Airport surveillance radar

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Daytona Beach International Airport Surveillance Radar. ASRDaytonBeach.jpg
Daytona Beach International Airport Surveillance Radar.

An 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. It is the main air traffic control system for the airspace around airports. At large airports it typically controls traffic within a radius of 60 miles (96 km) of the airport below an elevation of 25,000 feet. The sophisticated systems at large airports consist of two different radar systems, the primary and secondary surveillance radar. [1] 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 secondary surveillance radar consists of a second rotating antenna, often mounted on the primary antenna, which interrogates the transponders of aircraft, which transmits a radio signal back containing the aircraft's identification, barometric altitude, and an emergency status code, which is displayed on the radar screen next to the return from the primary radar. [1]

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The positions of the aircraft are displayed on a screen; at large airports on multiple screens in an operations room at the airport called in the US the Terminal Radar Approach Control (TRACON), monitored by air traffic controllers who direct the traffic by communicating with the aircraft pilots by radio. They are responsible for maintaining a safe and orderly flow of traffic and adequate aircraft separation to prevent midair collisions.

An ASR-9 airport surveillance radar antenna. The curving lower reflector is the primary radar, while the flat antenna on top is the secondary radar. Radio frequency energy enters and leaves the antenna via the two small orange horn feeds visible on the right foreground, and is guided to and from the radar processing circuitry through the black waveguides curving from the feeds into and down through the rotating central mount. ASR-9 Radar Antenna.jpg
An ASR-9 airport surveillance radar antenna. The curving lower reflector is the primary radar, while the flat antenna on top is the secondary radar. Radio frequency energy enters and leaves the antenna via the two small orange horn feeds visible on the right foreground, and is guided to and from the radar processing circuitry through the black waveguides curving from the feeds into and down through the rotating central mount.
An early LP23 airport surveillance radar antenna at Orly airport, near Paris, France, in 1964 P05 - 1964-LP23 au ras du sol.JPG
An early LP23 airport surveillance radar antenna at Orly airport, near Paris, France, in 1964

Primary radar

Radar was developed during World War II as a military air defense system. The primary surveillance radar (PSR) consists of a large parabolic "dish" antenna mounted on a tower so it can scan the entire airspace unobstructed. It transmits pulses of microwave radio waves in a narrow vertical fan-shaped beam about a degree wide. In the US the primary radar operates at a frequency of 2.7 - 2.9 GHz in the S band with a peak radiated power of 25 kW and an average power of 2.1 kW. The dish is rotated at a constant rate about a vertical axis so the beam scans the entire surrounding airspace about every 5 seconds. When the microwave beam strikes an airborne object, the microwaves are reflected and some of the energy (sometimes called the "echo") returns to the dish and is detected by the radar receiver. Since the microwaves travel at a constant speed very close to the speed of light, by timing the brief interval between the transmitted pulse and the returning "echo" the radar can calculate the range from the antenna to the object. The location of the object is displayed as an icon on a map display called a "radar screen". The screen may be located in the control tower, or at large airports on multiple screens in an operations room at the airport called in the US the Terminal Radar Approach Control (TRACON). The primary radar's main function is to determine the location, the bearing and range to the aircraft. Air traffic controllers continuously monitor the positions of all the aircraft on the radar screen, and give directions to the pilots by radio to maintain a safe and orderly flow of air traffic in the airspace.

Secondary radar

Video of radar screen at Nice Côte d'Azur Airport, Nice, France, showing aircraft preparing to land under the direction of the approach controller. The speed is increased to show the motion. Each aircraft is represented by an icon with a tail to show the direction of motion, with text beside it showing the aircraft's identifying flight number and altitude provided by secondary radar.

The need for a secondary radar system developed from the limitations of primary radar and need for more information by air traffic controllers due to the increasing postwar volume of air traffic. The primary radar displays a "return" indiscriminately from any object in its field of view, and cannot distinguish between aircraft, drones, weather balloons, birds, and some elevated features of the terrain (called "ground clutter"). Primary radar also cannot identify an aircraft; before secondary radar aircraft were identified by the controller asking the aircraft by radio to turn onto a specified heading. Another limitation is that primary radar cannot determine the altitude of the aircraft.

