Owais Crawford
Airport surveillance radar (ASR) systems are used to detect and display the presence and position of aircraft in the airspace around airports. ASRs are designed to provide short-range coverage in the general vicinity of an airport and to handle terminal area traffic through the observation of precise aircraft locations on a radarscope. The primary radar consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport. The secondary radar, often mounted on the primary antenna, interrogates the transponders of aircraft to transmit data on aircraft altitude, identification code, and emergency conditions.
| Characteristics | Values |
|---|---|
| Purpose | To detect and display the presence and position of aircraft in the terminal area, the airspace around airports. |
| Control system | The main air traffic control system for the airspace around airports. |
| Range | 40-60 nautical miles (75-110 km) |
| Altitude | Below 25,000 feet (7,620 metres) |
| Antenna type | Parabolic "dish" antenna |
| Antenna rotation | 12-15 revolutions per minute |
| Antenna gain | 34 dB |
| Beamwidth | 5° in elevation and 1.4° in azimuth |
| Frequency | 2.7-2.9 GHz (S band) or 2700-2900 MHz (E band) |
| Peak radiated power | 25 kW |
| Average power | 2.1 kW |
| Display | Radar screen, often located in the control tower or operations room |
| Backup | Diesel generator to continue operating during power outages |
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What You'll Learn
Airport Surveillance Radar (ASR)
The systems at large airports consist of two different radar systems: the primary and secondary surveillance radar. The primary radar typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport. It detects the position and range of aircraft by microwaves reflected back to the antenna from the aircraft's surface. The dish rotates at a constant rate about a vertical axis so the beam scans the entire surrounding airspace about every 5 seconds. The antenna has a gain of 34 dB, a beamwidth of 5° in elevation and 1.4° in azimuth. It rotates at a rate of 12.5 RPM so the airspace is scanned every 4.8 seconds.
The secondary surveillance radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft. Military, commercial, and some general aviation aircraft have transponders that automatically respond to a signal from the secondary radar by reporting an identification code and altitude. The secondary radar uses a second radar beacon antenna attached to the top of the primary radar antenna to transmit and receive aircraft data for barometric altitude, identification code, and emergency conditions.
The current generation of radar is the ASR-9, which was developed by Westinghouse Electric Corporation and first installed in 1989, with installation completing in 1995. The ASR-9 was the first airport surveillance radar to detect weather and aircraft with the same beam and be able to display them on the same screen. It has a digital Moving Target Detection (MTD) processor that uses doppler radar and a clutter map to provide advanced ability to eliminate ground and weather clutter and track targets. It is theoretically capable of tracking a maximum of 700 aircraft simultaneously.
The positions of the aircraft are displayed on a screen; at large airports, on multiple screens in an operations room at the airport called the Terminal Radar Approach Control (TRACON), monitored by air traffic controllers who direct the traffic by communicating with aircraft pilots by radio. They are responsible for maintaining a safe and orderly flow of traffic and adequate aircraft separation to prevent mid-air collisions.
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Primary and Secondary Surveillance Radar
Airport surveillance radar (ASR) is a radar system used at airports to detect and display the presence and position of aircraft in the terminal area, the airspace around airports. ASRs are designed to detect aircraft out to a range of 40 to 60 miles and an elevation of 25,000 feet.
The design of ASRs is strictly controlled by government agencies due to their safety purposes, uptime requirements, and need to be compatible with all aircraft and avionics systems. ASRs consist of two different radar systems: primary and secondary surveillance radar.
The primary radar typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport. The dish rotates at a constant rate about a vertical axis, scanning the entire airspace every 4.8 to 5 seconds. When the microwave beam strikes an airborne object, the microwaves are reflected back to the dish, and the radar receiver detects the "echo" to calculate the range and position of the object. The primary radar's main function is to determine the location, bearing, and range of aircraft.
The secondary surveillance radar (SSR) consists of a second rotating antenna, often mounted on the primary antenna. SSR relies on targets equipped with a radar transponder, which reply to interrogation signals by transmitting encoded data such as an identity code, altitude, and other information. SSR is based on military Identification Friend or Foe (IFF) technology, which was developed to identify friendly aircraft. SSR overcomes some limitations of primary radar by providing aircraft identification and altitude in a single reply, improving accuracy and reducing the number of interrogations/replies per aircraft.
Both primary and secondary surveillance radars play a crucial role in air traffic control, ensuring safe and efficient operations at airports.
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Radar's range and altitude
Airport Surveillance Radar (ASR) is a mid-range radar system used to detect and display the presence and position of aircraft in the airspace around airports. ASR is designed to provide short-range coverage in the general vicinity of an airport, typically within a radius of 40 to 60 nautical miles (75 to 110 km) of the airport.
