Helicopter towing large sensor

Detailed Description
This helicopter will fly along pre-planned flight paths in the Coalinga area at a relatively low to the ground at 100-200 feet above the surface. A sensor that resembles a large hula-hoop will be towed beneath the helicopter to measure small electromagnetic signals that can be used to map geologic features below Earth’s surface.
Sources/Usage
Public Domain.
Credit U.S. Geological Survey