The United States Air Force Space Command (AFSPACECOM) is tasked with providing warning of strategic and tactical ballistic missile warning. Although the threat of such a missile attack is more remote than ever, many missiles still remain in various stages of operational capability throughout the world.
Therefore, USAF continues to operate radar and satellite systems to provide early warning and transmit critical data to senior decision makers in the National Command Authority (NCA). The sensors employed to provide warning are:
• Defense Support Program (DSP):
This space-based system consists of satellites positioned about 22,300 miles above the equator. The satellites monitor areas known to have ballistic-missile launch capability along with large ocean areas. Satellite sensors detect the heat generated from a missile launch and transmit the data to ground stations that receive and provide analysis of the information. First launch of a DSP satellite was in the early 1970s.
• BMEWS: This radar system consists of 1950s-technology radars consisting of three large detection radars and a tracking radar located at three northern sites.
• Pave Paws: This system was developed in the mid-1970s to provide warning of a sea-launched ballistic missile threat. The system consists of a series of four sites located on the periphery of the continental United
States.
• PARCS: PARCS (Perimeter Acquisition Radar Attack Characterization System) consists of a single radar located at Cavalier Air Force Station, North Dakota. This single-faced,
phased-array radar provides warning
and data on ICBM and SLBM attacks. It entered its present role in 1976 when the radar was transferred from the US Army.
• Cobra Dane: A single-faced, phased-array radar located at Shemya AFB, Alaska. It collects data on ballistic missile launches to the Northwest and over the Pacific.
‘ Conventional Radars: Two conventional radars are located at Pirinclik Air Station, Turkey, to collect space and missile activity data and provide limited warning. One radar provides tracking data and the other provides detection.
Ballistic Missile Early-Warning System/BMEWS (AN/FPS-49)
The BMEWS consists of three radar installations located at Fylingdales Moor, England; Thule, Greenland; and Clear, Alaska. Each site has radars used to detect land-based ballistic missile attacks against the United States, to track objects in orbit, and to monitor other Russian rocket launchings.
Each BMEWS site has different radar
equipment. Fylingdales Moor has an AN/ FPS-49 surveillance and tracking radar.
Clear has an AN/FPS-92 tracking radar,
an update of the FPS-49, as well as three large AN/FPS-50 surveillance radars. All three sites had their data processing and tactical control capabilities updated in the early 1980s.
Fylingdales is under the command and control of the Royal Air Force; the other two sites are under the US Air Force
BMEWS
U.S. OOVKUNMl-’.NT DKl’AKl MUNI OF IJKFLNSI’1.
Space Command. All three are linked for data transfer between them.
The FPS-49 tracking radar has an 82-ft (25-m) parabolic dish housed in a 141-ft (43-m) diameter radome. Maximum range is approximately 2,700 nm (3,110 mi; 5,000 km), and the radar operates in
the B/C (UHF) band. The radar was
manufactured by RCA Corp.
The FPS-50 has a distinctive fixed parabolic-torus reflector that is 400 ft
(122 m) wide and 165 ft (50 m) high. It
operates in the B-band (425 MHz) at a peak power of 5 MW. Maximum range is
2,650 nm (3,052 mi; 4,910 km), and it
covers an arc of 160° and has an elevation of +3.5° to +7°. The radar was built by General Electric Co.
Thule had four FPS-50s and one FPS-49A that were recently replaced with a solid-state, phased-array system built by Raytheon Corp., which is similar to the AN/FPS-115 PAVE PAWS installation. The radar began operations in July
1987, and the older antennas were dismantled.
The more recent Thule radar has two phased-array faces, each covering 120°, in a structure that stands 92 ft (28 m) high. Its maximum range is approximately
2,850 nm (3,280 mi; 5,280 km), and its
beams can be elevated electronically
from +3° to +85°.
DEVELOPMENT •
The initial operational capability of the FPS-49/50 was in 1962; Thule’s phased array was in 1987.
The BMEWS is operated by the US Air
Force Space Command.
