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What is ASR in Aviation? (Airport Surveillance Radar)

Updated: February 18, 2024

Airport Surveillance Radar (ASR)

Airport surveillance radar (ASR), also known as primary surveillance radar (PSR), is a crucial component of aviation infrastructure that plays a vital role in ensuring the safety and efficiency of air traffic control systems at airports. ASR systems provide real-time information about the position, altitude, and speed of aircraft within their coverage area. This article will delve deeper into the workings of airport surveillance radar, its importance, and its impact on aviation operations.

How Does Airport Surveillance Radar Work?

At its core, airport surveillance radar relies on the principle of radio wave reflection to detect and track aircraft within its range. The radar system consists of a transmitter, which emits radio waves, and a receiver, which captures the reflected waves. By analyzing the time it takes for the radio waves to return after hitting an object, such as an aircraft, the radar system can determine the distance, direction, and speed of the aircraft.

The ASR system operates using the pulse radar technique, where short bursts of radio waves, known as pulses, are transmitted and then received. The time it takes for these pulses to return provides vital information about the aircraft's position and movement. The radar antenna, typically located at the airport, rotates to cover a 360-degree area around the airport, ensuring comprehensive surveillance coverage.

Primary Surveillance Radar (PSR) vs Secondary Surveillance Radar (SSR)

It's important to differentiate between primary surveillance radar (PSR) and secondary surveillance radar (SSR) when discussing airport surveillance radar. While both systems serve the purpose of aircraft surveillance, they differ in their functionalities and capabilities.

ASR, also referred to as PSR, relies solely on radio wave reflections to detect and track aircraft. It does not require any equipment on the aircraft itself. PSR provides essential information such as aircraft position, altitude, and speed, but it does not offer additional data such as aircraft identification or flight information.

On the other hand, secondary surveillance radar (SSR) complements PSR by utilizing transponders installed on aircraft. These transponders transmit a unique identification code and additional flight information when prompted by the SSR system. The SSR system, in conjunction with PSR, provides air traffic controllers with a more comprehensive and accurate picture of the airspace.

The Importance of Airport Surveillance Radar

ASR plays a critical role in aviation safety by providing air traffic controllers with real-time information about aircraft movements. This information allows controllers to monitor and manage the flow of air traffic, ensuring safe separation between aircraft and efficient use of airspace.

One of the primary functions of ASR is to detect and track aircraft during takeoff, landing, and taxiing. By providing accurate information about an aircraft's position, altitude, and speed, ASR enables air traffic controllers to guide pilots and ensure safe spacing between aircraft. This is especially crucial during low-visibility conditions, such as fog or heavy rain, when pilots heavily rely on radar guidance to navigate safely.

Additionally, ASR plays a vital role in detecting and tracking unauthorized or unidentified aircraft within the vicinity of an airport. By continuously monitoring the airspace, ASR can alert authorities of any potential security threats or unauthorized intrusions. This capability enhances airport security and allows for swift response and intervention if necessary.

The existence of a reliable airport surveillance radar system is also a prerequisite for the implementation of other advanced air traffic control technologies, such as radar-based automation systems and collision avoidance systems. These technologies rely on accurate radar data provided by ASR to function effectively, further enhancing aviation safety and efficiency.


Airport surveillance radar (ASR) is an indispensable tool for air traffic control systems at airports. By providing real-time information about aircraft positions, altitudes, and speeds, ASR enables air traffic controllers to ensure safe and efficient operations. The primary surveillance radar (PSR) component of ASR detects and tracks aircraft using radio wave reflections, while secondary surveillance radar (SSR) complements PSR by incorporating aircraft transponders for additional data. The importance of ASR in aviation safety and security cannot be overstated, as it enables controllers to manage air traffic effectively and respond swiftly to any potential threats or unauthorized intrusions. With the continuous advancements in radar technology, airport surveillance radar systems are becoming even more sophisticated and reliable, further improving aviation operations worldwide.

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