Which type of radar does not depend on the reflection of signals?

The correct answer, which is ADS-B (Automatic Dependent Surveillance–Broadcast), is a type of surveillance technology that does not rely on the reflection of signals as traditional radar systems do. Instead, ADS-B utilizes GPS positioning information that aircraft continuously broadcast to provide their location, velocity, and intentions to air traffic control and other aircraft. This system operates with the aircraft announcing its own information, which is then received by ground stations and other aircraft.

In contrast, primary radar operates by emitting radio frequency signals that reflect off objects, such as aircraft, which return the signals to the radar system for detection. Secondary radar also relies on the reflection of signals but requires an active transponder in the aircraft that responds to interrogations from the ground station. Contact radar is a more traditional form of radar that directly detects the position of aircraft through reflected signals.

Therefore, the unique characteristic of ADS-B is its dependence on GPS data instead of reflected radar signals, making it an innovative and modern approach to air traffic surveillance that enhances situational awareness.