Which component sends the challenge (interrogation) to the aircraft?

The component that sends the challenge, or interrogation, to the aircraft is the interrogator. This device is crucial in air traffic control and military operations, as it emits signals to request information from transponders onboard the aircraft. When the interrogator sends out a query, the aircraft's transponder responds with its identification and altitude information. This interaction is essential for situational awareness, ensuring that air traffic controllers can track and manage aircraft effectively and safely.

Understanding the role of the interrogator helps clarify the communication process in air traffic management, as it initiates the inquiry that allows for real-time data exchange between ground and airborne systems.