the sky: An engineer's quiet search for extraterrestrial intelligent life
by David Pescovitz
The Allen Telescope Array (ATA) at UC Berkeley's Hat Creek Radio Observatory, now under construction, will ultimately comprise 350 antenna dishes and be one of the most powerful telescope arrays in the world. A radio telescope, it collects photons in the radio spectrum, then focuses those waves onto an electronic receiver, giving it unprecedented sensitivity for detecting very faint signals. The ATA is the foundation of the SETI project, the Search for Extraterrestrial Intelligence.
SETI/RICK FORSTER PHOTO
Not far from Mount Lassen in a field near the mountain hamlet of Hat Creek, California, an array of antenna dishes is pointed toward the starry night. The array — a radically new kind of radio telescope — and the scientists who mind it are waiting for a signal that will, literally, change the world.
Whatever form that signal takes, it will mean one thing: We are not alone in the universe. The antenna array —only a portion of which is now online and ready to receive signals—will form a giant ear listening for intelligent beings in space, key to the extraordinary effort known worldwide simply as SETI, the Search for Extraterrestrial Intelligence.
One of the driving forces behind SETI, Berkeley Professor in the Graduate School William “Jack” Welch, of electrical engineering and astronomy, can often be spotted flying high over the Cascade foothills in his Cessna 210, zipping between the campus and Hat Creek. For Welch, a key designer of the antenna array, it’s a matter of when, not if, that signal will be detected.
“We know there are hundreds of billions of stars in our own galaxy, and a hundred billion other galaxies, each with hundreds of billions of stars,” says Welch. “With such staggering numbers and evidence that so many stars host planets that could be candidates for life, it’s inevitable that somewhere out there, there is intelligent life.”
The visionaries behind SETI
Once an extraterrestrial transmission is detected, there’s an established, though informal, protocol for whom to inform, says Welch with a grin. It’s no longer the President of the United States or even the Secretary General of the United Nations who gets the first call. It is investor and philanthropist Paul G. Allen, cofounder of Microsoft. A major underwriter of the SETI project, he will be the first to know when the aptly named Allen Telescope Array, or ATA, has breaking news to report.
“I am very excited to be supporting one of the world’s most visionary efforts to seek basic answers to some of the fundamental questions about our universe,” says Allen. “The developments taking place with this new instrument will change the landscape of how telescopes will be built in the future.”
A joint effort between Berkeley and the SETI Institute in Mountain View, California, the ATA will be fully operational within the next few years when funding has been secured to complete the 350-antenna array. With unprecedented sensitivity over a wide range of wavelengths centered in the centimeter radio band, it will take its place as one of the world’s most powerful telescopes, according to Welch, who has worked on this current SETI project since its inception in 1997.
When most people think of astronomy, they envision gazing at the stars through an optical telescope, a system of mirrors and lenses that collects light. The ATA, however, was designed for radio astronomy, a different branch of the science. Rather than gathering visible light, a radio telescope collects photons in the radio spectrum. The telescope then focuses those waves onto an electronic receiver, similar in many ways to an everyday transistor radio, but capable of tuning in much higher frequencies and detecting much fainter signals.
The ATA’s unique capabilities will allow it to span the equivalent of about four-and-a-half octaves, while most radio telescopes span less than half an octave, and optical telescopes span perhaps one or two. The ATA will scour billions of radio channels for narrowband signals, indicative of intelligent origin. These kinds of signals, less than one hertz wide, can be generated only by transmitters built for that specific purpose. According to the SETI Institute’s researchers, “If ET and friends are decent or at least competent engineers, they’ll use narrow-band signals as beacons to get our attention.” It’s like listening for a station as you twist your radio’s knob through all the static.
Until now, SETI has had to borrow time from other radio telescopes around the world, whenever those observatories could spare it from their own projects. Even so, some 800 stars identified as likely candidates for hosting Earth-like planets, and possibly life, have been scanned. Observations begin in earnest this spring, and once the ATA is fully built and operational, the tools will finally begin to be commensurate with the enormousness of the task. “At that time, it will vastly expand our capabilities, speeding up our search and exploration by a factor of at least 100,” says Welch.
