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Chapter 2

Air Defense Artillery Control Systems

The exchange of information between missile fire units and command posts must be instantaneous. Army air defense artillery units require timely and continuous information on the location of friendly and hostile aircraft. Immediate collection and dissemination of target data are required to insure rapid fire unit response and concentration of effort directed toward the enemy threat. To provide air defense artillery commanders with this required capability, the Army employs electronic fire distribution systems and associated equipment.


Oldest of the US Army electronic fire distribution systems currently in use is the Missile Master (AN/FSG-1), having become operational in 1957 (fig 31). Missile Master systems, located only within CONUS, provide a rapid and accurate flow of information between the AADCP, air defense artillery fire units, adjacent AADCP's, and SAGE. Track information and commands are transmitted as digital data by automatic data link between the AADCP and missile fire units. At the fire units, track information and commands are converted from digital data and presented on the commander's consoles. Using electronic displays and controls, the air defense artillery commander can monitor or direct the actions of 24 Nike Hercules batteries against approximately 50 targets.

(figure 31 - 2 large radar domes and some buildings in a city environment - is not included in this conversion)

Figure 31. Missile Master installation.

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Major items of equipment in the Missile Master system include an AN/FPS-33 defense acquisition radar (DAR) or similar radar, two height-finder radars, in some instances defense support radars (gap filler), a tracking subsystem, a tactical display subsystem, automatic data link transmitters and receivers, and computing and storage equipment (fig 32).

Figure 32. Missile Master data flow.

Figure 32. Missile Master data flow.

The DAR provides slant range and azimuth of targets to the tracking subsystem. Associated identification, friend or foe (IFF), equipment furnishes IFF video to the tracking subsystem .

The two height-finder radars furnish data to the range-height determining equipment of the tracking subsystem. The tracking subsystem consists of two surveillance and entry (S&E) consoles, a channel status unit, six tracking consoles, and two range-height indicator (RHI) consoles. The S&E consoles display acquisition radar data, generated tracks, and tracks from Air Force fire distribution systems SAGE/BUIC (backup interceptor control). A channel status unit, using illuminated indicators, shows the status of data channels in the Missile Master system. Tracking consoles display acquisition radar data the same as the S&E consoles. Tracks are assigned from S&E consoles to the tracking consoles for monitoring and updating. The height determination equipment contains two RHI consoles, which receive and display height and range data from the height-finder radars. Track data are sent from the tracking subsystem to the memory storage equipment.

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The tactical display subsystem includes three tactical monitor consoles --friendly protector console, operations officer's console, and Army air defense commander's console. The tactical display subsystem receives track information from the system storage and displays it as symbology on the subsystem consoles. The tactical monitor consoles have the necessary controls to sendcommands to the batteries and to correlate battery tracks with targets. Symbology and illuminated indicators present the battery status of the eight batteries under the control of each tactical monitor console. The friendly protector console has a HOLD FIRE pushbutton for each battery in the defense. Track symbology enables the friendly protector to determine that a friendly aircraft is being tracked and also the battery that is trackingit. A HOLD FIRE command is sent to the battery by pressing the proper HOLD FIRE pushbutton. The Army air defense commander's console and the operations officer's console are identical, displaying the same symbology as the other tactical consoles. Indicators show the status of the batteries, but direct data commands cannot be sent from these consoles. A signal from either ofthese consoles determines whether friendly data, hostile data, or both will be passed from storage by the output control. The data to be passed are accepted by the transmitter and passed to the battery. Report-back data are sent back to the receiver by the batteries, where they are passed to system storage for retransmission to other units, SAGE, the tactical display subsystem, the tracking subSystem, and BUIC under certain operational conditions. Battery data link transmissions are converted from digital format to analog and from analog to digital data at the battery by the fire unit integration facility (FUIF), normally the AN/FSA-25 or AN/FSA-25A.


The battery integration and radardisplay equipment (BIRDIE) systems AN/GSG-5 and AN/GSG-6 (figs 33 and 34) were developed to provide compact, reliable, and transportable

(figure 33 - 2 rooms that look trailerable with (?electronic? cabinets) and one console in one room and 2 consoles in the other room - is not included in this conversion)

Figure 33. AN/GSG-6 (BIRDIE) system.