Secondary surveillance radar (SSR), also called the air traffic control radar beacon system (ATCRBS) had its origin in Identification Friend or Foe (IFF) systems used by military aircraft during World War II. All aircraft are required to carry an automated microwave transceiver called a transponder. The secondary radar is a rotating flat antenna, often mounted on top of the primary radar dish, which transmits a narrow vertical fan-shaped microwave beam on a frequency of 1030 MHz in the L band with peak power of 160 - 1500 W. When it is interrogated by this signal, the aircraft's transponder beacon transmits a coded identifying microwave signal at a frequency of 1090 MHz back to the secondary radar antenna. This coded signal includes a 4 digit number called the "transponder code" which identifies the aircraft, and the aircraft's pressure altitude from the pilot's altimeter. This information is displayed on the radar screen beside the aircraft's icon for use by the air traffic controller. The transponder code is assigned to the aircraft by the air traffic controller before takeoff. Controllers use the term "squawk" when they are assigning a transponder code, e.g., "Squawk 7421".

Transponders can respond with one of several different "modes" determined by the interrogation pulse from the radar. Various modes exist from Mode 1 to 5 for military use, to Mode A, B, C and D, and Mode S for civilian use. Only Mode C transponders report altitude. Busy airports usually require all aircraft entering their airspace to have a mode C transponder which can report altitude, due to their strict requirements for aircraft altitude spacing; this is called a "Mode C veil".

Types

Due to its crucial safety purpose, extreme uptime requirements, and need to be compatible with all the different types of aircraft and avionics systems, the design of airport surveillance radar is strictly controlled by government agencies. In the US the Federal Aviation Administration (FAA) is responsible for developing airport surveillance radar. All ASRs have the common requirements of detecting aircraft out to a range of 60 miles and an elevation of 25,000 feet. Upgrades are released in "generations" after careful testing:

ASR-7

An ASR-7 Operator control panel and display as used in 1981. The unit uses a 15-inch P7 CRT having a non-rotating deflection yoke, vector monitor technology, and built-in electronics to provide drive signals for the familiar rotating PPI sweep. ASR-7 PPI CRT Display Front View.jpg
An ASR-7 Operator control panel and display as used in 1981. The unit uses a 15-inch P7 CRT having a non-rotating deflection yoke, vector monitor technology, and built-in electronics to provide drive signals for the familiar rotating PPI sweep.

This is an obsolete system that is completely out of service.

ASR-8

ASR 8 is the analog precursor to the ASR 9. The military nomenclature for the radar is AN/GPN-20. It is an aging radar system that is obsolete, not logistically supported, does not provide digital inputs to new terminal automation systems, and does not provide a calibrated precipitation intensity product nor any storm motion information. [2] It is a relocatable, solid-state, all-weather radar with dual-channel, frequency diversity, remote operator controls, and a dual beam tower mounted antenna. The radar provides controllers with range azimuth of aircraft within a 60 nautical mile radius. ASR 8 used a klystron as transmitters power amplifier stage with a load of 79 kV and 40A. The two operational frequencies have a minimum separation of 60 MHz.

The US Army/Navy designator AN/GPN-20 refers to a modified version of the ASR 8 used by the USAF containing a magnetron tube as transmitter. To improve the magnetron's frequency stability the magnetron tuning is driven by the AFC.

ASR-9

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 military nomenclature for the radar is AN/GPN-27. Currently it is operating at 135 locations and is scheduled to continue in use until at least 2025. 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 which uses doppler radar and a clutter map giving advanced ability to eliminate ground and weather clutter and track targets. It is theoretically capable of tracking a maximum of 700 aircraft simultaneously.

The klystron tube transmitter operates in the S-band between 2.5 and 2.9 GHz in circular polarization with a peak power of 1.3 MW and a pulse duration of 1 μs and pulse repetition frequency between 325 and 1200 pps. It can be switched to a second reserve frequency if interference is encountered on the primary frequency. The receiver has the sensitivity to detect a radar cross-section of 1 meter2 at 111 km, and a range resolution of 450 feet. The antenna covers an elevation of 40° from the horizon with two feedhorns which create two stacked overlapping vertical lobes 4° apart; the lower beam transmits the outgoing pulse and is used to detect distant targets near the horizon, while the upper receive-only beam detects closer higher elevation aircraft with less ground clutter. The antenna has a gain of 34 dB, 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 electronics is dual-channel and fault tolerant. It has a remote monitoring and maintenance subsystem; if a fault occurs a built-in test detects and isolates the problem. Like all airport surveillance radars it has a backup diesel generator to continue operating during power outages.