Seeking the mysteries of the cosmos
The telescope will cover frequencies between 1,000 and 10,000 MHz in the centimeter radio band, a range five times greater than Project Phoenix, the SETI Institute’s previous search. Precisely situated and distributed across more than a hundred acres of dry, lava-strewn landscape in the Hat Creek Valley, the 350 combined dishes will have more collecting area and far greater flexibility than the much more expensive 100-meter class radio telescopes, situated in only a few sites around the world. The ability to monitor a huge range of wavelengths at once is key to the design, as it will enable astronomers to observe other cosmic phenomena simultaneously with the SETI search.
Professor Barred Spiral Galaxy NGC 1300, one of the hundred billion other galaxies with which we share the sky. “With such staggering numbers and evidence that so many stars host planets that could be candidates for life," says Welch, "it’s inevitable that somewhere out there, there is intelligent life.”
COURTESY OF HUBBLE SPACE TELESCOPE SCIENCE INSTITUTE
For example, Welch and his colleagues will use the array to make a cosmological map of the atomic hydrogen all around us. The visible universe may be composed of up to 90 percent hydrogen, the most abundant element known. Determining its spatial distribution in nearby galaxies could provide insight into the evolution of the cosmos and the mysteries of dark matter. “Looking out into space is looking back in time,” Welch says. “The information we tease out of the dark matter as we look out at other galaxies will tell us a lot about the beginning of the universe.”
The team will also seek out “transient sources,” radio emissions that “go bump in the night,” Welch says, and then vanish. Some transient sources such as supernovae and gamma ray bursts are well known, but Welch believes that other phenomena are waiting to be identified. The ATA will be the most sensitive instrument ever used to detect these transient events, one of which could be the signal the world has long been waiting to hear.
“With the ATA’s ability to quickly image a huge patch of sky, which is an extraordinary advance, I’ll be surprised if we don't find some very interesting new transient sources,” he says.
Welch, who served as director at the Hat Creek Radio Observatory for two decades until 1996, and his Berkeley and SETI Institute colleagues first conceived of the ATA in 1997. Allen contributed $11.5 million to design and develop technology, with an additional $1 million from former Microsoft Chief Technology Officer Nathan Myhrvold. In the spring of 2003, pleased with the progress, Allen committed an additional $13.5 million, contingent on Berkeley and the SETI Institute raising $16 million on their own, an endeavor they are working on right now.
Each of the antennas in the array costs roughly $100,000. While that’s certainly not chump change, the ATA is an instrument that’s all about doing more with less. According to ATA project manager Dave DeBoer, every engineer on the team, consciously or not, kept a detailed mental tally of cost as they worked.
“We can make high-quality receivers, but the challenge was whether we could do it cheaply,” says DeBoer, who also teaches microwave engineering in the Department of Electrical Engineering and Computer Sciences. “It got down to the point of asking ourselves whether we really needed a particular connector or not. They may be just $15 each, but that adds up when you’re talking about 4,000 of them.”
The dishes themselves are fabricated by Andersen Manufacturing, an Idaho-based company best known these days for making trailer hitches. Years ago, the proprietor developed a novel method to cast backyard satellite television dishes in a one-shot process that results in exceptionally smooth parabolic antennas. Now Andersen is SETI’s dish supplier.
To achieve the telescope’s wideband sensitivity, Welch and his colleagues devised a bit of ingenious antenna feed technology. In traditional pyramid-shaped log-periodic feeds, like those used in the ATA, the signal is picked up at the tip of the structure and runs down wires to the receiver.
“You can get antennas based on that principle at Radio Shack, but the design has always had a profoundly bad feature,” Welch says. “When the cable runs down the spine from the tip to the base of the long feed, much of the signal gets lost along the way.” The Berkeley researchers’ solution was to shoehorn the receiver components inside the feed itself. The amplifier and cooling system are then attached just behind the tip of the feed terminals. Placing the cryocooler this close to the terminals reduces the destructive thermal noise present in every receiver. After all, DeBoer explains, electromagnetic waves carrying signals transmitted by an alien civilization may have been traveling in space for thousands of years before reaching Earth. It would be wise, he says, to treat those waves gently.
“It's just one new wrinkle for a technology that was originally developed in the 1950s, but it enables our feed to have essentially no limitation on bandwidth,” Welch says. “Instead of building lots of different feeds and receivers to work at different frequencies, ours can listen to many frequencies at once.”
