Definition
A model of short-range terminal radar system used by Terminal Radar Approach Control (TRACON) facilities to detect and track aircraft within roughly 60 nautical miles of an airport. The ASR-9 combines primary radar (which detects aircraft by reflecting radio energy off the airframe) with a secondary surveillance radar (which interrogates aircraft transponders to receive identification and altitude data). It also includes a weather channel that displays six levels of precipitation intensity on the controller's scope.
Plain English
A specific type of airport radar that controllers use to see aircraft and weather around a busy terminal area. It picks up aircraft both by bouncing radio signals off them and by talking to their transponders, and it shows controllers where rain and storms are.
Context Anchor
Seen in discussions of TRACON services, radar approach control, and the equipment controllers use to watch traffic near busy airports.
Derivation
ASR stands for Airport Surveillance Radar. The 'surveillance' part means the radar's job is to keep a continuous watch over a defined area. The '9' is simply the model number — it's the ninth generation of this radar family. Knowing this helps you read references like ASR-8, ASR-9, and ASR-11 as different models of the same kind of equipment, not different kinds of radar.
Why Pilots Care
Controllers depend on it to separate and sequence arriving and departing aircraft safely.
Intuition Check
Do not read “equipment” as a loose reference to any airport electronics. In this context, ASR-9 equipment means a specific airport surveillance radar system used by air traffic control.
Example Sentence 1
The TRACON's ASR-9 equipment allowed the controller to vector us around a level-three precipitation cell on the way to the airport.
Example Sentence 2
Technicians performed routine checks on the ASR-9 equipment to maintain continuous radar coverage.