The New Horizons spacecraft has a new "audience" for the electronic signals it beams back to Earth. In a successful September demonstration of its growing capabilities, the Allen Telescope Array (ATA) detected transmissions from New Horizons while the spacecraft was more than a billion miles from home.

The ATA is a radio interferometer used for astronomical research and searches for signals of intelligent, extraterrestrial origin. A joint effort of the SETI Institute and the Radio Astronomy Laboratory at the University of California, Berkeley, it's being constructed at the Hat Creek Radio Observatory in Northern California.

The SETI Institute routinely observes spacecraft such as New Horizons, which serve as an excellent test signal for confirming the correct functioning and effectiveness of the SETI signal-detection systems.

"We look forward to checking in with New Horizons as a routine, end-to - end test of our system health," says Jill Tarter, director of the Institute's Center for SETI Research.

"As this spacecraft travels farther, and its signals grow weaker, we will be building out the Allen Telescope Array from 42 to 350 antennas, and thus can look forward to a long-term relationship."

For the New Horizons observation, made Sept. 10, operators used a synthesized beam formed with 11 of the array's 6.1-meter (20 foot) antennas - a method called "beamforming" that electronically combines the antennas into a single virtual telescope. The 8.4-GHz spacecraft carrier signal was then fed into the SETI Prelude detection system.

"We're happy to be the ATA's new friend in the sky, helping SETI to verify the operations of their electronics," says New Horizons Principal Investigator Alan Stern. "It's also nice to know that someone else is checking in on us during our long voyage to Pluto and beyond."