Jack Welch's early role
In some ways, the design is the culmination of research that Welch began in the 1950s when he was a graduate student in electrical engineering at Berkeley. EE professor Samuel Silver was just launching a program to study the atmosphere by analyzing radio waves. An expert in antenna design, Welch helped the group build a small telescope for their atmospheric research. The researchers soon realized that the tool was also useful in the then-nascent field of radio astronomy. With his research focus shifted to astronomy, Welch became a fixture at the Space Sciences Laboratory, directed by Silver. That’s where he met Nobel laureate Charles Townes, who had just arrived at Berkeley. Impressed with Welch’s pioneering radio astronomy work, Townes encouraged the young scientist to search for complex molecules in space.
Professor William “Jack” Welch, who holds the Watson and Marilyn Alberts Chair in the Search for Extraterrestrial Intelligence, and former astronomy undergraduate Cassandra Vanoutryve with the ATA antenna feed, the spiky device that collects signals from interstellar space, at the Hat Creek Radio Observatory.
RICK FORSTER PHOTO
“I had thought about that before, but everyone told me that the prospects weren’t good for finding any molecules made up of more than two atoms,” Welch says. “Charlie told me to ignore their advice.” With Townes’s encouragement, and a very tight budget, Welch built his first telescope and receiver at Hat Creek. Using that instrument, the two made the groundbreaking 1968 discovery of ammonia in interstellar space and, later, water molecules.
“When we discovered that water is everywhere, I realized it meant life is probably everywhere too,” Welch says, visibly moved as he remembered that life-changing moment. “That was when I truly felt that SETI was a very important thing to do.”
Around that time, Welch met astronomer Jill Tarter, a Berkeley alumna, who had participated in early SETI projects. All clichés aside, love was in the stars. The two married and became scientific collaborators, with Tarter eventually becoming director of the Center for SETI Research at the SETI Institute, and Welch, holder of Berkeley’s Watson and Marilyn Alberts Chair in the Search for Extraterrestrial Intelligence.
Welch retired from teaching last July. Still dedicated to his research, he’s on campus nearly every day, except when he flies out to Hat Creek to assist in the assembly and tuning of the new array dishes. With the first 42 antennas now operational, the ATA will embark on a SETI survey of the Inner Galactic Plane, conducting broad sweeps aimed near the center of the Milky Way. While the galactic center isn’t likely to harbor life, the survey could potentially pick up signals coming in from many stars along the path between Earth and the center of the galaxy. Then, once the completed ATA is online, a systematic targeted search of nearby stars like our Sun will begin. The SETI Institute’s Project Phoenix surveyed 800 stars, but thanks to the ATA’s large bandwidth and multi-tasking capabilities, the array will begin searching for signals that could be emanating from the nearest 100,000 stars, then eventually move beyond those to survey another one million nearby stars.
DeBoer says he rarely has time to consider the head-spinning significance of such a massive search or what it might find. Indeed, progress on the ATA is also important and cause for close scrutiny because it’s a test bed for the Square Kilometre Array, an international effort over the next decade to build a radio telescope array one hundred times larger than the ATA.
“Mostly, I’m too busy trying to get this thing to work to think about anything other than the engineering,” DeBoer says. “But there are those beautiful nights when I’m alone working on the telescope and I think about the broader implications of what we’re doing here.”
And in case he happens to forget, he only needs to close his eyes and listen. The drive motors on the dishes squeak at different frequencies when they’re activated. Occasionally, the software team playfully programs the motors to whir out different melodies. A particular favorite is the theme from Close Encounters of the Third Kind.
“The idea that we’re the only form of life is just not tenable,” says Welch. “We know of more than 100 organic molecules that have already been detected in interstellar space. It’s just a matter of whether or not the deliberate signal will have taken so long to arrive that the senders might have already vanished.”
DAVID PESCOVITZ writes Lab Notes, the College’s award-winning online research digest, and is coeditor of the popular blog Boing Boing.net. He also writes ScienceMatters@Berkeley, an online publication of the College of Letters and Science and College of Chemistry, and has been featured in Wired, Scientific American, IEEE Spectrum, and the New York Times.
BOB SANDERS, UC Berkeley Media Relations, contributed to this story.