Germany's Atlas Elektronik reports that its SeaCat autonomous unmanned underwater vehicle has successfully completed a seven-hour mission.

The vehicle traveled through the 14.9-mile Albstollen water supply tunnel in the state of Bade-Wurttemberg, inspecting for possible damage.

The inspection was the first visual inspection of the tunnel, near Stuttgart, in 40 years.

"Never before has a water-filled tunnel of this length been inspected by a diving robot navigating on its own," said Sven Hesse, head of the UUV program at Atlas Elektronik. "And rarely has such an entirely autonomous vehicle completed such a demanding task."

The SeaCat, which measures about 8 feet in length and 11.8 inches in diameter, is torpedo shaped. It can be operated either remotely or fully autonomously for up to eight hours. Its payload includes a number of sensors as well as a video camera.

Atlas said it can be used for inspection and mapping of inshore lakes, coastal sea areas, harbors and marine structures.

For inspection of the tunnel, the vehicle was equipped with both sensors and a camera that recorded visual information. The unit was kept centered with the use of laser distance sensors.

Both remote control and autonomous modes were used. During the first 300 yards of exploration, an operator controlled the vehicle's actions with the use of a fiber-optic cable. It then was switched to autonomous mode, moving along the length of the tunnel at about 3 feet a second.

Atlas, a joint venture of ThyssenKrupp and EADS, said the inspection indicated that the water tunnel was in good condition after 40 years of continuous use.

The Albstollen tunnel -- with a diameter of 7.3 feet -- is part of the largest long-distance water distribution system in Germany. Inspection of the tunnel occurs regularly but through measurements of the hydraulic friction losses and through the leakage rate.

SeaCat provided its first visual inspection.

"We can certainly be proud of this achievement: it proves that Atlas Elektronik is right on course to carve out a world leading role in this new field of technology," said Atlas Elektronik Managing Directors Volker Paltzo and Dieter Rottsieper.

Atlas Elektronik manufactures -- in addition to UUVs -- maritime command-and-control systems, mine warfare systems and other products