…continuedSETI Searches Today
Run by the SETI Institute of Mountain View, California, Project Phoenix concluded a nine-year search program in 2004. Phoenix was the biggest-ever "targeted search." That is, it performed a sensitive examination of a relatively few targets: about 800 mostly solar-type stars closer than 150 light-years and older than 3 billion years (when their ages could be judged), as well as the very closest stars regardless of their type.
Using a truck trailer filled with custom-built equipment, Project Phoenix traveled to radio telescopes around the world to monitor its chosen stars. It spent its final six years encamped at the 305-meter Arecibo radio telescope in Puerto Rico, the world's largest, where it had the use of the huge dish for about 5 percent of the time.
Project Phoenix scanned more than two billion radio channels between 1.2 and 3.0 gigahertz with a razor-thin resolution of 0.7 hertz per channel. Any signal this narrow in frequency would surely be artificial. By comparison, the narrowest microwave frequency produced anywhere in nature (by an interstellar maser) is about 300 hertz wide.
Project Phoenix rose from the ashes of an ambitious SETI search designed by NASA, which Congress canceled in 1993 soon after it had gotten started. Capitalizing on the $58 million already spent, the privately funded SETI Institute secured the equipment to continue the targeted-search half of the NASA project. (The other, more important half, a less sensitive but very wideband survey covering much of the Milky Way, was lost.) The SETI Institute has been funded by several large donors from the high-tech industry, where SETI has long fired imaginations. (For instance, see the Wall Street Journal article from Feb. 13, 2009, on the SETI Institute's Jill Tarter winning high tech's influential $1 million TED Award.) The SETI Institute is funded to a lesser extent by many small donors; memberships start at $50 per year.
As Project Phoenix ended, a more ambitious effort was taking its place. Phoenix components were upgraded and moved to the next-generation Allen Telescope Array (ATA), which the SETI Institute has built in northern California. The ATA, if expanded to its full intended size, should ultimately be able to examine 1 million or more stars individually, and it has wide-field SETI abilities as well. In October 2007 the SETI Institute announced that the ATA's first 42 dishes had begun science observations. If enough money appears, the ATA plans to expand to 350 dishes. By April 2009, ATA-42 was successfully making various astronomical sky-survey observations, as described by Welch and Tarter in a paper detailing the system's construction and performance.
In May 2009, ATA-42 began searching for artificial signals in a sweep of the Milky Way's plane toward the galactic center. The area of sky being covered by this Galactic Center Survey is 2° by 10° in size. That's only one two-thousandth of the celestial sphere, but it's an extremely star-rich area, including about 40 billion stars within 30,000 light-years. The survey is covering all the frequencies in the broad “waterhole” range from 1420 to 1720 MHz. More details.
Strengths: Project Phoenix examined nearby stars for artificial signals in greater depth than any other program. It spanned a wide fraction of the "microwave window," nearly 2 gigahertz worth. It was built around robust methods for distinguishing false alarms from a real interstellar signal, including simultaneous observations by the 76-meter Jodrell Bank radio dish thousands of kilometers away in England. This would allow it to chase down and confirm a genuine signal in real time, a big plus; sorting out false alarms caused by the massive radio interference from human civilization is a severe problem for all radio SETI efforts.
Weaknesses: Phoenix looked at only a paltry 800 or so stars out of the billions in our galaxy.
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