The Fylingdales FPS-49 was replaced by a phased-array system in the early 1990s that became operational on October 1, 1992. Raytheon won the US Air Force $166.8-million contract for full system upgrade at Fylingdales in June 1988. Unlike the Thule system, the Fylingdales radar has three faces and offers full 360° cover-
age. Each face of the array consists of 2,560 active elements and is capable of tracking up to 800 objects simultaneously. Since becoming operational, the new radar averaged tracking about 6,000 satellite tracks a week, compared to 2,000 a week with the older system.
The Alaskan BMEWS site was upgraded in the early 1990s to a dual-faced, phased array.
The former Soviet Union had argued that the Thule and Fylingdales Moor radars violated the 1972 Anti-Ballistic Missile (ABM) agreement’s provisions forbidding installation of ABM radars beyond a signatory’s national borders. The Reagan administration countered that the Thule radar can be upgraded because the modifications are based on technology not understood in 1972. When the Soviets admitted that their Phased-Array Radar (PAR) at Krasnoyarsk violated the ABM treaty, they also contended the two US radars were in similar violation.
PAVE PAWS (AN/FPS-115)
The AN/FPS-115 Precision Acquisition Vehicle Entry Phased Array Warning System (PAVE PAWS) radar is a large, solid-state-technology, phased-array radar system with the primary role of detecting and tracking Submarine-Launched Ballistic Missiles (SLBM). It is a part of the North American Air Defense Command (NORAD) early-warning system as well as. the Worldwide Military Command and Control System (WMCCS). These radars replaced the older FPS-85 and FSS-7 SLBM warning radars.
The four PAVE PAWS installations are located near the US coastlines. The first PAVE PAWS was erected at the former Otis AFB (now Cape Cod Air Force Station) , Massachusetts, and covers most of the Atlantic Ocean area. The second, at Beale AFB in California, watches the Pacific Ocean. The third and fourth—at Robins AFB, Georgia, and Eldorado AFS,
PAVE PAWS
U.S. GOVERNMENT DEPARTMENT’ OF DEFENSE
Texas—cover the southern US coast. Some overlap in coverage occurs with the four sites.
Each radar installation is a 10-story building covering 76,732 ft* (7,129 m*) with three faces that tilt 20° from the vertical. Triangular segments fill in the sides such that the base is six-sided and the top is triangular. Two adjacent faces contain flat, octagonal, phased-array antennas measuring 102 ft {31.1 m) across.
Each electronically scanned and steered antenna has the capacity to hold approximately 5,400 individual elements. The Otis AFB installation has 1,792 active elements in each face, and Beale 3,584 after an update. Robins and Eldorado can use all 5,354 elements. Two computers direct each of the PAVE PAWS and are housed in the same structures.
An often-cited measure of the radar’s capability is its ability to track a basketball-size object at distances up to 1,050 nm (1,200 mi; 1,931 km). This proves useful in its primary anti-Sea-Launched Ballistic Missile (SLBM) mission as well as in supporting the Air Force’s Spacetrack satellite tracking system.
DEVELOPMENT •
Initial operational capability at Otis AFB in 1979, Beale AFB in 1980, Robins AFB in 1986, and Eldorado Air Force Station in 1987. In February 1989, sources reported that the
PAVE PAWS near Robins AFB had to be shut down periodically to eliminate the risk of detonating explosives on military aircraft that land at the base.
VARIANTS •
PARCS (Perimeter Acquisition Radar Characterization System): Not a variant of PAVE PAWS but a predecessor that operates in the same band. Built to support the never-completed Safeguard anti-ballistic missile system installation at Grand Forks, North Dakota. Has one phased-array radar face with 110° coverage pointing northward and remains in service to supplement PAVE
PAWS. Compared to the PAVE PAWS,
PA2 RCS h2as a larger antenna (10,602.4 ft2/985 m2), a shorter pulse width (400550 microseconds), slightly wider elevation arc (1°-90°), and a longer operating
cycle (20-50%).
COMBAT EXPERIENCE •
None.
