AN/ALR-20(A) is an airborne wideband tuned radio frequency receiver providing a panoramic display of Radio Frequency (RF) spectrum on US Air Force B-52 Stratofortress aircraft. As a stand-alone system, it is used by the Electronics Warfare Officer (EWO) to evaluate and determine various classifications of threats to the aircraft, [1] identifying various signals including search, acquisition, and tracking radars as well as communications. Because it allows a broad view of the RF spectrum, its situational awareness also provides for analysis of the efficacy of jamming techniques employed by the EWO using other systems. First manufactured in the late 1960s, the system is a passive Electronic Support Measures (ESM) tuned radio frequency receiver. [2] [3] It is the primary tool used by the EWO to evaluate threats. [4]
First developed in the early 1960s, [3] [5] the ALR-20 began appearing on B-52D bombers (before 1967) [6] and B-52Gs in 1967-1969. [7] [8] In accordance with the Joint Electronics Type Designation System (JETDS), the "AN/ALR-20" designation represents the 20th design of an Army-Navy electronic device for passive countermeasures signal receiver. The JETDS system also now is used to name Air Force systems.
The ALR-20 did not undergo any significant upgrades or design changes until the 1980s. In the 80s, solid-state components were added to the system's tuners upgrading older tube-based technology. Until the late 1990s, the ALR-20's panoramic receiver display utilized Cathode-Ray Tube (CRT) technology. At the beginning of the 1990s, the outdated panoramic display (using old cathode ray tube technology) needed replacement due to the existing display becoming unsupportable. This replacement was delivered in the late 1990s. At that time, tuners and the power supply were determined to also need replacement for the same reasons. [3] Today, deployed on B-52H bombers, the system still provides the EWO a display of six different RF bands, allowing for detection and identification of threat signals. [3] [9]
Into the early 2000s, it was determined the system was "becoming unsupportable due to vanishing vendors and obsolete technology". [5] Under the B-52 Situational Awareness Defensive Improvement (SADI) program, the ALR-20 is expected to be replaced with a defensive system upgrade. The upgrade is expected to create up to thirty-fold improvements in reliability. [10] Efforts to replace the ALR-20 continued into the mid-2000s, while some work was done to continue maintaining line replaceable units (LRUs). In 1999, ninety-one LRU-1s, fifty-four LRU-3s, thirty-six LRU-8s, eighty-three LRU-9s were repaired at a total cost of over $315,000. [11] According to the Air Force's Fiscal Year (FY) 2004/2005 budget estimates, SADI would cost just over $70.9 million. [5]
Electronic Warfare Officers undergo extensive training concerning the ALR-20 panoramic system. [12]
The ALR-20's panoramic display is the EWO's primary source for analysis of potential threats through a very wide part of the electromagnetic spectrum. [13] The early cathode-ray tube for the display (seen in the image to the right) had an orange tint displaying six different horizontal lines that represented a part of the spectrum. The signals displayed on those lines may be quickly analyzed allowing the EWO to bring the proper countermeasures for multiple different threats at once. [13] [14]
In military telecommunications, electronic support (ES) or electronic support measures (ESM) gather intelligence through passive "listening" to electromagnetic radiations of military interest. They are an aspect of electronic warfare involving actions taken under direct control of an operational commander to detect, intercept, identify, locate, record, and/or analyze sources of radiated electromagnetic energy for the purposes of immediate threat recognition or longer-term operational planning. Thus, electronic support provides a source of information required for decisions involving electronic protection (EP), electronic attack (EA), avoidance, targeting, and other tactical employment of forces. Electronic support data can be used to produce signals intelligence (SIGINT), communications intelligence (COMINT) and electronics intelligence (ELINT).
Electromagnetic warfare or electronic warfare (EW) is warfare involving the use of the electromagnetic spectrum or directed energy to control the spectrum, attack an enemy, or impede enemy operations. The purpose of electromagnetic warfare is to deny the opponent the advantage of—and ensure friendly unimpeded access to—the EM spectrum. Electromagnetic warfare can be applied from air, sea, land, or space by crewed and uncrewed systems, and can target communication, radar, or other military and civilian assets.
A line-replaceable unit (LRU), lower line-replaceable unit (LLRU), line-replaceable component (LRC), or line-replaceable item (LRI) is a modular component of an airplane, ship or spacecraft that is designed to be replaced quickly at an operating location. The different lines (distances) are essential for logistics planning and operation. An LRU is usually a sealed unit such as a radio or other auxiliary equipment. LRUs are typically assigned logistics control numbers (LCNs) or work unit codes (WUCs) to manage logistics operations.
