GE AN/FPQ-16 Enhanced Perimeter Acquisition Radar Attack Characterization System
The distinguishing feature of Cavalier Air Force Station has several subsystems of the EPARCS:
Not visible is the underground PAR Power Plant connected by a Personnel and Equipment Tunnel of 130 ft long (40 m) to the PAR Building, which is a 128 ft high (39 m) reinforced concrete structure hardened against nuclear detonation effects (airflow/pressure, thermal radiation, and EMP). The array face inclined 25˚ from vertical is surrounded by a wall 7 ft thick (2.1 m), and the base is 200 ft square (61 m) × 11 ft thick (3.4 m)
The GE AN/FPQ-16 Enhanced Perimeter Acquisition Radar Attack Characterization System (EPARCS) is a USAF combination "Q" system that "monitors and tracks over half of all earth-orbiting objects" (>20,000 tracks per day). EPARCS has "the most powerful[specify] of five missile warning and space surveillance radars operated by the 21st Space Wing [cf. those at] Clear AFB, [sic] Alaska, Beale AFB, Calif., Cape Cod Air Station, Mass., and Thule AFB, [sic] Greenland." The "PAR I" Perimeter Acquisition Radar was fielded during the United States Army's Safeguard Program for ballistic missile defense on one of the sites of the Stanley R. Mickelsen Safeguard Complex. The system and its station transferred to the USAF in 1977 (PAR II planned for Montana was never built.)
Perimeter Acquisition Radar
The Perimeter Acquisition Radar (PAR) could originally acquire an object the size of a basketball 24 cm (9.4 in) at 3,300 km (2,100 mi), e.g., a warhead from a submarine-launched ballistic missile launched in Hudson Bay; and the resolution at similar range was enhancable to less than 9 cm (3.5 in). Original PAR equipment included:
- a Beam Forming Network (BFN), the phased array of 6888 elements—originally 6144 GE crossed-dipoles of beryllium copper—also had "6144 Phase shifters<!-, the 6144 active folded dipole antenna elements -->...plus the  dummies".) The antenna elements "inclined 45 degrees toward the array face", a "phase shifter platform" was inside of the PAR Building's sloped wall, and a "microstrip high power UHF phaser" was later developed for the BFN.
- a Beam Steering Computer with Sensor Control System Program  for steering/controlling the BFN
- a Beam Power Supply with Power Supply Control set 
- a duplex Digital Data Group for timing signals in the electronic equipment
- a Radar Maintenance Console to allow monitoring of antenna beam shape
- a Radar Return Generator for simulation of intermediate frequency (IF) signals into the signal processor's IF input.
In addition to the PAR, the system includes a 14 megawatt electricity system with five, 16 cylinder diesel/natural gas Cooper Bessemer engines for 5 GE generators. A small "antenna measuring radar" with radome was on the building's top (later replaced by a satellite communications antenna.) EPARCS also includes an electrical substation and heat sink.
The PAR Data Processor--with Central Logic and Control including redundant Processor, Program Store, and Variable Store units—provided missile/satellite track data for communications equipment to transfer to NORAD, etc. and was listed as a separate procurement item from the Perimeter Acquisition Radar by the Congressional Record. For the Advanced Data Communication Control Procedure, the ADCCP communication processor invented in the 1980s by Lynn O Kesler "translates messages between" the PARCS data transmission controller and Cheyenne Mountain.
BMEWS AN/FPS-50 radar fans were scanning for Cold War ICBMs by FOC in October 1961, the same month the USSR launched/detonated the 1st armed SLBM on the 20th. On July 31, 1962, NORAD recommended a radar to close the BMEWS gap between the Alaska and Greenland stations for low-angle missiles (i.e., below the 15-65˚ elevation for which BMEWS was designed.) The WSMR's Multi-function Array Radar (MAR I) for Nike Zeus anti-ballistic missile testing was constructed beginning in March 1963 and "was the first phased array radar developed by the US Army"—the next generation phased array Common Aperture Multi-function Radar (CAMAR) at Kwajalein Island was never completed. In 1965, "a limited NIKE-X deployment was proposed" and resulted in a 12-month "definition and selection" period for the Perimeter Acquisition Radar, a successor to MAR I. PAR was specified to use a TWT "scaled [up] model of the proven [MAR] L-band design" and chiirp pulse components "available from the ZEUS Acquisition Radar" ("by October 1966, Bell Laboratories had established the PAR requirements".) After proposals from contractors were evaluated in December 1966, General Electric was contracted to conduct Phase I that included specifying detailed requirements (completed by April 1967, the month when UHF was selected to mitigate "nuclear blackout" effects--"SPARTAN-Induced PAR Blackout".) In 1967 the planned PAR mission was changed from "an early warning system to one that could provide tracking for the SPARTAN [missile] intercept role."