SPECIFICATIONS •
MANUFACTURER Raytheon
ANTENNA AREA 8,126.7 ft2 (755 m2)
BAND B (420-450 MHz)
COVERAGE
azimuth 240° elevation +3°/+85° RANGE approx 3,000 nm (3,455 mi;
5,560 km)
PEAK POWER PER ELEMENT 322 W AVERAGE POWER 64-290 kW
PULSE WIDTH 300-5,000 microsec
BEAMWIDTH
transmitting 2° receiving 2.2°
OPERATING CYCLE ll%-25%
Cobra Dane
The Cobra Dane is a large US phased-array radar located at Shemya AFB on Shemya Island in the Aleutian chain. It is used primarily for tracking objects in space and was formerly used to track Soviet missile test flights. In the flight-test tracking mode, Cobra Dane can follow 100 targets at once. As part of the early-warning network, the radar can provide tracking data on 200 targets, although this is not a major function. The computer, processing, and “back-end” radar equipment are being upgraded or replaced under a contract awarded in April 1990.
The single, circular, phased-array radar face is approximately 98 ft (30 m) in diameter and has about 35,000 elements, of which 15,000 are active. The radar faces southwest and covers an arc of 120°. The
Cobra Dane
U.S. GOVERNMENT DEPARTMENT Ol’1 DEFENSK
Cobra Dane’s Control Data Corp. Cyber 74-18 computer operates at 1 Million Instructions per Second (MIPS) and has a 131,000-word core memory. As part of the upgrade program, two Digital Equipment Corp. Vax 6000 series computers will replace the Cyber 74-18, one backing up the other. The DEC machines operate at 12 MIPS and have a main memory of 64 megabytes.
When upgrades were completed, the system improved its ability to catalog space objects from 5,000 separate objects to 12,000 initially and 15,000 if a growth option is exercised.
The Cobra Dane’s range for space
tracking is 25,000 nm (28,788 mi; 46,325
km). It is operated by the US Air Force Space Command.
DEVELOPMENT •
The Cobra Dane’s initial operational capability was in 1977. It was manufactured by Raytheon Co. In April 1990, the Air Force awarded a contract worth up to $83.3 million to Raytheon to upgrade the digital signal and data processing. Raytheon is responsible for systems engineering and integration as well as developing radar-related software. TRW developed the application software for real-time mission operations, test and training simulation, and off-line data analysis. Control Data is responsible for technical support services development, operating systems, and applications.
Over-the-Horizon Backscatter Radar (AN/FPS-118)
The AN/FPS-118 radar system consists of a transmitter and a receiver located approximately 100 miles (161 km) apart. The OTH-B uses emissions bounced off the ionosphere to acquire targets up to
2,000 nm (2,303 mi; 3706 km) away; its dependence on atmospheric conditions has been a source of concern, but the
OTH-B is the only ground-based system with such a range. Minimum range is approximately 500 nm (576 mi; 927 km); the radar is blind to targets less than 500 nm away.
The first installation in Maine is a trial version (known as the Experimental Radar System/ERS) constructed by General Electric and, although a part of the operational system, it is less capable than those that had been planned for the North Central and West Coast. It is in limited operational use and has been renamed the East Coast Radar System (ECRS); the three sectors together cover a 180° arc from 16H° to 196V&0, relative to true north.
There are 12 100-kW Continental Electronics/Varian elemental transmitters per 60° sector. The antennas can transmit in several different modes for surveillance and tracking. The emissions are received and processed by a 4,980-ft (1,518-m) receiver array at Columbia Falls.
DEVELOPMENT •
The Maine site was accepted by the Air Force Operational Test and Evaluation Center in April 1990; the West Coast site was transferred to the Air Force in December 1990. Subsequently, USAF decided to shut down the West Coast system but maintain the site with a skeleton crew and reduce operations to 40 hours per week at the East Coast site, saving an estimated $37 million per year.
The Alaskan site was planned for completion in 1995. The first contract for the North Central site was planned for awarding in 1991. Both systems were canceled in late 1990.
VARIANTS •
Preplanned Product Improvement (P3I) program began in FY1988 for the central US and Alaska systems, involving an upgrade of the system sensitivity. Hardware changes were also part of the program. The P3I was canceled when the OTH-B was cut back.
