The hunt for extraterrestrial life just lost one of its best tools. The Allen Telescope Array (ATA), a field of radio dishes in rural northern California built to seek out transmissions from distant alien civilizations, has been shuttered, at least temporarily, as its operators scramble to find a way to continue to fund it.

In an April 22 letter to donors, Tom Pierson, CEO of the SETI Institute in Mountain View, Calif., explained that the ATA has been put into "hibernation," meaning that "starting this week, the equipment is unavailable for normal observations and is being maintained in a safe state by a significantly reduced staff." The ATA is a partnership between the SETI Institute, which is responsible for building the telescope array, and the University of California, Berkeley, which is responsible for operating it. Astronomer Franck Marchis, who is affiliated with both institutions, broke the news on his blog April 22.

The search for extraterrestrial intelligence—SETI for short—is hardly fringe science, but the field has not enjoyed the financial support available to disciplines that return more immediate, predictable benefits to society. The nonprofit SETI Institute was founded in 1984 and has mostly relied on private donations to support its research. NASA had bankrolled a number of early SETI Institute projects, but Congress canceled NASA's short-lived SETI program in 1993.

The plans for the ATA called for a total of 350 individual six-meter radio antennas, all working in concert to detect radio emissions from civilizations that might exist elsewhere in the galaxy. But the array's growth stalled after the first phase of construction in 2007, when 42 dishes were completed at a cost of $50 million. Microsoft co-founder Paul Allen, the telescope array's billionaire namesake, contributed half of that sum, according to the SETI Institute.

Funding is considerably scarcer now. U.C. Berkeley's Radio Astronomy Laboratory has relied on funds from the National Science Foundation and the state of California to operate the Hat Creek Radio Observatory (HCRO) where the ATA is based, Pierson explained in his letter, and both of those sources have dried up. "NSF University Radio Observatory funding for HCRO has been reduced to approximately one-tenth of its former sum," Pierson wrote. "This is compounded by growing State of California budget shortfalls that have severely reduced the amount of state funds available to the Radio Astronomy Lab." ATA operations cost about $1.5 million per year, Pierson said, and the SETI science campaign at ATA costs another $1 million annually.

The SETI Institute would like to use the ATA to listen in on any radio waves that might be emanating from the extrasolar planets now being found by NASA's Kepler spacecraft. In February, Kepler scientists announced that they had compiled a list of 1,235 possible planets orbiting distant stars, including several that might be habitable. A current SETI Institute fundraising campaign is now aimed at raising $5 million to conduct a two-year search of Kepler's most promising finds using the ATA, in the hopes that one of those worlds is inhabited by a technological civilization sending out radio waves.

The ATA is not the only radio telescope facility that can be used for SETI searches, but it is probably the instrument most committed to the task. SETI researchers elsewhere have to borrow time on telescopes where competition for observing time can be fierce or piggyback their searches on other ongoing observations.

Pierson said that the SETI Institute has been working for more than two years to find a new funding stream, for instance by offering up the ATA's services to the U.S. Air Force to assist in tracking orbital debris that can endanger defense satellites. "We are continuing discussions with the USAF and remain hopeful that this effort will help provide future operating funds," he wrote.

ATA photo: SETI Institute