They are code-named "Juno," and their whirring presence has caused criminals to hide beneath cars and porches, to hang from building ledges and to lie motionless on roof tops often in vain attempts to elude detection.

In much the same way that a sudden light in a dark kitchen immobilizes roaches, Juno often keeps suspects rooted to the scene of the crime because they fear imminent discovery.

Juno is the code word for each of four Bell 47 helicopters, costing about $65,000 each, piloted by D.C. police. On alert 24 hours a day, the choppers are used to assist police on the ground in searching crime scenes and to provide wide-area surveillance of large crowds, demonstrations and parades.

On any given night, Juno's giant spotlight, called "Night Sun," with a power of 3.3 million candles - strong enought to illuminate an entire football field - probes dark depths to light up wooded areas, rooftops and vacant strips of land along railroad tracks, seeking suspects as they attempt to hide.

From the air, Juno pilots and observer-navigators, who ride "shotgun" in the two-seater craft, can spot the flowered jackets, and most model cars of those who try to evade the law.

"If we can get a description of the person and get there soon after the crime occurs, we can find them," said Jackson. "Over the years, we've developed a sharpness."

Roy L. Collins, an observer who flies with Jackson, calls the sharpness a "sixth sense."

Sometimes Juno's noise and powerful light shining obtrusively onto rooftops and into homes of the innocent, annoy city residents.

But Juno pilot Alfred V. Jackson, who lives in Southeast Washington where Juno is called frequently, said people have become accustomed to the helicopter, knowing police are fighting crime.

"We aren't exactly quiet, but we do try to be neighborly," Jackson said.

"The first time the farmers came to town [to demonstrate against law profits from agriculture last winter] we had no idea what we were dealing with," said Robert Klotz, deputy chief in charge of the D.C. Police Special Operations and Traffic Division.

"I got up in one of the Junos and we were able to count the trucks coming in and then to let the ground units know how many we could expect." Klotz said.

"Most recently, during the Marine Marathon, we used a videotape camera to tape the event so we could study it afterwards to determine what to do next year [to route vehicular traffic]," he said.

"It's fun sometimes watching them [criminals] trying to get away from us," said Jackson, one of 10 pilots in the squadron.

"Like the time recently when we responded to a call about a stolen auto, a Gremlin stolen by juveniles who tried to escape on Suitland Parkway," Jackson said.

"Within a minute of the call, we were on top of them and we directed the scout cars right to them - there was no place they could hide."

Recently, Juno assisted police in catching a suspect hiding behind some apartments in the rear of the 3900 block of 4th street SE.

"Officer Robert Jolley stopped a 1976 Chevette at a traffic stop . . . after hearing of an auto meeting the same description that had been stolen from the 2100 block of G Street NW," said 7th District Sgt. David Richardson.

"When Jolley stopped the car, the kid bailed out and ran four blocks to the apartments on 4th Street," he said. "Jolley couldn't find the kid. He requested Juno's assistance and Juno lit up the area with the Night Sun. Officers on the ground saw the kid hiding underneath a parked car in the lot."

On one recent routine day, Juno responded to the following actions:

A 12:11 p.m. burglary at East Capitol Street and Benning Road SE, in which a refrigerator had been stolen from a home. Juno circled the area, spotted a group of people standing beside a refrigerator at the rear of a blue station wagon and alerted ground police who, after arriving on the scene, arrested and charged three people with burglary.

A 4:35 p.m. burglary at Hart Junior High School at 6th Street and Mississippi Avenue SE. Juno, arriving before police scout cars, orbited around the school to prevent anyone from leaving without being seen. Two people were subsequently arrested inside the building and charged with burglary.

A 7:45 p.m. burglary in progress in the 2000 block of Martin Luther King Avenue SE. Again, Juno circled the area, ground police arrived minutes later and three people were arrested, two inside and one outside who attemped to escape.

'Most of our useful work is done with religious, political, educational in burglary cases," said John J. Hawkins, operation sergeant for the helicopter squadron. "In burglary cases, someone - a neighbor or just someone going down the street - notices something suspicious and calls the police. Burglars are unaware of the call and stay inside. When they hear Juno, they just wait inside until the police come."

"Robberies and other crimes are different because the police don't know about them until after they have been committed," Hawkins said. "But if we know something is going on, we can get there usually before police can on the ground."

During the 12-month period ending Sept. 30, Juno logged 22,091 calls for assistance, Hawkins said. Last month alone, Juno answered calls for more than 150 burglaries, 30 holdups 170 rooftop searches and more than 136 calls for everything from assistance in spotting stolen autos to locating traffic accidents, searching the waterfront and observing other crimes in progress.

Twenty-four persons were arrested and charged with 31 offenses during October, a month in which Juno answered 1,846 calls for assistance, said Lt. James Hampton, chief of the D.C. helicopter branch.