Ashes of the Phoenix

Star field
In a universe brimming with stars, the search is on if life exists elsewhere

Project Phoenix has left the building. There are empty spaces at Arecibo Observatory, but not for long. A new computer cluster is destined for the space occupied by fifteen Programmable Detection Modules. The cabinets that stored the spare components for the Phoenix search system are already reassigned to the RFI Monitoring and Electronics groups.

For the staff at Arecibo, another SETI project has ended, and life at the observatory goes on. But for us, life is in transition as we wrap up one project and begin another. As we wait in California for our equipment to arrive from Puerto Rico, it is a good time to look back on Project Phoenix. It wasn’t "just another" SETI project.

Arecibo Telescope
Arecibo. World’s largest dish, radio telescope. Puerto Rico.

Phoenix rose from the ashes of the NASA SETI Program that was terminated by the US Congress in 1993. The SETI Institute secured use of some of the search equipment developed for NASA under a long-term loan agreement and raised private funds to conduct a search. In the following year, Institute scientists and engineers doubled the size of the search system. In February 1995, just one month after the original NASA schedule, Project Phoenix began its targeted search of nearby stars.

The origin of Phoenix, while unusual, is not the reason it was unlike any other SETI project. Phoenix observed hundreds of stars over billions of frequency channels, with high sensitivity, and real-time signal detection and verification. No other search can compare on any aspect.

A few searches have looked at some nearby stars in specific frequency bands. Phoenix observed more than 700 stars, using some of the world’s largest telescopes, over all available frequencies between 1200 and 3000 MHz with channels only 0.7 Hz wide.

A few searches have used large telescopes, but they typically scan the sky and are limited to a single frequency band. Most of the time, these searches do not observe stars in our galaxy, but are actually looking at stars millions of light years away. In the fraction of time they observe stars in the Milky Way, they only spend 10 to 20 seconds per star. Phoenix only observed nearby stars in our galaxy and so could devote from 100 to 550 seconds per star per frequency band.

Almost all previous searches have one thing in common, unresolved signals. When you search for communication signals from interstellar distances, you will certainly detect signals from the Earth and its satellites. Phoenix perfected the real-time processing and verification techniques pioneered by Paul Horowitz of Harvard University.

The Milky Way. Credit: Akira Fujii

In a two-stage pipeline, Phoenix collected data and detected signals. Any signals not in a database of recent terrestrial interference were subjected to a type of observation unique to Phoenix. Using a second telescope, the star would be re-observed at the frequency of the candidate ET signal. The rotation of the Earth produces a distinct and different Doppler shift at the two telescopes. This technique, called pseudo-interferometry, would rule out signals not coming from the direction of the star. With this process and other tests, Project Phoenix has no unresolved signals.

So after nine-plus years of bringing a complex system of electronics to Australia, West Virginia, Georgia, England and Puerto Rico, Project Phoenix is over. We observed more than a million star-MHz, processed millions of signals, but found no evidence of another technological civilization in our galactic neighborhood. Only one task remains, to write the papers for the scientific journals. In the process of writing those reports, we also gather the "lessons learned," an important part of preparing for the next search.

Years from now, Phoenix will be seen as humanity’s first systematic survey of the nearby stars.

It was a major advance over all other SETI programs, but its superlatives will not last. New, more powerful searches will be made in the coming decades that will make the sensitivity, number of stars and frequency coverage of Phoenix seem small in comparison.

But, it will always be our first big step in exploring our part of the Milky Way.

Related Web Pages

SETI Institute
What Does ET Look Like from 40 Light Years Away?
Anybody Out There? Part I
Anybody Out There? Part II
Search for Life in the Universe: Neil deGrasse Tyson Interview
Aliens Depend on Time to Grow Brains