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systems to economically integrate Nike Hercules batteries. 'Ihrough SAGE direction centers, and backup interceptor control stations in certain operational modes, BIRDIE systems are integrated into the overall air defense of CONUS.

Figure 34. AN/GSG-6 (BIRDIE) system.

Figure 34. AN/GSG-6 (BIRDIE) system.

Major components of the AN/GSG-5 system include DAR AN/FPS-36, AN/FPS-69, or any acquisition radar with a pulse rate of 200 to 400 pulses per second, and the necessary AADCP equipment.

The DAR furnishes target slant range and azimuth, but no height data, to the AADCP. The DAR has IFF equipment which is used for identification.

The AADCP contains display equipment, computer and storage facilities, voice communications, and power and testing equipment. The situation display console has controls and indicators that enable the controller to enter target identity, position, and velocity into the memory system. The controls and indicators also enable the controller to make or erase target assignments to batteries and to dump data from the memory system. The plan position indicator (PPI) displays video from the DAR, local track symbols, SAGE/BUIC track symbols, battery return symbols, and other symbols as selected by the controller.

The AN/GSG-5 can integrate a maximum of 16 Nike Hercules batteries and display approximately 30 SAGE/BUIC and local tracks plus 16 battery returns. If modified for Hawk, the AN/GSG-5 can integrate eight batteries. The computer and storage system allows

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semiautomatic tracking of targets up to a velocity of 2,250 knots. The automatic data link (ADL) permits automatic transmission of digital data between AN/GSG-5 and SAGE/BUIC. The battery datalink (BDL) transmits data from the AN/GSG-5 to the batteries; the batteries transmit data back to the AN/GSG-5 and all other integrated batteries. This baffery-tobattery data transmission is known as repeat-back data.

The AN/GSG-6 system (fig 34) is similar to the AN/GSG-5 system but does not include computer and storage equipment. This system has a maximum capability of integrating two Nike Hercules batteries. The FUIF used with the BIRDIE system may be the AN/FSA-41, AN/FSA-68, or AN/FSA-69. Modifications to the coordinate data set receiver-transmitter allow for use of either pulse-code-modulated (PCM) or frequency-shift- modulated (FSM) transmission methods.


The Missile Monitor (AN/MSG-4) fire distribution system was developed by the US Army to coordinate the fire of Nike Hercules and Hawk missile batteries with the army in the field. These systems make it possible to observe and influence the entire air battle from the widest viewpoint so separate actions of numerous batteries can be supervised and unified into an integrated defense.

The AN/MSG-4 system is composed of two basic subsystems: the AN/MSQ-28), AN/MSQ-28B, or AN/MSQ-56 subsystem located at group/brigade level and the AN/MSQ-18 (or AN/TSq-38 which is helicopter-transportable) subsystem located at battalion and battery levels.

The AN/MSQ-28B system (fig 35) includes a frequency-scan, three-dimensional radar AN/MPS-23A, a radar data processing center (RDPC), and a weapons monitoring center (WMC). The AN/MPS-23A radar provides target detection, furnishing range, azimuth, and elevation angle of the target. The antenna rotates mechanically in azimuth and scans elecuonically in elevation. The AN/MPS-23A is equipped with IFF equipment. The RDPC (fig 36) provides initial display of targets, a means for interrogation of targets, and automatic tracking. Tracking is accomplished at six detector-tracker (DT) consoles in the RDPC. Height dataareobserved on two range-height indicator consoles. The H, X, and Y coordinates of targets, plus X and Y velocities, are stored as track data and sent to the WMC.

The WMC (fig 37) provides the group/brigade commander with an immediate presentation of the tactical situation at all times. Track marker data are displayed in the form of symbology on weapons monitoring consoles. Battery status also is received from the battery and displayed on these consoles. This combined symbolic and read-out display of information enables the commander to view the entire air battle and make assignments from the WMC to the batteries under his control. The WMC can accept and utilize data from Air Force agencies and adjacent defenses. The AN/MSQ-28 system has the capability of directing more than 30 fire units against more than 150 targets.