ASR-11 or Digital Airport Surveillance Radar (DASR)

The Digital Airport Surveillance Radar (DASR) is the new generation of fully digital radar that is being developed to replace the current analog systems. The US Air Force Electronics Systems Center, the US Federal Aviation Administration, US Army and the US Navy procured DASR systems to upgrade existing radar facilities for US Department of Defense (DoD) and civilian airfields. The DASR system detects aircraft position and weather conditions in the vicinity of civilian and military airfields. The civilian nomenclature for this radar is ASR-11. The ASR-11 will replace most ASR-7 and some ASR-8. The military nomenclature for the radar is AN/GPN-30. The older radars, some up to 20 years old, are being replaced to improve reliability, provide additional weather data, reduce maintenance cost, improve performance, and provide digital data to new digital automation systems for presentation on air traffic control displays. [3] The Iraqi Air Force has received the DASR system. [4]

ASR 910, a German derivate of AN/TPN-24, Radartower in Neubrandenburg (Western-Pomerania/ Germany) Asr910.jpg
ASR 910, a German derivate of AN/TPN-24, Radartower in Neubrandenburg (Western-Pomerania/ Germany)

Display systems

ASR data is displayed on Standard Terminal Automation Replacement System (STARS) display consoles in control towers and Terminal Radar Approach Control (TRACON) rooms, usually located at airports.

The Standard Terminal Automation Replacement System (STARS) is a joint Federal Aviation Administration (FAA) and Department of Defense (DoD) program that has replaced Automated Radar Terminal Systems (ARTS) and other capacity-constrained, older technology systems at 172 FAA and up to 199 DoD terminal radar approach control facilities and associated towers.

STARS is used by controllers, at all terminal radar facilities in the US to provide air traffic control (ATC) services to aircraft in the terminal areas. Typical terminal area ATC services are defined as the area around airports where departing and arriving traffic are served. Functions include aircraft separation, weather advisories, and lower level control of air traffic. The system is designed to accommodate air traffic growth and the introduction of new automation functions which will improve the safety and efficiency of the US National Airspace System (NAS). [5]

Airport Surveillance Radar is beginning to be supplemented by ADS-B Automatic dependent surveillance-broadcast in the US and other parts of the world. As of Spring 2011, ADS-B is currently operational at most ATC facilities in the US. ADS-B is a GPS based technology that allows aircraft to transmit their GPS determined position to display systems as often as once per second, as opposed to once every 5–6 seconds for a short range radar, or once every 12–13 seconds for a slower rotating long range radar. The FAA is mandating that ADS-B be fully operational and available to the NAS by the year 2020. This will make possible the decommissioning of older radars in order to increase safety and cut costs. As of 2011, there is no definitive list of radars that will be decommissioned as a result of ADS-B implementation.

See also

Lists

Related Research Articles

<span class="mw-page-title-main">Air traffic control</span> Service to direct pilots of aircraft

Air traffic control (ATC) is a service provided by ground-based air traffic controllers (people) who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled airspace. The primary purpose of ATC worldwide is to prevent collisions, organise and expedite the flow of traffic in the air, and provide information and other support for pilots.

<span class="mw-page-title-main">Traffic collision avoidance system</span> Aircraft collision avoidance system

A traffic alert and collision avoidance system is an aircraft collision avoidance system designed to reduce the incidence of mid-air collision (MAC) between aircraft. It monitors the airspace around an aircraft for other aircraft equipped with a corresponding active transponder, independent of air traffic control, and warns pilots of the presence of other transponder-equipped aircraft which may present a threat of MAC. It is a type of airborne collision avoidance system mandated by the International Civil Aviation Organization to be fitted to all aircraft with a maximum take-off mass (MTOM) of over 5,700 kg (12,600 lb) or authorized to carry more than 19 passengers. CFR 14, Ch I, part 135 requires that TCAS I be installed for aircraft with 10-30 passengers and TCAS II for aircraft with more than 30 passengers. ACAS/TCAS is based on secondary surveillance radar (SSR) transponder signals, but operates independently of ground-based equipment to provide advice to the pilot on potentially conflicting aircraft.

<span class="mw-page-title-main">Secondary surveillance radar</span> Radar system used in air traffic control

Secondary surveillance radar (SSR) is a radar system used in air traffic control (ATC), that unlike primary radar systems that measure the bearing and distance of targets using the detected reflections of radio signals, relies on targets equipped with a radar transponder, that reply to each interrogation signal by transmitting encoded data such as an identity code, the aircraft's altitude and further information depending on its chosen mode. SSR is based on the military identification friend or foe (IFF) technology originally developed during World War II; therefore, the two systems are still compatible. Monopulse secondary surveillance radar (MSSR), Mode S, TCAS and ADS-B are similar modern methods of secondary surveillance.