COMBAT EXPERIENCE •
In late 1987 the Maine OTH-B radar had its first successful operational use when it picked up two Soviet Tu-142 Bear long-range antisubmarine aircraft at a range of 912 nm (1,050 mi; 1,690 km).
SPECIFICATIONS •
MANUFACTURER General Electric
FREQUENCY 5-28 MHz RANGE
max 1,800 nm (2,073 mi;
3,335 km) minimum 500 nm (576 mi; 927 km)
EFFECTIVE RADIATED POWER 100 MW BEAMWIDTH 7.5° EAST COAST SITE OPERATIONS CENTER
size 32,500 ft2 (3,019 m2)
air-conditioning equipment
180 US tons (163 metric tons)
office 30 US tons (27
metric tons) power normal: 2,000 kW
standby: l,200kW
UPS for 15 min: 465 KV ampere
consoles 30 Aydin displays operators officers: 37
enlisted: 337
civilian: 13
support: 89
SOUNDER ANTENNAS
tower height
sector 1:130 ft (40m)
sectors 2-3: 148 ft (45m)
pole height sector 1: 34 ft (10 m)
sectors 2-3: 42 ft (13m) foundations sector 1: 2,430 ft3 (69 in3)
sectors 2-3: 1,161ft2
(33 m2)
TRANSMITTERS
power 100 kW each
Transmitter Antenna Bands
A 5.00-6.74 MHz
B 6.74-9.09 MHz
C 9.09-12.25 MHz
D 12.25-16.50 MHz
E 16.50-22.25 MHz
F 22.25-28.00 MHz
RECEIVEANTENNAS (MAIN ANTENNA) tower height
sectors 1-3 65 ft
(20m)
length sectors 1-3 4,980 ft
(1,518m)
number of elements
sectors 1-3 246
Seek Igloo (FPS-117/124)
Seek Igloo is a program to lower the operations and maintenance costs of the Alaskan early-warning radar network. The FPS-117 is part of the North Warning System (NWS) to replace the existing Distant Early Warning (DEW) Line, a series of bomber warning radars located along Canada’s northern border, 15 FPS-117 radars replaced 31 AN/FPS-19 and AN/ FPS-30 radars.
The FPS-117s have been mounted on existing DEW towers in Canada and Alaska, except for those at Baffin Island and two sites on the northeast coast of Labrador. The FPS-117 is a solid-state, three-dimensional, planar phased-array radar developed from the GE 592, an export-oriented, transportable variant of the AN/TPS-59 ground radar. The FPS-117 operates in the D-band and has a frequency bandwidth of 185 MHz. The radar scans electronically in elevation while rotating in azimuth. The radar requires no on-site personnel; maintenance is performed by three radar technicians who visit the site as necessary.
Unlike most radars, the FPS-117 has a distributed, redundant network of transceivers and power supplies connected directly to the antenna. Each transceiver requires relatively little power. Using distributed redundancy, the manufacturer claims higher reliability while retaining accuracy, range, and the ability to operate effectively in spite of heavy Electronic
Countermeasures (ECM) and environmental clutter. 44 row feeds and four column feeds constitute the surface of the antenna. Each row feed forms mono-pulse pencil beams with a linear, frequency-modulated waveform. Behind each row feed are the transistorized power generators, power modules (100-watt amplifiers), and receivers.
The transmitters have pulse-to-pulse frequency agility, being able to choose among 20 frequencies in a quasi-random manner. The transmitters are also capable of initiating pseudo-random Pulse Repetition Frequency (PRF) and pseudorandom beam positioning.
The receiver offers Moving Target Indicator (MTI) processing, Constant False-Alarm Rate (CFAR) processing, pulse compression, low sidelobes and sidelobe blanking, Doppler filtering for “look-down” situations, and automatic environment clutter rejection.
