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- A -
Army Air Defense Operations Center. Part of the MSR's tactical operational center located on the second floor of the MSCB, it provided a link with other air defense operations. More information.
Anti-Ballistic Missile; a defense against ballistic missiles.
Ancillary Room
Actually 2 MSR level 1 rooms: 130 (transmitter cooling room), 131 (oil pumping room). Contained equipment for the purification, filtering, circulation, and heat exchanging of the high purity water, dielectric oil, and dielectric gas (SF6) used by the transmitter. More information.
Anechoic Chamber
An anechoic chamber (an-echoic meaning non-echoing or echo-free) is a room designed to stop reflections of either sound or electromagnetic waves. There were four such chambers in the MSR: rooms 401, 402, 403, 404, which held the antenna feed horn equipment behind each of the four phased array antennas. Also called the RF (radio frequency) chamber. Described by Ves Fulp as "the largest microwave oven in the world." More information.
Antenna Face Switches
Under software control, this bank of three high power RF switches connected the combined output of the MSR klystrons to one of the four antenna faces. More information.
The U.S. Air Force official name for the PARCS radar (formerly the Safeguard PAR). More information.
Area Defense
Long range destruction of incoming re-entry vehicles before they have re-entered the atmosphere (exoatmospheric). This technique can be used to protect a large geographical area, thus the term "area defense". See Terminal Defense. More information.
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- B -
Bird Screens
Two 'holes' in the rear wall of the PAR building that provided fresh air intake and air exhaust for the building. The upper air intake, on the fifth level, incorporates a plenum chamber as does the lower air exhaust, located on the second level mezzanine. The air intake led to equipment in the CBR filter room. Photo.
Ballistic Missile Defense Center. Safeguard central command center. More information.
Ballistic Missile Defense Operations Center. Located on the second floor of the MSCB, it provided the major tactical control of the Safeguard system. It contained the Tactical Control Consoles for the Tactical and Assistant Tactical Control Officers and the Operations Officer. At the Tactical and Assisstant positions were two sets of key control devices which had to be enabled simultaneously by the two officers in order to allow the system to engage targets. This was part of the Nuclear Surety provided by the system.
More information (1). More information (2).
Beneficial Occupancy Date. The construction completion date.
Beam Steering Computer. From steering angle instructions, the BSC calculates the phase setting for the phase shifter in each MSR antenna array element.
Buttoned Up
Prepared for nuclear attack. This included closing of all blast doors and sealing via pneumatic gas seals in the doors, activating the decontaminated air supply (CBR filtered), and switching to locally generated power.
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- C -
Controlled Area Sentry Station. An access control point for a controlled area. More information.
Cathodic protection
See Grounding Counterpoise.
Chemical, Biological, Radiological. The hardened SRMSC structures had facilities to prevent contamination by these biohazards while "buttoned up" during a nuclear attack.
Central Logic and Control Translator. A programming language and compiler used to write the application software for the Safeguard data processing system. More information.
Central Logic and Control. The Safeguard data processing hardware system. More information.
Concrete Missile Early Warning System. Initial name given to the Safeguard PAR after takeover by the U.S. Air Force in 1977. More information.
Along with the surge resistor, the crowbar's primary purpose was to protect the MSR's klystrons from being destroyed by internal arcing or other malfunctions. Using a vacuum spark gap, the crowbar fired in case of TWT arcing, interlock operation, or other faults requiring rapid removal of high voltage. More information.
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- D -
Digital Control Group. Consists of two redundant DCU's. Provides the interface between MSDP and analog parts of radar.
Digital Control Unit. Provides the interface between MSDP and analog parts of radar. Two redundant DCU's make up the DCG.
DDA <$
Digital Data Amplifier. Part of the MSR beam steering system, there was a DDA for each antenna element (phase shifter). More information.
Data Processing System. The CLC hardware, software, and peripheral devices. More information.
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- E -
Exclusion Area Sentry Station. An access control point for an exclusion area. More information.
Electronic Counter Measures. To jam or confuse transmissions.
Exercise Control Unit. Digital interface equipment between the CLC and radar analog hardware used to facilitate simulation of a threat environment.
