ET search reaches home phones (actually, modems)

With new software, home computers can help astronomers crunch datafrom distant galaxies.

A trio of scientists has amassed an army that even Stormin' Norman Schwarzkopf might envy, and each day 1,000 eager recruits join its ranks.

Now 250,000 strong, these volunteers are gearing up to help find ET.

Harnessing the number-crunching power of today's home computers, the reach of the World Wide Web, and special free software scheduled for release next month, participants will comb signals from the world's largest radio telescope for signs of alien civilizations.

The two-year effort, called SETI@home, could mark a watershed in the search for extraterrestrial intelligence.

By building what in effect is the world's largest supercomputer via the Web, the search effort will have unique capabilities, notes Daniel Wertheimer, chief scientist for SETI@home and the lead investigator for SERENDIP, the University of California at Berkeley's SETI project. SETI@home will be 10 times more sensitive to weak signals than previous efforts, and "we can look for a wider variety of signal patterns."

More broadly, say others, the project gives people an opportunity to truly participate in a major scientific enterprise. Typically, people get tapped for contributions for SETI efforts or are invited to log onto the Web to "look at pretty pictures," says Charlene Anderson, associate director of the Planetary Society, a nonprofit group in Pasadena, Calif., that supports space exploration. "Now, you can be crunching the numbers. You don't need a PhD, and you are playing a real role. You could be the one to find the signal."

The data come from special receivers connected to the 1,000-foot radio telescope at Arecibo, Puerto Rico. The information is recorded on tape and shipped back to the mainland, where SETI@home researchers will load the information onto a central server. The data are cut into digestible-size chunks (250 kilobytes) in preparation for distribution to the project's far-flung participants.

THE project's architects have tried to make the effort as simple as possible. The software is designed to replace home-computer screen-saver software, which kicks in when a computer enters a period of prolonged inactivity. The SETI@home software contacts its home server via the Internet, pulls a chunk of data down, and analyzes it during the time when a screen saver ordinarily would run. Once the software finishes its work, it instructs the computer to log back on to SETI@home's server, uploads the results, and retrieves the next batch of data to be analyzed.

Each chunk of data is tagged to identify the participant. In screen-saver mode, the software could take several days to analyze one chunk. If the program is left to run uninterrupted, the job could take as little as 10 to 12 hours.

What are scientists looking to find? "A strong signal at some frequency," Mr. Wertheimer says. "That gets our attention."

If the signal is strong enough, and if man-made sources are ruled out, the team will ask other radio telescopes involved in SETI research to confirm the observation.

A key test lies in whether the signal repeats in ways that don't have a ready astrophysical explanation. Researchers point out that SETI efforts have detected intriguing signals in the past, but they didn't repeat.

While it is running, the program replaces flying Windows or bubbly tropical- fish screen-savers with graphs showing how the software's work is progressing, maps showing where interesting signals have appeared, or maps displaying information about the worldwide team of volunteers.

"It's a perfect match," says David Anderson, SETI@home project manager, of the approach. "SETI efforts are a large signal-processing problem limited by computer power" and all that computer idle time in schools, homes, and offices represent a solution to the computer-power problem.

Funding for the $300,000 effort has come from Paramount Pictures, the Planetary Society, and Berkeley, with support from Sun Microsystems, Fujifilm, and other suppliers. Wertheimer says that the project has enough funding to complete its first year.

* The World Wide Web home page for the project can be found at www.setiathome.ssl.berkeley.edu