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Guardrail Common Sensor

The Guardrail Common Sensor [GR/CS] is a Corps Level Airborne Signal Intelligence (SIGINT) collection/location system that integrates the Improved GUARDRAIL V (IGR V), Communication High Accuracy Airborne Location System (CHAALS), and the Advanced QUICKLOOK (AQL) into the same SIGINT platform -- the RC-12K/N/P/Q aircraft. Key features include integrated COMINT and ELINT reporting, enhanced signal classification and recognition, fast Direction Finding (DF), precision emitter location, and an advanced integrated aircraft cockpit. Preplanned product improvements include frequency extension, computer assisted on-line sensor management, upgraded data links and the capability to exploit a wider range of signals.

GR/CS is an essential member of the Precision SIGINT Targeting System (PSTS). PSTS is a joint-service and defense-agency effort that uses both tactical and national systems to provide a near real-time, precision-targeting, sensor-to-shooter capability. The Guardrail Common Sensor (GR/CS). It is considered to be among the most accurate and timely of signal intelligence (SIGINT) reporting platforms.

GR/CS provides near real-time SIGINT and targeting information to Tactical Commanders throughout the corps area with emphasis on Deep Battle and Follow-on Forces Attack support. It collects selected low, mid, and high band radio signals, identifies/classifies them, determines locations of their sources, and provides near-real-time reporting to tactical commanders. The system uses an integrated processing facility (IPF) which is the control, data processing, and message center for the overall system.

Each system consists nominally of twelve aircraft which normally fly operational missions in sets of three. Up to three airborne relay facilities (ARF)/aircraft intercept communications, noncommunications emitter transmissions, and gather LOB and TDOA data. They then transmit this data to the IPF. The ARF/aircraft also serve as the relay platforms for communications between the IPF and the supported commands. The typical system configuration uses one Integrated Processing Facility (IPF), two or three Airborne Relay Facilities (ARFs), approximately nine (up to a maximum of 32) Commanders Tactical Terminals (CTTs), and an Auxiliary Ground Equipment (AGE) van. Special Purpose Equipment (STE) vans are included for maintenance and troubleshooting.

This system incorporates the Communication High Accuracy Airborne Location System (CHAALS) to achieve target locations for its COMINT system, and CHALS-X, which is a continuation of the project which developed the CHAALS precision location subsystem currently in GR/CS systems 4 and 1. The CHALS-X system provides the targeting capability required to support the Division Commander's requirements to locate and kill the enemy by providing for precise location of High Value Targets (HVTs). Airborne systems mixed with ground based systems will be capable of precisely locating enemy weapon systems and units (regardless of whether the enemy uses conventional or modern radios) producing target locations sufficiently accurate for first round fire for effect by organic artillery. It utilizes the previously developed Time-Difference-Of-Arrival/Differential Doppler (TDOA/DD) techniques and incorporates advances in electronics state of the art and distributed processing to provide for improved capabilities; increases frequency range, adds frequency hopping radios to the target set, and decreases size/weight/power requirements of processing subsystems (3 racks of computer equipment now reduced to two boxes which fit into a standard 19 inch rack). The continued evolution of Target Accuracy Geolocation capability using TDOA/DD is a technology advantage over any other country and has been restricted from release to foreign countries.

GR/CS Targeting accuracy is also provided by the ELINT system. Ground to ground (including CTT) communications links also provide an interface with fixed locations and tactical users. Automated addressing to CTT field terminals provides automated message distribution to tactical commanders in near real time. Planned improvements include expanded COMINT/ELINT collection, LPI capability, embedded training, CTT(3 channel) retrofit, and automated reporting.