Electrical Distribution Center. Hardened, underground facilities in the launch areas that provided regulated and unregulated electrical power for the missiles and for utility functions. More information.
Electromagnetic pulse. A large burst of electromagnetic energy released by a nuclear detonation.
Equipment Rreadiness Center. Part of the PAR and MSR tactical operational centers, it consisted of an Equipment Readiness Console and large automatic status display panels for all major equipment areas. Photo <$,   More information.
A brand of neutral grain spirit that is commonly added to a variety of other drinks, such as soft drinks, energy drinks, fruit juice, and iced tea. It was also used as a solvent to clean burn/arc marks off ceramic components of the MSR transmitter. More information.
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- F -
FAR Test Antenna
There were two of these test antennas mounted on towers located on opposite sides (WNW and ESE) of the MSCB (MSR pyramid). They were used to measure and evaluate the MSR's four phased array antennas at far-field range, where the antenna under test (MSR array) is placed in the far-field of a range antenna (FAR test antenna). Typical antenna parameters measured are gain, radiation pattern, beamwidth, polarization, and impedance.
Photo 1, Photo 2 (labelled "Test Tower #1" and "Test Tower #2"), Photo 3, Photo 4, Photo 5.
Ferrite Switches
See Antenna Face Switches.
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- G -
Grounding Counterpoise
An underground grid located at the MSR, PAR, and the four RSL's. Also known as the "Grounding and Cathodic Protection System," its purpose was to counter the electrical surges generated by a nearby nuclear detonation. More information (item f).
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- H -
H Building
Located between the admin and family housing areas, this building was shaped like the letter H. During construction, the Corps of Engineers used it as their headquarters. After construction was completed and the site activated, the admin building became the headquarters and the H building was used for general office space (housing office, re-enlistment office, print/copy service, etc.). Photos (A08-A09).
Historic American Engineering Record. HAER documents were prepared about the SRMSC as part of the process of placing the complex on the National Register of Historic Places. See References for more information.
Heat Sink
Facility to provide cooling of PAR and MSR components while "buttoned up" during a nuclear attack. Water for component cooling was re-circulated through an underground storage cavern where its heat was dumped. Photo (B21).
Hercules Tracker
Nike Hercules target tracking radar that was installed on the roof of the PAR building to aid in alignment of the phased array radar.
High Level Waveguide Switches
Controlled the output RF power from each klystron. These outputs could be (a) combined and fed to the antenna (the normal condition) or (b) fed into high-power dummy loads (one or both klystrons). Also called the "kludge". More information.
High Level Transmitter. The driver and final stages of the MSR transmitter; furnishes the RF energy to the antennas via two klystrons (twystrons). See LLT. More information.
Human Reliability Program (U.S. Air Force). The Air Force's equivalent to the Army's PRP.
High Voltage Power Source. Provided power supply for microwave generation equipment that powered the radar systems at the PAR and MSR. More information.
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- I -
Intercontinental Ballistic Missile. More information.
Intermediate Frequency.
Input Output Controller. Controlled the transfer of data between the CLC and its peripherals.

Initial Operational Capability. The first date on which a system is deemed operational.
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- J -
- K -
Kirk Key System
A keyed safety interlock system for the protection of personnel and equipment. Primary use was in MSR transmitter areas. Several diagrams can be found in the miscellaneous section of the MSR transmitter photo gallery.
See High Level Waveguide Switches.
An electron tube used to generate or amplify electromagnetic radiation in the microwave region by velocity modulation. Klystrons provided the microwave energy used by the MSR radar system. (Also see twystron.) More information.
Klystron Hat
A tank-like shield over the water cooled collector portion of the klystron. Located on the platform above each of the two klystron tanks, the "hat" weighed approximately 6,000 pounds and was constructed of 3/4 inch lead with a 1/4 inch stainles steel liner to provide X-ray protection. More information.
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- L -
Launch area antenna. Located adjacent to each missile launch cell, the LAA's were used for radar communication with the missiles at the MSR complex prior to launch (while they are still in their underground silos). More information (photo 031).
Limited Area Sentry Station. An access control point for a limited area. More information.