<span class="mw-page-title-main">Precision approach radar</span> Type of radar guidance system

Precision approach radar orPAR is a type of radar guidance system designed to provide lateral and vertical guidance to an aircraft pilot for landing, until the landing threshold is reached. Controllers monitoring the PAR displays observe each aircraft's position and issue instructions to the pilot that keep the aircraft on course and glidepath during final approach. After the aircraft reaches the decision height (DH) or decision altitude (DA), further guidance is advisory only. The overall concept is known as ground-controlled approach (GCA), and this name was also used to refer to the radar systems in the early days of its development.

The air traffic control radar beacon system (ATCRBS) is a system used in air traffic control (ATC) to enhance surveillance radar monitoring and separation of air traffic. It consists of a rotating ground antenna and transponders in aircraft. The ground antenna sweeps a narrow vertical beam of microwaves around the airspace. When the beam strikes an aircraft, the transponder transmits a return signal back giving information such as altitude and the Squawk Code, a four digit code assigned to each aircraft that enters a region. Information about this aircraft is then entered into the system and subsequently added to the controller's screen to display this information when queried. This information can include flight number designation and altitude of the aircraft. ATCRBS assists air traffic control (ATC) surveillance radars by acquiring information about the aircraft being monitored, and providing this information to the radar controllers. The controllers can use the information to identify radar returns from aircraft and to distinguish those returns from ground clutter.

<span class="mw-page-title-main">Area control center</span> Air traffic control facility

In air traffic control, an area control center (ACC), also known as a center or en-route center, is a facility responsible for controlling aircraft flying in the airspace of a given flight information region (FIR) at high altitudes between airport approaches and departures. In the US, such a center is referred to as an air route traffic control center (ARTCC).

<span class="mw-page-title-main">Transponder landing system</span> All-weather, precision landing system

A transponder landing system (TLS) is an all-weather, precision landing system that uses existing airborne transponder and instrument landing system (ILS) equipment to create a precision approach at a location where an ILS would normally not be available.

<span class="mw-page-title-main">Transponder (aeronautics)</span> Airborne radio transponder

A transponder is an electronic device that produces a response when it receives a radio-frequency interrogation. Aircraft have transponders to assist in identifying them on air traffic control radar. Collision avoidance systems have been developed to use transponder transmissions as a means of detecting aircraft at risk of colliding with each other.

In aviation, a ground-controlled approach (GCA) is a type of service provided by air-traffic controllers whereby they guide aircraft to a safe landing, including in adverse weather conditions, based on primary radar images. Most commonly, a GCA uses information from either a precision approach radar or an airport surveillance radar. The term GCA may refer to any type of ground radar guided approach such as a PAR, PAR without glideslope or ASR. When both vertical and horizontal guidance from the PAR is given, the approach is termed a precision approach. If no PAR glidepath is given, even if PAR equipment is used for lateral guidance, it is considered a non-precision approach.

The National Airspace System (NAS) is the airspace, navigation facilities and airports of the United States along with their associated information, services, rules, regulations, policies, procedures, personnel and equipment. It includes components shared jointly with the military. It is one of the most complex aviation systems in the world, and services air travel in the United States and over large portions of the world's oceans.

<span class="mw-page-title-main">Radio</span> Use of radio waves to carry information

Radio is the technology of communicating using radio waves. Radio waves are electromagnetic waves of frequency between 3 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates oscillating electrical energy, often characterized as a wave. They can be received by other antennas connected to a radio receiver, this is the fundamental principle of radio communication. In addition to communication, radio is used for radar, radio navigation, remote control, remote sensing, and other applications.

ASR-11 is a Digital Airport Surveillance Radar (DASR,) an advanced radar system utilized by the United States as the next generation of terminal air traffic control. The ASR-11 is an upgraded, advanced version of the previous ASR-9 radar. This next generation radar system has been developed through a joint effort by the Federal Aviation Administration, the Department of Defense and the United States Air Force, who took most of the lead development tasks.

<span class="mw-page-title-main">Automatic Dependent Surveillance–Broadcast</span> Aircraft surveillance technology

Automatic Dependent Surveillance–Broadcast (ADS-B) is an aviation surveillance technology and form of electronic conspicuity in which an aircraft determines its position via satellite navigation or other sensors and periodically broadcasts its position and other related data, enabling it to be tracked. The information can be received by air traffic control ground-based or satellite-based receivers as a replacement for secondary surveillance radar (SSR). Unlike SSR, ADS-B does not require an interrogation signal from the ground or from other aircraft to activate its transmissions. ADS-B can also receive point-to-point by other nearby equipped "ADS-B In" equipped aircraft to provide traffic situational awareness and support self-separation. ADS-B is "automatic" in that it requires no pilot or external input to trigger its transmissions. It is "dependent" in that it depends on data from the aircraft's navigation system to provide the transmitted data.

