What does "SSR" stand for in radar communications?

"SSR" stands for Secondary Surveillance Radar. This system is crucial in modern air traffic control as it enhances the capabilities of primary radar. While primary radar relies on the reflection of radio waves off objects (like aircraft) to detect their presence and location, secondary surveillance radar operates by receiving signals from transponders installed in the aircraft.

When the aircraft's transponder receives an interrogation signal from the SSR ground station, it responds by sending back information such as the aircraft's identification, altitude, and velocity. This communication provides air traffic controllers with essential information for managing air traffic more effectively and efficiently. The use of secondary surveillance radar allows for more accurate tracking of aircraft and helps reduce the risk of mid-air collisions, making it a fundamental technology in aviation safety.

The other choices do not accurately describe the function or type of radar involved in this context, thereby reinforcing the importance of understanding the role of secondary surveillance radar in air traffic management.