The decision to deploy was in September 1967, and detailed design of the nuclear-hardened building began in June 1968 (a 1969 Congressional bill funded procurement of the PAR and its data processor.) A Hardness Verification Test Program confirmed the PAR antenna elements could "withstand nuclear attack with minimal degradation of electrical and mechanical properties", and the research and development PAR was planned for an operational site "where it would become part of the operational system after the R&D phase was completed". The "SENTINEL Area Defense Plan" to protect city/industrial areas scheduled a 1st deployment at the Boston area. In March 1969 the "SENTINEL Area Defense System" was reoriented to defending ICBM sites, and a 1969 "Construction Foundation Report" was prepared by the Army Corps of Engineers (in May 1969, Nixon asked for funding to procure 10 more sites).
Safeguard Anti-Ballistic Missile System
The Safeguard Anti-Ballistic-Missile System had become the United States' planned ABM program by July 8, 1969 ("Nixon's Safeguard" cf. "Johnson's city-oriented Sentinel system"), and North Dakota was chosen for Safeguard's emplacement of the PAR "Limited Engineering Development Model" (LEDM) which through May 1971 was used for verification at a development facility[which?] in Syracuse, New York. Following site procurement and terrain preparation, 1970 contracts were let for PAR-1 in North Dakota (April 1) and PAR-2 in Montana (May), and a site protecting Whiteman Air Force Base missiles was to be completed by July 1975. Only Grand Forks had facilities (road & rail siding) by May 18, 1970; and as late as August 31, 1970, twelve PARs were planned in the United States (cf. the 1970 conceptual "Hardsite" ABM system with "radar-computer units...so numerous [to] be unattractive for enemies to...knock out --and a 1971 plan to make ABM defenses mobile.) A Senate vote in August 1970  approved the Whiteman and Warren Air Force Base sites  (the 3rd site was under construction by May 1, 1971. Assembly/testing of the PAR array in North Dakota (for the Grand Forks ICBM field and partial coverage of the Dakotas-Colorado fields) began during 1972 with Donald Good as the " Lead Antenna Engineer on the installation team". By August 19, 1972, Montana construction was being dismantled 6 due to the SALT I Anti-Ballistic Missile Treaty signed on May 26, 1972. An initial radar alignment was completed in August 1973 using measurements from the separate "antenna evaluation radar" used while a test object reflected a lone beam from an array element. PAR software was developed at the Tactical Software Control Site at Madison, New Jersey; and in August 1973 the 1st satellite was tracked. "The entire facility was handed over to the U.S. Army Safeguard Command on September 3, 1974" (missiles arrived Spring 1975.) The site was netted with the complex' "Missile Launch Area" with its Missile Site Radar, as well as the Cheyenne Mountain Ballistic Missile Defense Center, PAR Initial Operational Capability was in April 1975, and the entire Mickelson complex "became operational on October 1, 1975".
"The House of Representatives voted on October 2, 1975, to deactivated the Grand Forks, North Dakota, ABM base because of Safeguard's technical limitations [and] in 1976, after spending $6 billion, Congress cut off funds…" (the Mickelson complex "was inactivated on February 10, 1976.") "The PAR was leased to the U.S. Air Force (USAF) in September 1977" and its mothballed radar station "was handed over to the Air Force in October 1977". Initially the USAF designated the site's system of systems as the Concrete Missile Early Warning System (CMEWS)[specify] (namesake of the nearest community) but later renamed it the Perimeter Acquisition Radar Attack Characterization System (PARCS). Assigned in 1983 to pass "tactical warning and attack assessment data" from the PARCS to Cheyenne Mountain was the 1st Space Wing's Detachment 5 (1986 10th Missile Warning Sq, 1992 10th Space Warning Squadron).
The Enhanced[specify] Perimeter Acquisition Radar Attack Characterization System (EPARCS) was established by 1989 (the "AN/FPQ-16" had become a Major Defense Acquisition Program) and was planned to be closed in September 1992. Instead in 1993, ITT Federal Services took over operations and maintenance from PRC, Inc., and a narrative about the radar was published by Earth Technology Corporation. Since receiving a $6.7M operations, maintenance, and logistics contract in 2003, BAE Systems has maintained the radar and other EPARCS subsystems (an extension was granted in 2012).
Deployment of the Solid State Phased Array Radar System (SSPARS) replaced BMEWS and upgraded AN/FPS-115 PAVE PAWS with solid state power amplifiers (e.g., with a 1987 AN/FPS-120 at Thule); but for the EPARCS with "obsolete radar technology" in 1994 and for Cobra Dane in Alaska, L-3 Communications was contracted to supply 2004-9 TWTs. Late in the 2000s decade the USAF began upgrading SSPARS to use Boeing AN/FPS-132 Upgraded Early Warning Radars (UEWR)—e.g., replacing the 1992 AN/FPS-126 at RAF Fylingdales. In 2010, a committee assessed the status of the EPARCS  and by February 1, 2012, "the USAF embarked on a modernisation programme for its AN/FPQ-16" as with the Clear AFS "UEWR modernization [began] in FY12" for replacing Clear's AN/FPS-123.
|phased array under construction with equipment in front (without antenna measuring radar)|
|1972 PAR Building (TIME magazine)|
- Nuclear weapons and the United States
- PAVE PAWS
- Ballistic Missile Early Warning System
- Missile Defense Alarm System
- Defense Support Program
- United States Space Surveillance Network
- Historic American Engineering Record (HAER) No. ND-9-P, "Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma vicinity, Cavalier County, ND"
- Lewis, George, ed. (April 12, 2012). "Space Surveillance Sensors: The PARCS (Cavalier) Radar". MostlyMissileDefense.com. Retrieved 2014-03-25.