The FPS-124 is a cylindrical phased-array radar that is approximately 12 ft (3.66m) tall. It is cooled by 11 fans, which are the only moving parts in the system. FPS-124 is designed to be unattended, being monitored by a two-way link to satellites and having a mean time between critical failures of 4,000 hours (over 166 days). It will provide warning against small targets out to approximately 70 nm (81 mi; 130 km); coverage is 360°. The United States and Canada shared the approximately $640-million cost in a 60/40 ratio. Maintenance of the FPS-117 is contracted out to civilian firms.
DEVELOPMENT •
The Seek Igloo’s initial operational capability was in 1987. FPS-117 and FPS-124 developed by Unisys Defense Systems, McLean, Virginia. The 11 FPS-117s emplaced in Canada and four in Alaska are operational; four more were ordered in July 1991 for installation in Newfoundland, Nova Scotia, and British Columbia. The Unisys FPS-124 radar began Initial Operational Test and Evaluation (IOT&E) in the
summer of 1988; further testing took place in June 1989. A $326.5-million contract for 37 production FPS-124s was awarded to Unisys in October 1990. In May 1991, the NORAD agreement was renewed for five years.
Three FPS-117s are also used by Germany in the NATO air defense network, and the US Air Force installed two FPS-117s in the northern part of Iceland.
Two FPS-117s were ordered by Saudi Arabia as part of the Peace Shield program, and a total of 17 FPS-ll7s are planned. Two FPS-117 systems are part
of the $207-million Royal Thai Air Defense System (RTAD). RTAD, consisting
of sensor systems and 31 microwave stations, was designed, developed, and tested over four years by Unisys. The $43-million cost of the FPS-117s is part of the US Military Assistance Program (MAP) to Thailand. The RTAD became operational in January 1990.
South Korea and Italy announced in February 1990 that they had ordered seven FPS-117 systems at a total cost of $130 million. South Korea ordered three systems, bringing the number of FPS-117s to eight. Italy ordered four systems, making them the seventh NATO nation to use the FPS-117.
Turkey signed a $15-million contract in October 1991 for one FPSA117 and an option for two more systems. Other operators of the system include Great Britain, Belgium, and Canada.
SPECIFICATIONS •
MANUFACTURER General Electric
WEIGHTS
total 37,100 Ib (16,828kg)
transceiver group
30,000 Ib (13,608kg)
process and control
5,700 Ib (2,585 kg)
operation control
1,400 Ib (635kg)
DIMENSIONS
height 24 ft (7.32 m)
width 24 ft (7.32m)
BAND D POWER
effective radiated
125 MW total system use
70 kW max peak 24.75 kW
duty factor 16%
RANGE
max 200 nm (230 mi; 371 km)
minimum 5 nm (5.8 mi; 9.3 km)
MAX ALTITUDE 100,000 ft (30,480 m)
ELEVATION -6°/ + 20°
PULSE WIDTH
short range 51.2 microsec
compressed to
0.8 microsec long range 409.6 microsec
compressed to
1.6 microsec
AZIMUTH 360° ACCURACY
range at 200 nm
0.25 nm (465 m) azimuth 0.18° altitude at 100 nm
less than 3,000 ft (914m) elevation at 160 nm
less than 6,000 ft
(1,829m)
MEAN TIME BETWEEN FAILURE (MTBF)
l,076hr
MEAN TIME TO REPAIR 30 min
PERIODIC MAINTENANCE TIME PER YEAR 35 hours
Relocatable Over-the-Horizon Radar (ROTHR/ TPS-71)
The AN/TPS-71 ROTHR is a tactical ionospheric backscatter radar system in development for the US Navy and similar in concept to the US Air Force AN/FPS-118 Over-the-Horizon-Backscatter (OTH-B) strategic early-warning radar system.
The ROTHR system consists of the transmitter and receiver sites. The transmitter installation uses two antenna arrays and a power generator. Each of the log periodic antennas uses 16 radiating elements. Each element or “curtain” consists of a series of dipole radiating elements hung at different lengths on a catenary (i.e., a wire suspended from a tower). Each dipole element is tuned to a specific frequency. The antennas transmit on a selected frequency using the arrays, which radiate throughout either the low or high band.
