Which radar system relies on reflected signals?

The correct answer is Primary Radar because it operates by emitting a radio signal that travels through the atmosphere until it encounters an object, such as an aircraft. When the signal hits the object, it reflects back to the radar antenna. The system measures the time taken for the signal to return and uses this information to determine the distance to the object. This method of detection relies solely on the reflection of the signals from the target back to the radar system, which distinguishes it from other radar technologies.

Secondary Radar, on the other hand, functions differently by using transponders on aircraft that respond to signals sent from the radar. ADS-B (Automatic Dependent Surveillance–Broadcast) is a surveillance technology that relies on aircraft broadcasting their position and other information rather than reflecting signals back from a radar. Ground-based Radar can refer to any radar system that is positioned on the ground, including both primary and secondary systems, thus it does not specify the use of reflected signals specifically.