MANASSAS, Va. — The military is looking to something old as a new weapon in the war on terrorism: blimps.

The blimps wouldn't be like those that hover over football stadiums and concerts. These would be equipped with cutting-edge sensors and high-resolution cameras that could scour the landscape or oceans.

Think of it as a 200-foot-long eye in the sky.

The Office of Naval Research (search) is working with Honolulu-based Science & Technology International (search) to develop the idea.

From thousands of feet up, STI's advanced optical sensor system can spot targets on the ground or deep under water and then track their movements, said Stephen Huett, ONR's project manager for the program.

Huett envisions the blimps policing U.S. harbors to pinpoint terrorist divers, suspicious boats or other unusual activity. They also could provide increased surveillance at military bases or assist with border patrols, he said.

The helium-filled airships have a number of advantages over planes or helicopters. They're quiet and smooth-riding, which is important for those monitoring the high-tech equipment inside. They're also about 30 percent cheaper to operate and can hover over a target anywhere from 12 hours to three days, Huett said.

The Navy contract is worth about $4 million, according to Huett.

Civil libertarians expressed concern that the blimps will be another government tool that infringes on privacy.

"What is increasingly happening is people are coming under routine surveillance without good cause," said Barry Steinhardt, director of the technology and liberty program at the American Civil Liberties Union (search). "It's no longer fanciful to talk about a '1984'-like society."

An intelligence policy specialist at the Federation of American Scientists, Steven Aftergood, said, "People are going to behave differently even in their own back yards if they know that someone may be watching."

Michael Greenberger, a law professor and director of the University of Maryland Center for Health and Homeland Security, said blimps could be an important addition to homeland defense.

"This is not a substantial infringement and is something that would be helpful," said Greenberger, who worked in counterterrorism for the Justice Department during the Clinton administration.

Blimps have been used by the military before, including for anti-submarine patrols during World War II.

STI's blimp can travel up to 60 mph and fly at an altitude of about 2,000-3,000 feet -- out of reach of small arms fire, Huett said.

While they might seem like large targets that aren't very stealthy, Huett said the blimps don't plummet from the sky if punctured by gunfire.

"It's like attacking an elephant with a fork. It's not easy to bring down," he said.

STI provided media demonstrations of the sensor technology as well as blimp rides this week in Manassas, Va. However, the 200-foot white blimp with a green and blue STI logo was grounded for at least two days because of mechanical problems.

The company's sensor technology is mounted in a 30-foot gondola, where the six-person crew -- including two pilots -- would sit during a surveillance mission.

From Virginia, the blimp will head to San Diego for a four-month testing period.