Launch Area Utility Tunnel. Connected the MSR/MSCB/MSPP underground complex with the MSR missile launch area to provide power and other utilities required at the launch area. More information (1). More information (2).
Low Level Transmitter. The exciter and buffer (TWT) stages of the MSR transmitter that drive the high level transmitter. See HLT. More information (in the HLT descriptions).
Launch Preparation Equipment Chamber. Part of the underground Sprint launch station. Diagram of the Sprint launch station.
Launch Preparation Equipment Vault. The lower of two 11.5 x 9 ft vaults that were part of the underground Spartan launch station. (Also see MEEV.) Diagram of the Spartan launch station.
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- M -
Maintenance and Diagnostic Subsystem. Test equipment and software that supported digital equipment maintenance. More information.
Missile Direction Center. The MSR site and its remote launch facilities.
Mechanical & Electrical Equipment Vault. The upper of two 11.5 x 9 ft vaults that were part of the underground Spartan launch station. (Also see LPEV.) Diagram of the Spartan launch station.
U.S. land based intercontinental ballistic missile (ICBM). More information.
Missile Site Control Building. The structure that housed the Missile Site Radar (MSR) and associated underground radar, command/control, and data processing facilities. More information.
Missile Site Data Processor. The MSR DPS system located on the second floor of the MSCB. More information.
Missile Site Power Plant. The hardened underground facility that provided stand-alone power and other utilities required to operate the MSR battle management systems. More information.
Missile Site Radar. A high capacity, multi-faced phased array radar used for ICBM re-entry vehicle target tracking and defensive missile tracking and guidance. Term also used to refer to the entire MSR complex. More information.
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- N -
No Lone Rule
See Two Man Rule.
North American Air Defense Command. This U.S. Air Force installation located within Cheyenne Mountain in Colorado housed the Safeguard BMDC (Ballistic Missile Defense Center). (Now called the North American Aerospace Defense Command.) More information.
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- O -
- P -
Perimeter Acquisition Radar. A large, northward facing single-faced phased array, this radar was the long range "eye" of the Safeguard system. Its purpose was to detect incoming ICBM re-entry vehicles as they passed over the north pole. More information.
PAR Building (the structure that housed the PAR and associated equipment).
Perimeter Acquisition Radar Characterization System, sometimes also referred to as the Perimeter Acquisition Radar Attack Characterization System or the Perimeter Acquisition Ranging and Characteristic System. The U.S. Air Force uses the PARCS name for the former Safeguard PAR since it is now part of the Air Force early warning and space track system. More information.
Perimeter Acquisition Radar Operations Center. Contained the tactical command and control group equipment required to control the PAR system.
Perimeter Acquisition Radar Power Plant. The hardened underground facility that provided stand-alone power and other utilities required to operate the PAR surveillance systems.
Personnel, Equipment, and Utility Tunnel. Connected the MSR/MSCB and the LAUT to the missile site power plant (MSPP). Its lower level provided access to the underground complex for personnel and equipment via the connecting entrance tunnel. Its upper level furnished the MSCB and launch area (via the LAUT) with necessary utilities (electrical power, cooling water, high purity water, hot water, nitrogen, ventilating air, and compressed air). More information.
Phased Array
A high capacity radar system that can simultaneously track a large number of targets. The beam is steered electronically rather than mechanically by using a computer to continuously vary the phase of the radar signal fed to an array of identical antenna elements.
Personal Reliability Program (U.S. Army). All Army personnel involved with nuclear weapons had to be members of the PRP. More information.
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- Q -
Q-channel antenna
The smaller antenna array located to the lower right of each of the four main MSR arrays. Its purpose was to reject or "blank" signals received on the array sidelobes (portions of the antenna response pattern not contained in the main beam). Photo (B14).
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- R -
Radio Frequency.
Radio frequency interference. Some sources of RFI are electronic equipment, lightning, and nuclear detonations.
Remote Launch Operations Building. The hardened underground structure that provided the operational facilities at each of the four RSL's (Remote Sprint Launch Sites). More information.
