What is the primary purpose of a secondary surveillance radar?

The primary purpose of secondary surveillance radar is to identify aircraft transponders. This type of radar relies on signals emitted from aircraft transponders, which are devices that respond to incoming radar signals. When the ground radar sends out a challenge signal, the transponder on the aircraft replies with specific information, such as its identification and altitude. This exchange provides air traffic control with precise data about the location and status of each aircraft within the radar coverage area.

This capability significantly enhances situational awareness for air traffic controllers and improves the efficiency of air traffic management, especially in busy airspace. The use of secondary surveillance radar allows for better separation of aircraft and assists in maintaining safe distances, as the information received directly from the transponder includes both the aircraft's location and its intention to follow specific flight paths.

In contrast, tracking weather patterns, measuring air density, and monitoring vertical speed are functions associated with other systems or sensors, and do not involve the primary role of secondary surveillance radar.