An electronic countermeasure (ECM) is an electrical or electronic device designed to trick or deceive radar, sonar, or other detection systems, like infrared (IR) or lasers. It may be used both offensively and defensively to deny targeting information to an enemy. The system may make many separate targets appear to the enemy, or make the real target appear to disappear or move about randomly. It is used effectively to protect aircraft from guided missiles. Most air forces use ECM to protect their aircraft from attack. It has also been deployed by military ships and recently on some advanced tanks to fool laser/IR guided missiles. It is frequently coupled with stealth advances so that the ECM systems have an easier job. Offensive ECM often takes the form of jamming. Self-protecting (defensive) ECM includes using blip enhancement and jamming of missile terminal homers.
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Electronic counter-countermeasures (ECCM) is a part of electronic warfare which includes a variety of practices which attempt to reduce or eliminate the effect of electronic countermeasures (ECM) on electronic sensors aboard vehicles, ships and aircraft and weapons such as missiles. ECCM is also known as electronic protective measures (EPM), chiefly in Europe. In practice, EPM often means resistance to jamming. A more detailed description defines it as the electronic warfare operations taken by a radar to offset the enemy's countermeasure.
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In the U.S. Air Force, an electronic warfare officer (EWO) is a trained aerial navigator who has received training in enemy threat systems, electronic warfare principles and overcoming enemy air defense systems. These officers are specialists in finding, identifying and countering air defense systems and also radar-, infrared- and optically guided surface-to-air missiles, anti-aircraft artillery as well as enemy fighter planes. In aircraft that could penetrate enemy airspace EWOs protect their aircraft using radar jamming, chaff and flares to deceive potential threats. In other aircraft EWOs work to gather intelligence information on potential enemy air defense systems and communication systems.
The Combat Aircraft Systems Development & Integration Centre (CASDIC) is a laboratory of the Indian Defence Research and Development Organisation (DRDO). Located in Bangalore, Karnataka, India, It is one of the two DRDO laboratories involved in the research and development of airborne electronic warfare and mission avionics systems.
The Boeing B-52 Stratofortress is an American long-range, subsonic, jet-powered strategic bomber. The B-52 was designed and built by Boeing, which has continued to provide support and upgrades. It has been operated by the United States Air Force (USAF) since the 1950s, and NASA for nearly 50 years. The bomber can carry up to 70,000 pounds (32,000 kg) of weapons and has a typical combat range of around 8,800 miles (14,200 km) without aerial refueling.
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A "Phase VI ECM Defensive Avionics Systems" upgrade, codenamed "Rivet Ace", was begun more or less near the end of the EVS upgrade. It included a comprehensive update of countermeasures systems for the B-52G and B-52H, including: An AN/ALR-20A wideband countermeasures receiving set, with antennas littered all over the aircraft. The "20 Scope" is the primary tool for detecting and analyzing threats.
...replacing the AN/ALR-20 Panoramic Receiver System. The present AN/ALR-20 system, designed in the 1960's, is becoming unsupportable due to vanishing vendors and obsolete technology and has extremely limited SOJ support capability.
The B-52D also received new upgrades to improve its combat effectiveness, most significantly with the "Rivet Rambler" program, conducted from 1967 through 1969 to provide an improved ECM suite. Rivet Rambler, more officially referred to as the "Phase V ECM Fit", fitted the B-52Ds with the following gear: An AN/ALR-20 panoramic receiving set.
During 1967-1969... This involved the fitting of... one AN/ALR-20 panoramic receiver set. The Phase VI ECM Defensive Avionics Systems upgrade... was started in December of 1971, but it took several years of development and testing. The equipment added as part of Phase VI consisted of an AN/ALR-20A countermeasures receiver
B-52Ds were equipped with an extensive suite of electronic countermeasures during the 'Rivet Rambler' programme of 1967 to 1969... This included the addition of... the AN/ALR-20 panoramic receiving set
Through the SADI program, Boeing will replace the aging ALR-20A Electronic Countermeasures Receiver System and the ALR-46 Radar Warning Receiver on the B-52 Stratofortress. These upgrades are expected to offer up to a thirty-fold improvement in system reliability.
The AN/ALR-20 radar warning system that detects and prioritises multiple threats...