Remote Sprint Launch site. These were arrayed around the central MSR complex at roughly northeast/northwest/southeast/southwest locations. More information.
ICBM Re-entry Vehicle containing the nuclear warhead(s). These were the targets that Safeguard was designed to destroy.
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- S -
Adjutant / administration officer.
Intelligence officer.
Operations / training officer.
Supply / logistics officer.
Safeguard Communications Agency. SAFCA provided the communications network that tied the various Safeguard sites into a single co-ordinated system. More information.
Safeguard Command. The Army command that operated the SRMSC system.
Safeguard System Command. The Army command with responsibility for construction and activation of the SRMSC.
Safeguard Systems Evaluation Agency.
Sally Port
A double gate at a sentry station providing access control to a restricted area. Both "vehicle" and "man" versions were used. Originally used in describing fortifications for castles, towers, etc. meaning "a discreet exit which allows the defenders to 'sally forth' and engage the attackers." More information.
Sulfur hexafluoride (SF6) was used as a gaseous dielectric medium in all of the MSR's high power waveguide runs between the klystron output windows and the four antenna feed horn windows located in the anechoic chambers. More information.
The portion of an antenna response pattern which is not contained in the main beam. (See Q-channel antenna.)
U.S. Army Space and Missile Defense Command. Maintained the Mickelsen complex in caretaker status.
Safeguard Nike-X, the CLC assembly language. More information.
Security Operations Control Center. The facility that housed alert teams and the console used to monitor alarms, closed circuit television monitors, and other security information. There was a SOCC at the MSR complex, the PAR complex, and each of the four RSL's. Term also used to refer to the security console itself (Security Operations Control Console). Photo (D25).
The long range defensive missile used for "area defense". More information.
The very high acceleration defensive missile used for "terminal defense". More information.
Sprint Remote Control Equipment. Located in the Remote Launch Operations Building (RLOB) at each of the four Remote Sprint Launch Sites (RSL's), this equipment provided the pre-launch interface between the MSR (digital commands) and the Sprint missiles (analog commands). This functionality was not required at the MSR complex; the MSR communicated via its radar beam directly with the missiles in their underground launch cells by using the Launch Area Antennas (LAA's).
Acronym for Stanley R. Mickelsen Safeguard Complex.
System Readiness Verification. A separate computer system to evaluate performance of the tactical computer system (DPS) via various program generated simulated threat scenarios. More information.
Safeguard Tactical Computer Simulator. Used for unit/task level debugging of programs. More information.
Safeguard Threat Action Generator. A software facility that enabled the simulation of a Safeguard threat for use by the system exerciser.
Strategic Command. The agency that plans and targets all U.S. nuclear forces and issues National Command Authority orders authorizing the use of nuclear force. More information.
Surge Resistor
See Crowbar.
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- T -
Terminal Defense
A "last ditch" effort to destroy incoming re-entry vehicles that have survived "area defense". This defense occurs within the atmosphere (endoatmospheric) only a short time before the RV's reach their targets, thus the term "terminal defense". More information.
Technical Maintenance Repair Center. The PAR and MSR both had a TMRC.
Tactical Software Control site. A collection of Safeguard hardware that provided a duplicate of the software environment at a deployed tactical site.
Tactical Support Equipment. Air conditioning, electrical lines, cooling system, utilities, etc.
Two Man Rule
Part of the security protocol for nuclear weapons requiring that no lone individual shall have access to a nuclear weapon. More information.
Traveling Wave Tube. An electronic signal amplifier characterised by wide bandwidth, high gain, and linearity. Used in the PAR radar system.
Very-high-power, hybrid microwave tube, combining the input section of a high-power klystron with the output section of a traveling wave tube, characterized by high operating efficiency and wide bandwidths. (From Used in the MSR radar system. More information.
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- U -
Universal missile building. Earth shielded structure located within the MSR complex. Used for checkout and assembly of both Spartan and Sprint missiles. Photo 1, Photo 2.
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- V -
- W -
Western Electric Company
Weapon System Contractor
Weapons System Equipment
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- X -
Execution Preparation Facility. Performed the linkage editor functions for software to be executed on the CLC.
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- Y -
- Z -