Definition
A target on a radar display generated by the reply signal from an aircraft's transponder when interrogated by the radar's secondary surveillance system, rather than by a reflected radio echo from the aircraft itself.
Plain English
It is the blip a controller sees that comes from the aircraft's transponder talking back to the radar, not from the radar bouncing a signal off the aircraft.
Context Anchor
You may encounter this term in air traffic control radar discussions, especially when a controller is identifying an aircraft or noticing a transponder problem.
Derivation
Called secondary because it relies on a second, cooperative signal — the transponder's reply — instead of the primary radar's direct echo off the aircraft's skin.
Why Pilots Care
Secondary radar targets give controllers aircraft identity and altitude, enabling more precise traffic separation and advisories than primary radar alone can provide.
Grounding Statement
A secondary radar target exists because the aircraft answers the radar’s electronic question.
Intuition Check
“Secondary” does not mean unimportant; it means the target comes from an aircraft reply signal rather than a simple radar reflection. “Target” does not mean something being attacked; here it means the radar symbol or return representing an aircraft.
Example Sentence 1
After the transponder was reset, the controller reported a clean secondary radar target with altitude readout.
Example Sentence 2
With secondary radar coverage, the pilot received vectors that accounted for the displayed altitude of nearby traffic.