The Radio Remote Receiving Set (AN/ARW-83) is commonly referred to as the Airborne Relay Facility (ARF). The ARF consists of equipment installed in a modified Beechcraft Super King Air aircraft with a military designation of RC-12. The ARFs are manned only by the pilots during a mission. ARF mission equipment is remotely controlled by operators in the Integrated Processing Facility (IPF). The Guardrail systems currently in service include the Guardrail V (RU-21H aircraft), the Guardrail Common Sensor Minus (RC-12H aircraft), and the Guardrail Common Sensor (RC-12K/N/P aircraft). Guardrail Common Sensor (GRCS) combines the Improved Guardrail V (IGRV) Communication Intelligence (COMINT) sensor package with the Advanced Quicklook electronics signals (ELINT) intercept, classification, and direction-finding capability, and a Communication High Accuracy Airborne Location System (CHAALS). GRCS shares technology with the Ground-Based Common Sensor, Airborne Reconnaissance Low, and other airborne systems.

GRCS comprises a series of special purpose detecting systems - AN/USD 9B thru E. The GRCS systems are tactical, remotely controlled, airborne mission equipment, and ground-based intercept and emitter location systems. They have an external near real-time reporting capability that can be operated in six modes (local, isolated, remote, interoperable, training, or maintenance/calibration). These systems are assigned to a B company, military intelligence battalion, aerial exploitation, as part of a corps military intelligence brigade.

The GRCS System 1, AN/USD-9C, and System 2, AN-USD-9E, are the latest addition to this family. They have the additional capability to operate worldwide via the GRCS Tethered Medium Earth Terminal (TMET) and the Direct Air to Satellite Relay (DASR) Aircraft (RC-12Q). Other major system improvements are:

• The new UNIX-based work stations.
• Faster (Micro 5) mainframe computers.
• The fiber-optics distributed data interface (FDDI) local area network (LAN).
• The GRCS Data Distribution System (DDS), elementary special signals processing.
• The GRCS Integrated Processing Facility (IPF) rapid deployment capability (two vans minimum vice four).
• The entire system (less aircraft) will be C-130 transportable.

Information is processed and reported to joint consumers via TRIXS broadcast primarily over the Joint Tactical Terminal (JTT) which is a subsystem of the GRCS DDS.

A typical mission requires the aircraft to orbit to the rear and parallel to the forward line of own troops (FLOT). The IPF sends commands to and receives information from the Airborne Relay Facility (ARF) through a secure data link. The operators in the IPF process the collected information and report the intelligence to the tactical commanders and other possible joint consumers via the JTT relay on board the aircraft.

The RC-12D Improved Guardrail V aircraft is based on the King Air Model A200CT. This US Army special electronic mission version carries the AN/USD-9 Improved Guardrail remote-controlled communications intercept and direction-finding system. Other equipment includes aircraft survivability equipment (ASE) systems, Carousel IV-E INS and Tacan system, radio datalink, the AN/ARW-83(V)5 airborne relay with antennas above and below wings, wingtip elint/comint pods. Associated ground equipment includes the AN/TSQ-105(V)4 integrated processing facility, AN/ARM-63(V)4 AGE flightline van and AN/TSC-87 tactical commander's terminal. The system prime contractor was formerly ESL, and currently TRW. The US Army had 13 RC-12D Improved Guardrail Vs converted from C-12Ds, with deliveries starting in mid-1983; one was assigned to to Forces Command at Fort McPherson, Georgia, and the remainder to 1st Military Intelligence Battalion, Wiesbaden, Germany, and 2nd MIB at Stuttgart, Germany. The German-based aircraft were reassigned late 1991 and are currently with 3rd, 15th and 304th MIBs at Camp Humphreys (South Korea), Fort Hood (Texas) and Fort Huachuca (Arizona). One was converted back to an earlier configuration as C-12D-1. Five new-build aircraft were sold to Israel for 191 Squadron at Sde Dov.

In 1976, the Guardrail V began development in order to develop and provide a supportable Corps level system to the Army, until Cefly Lancer development was completed. Guardrail I through IV were considered to be theater level assets. The Guardrail V aircraft were converted from earlier Guardrail I/IIA aircraft, RU-21D Laffing Eagle machines, and U-21G airframes. Designated as RU-21H, the big improvement was the addition of wingtip pods to replace many of the blade antennas of the previous Guardrail aircraft.

