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“Obviously, we’re not looking into apartments,” Mr. Diaz said during a recent flight. “We don’t invade the privacy of individuals. We only want to observe anything that’s going on in public.”

The helicopter’s powers of observation come from a high-powered robotic camera mounted on a turret projecting from its nose like a periscope. The camera has infrared night-vision capabilities and a satellite navigation system that allows police to automatically zoom in on a location by typing in the address on a computer keyboard.

The surveillance system can beam live footage to police command centers or even to wireless hand-held devices.

“The commander on the ground can see what we’re seeing,” Mr. Diaz said.

On this flight, the helicopter used the camera to look for signs of trouble at several key transportation sites: the decks of Staten Island ferry terminal, the stanchions of the Verrazzano-Narrows Bridge, the giant air vents feeding the Lincoln Tunnel. All of them passed inspection.

Without leaving Manhattan airspace, the chopper also was able to get a crystal-clear picture of jetliners waiting to take off from LaGuardia Airport and to survey Kennedy International Airport’s jet fuel lines, which were targeted in a plot uncovered last year.

The chopper has helped track down fleeing suspects, including a recent case of a gunman who had shot his wife in Queens. As officers on the ground worried about how to approach the suspect’s car, the camera in the sky hovered overhead, peeked inside the vehicle and found that he had already shot and killed himself.

During Pope Benedict XVI’s recent visit, 23 patrolled the skies, at one point receiving a call from officers who had spotted a suspicious man with a camera on a rooftop near the pontiff’s residence. Mr. Diaz radioed back that it was a false alarm.

“There was a modeling shoot going on,” he said.