Radar cross section is used to detect planes in a wide variation of ranges.

He also realized how difficult it was to land safely or to detect other planes at night or when it was overcast.

The North American Aerospace Defense Command, meanwhile, is scheduled to build by 1992 a radar network across the southern United States to detect low flying planes.

They detect and track ships, planes, and missiles.

Ground-based radar can detect only 50 miles offshore and even radar balloons, floating at an altitude of 15,000 feet, cannot detect planes farther than 150 miles away.

They can detect different planes of polarised light.

The radar balloons can detect planes as far as 150 miles away and cost much less than radar-tracking Awacs aircraft.

The radar balloons can detect planes flying as low as 500 feet.

Floating at about 15,000 feet, the balloons can detect low-flying planes as far away as 145 miles.

At 17, he joined the Navy and helped develop an early warning radar system to detect incoming Japanese planes.