The JU-21A LEFT JAB conducted "Radio Research" -- the cover designation for certain units operating under the direction of the U.S. Army Security Agency Group, Vietnam. All missions of this agency were highly classified. Other variants were the RU-21A, B and C CEFIRM LEADER, RU-21D LAFFING EAGLE, RU-21E LEFT FOOT, RU-21G GUARDRAIL I / II / III, RU-21H GUARDRAIL V, and RU-21J CEFLY LANCER.

On March 4, 1971, a JU-21A with a crew of five departed South Vietnam on an intelligence gathering mission in the area of the Demilitarized Zone separating North and South Vietnam. Contact was lost with the aircraft, it did not return from its mission, and the crew was initially declared missing. A search effort to locate the missing aircraft and crew failed to locate them along its known flight path and the aircrew was declared missing. In late June and early July 1992, a joint U.S./Vietnamese team visited the area of the reported JU-21A crash site in Gio Linh District. Witnesses were interviewed who claimed to have visited the crash site during the war and reported seeing 4-5 remains at the site. There were differences in first hand and hearsay accounts of the locations of the bodies but the sum of the information was that the individuals had died and their remains buried in the area.

The US Army Aviation Engineering Flight Activity operates a modified CH-47C helicopter as an airborne spray tanker for helicopter qualification tests in artificial icing conditions. The operational performance and spray cloud characteristics of the Helicopter Icing Spray System were evaluated in the course of several test programs during the 1984 and 1985 icing seasons in Duluth, Minnesota. Configuration changes made during the first two phases of this program reduced previous spray system problems of water leakage, freezing, and non-uniform flow patterns from the boom assembly. In-flight spray cloud data were taken with a JU-21A aircraft using particle measuring spectrometers.

The RC-12G is a US Army special electronic mission aircraft based on the King Air A200CT. Generally similar to RC-12D, the maximum takeoff weight is increased to 6,800 kg (15,000 lb). The mission equipment contractor is Sanders Associates. Three delivered were in 1985 after conversion from C-12D airframes. These aircraf served with the 138 MI Company at Orlando, Florida, and are currently stored at Fort Sill, Oklahoma.

The RC-12H Guardrail Common Sensor (System 3 Minus) is a US Army special electronic mission aircraft that is generally similar to the RC-12D, though with the maximum takeoff weight increased to 6,800 kg (15,000 lb). System contractor ESL Inc. delivered six in 1988 for the 3rd MI Battalion at Camp Humphreys in Pyongtaek, South Korea.

The RC-12K Guardrail Common Sensor (System 4) is similar to RC-12H, with a more powerful 1,100 shp PT6A-67 turboprop engine and a maximum takoff weight increased to 7,250 kg (16,000 lb). The US Army ordered nine in October 1985, of which eight replaced RC-12Ds in 1st MI Battalion in May 1991. One of these was subsequently being lost in an accident. The ninth US Army aircraft was retained by Raytheon for conversion to the RC-12N configuraiton. An additonal two aircraft of this configuration were delivered to Israel in May-June 1991.

The RC-12N Guardrail Common Sensor (System 1) is generally similar to RC-12K, though with 7,350 kg (16,200 lb) maximum takeoff weight, and equipped with dual EFIS and aircraft survivability equipment/avionics control system (ASE/ACS). The ASE suite includes the AN/APR-39 radar warning receiver, AN/APR-44 radar warning system, AN/ALQ-136, AN/ALQ-156 and AN/ALQ-162 countermeasure sets chaff/flare and M130 dispensers. The avionics suite includes AN/ARC-186 or AN/ARC-201 VHF-FM radio, AN/ARC-164 Have Quick II UHF-AM radio; AN/APX-100 IFF transponder; three KY-58 and one KIT-1A secure communications systems; Carousel IV INS; AN/ASN-149 GPS receiver. The prototype RC-12N was converted from an RC-12K. A total of 15 were converted by E-Systems and delivered 1992-93 to the 224th MI Battalion at Hunter AAF, Georgia and 304th MI Battalion at Libby AAF, Fort Huachuca, Arizona. One of these was lost in accident.