The AN/MPN is a mobile Ground-controlled approach radar first used during World War II. "MPN" is Joint Electronics Type Designation System nomenclature for (Ground) Mobile (M), Pulsed (P), Navigation aid (N).

<span class="mw-page-title-main">Anchorage Air Route Traffic Control Center</span> Air traffic control facility in Alaska

Anchorage Air Route Traffic Control Center (PAZA/ZAN) is an Area Control Center operated by the Federal Aviation Administration and is located just outside the main gate of Joint Base Elmendorf-Richardson at 700 North Boniface Parkway in Anchorage, Alaska, United States. The Anchorage ARTCC is one of 22 Air Route Traffic Control Centers in the United States.

<span class="mw-page-title-main">Primary radar</span>

A primary radar or primary surveillance radar (PSR) is a conventional radar sensor that illuminates a large portion of space with an electromagnetic wave and receives back the reflected waves from targets within that space. The term thus refers to a radar system used to detect and localize potentially non-cooperative targets. It is specific to the field of air traffic control where it is opposed to the secondary radar which receives additional information from the target's transponder.

<span class="mw-page-title-main">ASR-9</span> United States Aircraft Radar

ASR-9 is an airport surveillance radar system admitted into the National Airspace System (NAS), to be utilized by the Federal Aviation Administration to monitor civilian and commercial air traffic within the United States. Developed by Westinghouse, ASR-9 was the first radar system to display air traffic, and weather conditions simultaneously. The ASR-9 is mainly intended to monitor and track aircraft below 25,000 ft and within forty to sixty nautical miles from the airport of operation. The ASR radar systems were widely used where an advanced radar system was needed, consisting of 135 different ASR-9 operating locations around the U.S. The FAA is currently working to upgrade the remaining ASR-9 radar sites to a modernized digital version known as the ASR-11.

Airport surveillance and broadcast systems are a set of runway-safety tools that display aircraft on and near an airport.

IFF Mark X was the NATO standard military identification friend or foe transponder system from the early 1950s until it was slowly replaced by the IFF Mark XII in the 1970s. It was also adopted by ICAO, with some modifications, as the civilian air traffic control (ATC) secondary radar (SSR) transponder. The X in the name does not mean "tenth", but "eXperimental". Later IFF models acted as if it was the tenth in the series and used subsequent numbers.

<span class="mw-page-title-main">Airway Transportation Systems Specialist</span>

Airway Transportation Systems Specialists', also known as (ATSSs; FV-2101) are Systems Electronics Technicians assigned to the Technical Operations (TechOps) section of the Federal Aviation Administration's Air Traffic Organization (ATO). Airway Transportation Systems Specialists possess theoretical and practical knowledge in electronic theory and characteristics, functions, operations, and capabilities of a variety of National Airspace System (NAS) systems. Airway Transportation Systems Specialists ensure the safety and efficiency of the NAS by performing preventive maintenance, corrective maintenance, and system modifications of air traffic control systems at ATCTs, TRACONs, and ARTCCs throughout the United States of America and its territories. ATSS generally possesses years of experience in a variety of U.S. National Airspace System (NAS) systems. Airway Transportation Systems Specialists are responsible for the maintenance, operation, fabrication, installation, and management of the technical infrastructure of the National Airspace System. Airway Transportation Systems Specialists work at different Systems Support Centers (SSCs) in the United States. Airway Transportation Systems Specialists install, maintain, repair, operate, and monitor hardware and software to ensure they work as designed. ATSS certifies equipment and services to ensure safe and efficient flight operations throughout NAS. The FAA workforce currently includes 5,200 ATSS nationwide.

References

  1. 1 2 "Airport Surveillance Radar". Technology. US Federal Aviation Administration (FAA) website. 2014. Retrieved April 23, 2017.
  2. "Radar Basics - ASR 8". www.radartutorial.eu. Retrieved 2019-08-20.
  3. FAA ASR-11 Website
  4. Advanced Radar Improves Iraqi Air Surveillance American Forces Press Service (Oct. 30, 2009).
  5. FAA STARS website Archived 2011-06-07 at the Wayback Machine