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(figure 35 - a drawing including items labled

- is not included in this conversion)

Figure 35. AN/MSQ-28B system.

(figure 36 - the interior of a ?trailer? with at least 8 18 inch CRTs arranged in one long console - is not included in this conversion)

Figure 36. Interior view of radar data processing center.

(figure 37 - the interior of a ?trailer? with at least 5 18 inch CRTs arranged in one long console - is not included in this conversion)

Figure 37. Interior view of weapons monitoring center.

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The battalion-level component of the AN/MSQ-18 is the battalion operations central (Bn OC) (fig 38). The Bn OC gives the battalion commander the capability of either monitoring reference data and the changing status, or making assignments to the firing battery, depending upon the method and mode of operation. It links the battalion with the group WMC and fire units, and displays battery status, target video, and symbology on each of two con soles. The electronic search central AN/GSS-1 (or AN/GSS- 7) of the battalion is connected to the Bn OC and can furnish radar data to the Bn OC. In turn, the Bn OC can insert these data into the data link, thus providing additional information to all fire units under WMC control in the normal method of operation.

(figure 38 - 2 18 inch CRTs arranged in one console with lots and lots of knobs and switches - is not included in this conversion)

Figure 38. Battalion operations central consoles.

(figure 36 - one small CRT and not more than 30 knobs and switches - is not included in this conversion)

Figure 39. Interior view of coder-decoder group.

The battery-level component of the AN/MSQ-18 is the coder-decoder group (CDG) (fig 39). The CDG, which functions as a link between battalion and battery, is a transmitterreceiver that permits exchange of data between the battery and other elements of the system. Information which may have originated at the WMC, Bn OC, or other fire units is received at the CDG in the form of binary digital data. The CDG converts these data for display at the battery control console. Information originating at the battery is converted to binary digital data by the CDG and sent to the Bn OC and WMC.

The AN/MSG-4 system has six data link switching methods of operation. Only three of these methods--normal, sector, and independent--are considered in tactical operations. In the normal method, the WMC sends reference information and commands through the Bn OC to the battery. The Bn OC monitors, but does not originate, commands to the batteries. In the sector method, reference information is sent to the Bn OC and the batteries and the Bn OC originates commands to the batteries. In the independent method, all reference information and commands originate at the Bn OC. The other three methods of operation are used for tests and emergencies.

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The primary means of transmitting information, using binary digital data, is by automatic data link. Common carriers of ADL include spiral-4 cable or microwave, but any carrier capable of handling pulses of 600 and 1500 cycles per second will suffice.


A new fire distribution system (AN/TSQ-51) has been developed and is currently being deployed to replace some first-generation fire distribution systems, primarily Missile Master. The new system will greatly reduce operational costs, simplify maintenance, and increase track handling capability over older systems. The mobile AN/TSQ-51 system requires no equipment air conditioning. It is composed of the necessary equipment for an AADCP and an associate remote radar integration station (RRIS). The AADCP utilizes two trailers, one containing track processing equipment, memory stores, and a computer and the other containing tracking and tactical display (general purpose) consoles and operations boards. The RRIS consists of a trailer containing a computer, memory stores, and tracking display (general purpose) consoles.

The AN/TSQ-51 is designed on the modular concept, allowing addition or deletion of major functions so that requirements of various defense complexes may be met economically. The system can receive and process data from US Air Force air defense command and control systems, adjacent AADCP's, remote radar integration stations, and local search radars. Data are automatically exchanged by digital data link and voice communication with air defense elements and both Nike Hercules and Hawk fire units.

The major functions performed by the AADCP equipment are target detection, acquisition, and identity; track correlation and threat evaluation; fire unit designation and fire coordination; and fire unit status monitoring.

The operational functions performed by the RRIS are those associated with detection, acquisition, and rate-aided tracking of video from the associated search radar and the automatic exchange of data with the AADCP to which it is supplying tracks.

Both the AADCP and the RRIS may be located at, and associated with, numerous types of existing search radars. The FUIF equipment or CDG used with existing Army fire distribution systems in CONUS and overseas is compatible with the AN/TSQ-51.


