Drake describes progress of search for extraterrestrial intelligence

By Nancy Hurrelbrinck

Despite TV images of Star Trek's U.S.S. Enterprise flitting about the universe, tracking interstellar radio waves is a much better bet than traveling in spaceships for finding intelligent life somewhere out in space.

It would take 100,000 years in a rocket going 36,000 miles per hour to reach the nearest star, and 200 times that to reach the nearest potential civilization; the chance of picking the right star is about one in 10 million, said Frank Drake, an astronomer at the University of California-Santa Cruz and president of the SETI Institute. SETI stands for the Search for Extraterrestrial Intelligence.

Addressing about 900 people at the Charlottesville Center for the Performing Arts last week, Drake described the progress of monitoring radio wave emissions from outer space, whether deliberately or incidentally beamed from another planet.

"We know that one day there will be a signal. There is life out there ­ that's the easy question,² Drake said. "The hard question is what it will take to find it."

His certainty that other civilizations exist derives from a theory of cosmic evolution scientists have developed over the last 50 years, predicting that life is likely to have developed on planets orbiting sun-like stars, he said. Drake developed an equation in 1961, known as the Drake Equation, to estimate the number of possible intelligent civilizations in the universe.

SETI technology has come a long way since the late 1950s, when scientists at the National Radio Astronomy Observatory (NRAO) in Green Bank, W. Va., used an 85-foot telescope with one channel to search for radio signals, said Drake, whose talk was the NRAO's 34th Janksy Lecture. The event is named for physicist Karl Jansky, who discovered radio emissions in space in 1933.

Now, through Project Phoenix, a privately funded program that succeeded the one at NASA, SETI is using a 1,000-foot telescope in Arecibo, Puerto Rico, that sits 500 feet in the air and can detect a billion frequency channels. It also transmits a signal in the form of a 20-million-watt, highly focused beam that outshines the sun by a factor of 10 million and could be detected from anywhere within the Milky Way.

"Given our own capabilities, it seems reasonable to search for signals from anywhere," he said.

"We need to search a wide range of channels. We have computer chips now that are made to perform as a multi-channel radio receiver" and can monitor 200 million channels, generating 56 million numbers per second, he said.

A signal would appear as a diagonal line (because the earth is rotating). Even a six-watt signal from the Pioneer spacecraft close to Pluto can be detected, he said. A notable signal received by the Arecibo telescope is verified by a 250-foot telescope in England.

"If the second telescope sees the signal, we compare it to the first one and can tell if it's local or from outer space," he said. "So far, we've never found a signal that's passed the test."

One signal that appeared to be a candidate -- it looked like a zipper, unlike the straight lines generated by satellites -- was received by both telescopes, but they discovered it was a Japanese spacecraft out beyond the moon, signaling for help because it was lost, he said. Another promising signal resembling a double helix turned out to be a tumbling Russian spacecraft with two antennae.

With permission to use the Arecibo telescope only 20 days per year, SETI has been planning for the past several years to build its own radio telescope, developing a new paradigm. Rather than building one huge dish, they will place about 1,000 3.6 meter dishes (like those used for cable television reception) adjacent to one another and operating as a single system, creating a one-hectare telescope.

Securing funding for SETI is challenging because "we can't make any promises," he said.

The new system "will give us a telescope dedicated to SETI 365 days a year," said, adding that using numerous small dishes will make it easy to expand the telescope.