WASHINGTON (AP) -- The USS Jimmy Carter, set to join the nation's submarine fleet Saturday, will have some special capabilities, intelligence experts say: It will be able to tap undersea cables and eavesdrop on the communications passing through them.
The Navy does not acknowledge that the $3.2 billion submarine, the third and last of the Seawolf class of attack subs, has this capability.
"There are limits to what I can say on the sub's capabilities, but let's just say the Jimmy Carter is uniquely capable to perform missions vitally important to the war on terror," said Rep. Rob Simmons, a Republican and former CIA officer whose district includes Groton, Connecticut, where the sub was built.
But intelligence community watchdogs have little doubt: The previous submarine that performed the mission, the USS Parche, was retired last fall. That would happen only if a new one was on the way.
Like the Parche, the Jimmy Carter was extensively modified from its basic design, given a $923 million hull extension that allows it to house technicians and gear to perform the cable-tapping and other secret missions, experts say. The boat's hull, at 453 feet, is 100 feet longer than the other two subs in the Seawolf class.
"The submarine is basically going to have as its major function intelligence-gathering," said James Bamford, author of two books on the National Security Agency.
Navy public information lauds some of the Jimmy Carter's special abilities: In the extended hull section, the boat can provide berths for up to 50 special operations troops, like Navy SEALs. It has an "ocean interface" that serves as a sort of hangar bay for smaller vehicles and drones to launch and return. It has the usual complement of torpedo tubes and Tomahawk cruise missiles, and it will also serve as a platform for researching new technologies useful on submarines.
The Jimmy Carter, like other submarines, will also have the ability to eavesdrop on communications -- what the military calls signal intelligence -- passed through the airwaves, experts say. But its ability to tap undersea fiber-optic cables may be unique in the fleet.
Communications worldwide are increasingly transmitted solely through fiber-optic lines, rather than through satellites and radios.
"The capacity of fiber optics is so much greater than other communications media or technologies, and it's also immune to the stick-up-an-antenna type of eavesdropping," said Jeffrey Richelson, an expert on intelligence technologies.
To listen to fiber-optic transmissions, intelligence operatives must physically place a tap somewhere along the route. If the stations that receive and transmit the communications along the lines are on foreign soil or otherwise inaccessible, tapping the line is the only way to eavesdrop on it.
The intelligence experts admit there is much that is open to speculation, such as how the information recorded at a fiber-optic tap would get to analysts at the National Security Agency for review.
During the 1970s, a U.S. submarine placed a tap on an undersea cable along the Soviet Pacific coast, and subs had to return every few months to pick up the tapes. The mission was ultimately betrayed by a spy, and the recording device is now at the KGB museum in Moscow.
If U.S. subs still must return every so often to collect the communications, the taps won't provide speedy warnings, particularly against imminent terrorist attacks.
"It does continue to be something of a puzzle as to how they get this stuff back to home base," said John Pike, a military expert at GlobalSecurity.org.
Some experts suggest the taps may somehow transmit their information, using an antenna or buoy -- but those modifications are easier to discover and disable than a tap attached to the cable on the ocean floor.
"Unless they have some new method of relaying the information, it doesn't serve much use in terms of warning," Bamford said. He contended tapping undersea communications cables violates a number of international conventions the United States is party to. Such communications could still be useful, though the task of sorting and analyzing so many communications for ones relevant to U.S. national security interests is so daunting that only computers can do it.
The nuclear-powered sub will be commissioned in a ceremony at 11 a.m. Saturday at the submarine base at New London, Connecticut. The ceremony marks the vessel's formal entry into the fleet. The former president, himself a submariner during his time in the Navy, will attend.
After sea trials, the ship will move to its home port in Bangor, Washington.