New York City - The NYPD will launch two new high-tech, radiation-detecting boats Friday as part of its defense against sea-borne terror attacks, the Daily News has learned.

The boats, the first of a fleet of 10, will circle Manhattan Island over the holiday weekend to safeguard against “dirty bombs.”

They look like most police harbor patrol boats, but carry sophisticated equipment that measures radioactive isotopes.

“If they are in the East River and a ship goes by they can tell if there is a dirty bomb onboard,” Richard Falkenrath, deputy commissioner of the Counterterrorism Bureau, said of the specially trained cops who will pilot the state-of-the-art watercraft.

The TRACS (Tactical Radiation Acquisition Characterization Systems) craft are the only boats of their kind, with permanent radiation equipment outfitted by the Department of Energy, said Lt. Robert Stapleton, head of the team manning the first boats.

Falkenrath said New York is the only city on the Eastern seaboard - and possibly the U.S. - to use the boats.

“We needed a response to the dirty bomb threat from maritime,” Falkenrath said.

The boats are the newest addition to the high-tech arsenal Police Commissioner Raymond Kelly has amassed since 2002.