The altitude range of ASR depends on the size of the airport. Large airports with sophisticated radar systems can detect aircraft below an elevation of 25,000 feet (7,620 meters). Smaller airports with less advanced radar systems may have a lower altitude range.
The primary radar system typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport. The secondary surveillance radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft to obtain additional information such as identification, barometric altitude, and emergency status codes.
The range and altitude of ASR can be affected by various factors, such as weather conditions, terrain, and the presence of dense objects or ground clutter. To overcome these limitations, some airports may employ multiple radars or advanced technologies such as ADS-B (Automatic dependent surveillance-broadcast), which provides more frequent updates on aircraft position and allows for the decommissioning of older radars.
Overall, the range and altitude of airport radar systems are crucial for maintaining safe and efficient air traffic operations. The specific capabilities of ASR can vary depending on the airport's size, location, and technological advancements, but the primary goal remains to ensure the safe and orderly flow of air traffic.
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Radar's design and development
Radar technology has evolved significantly since its early development before and during World War II, when it was used as a military air defence system. Today, radar systems are used for a wide range of applications, including air traffic control, marine navigation, meteorological precipitation monitoring, and autonomous vehicles.
The design and development of radar systems involve several key components. Firstly, a radar system consists of a transmitter that produces electromagnetic waves in the radio or microwave domain. These waves are then transmitted through an antenna, which can be a large parabolic "dish" or a rotating antenna. The transmitted waves reflect off objects and return to a receiving antenna, which may be the same as the transmitting antenna. The reflected waves provide information about the objects' locations and speeds.
To process this information, radar systems require a receiver and processor. This component analyses the reflected waves to determine the properties of the objects, such as their range, bearing, and speed. Modern radar systems use digital signal processing and machine learning techniques to extract useful information from very high noise levels. This allows radar systems to detect small targets even in the presence of larger radar echoes or "clutter" from the sea or land.
The development of radar technology has progressed through generations of upgrades and improvements. For example, the cavity magnetron, developed in the United Kingdom, enabled the creation of smaller radar systems with sub-meter resolution. Another key development was the introduction of pulse modulation, which provided more accurate and reliable radar performance compared to continuous-wave operation.
Today, radar technology continues to advance with the integration of millimeter-wave (mmWave) radar sensors. These sensors have a wide range of applications, including automotive systems, residential air conditioners, and industrial processes. mmWave radar technology improves autonomous driving capabilities, such as emergency braking and adaptive cruise control, and enables advanced features like gesture control and occupancy sensing in automotive and residential settings.
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Radar's use and function
Airport surveillance radar (ASR) systems are used to detect and display the presence and position of aircraft in the airspace around airports. ASR is a mid-range primary radar that usually operates in the frequency range of 2,700 to 2,900 MHz (E band). This frequency range is chosen because it provides low attenuation due to absorption in heavy rain regions, and it is high enough to accommodate highly directional antennas with relatively small dimensions and lower weight. ASR is designed to provide short-range coverage within a radius of about 60 miles (96 km) of the airport and an elevation of 25,000 feet (7,620 meters).
The primary radar consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace. When the microwave beam strikes an object, the microwaves are reflected, and some of the energy (the "echo") returns to the dish and is detected by the radar receiver. The primary radar's main function is to determine the location, bearing, and range of the aircraft. The primary radar also provides data on six levels of rainfall intensity.
The secondary surveillance radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft. Military, commercial, and some general aviation aircraft have transponders that automatically respond to a signal from the secondary radar by reporting an identification code and altitude. The secondary radar operates in the range of 1,030 to 1,090 MHz and provides rapid identification of aircraft in distress.
The positions of the aircraft are displayed on a screen in the control tower or, at large airports, on multiple screens in an operations room monitored by air traffic controllers. The data collected from the radar systems help controllers direct traffic and maintain a safe and orderly flow of aircraft to prevent mid-air collisions.
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Frequently asked questions
Airport surveillance radar (ASR) typically consists of a large rotating parabolic antenna dish that sweeps a vertical fan-shaped beam of microwaves around the airspace surrounding the airport.
The primary radar consists of a large parabolic "dish" antenna mounted on a tower so it can scan the entire airspace unobstructed.
The secondary radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft.
The purpose of airport radar is to detect and display the presence and position of aircraft in the terminal area, the airspace around airports.
The primary radar transmits pulses of microwave radio waves in a narrow vertical fan-shaped beam about a degree wide. When the microwave beam strikes an airborne object, the microwaves are reflected, and some of the energy (or "echo") returns to the dish and is detected by the radar receiver.
Airport surveillance radar systems can detect and track aircraft at altitudes below 25,000 feet (7,620 meters) and within 40 to 60 nautical miles (75 to 110 km) of the airport.
The antenna rotates at a rate of 12-15 RPM, so the airspace is scanned every 4-5 seconds.
