A huge radio telescope at Green Bank, West Virginia, was able to detect and lock onto a faint carrier signal from the Huygens Titan probe for more than two hours this morning, confirming the spacecraft's continued descent through the moon's atmosphere following a high-speed entry around 5:13 a.m. EST (1013 GMT).

A second radio telescope now has picked up the signal as well and Europoean Space Agency project scientist Jean-Pierre Lebreton said engineers were even able to confirm at least one of the probe's six on-board instruments had activated as planned.

Touchdown on Titan's surface was expected around 7:34 a.m.

But detection of a carrier - a feat equivalent to picking up a cell phone call from 751 million miles away - only means the spacecraft was alive and that it survived the rigors of atmospheric entry. Confirmation that actual science data was collected won't be available until 11:15 a.m. EST, after NASA's Cassini spacecraft relays recorded data to Earth.

"We've got a long way to go," said ESA science director David Southwood. "As far as i'm concerned,the baby is out of the womb, but we've yet to count the fingers and toes, so we've still got a long way to go. But it's a major step, a major engineering step. You can probably detect a certain relief on my face. That's real. But there's still a long way to go before the full baby is revealed."

NASA science chief Al Diaz said detection of the carrier signal "means that probably one of the most difficult entry activities ever done has just been accomplished successfully."