Before any commander can engage an airborne threat, he must know the location of the threat in relation to his unit. The location of the threat is expressed in terms of azimuth, elevation, and range from the unit. In most current air defense artillery fire distribution systems, two types of radars are used to provide these data: an acquisition radar to determine azimuth and range and a height-finder radar to determine elevation. Use of two radars rather than one presents obvious problems; e.g., two radars must be moved in a mobile situation, two radars must be maintained and repair parts stocked for each, and two radars must be emplaced on carefully selected terrain to prevent masking of the height-finder radar so that it can cover areas identical to those covered by the acquisition radar.

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A three-dimensional (3D) radar can furnish all of these data; i.e., azimuth, elevation, and range. This type of radar utilizes electronic scanning. One of the new classes of electronic scanningradars, the AN/MPS-23 (a component of the Missile Monitor FDS), provides three-dimensional search. It supplies azimuth, elevation, and range data simultaneously from a single antenna (transmitter and receiver) channel. The beam scans electronically in elevation while the antenna rotates in azimuth. The antenna frequency- scan operation is similar in principle to that of a slotted waveguide with the microwave energy radiated from the slots combining to form a beam. When the frequency is matched and phased with the distance between the slots, the direction of propagation is straight ahead. If the frequency of the energy is changed, relative phase differences are set up from one slot to the next, changing the direction of propagation accordingly. Continuous phase shifting is achieved by using variable frequency exciters in the transmitter. These exciters can be programed digitally to provide various patterns of beams scanning in elevation. The AN/MPS-23 incorporates moving target indicator circuits that blank out returns from stationary objects. It is capable of azimuth sector scanning as well as 6,400-mil rotational scan. Ir provides variable scan rates in elevation and azimuth and uses variable pulse repetition frequencies. The changing radiation frequency gives this radar inherent resistance against electronic jamming.

Another proposed type of 3D radar incorporates many desirable characteristics, such as mobility, compactness, light weight, ease of maintenance, and ability to operate in an ECM environment. Electronic equipment is sealed from such ambient conditions as sand and dust, salt spray, rain, and humidity and is cooled by built-in, air-to-air heat exchangers. Transportable by helicopter, cargo aircraft, or standard military vehicles, the lightweight 3D radar can be put into operation quickly at remote sites. Rugged, compact design enables the entire system to be packaged in two waterproof Fnclosures, 6.5 feet by 6.5 feet. The antenna package has a length of 12 feet and weighs 2,300 pounds; the electric equipment shelter has a length of 9 feet and weighs 3,500 pounds.

The antenna inclosure of this radar is uniquely designed for transportability and rapid assembly. The pedestal and simplified azimllth drive system are integral parts of the lower portion of the antenna package. Packed in the upper portion of the inclosure are the reflector panels and waveguide lengths. The thin-shelled parabolic reflector is assembled from four structural modules joined with quick-disconnect fasteners. Six men can perform the entire assembly and hookup procedure.


All air defense must start with a knowledge of the attacking forces. As a result, any air defense system must perform an aircraft tracking function which yields information that commanders can use to engage the attacking force. This tracking function can exist either as an integral feature of the air defense system (such as the defense acquisition radar) or by the addition of radars specifically deployed for the purpose of early warning or gap-filling.

The term, radar netting (fig 40), describes the process by which track data derived from several additional or remote radars are gathered at a single center to produce an integrated set of meaningful target information which can be distributed to all air defense elements concerned .

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Figure 40. Radar Netting concept.

Figure 40. Radar netting concept.

Radar netting can provide concurrent coverage of a selected area by more than one radar. Each remote radar, independeni of central computing facilities, can continue to furnish processed track data to another user even if its primary user is disabled. Another advantage is furnishing jam-strobe tracking or obtaining cross-bearings on a jamming target to determine its position by triangulation.

A radar netting system exchanges data among various radars, surface-to-air missile batteries, and command centers by advanced digital data transmission techniques. The standard operational system consists of the following subsystems: radar tracking station, radar netting unit, and battery terminal equipment.