- Kessler et al., “Ground Radar Detection,” pp. 137-138 (cited by http://mostlymissiledefense.com/2012/04/12/parcs-cavalier-radar-april-12-2012/ which has the quotation)
- "United States of America -- PARC Life". ChainHomeHigh.WordPress.com. November 28, 2012. Retrieved 2014-03-26.
- Harkavey, Robert E (1989). Bases Abroad: The Global Foreign Military Presence. Oxford University Press. Retrieved 2014-03-25. "Systems used primarily for early warning...Enhanced Perimeter Acquisition Radar Attack Characterization System (EPARCS)"
- "10th Space Warning Squadron". Peterson Air Force Base. Retrieved August 2012.
- Kuhn, Tom (March 1999). "On The Lone Prairie". Airman Magazine. Archived from the original on July 14, 2007. Retrieved March 2013. "26 American and two Canadian military members assigned"
- "Chapter 8: Perimeter Acquisition Radar" (report), ABM Research and Development at Bell Laboratories, retrieved 2014-03-15, "transistors of reasonable yield, high performance, and reliability were finally delivered by Texas Instruments" (text-searchable version available at AlternateWars.com)
- Good, Donald ("Oct 12, 2012"). "Cavalier Air Force Station in ND marks 35 years". Topix.com. Retrieved 2014-03-25.
- tbd, Mark (2011). "Perimeter Acquisition Radar (PAR), Concrete, ND" (trip report). Cold War Tourist webpage. Retrieved 2014-03-19.
- Figure 8-9 (image & caption), pp. 8–11 of Chapter 8: Perimeter Acquisition Radar
- Bonham, Kevin (January 10, 1993). "Cavalier Air Force Station: What does the future hold?" (newspaper images at SRMSC.org). Grand Forks Herald. pp. 1C–3C. Retrieved 2014-03-25.
- (Congressional Record -- Senate) Safeguard Anti-Ballistic-Missile System (Report). July 8, 1969. http://www.mocavo.com/Congressional-Record-Volume-115-7/423620/952. Retrieved 2014-03-25.
- 1962 NORAD/CONAD Historical Summary, July-December
- "Multi-function Array Radar I (MAR-I)". WSMR-History.org. Retrieved 2014-03-26.
- http://news.google.com/newspapers?id=lSYxAAAAIBAJ&sjid=wQEEAAAAIBAJ&pg=5775%2C1110247 http://news.google.com/newspapers?nid=1978&dat=19700901&id=23UiAAAAIBAJ&sjid=QqwFAAAAIBAJ&pg=958,90101 http://news.google.com/newspapers?nid=1842&dat=19700901&id=pycsAAAAIBAJ&sjid=H54FAAAAIBAJ&pg=3670,23360 http://news.google.com/newspapers?nid=1129&dat=19700901&id=x9cNAAAAIBAJ&sjid=3WwDAAAAIBAJ&pg=7280,10916
- Godfrey, Jim, 2d Lt (10SWS) ("2/2/2012"). "Cavalier Air Force Station: Instant to Watchful Instant". Peterson.AF.mil. Retrieved 2014-03-25.
- employee(s) of Teledyne Solutions, Inc (2003) (Cultural Resource Management Plan). (Report). US Army SMDC. http://gsaauctions.gov/ATTACHMENT/REGNF/FTWOR713001005/Cultural%20Resource%20Management%20Plan%202003.pdf. Retrieved 2014-03-25. "Perimeter Acquisition Radar Building Personnel & Equip Tunnel PAR Power Plant Limited Area Sentry Station Heat Sink Fuel Oil Pump House Electrical Substation Waste Stabilization Ponds Water Storage Reservoirs Community Center Gymnasium Limited Area Sentry Station Resident Engineer’s Office Fire Station Bachelor Officer’s Quarters Bachelor Enlisted Men’s Quarters Controlled Area Sentry Station Fresh Water Pump House Industrial Building Ballfield Helipad Safeguard Period Roads"
- Godfrey, Jim. "Cavalier Air Force Station: Instant to Watchful Instant". Peterson Air Force Base. Retrieved August 2012.
- "BAE Systems Awarded $60 Million in U.S. Air Force Contract Extensions to Maintain Space Radar and Telescope Systems". BAE Systems. November 27, 2012. Retrieved March 2014.
- "Fylingdales". Raytheon.co.uk. Retrieved 2014-03-08.