Power for the ROTHR is provided by generators housed in 10 shelters. Each generator uses four 5-kW amplifiers, producing up to 20 kW of power each. The amplifiers allow the generators to provide power for specific antenna elements. Power is fed unevenly to the antenna, with the outer elements receiving less power than the central elements, which receive the full 20-kW capacity. The antenna produces low sidelobes because of this gradual reduction of power. The lowered sidelobes reduce backscatter clutter, enhancing target detection. The receiving unit uses a single high-gain antenna with 372 dual monopole elements arranged in two rows that are 14 ft (4.27 m) apart. Each element pair uses a receiver to digitize incoming signals. The signals are then passed to a processor via a fiberoptic link. The processor forms the signal into a narrow receiving beam using digital beam-forming techniques. Targets are distinguished from clutter by their movement. Four computers are used to track detected targets. The system uses Digital Equipment Corp. Vax 8600 computers, which were to be replaced by newer Digital 6400 computers. Data is displayed in the Operations Control Center (OCC). ROTHR uses six interactive color workstations. Each workstation uses two raster displays and plasmas-touch screen controls. Frequencies available for use and locked-out frequencies can be displayed on a management spectral display system.
ROTHR differs from the strategic early-warning OTH-B system in that it has a tactical mission. The system is used todetect ships and aircraft beyond the horizon, supplementing surveillance by E-2C Hawkeye and E-3 AWACS airborne early-warning aircraft. The ROTHR enabled the Navy to detect former Soviet Union naval bombers and surface ships at a range up to 1,302 nm (1,500 mi; 2414 km). The total area that the2 ROTHR can monitor is 1.23 million nm2 (1.63 million mi2; 4.22 million km2). This area is scanned in 176 sectors called Dwell Information Regions (DIR). DIRs are not uniform in size but vary according to distance from transmitter site. The system can concentrate on a specific DIR, or scan all DIRs, returning to specific ones as needed. The system may be moved but is not truly mobile. A system may remain at a site for periods of over one year. A ROTHR site may be prepared ahead of deployment and needs little maintenance. All antennas, operations control equipment, transmitters, and power sources can be moved to a site if required. The ROTHR is bistatic; its transmitting and receiving sites are separated by 50100 nm (58-115 mi; 93-185 km), with the OCC colocated with the receiving site.
DEVELOPMENT •
A prototype ROTHR was tested in Virginia and was moved to Amchitka Island in Alaska in 1989 to be the first operational ROTHR system. While in Virginia, the system fully tracked 24 of 25 ships in one region and partially tracked the 25th ship. It also demonstrated a 95% availability rate over a continuous two-week test period. The system’s accuracy is classified, but the Wide Area Surveillance Systems program manager reported late in 1989 that the system had tracked an aircraft from flight through landing and only lost track as the aircraft entered a hangar. At least eight sites have been planned, including three on Guam, one in Hawaii, one in Virginia, and one in Europe.
The system’s initial operational capability was in 1989. An engineering
prototype was introduced in April 1984 and the operational evaluation in April 1989. Raytheon won a $273.7-million contract for the first three ROTHR systems in January 1990. The contract includes an option for another system and support equipment,
SPECIFICATIONS •
MANUFACTURER Raytheon
ANTENNA ARRAY
transmitting antenna
length: 1,200 ft (365.8m)
receiving antenna
length: 8,400 ft (2,560 m)
height, monopole
element: 19ft (5.79m)
range max: 2,000 nm (2,303 mi;
3,706 km)
minimum: approx 500 nm (576 mi; 927 km)
AZIMUTH COVERAGE 60° TRANSMITTING ANTENNA FREQUENCY
low band 5-12 MHz
high band 10-28 MHz MAX POWER 20 kW per generator AMPLIFIER POWER 5 kW each
Cobra Judy (SPQ-11)
The US AN/SPQ-11 Cobra Judy is a solid-
state, phased-array radar fitted in the USNS Observation Island (T-AGM 23) operated in the Pacific. The operation monitors the exo- and endo-atmospheric portions of Russian and Chinese ballistic