The radar tracking station (fig 41) Is a compact radar data processor which accepts track information from its associated acquisition radar. This track information enters the computer and is updated by manual tracking on the part of the console operator. The computer stores the track data in digital form, which are then made available by data link to any user in the netting system. The user receives position coordinates, velocity components, raid size, identification, track number, and target height.

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(figure 41 - 2 18 inch CRTs arranged in two adjacent consoles with lots and lots of knobs and switches - is not included in this conversion)

Figure 41. Interior view of radar tracking station.

(figure 42 - nothing recognizable to me - is not included in this conversion)

Figure 42. Radar netting unit at operations central.

Incoming track data from each radar tracking station must be received at the operations central and relayed to the missile batteries as well as to the other radar tracking stations. At the operations central, the radar netting unit (fig 42) acts as a sequencing and distribution device, channeling data from each radar tracking station to the missile batteries through their terminal equipment, to the operations centraldisplays, and to the other radar tracking stations.

As the on-site processor which ties the missile battery to the operations central, the battery terminal equipment (AN/GSA-77) functions as a two-way data link. Through the battery terminalequipment, the battery commander is continuously informed of targets which other batteries are tracking and engaging and targets which may constitute a threat to his defense area in the immediate future. Conversely, the battery terminal equipment also encodes the battery information into a digital message containing the coordinates of the target being tracked, battery status, and other data, such as parallax corrections. The battery terminal equipment is capable of integrating any air defense artillery missile battery with any of the air defense artillery fire distribution systems.

The AN/GSA- 77 system, a much-improved version over its predecessors, weighs less than 250 pounds, is small (2 feet x 2 feet x 1 foot), and requires little or no maintenance.


The present defense acquisition radars (DAR) have evolved from the early warning radar, AN/TPS-1. This radar included only the essentials required to provide early warning infermation. Similar but not identical equipment, the SCR-602A, appeared in the military radar inventory during World War II. Later the AN/TPS-1B radar was designed. The addition of

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moving target indicator circuits to the AN/TPS-1 produced the AN/TPS-1D, a medium-power search radar designed to detect targets in excess of 290 kilometers. It was first employed by the Air Force and the Navy.

Subsequent issue of the AN/TPS-1D satisfied the requirement for long-range radars at battalion level in air defense artillery units. In 1957, further improvements were provided by more stable moving target indicator circuits, better vertical antenna coverage, and a better display system which changed the nomenclature to AN/TPS-1G.

To make the AN/TPS-1D and AN/TPS-1G radars more compatible with unit mobility, they were packaged in a metal shelter and assigned a new name, electronic search central AN/GSS-1 (fig 43). This shelter contains, in addition to the radar, radio and telephone facflities, IFF equipment, and a manual plotting board. The shelter can be mounted on a 2.5-ton truck and can serve as an emergency battalion AADCP. When the larger 11- by 40-foot tripod-mounted antenna is provided with these radars, the assembly becomes electronic search central AN/GSS-7 (fig 44).

(figure 43 - a truck mounted shelter with radar antenna on top, antenna is maybe 5 feet by 20 feet, 4 steel poles between the ground and shelter appear to give some stability - is not included in this conversion)

Figure 43. Electronic search central AN/GSS-1.

Concurrently, the requirement for a radar with increased range for ARADCOM units resulted in modification of these radars to provide a fixed early warning radar, the AN/FPS-36. This radar employs the 11- by 40-foot antenna, which, with receiver changes, improves the reception of radar returns and extends the range coverage.

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(figure 44 - a very large antenna - is not included in this conversion)

Figure 44. AN/GSS-7 antenna.

(figure 45 - a very large antenna - is not included in this conversion)

Figure 45. AN/FPS-61 radar.

Further modification of the AN/FPS-36 resulted in the AN/FPS-56 radar. This radar consists of two AN/FPS-36 radars that transmit and receive through a common antenna, thus providing two operating channels and increased reliability. The addition of ECCM capabilities converted the AN/FPS-56 radar to the AN/FPS-61 ( fig 45).

The modification of the AN/TPS family of radars did not cease with the development of defense acquisition radars. These same radars are the basis for the development of the alternate battery acquisition radars discussed in chapter 3.

If you have comments or suggestions, Send e-mail to Ed Thelen

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Updated October 31, 1997