ASR-11 Overview

The ASR-11 (DASR) is an S-band, solid-state, terminal area, digital, primary and secondary surveillance radar.

The Airport Surveillance Radar Model 11 (ASR-11) is a digital, combined primary and secondary surveillance radar (SSR), short-range radar system with a 60 nautical mile (nmi) detection range for medium and small activity airports. The ASR-11 provides advanced digital primary radar including weather intensity surveillance with an integrated monopulse SSR system for use in the airport terminal area. The ASR-11 is used to detect and report the presence and location of an aircraft in a specific volume of airspace. The ASR-11 provides search radar surveillance coverage in controlled airspace primarily in terminal areas.

As of 06 February 2006 there have been 59 ASR-11 systems purchased with 8 additional systems to be purchased for a total of 67. The U.S. Department of Defense (DoD) owns the ASR-11 at Willow Grove that is maintained by the FAA. There are 20 operational ASR-11 systems plus two support systems. It is planned to have 10 additional systems become operational in fiscal year (FY) 2006. Eighteen ASR-11 systems have been commissioned in the National Airspace System (NAS) one of which is owned by the DoD.

ASR-11 (DASR)

ASR-11 is a new terminal air traffic control radar system that replaces current analog systems with new digital technology. The Air Force Electronics Systems Center and the Federal Aviation Administration are in the process of procuring DASR systems to upgrade existing radar facilities for 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 Government nomenclature for this radar is the ASR-11. The ASR-11 will replace existing ASR-7, ASR-8 and AN/GPN-12, -20 and -27 systems. These 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 controller displays.

Primary and Secondary Surveillance Radar

The ASR-11 system consists of two electronic subsystems: a primary surveillance radar and a secondary surveillance radar, sometimes called the beacon. The primary surveillance radar uses a continually rotating antenna mounted on a tower to transmit electromagnetic waves which reflect or backscatter from the surface of aircraft up to 60 miles from the radar. The radar system measures the time required for a radar echo to return and the direction of the signal. From this data the system can then measure the distance of the aircraft from the radar antenna and the azimuth or direction of the aircraft from the antenna. The primary radar also provides data on six levels of rainfall intensity. The primary radar operates in the range of 2700 to 2900 MHz. The transmitter generates a peak effective power of 25 kW and an average power of 2.1 kW. Average power density of the ASR-11 signal decreases with distance from the antenna. At distances of more than 43 feet from the antenna, the power density of the ASR-11 signal will fall below the maximum permissible exposure levels established by the Federal Communications Commission.

The secondary radar, also called the monopulse secondary surveillance radar, uses a second radar antenna attached to the top of the primary radar antenna to transmit and receive area aircraft data for barometric altitude, identification code, and emergency conditions. Military and commercial aircraft have transmitters that automatically respond to a signal from the secondary radar by reporting an identification code and altitude. The air traffic control uses this system to verify the location of aircraft within a 120-mile radius of the radar site. The beacon radar also provides rapid identification of aircraft in distress. The secondary radar operates in the range of 1030 to 1090 MHz. Transmitting power ranges from 160 to 1500 watts.

Other Equipment supporting ASR-11

ASR-11 Feedhorns

Other equipment used to support the ASR-11 may include moving target indicator reflectors and the monopulse secondary surveillance radar remote system monitor. The moving target indicator, located in line of sight and between 0.5 and 6 nautical miles from the primary radar antenna, is a small parabolic dish antenna and electronics used to provide a known geographic reference point on the radar display. Moving target indicator reflectors are used to align the primary radar, monitor its performance and provide fixed reference points, including the centerline of the runway and/or a fixed mileage reference point. Whenever possible, moving target indicator reflectors will be installed on existing buildings, poles or towers.

The monopulse secondary surveillance radar remote system monitor, located in line of sight and between 0.5 and 10 nautical miles from the radar antenna, provides a fixed location for monitoring the performance of the secondary radar by automatically replying with preset codes to secondary radar interrogations. Whenever possible, the monitor will be installed at existing facilities.

ASR-11 Facilities

The total ASR-11 system also includes the following facilities: an antenna tower, an electronic equipment shelter/building with heating, ventilation and air conditioning, a power distribution system, an uninterruptible power supply, a back-up emergency engine/generator set, fire detection, security, and cabling to connect the radar to the local radar approach control center. Telephone and power lines will also be provided to the site. The tower will be from 17 to 87 feet in height, depending upon local surrounding obstructions to the radar signal such as trees, buildings and local terrain. The radar antenna and lightning masts on the top of the tower add an additional 20 feet to the total height of the structure. An optional radome would extend approximately 10 feet above the antenna for a total structure height of 47 to 107 feet. The typical ASR-11 site is 140 by 140 feet plus a maintenance access road.

In order to ensure uninterrupted air traffic control monitoring, the existing radar must continue to operate while the replacement radar is sited, constructed and tested. This usually requires that a new site for the new radar be identified. Site preparation, electronic equipment installation, checkout and commissioning of the ASR-11 typically take 12 months to complete.

ASR-11 Antenna Driver Motors (15 HP)

Vendor

RAYTHEON CO., Command, Control, Communication and Information Systems, Marlborough, MA, USA

Quick Links

• US facilities upgrading to the ASR-11
• FAA ASR-11 home page
• ASR-11 photo gallery