The RC-12P Guardrail Common Sensor (System 2) has the same avionics and power plant as the RC-12N, though with different mission equipment (including datalink capability), fibre optic cabling, and smaller and lighter wing pods. The maximum takeoff weight is increased to 7,480 kg (16,500 lb). A total of nine aircraft were delivered to ESL (now TRW) at Moffett Federal Airfield in late 1994 and 1995, and these airframes remained there in 1999.

The RC-12Q Direct Air Satellite Relay consists of three RC-12Ps modified by Raytheon and TRW to act as `mother ships' to expand the RC-12P's operational area outside satellite `footprints'. The airframes were transferred to TRW in 1996 for outfitting, where they remained in 1999. The aircraft feature a prominent dorsal radome housing a satellite communications antenna.

On 16 April 1997 the 224th MI BN (AE) lost a RC-12N and two crewmembers in a fatal training accident. The following year on 06 November 1998 the 1st MI Bn (AE) lost a RC-12K and two crewmembers in a similar training accident. In both accidents the United States Army Safety Center Accident Boards listed in their recommendations to TRADOC to ‘Reevaluate the ATM Tasks for stalls, slow flight and Vmc.’ In February 1999, CG, USAIC & FH, MG John D. Thomas, sent a senior standardization instructor pilot and the 305th MI Bn Safety Officer to USAAVNC to review the RC-12K Accident Board findings to determine if training was a contributing factor. They recommended to MG Thomas that the TC 1-219 tasks for slow flight, stalls and Vmc be rewritten.

The Northrop Grumman Mission Systems-developed Guardrail Common Sensor System 2, called Guardrail 2000, will be a key component of the Army’s next-generation Aerial Common Sensor System that will provide battlefield commanders with the world’s most advanced tactical surveillance data for the 21st century. Guardrail 2000 is the seventh generation of successfully fielded Guardrail systems over the span of 29 years. Previous versions have been used to provide enemy location information during Desert Storm and to support the Bosnia peacekeeping effort. The system, comprised of a twin-engine Beechcraft airplane and a ground station that remotely controls the flow of intelligence data, forms the foundation for the Army Corps intelligence collection and serves as a critical element of the national intelligence collection infrastructure.

HISTORICAL BACKGROUND:

Jun 84 Contract awarded for GR/CS Systems 3 and 4.

Dec 88 GR/CS (minus) System 3 fielded to Korea.

Jun 89 AC-12K Production award (System 1).

Aug/Sept 90 GR/CS Systems 1 and 2 IPF and ARF Production contracts awarded.

Aug 91 GR/CS System 4 fielded to USAREUR.

Apr 94 GR/CS FY94-99 Program and Acquisition Plan approved by HQDA.

Aug 94 GR/CS System 1 Fielded to FORSCOM.

REQUIREMENTS DOCUMENT: ROC, 1 Oct 84, updated Nov 85 and revised in Apr 92.

TYPE CLASSIFICATION: GR/CS System #1 type classified LP.

PLATFORM CHARACTERISTICS:

                         RU-21H             RC-12D/H           RC-12K/N/P
Mission weight/payload:  10,200/1,126 lb    14,200/1,600 lb    16,000/2,000 lb 
Cruise speed:            176 kt             200 kt             250 kt 
Endurance:               4 hr               5(+) hr            5(+) hr 
Max range:               1,000 naut mi      1,200 naut mi      1,200 naut mi 

GUARDRAIL I RU-21 [1971]	GUARDRAIL II/IIA RU-21 [1972]	GUARDRAIL IV RU-21 [1974]
GUARDRAIL V RU-21 [1978]	GUARDRAIL V RU-21 [1978]	IMPROVED GUARDRAIL V RC-12D [1984]
IMPROVED GUARDRAIL V RC-12D [1984]	IMPROVED GUARDRAIL V RC-12D [1984]	IMPROVED GUARDRAIL V RC-12D [1984]
GUARDRAIL COMMON/SENSOR (SYSTEM 3) RC-12H [1988]	GUARDRAIL COMMON/SENSOR (SYSTEM 4) RC-12K [1991]	GUARDRAIL COMMON/SENSOR (SYSTEM 1) RC-12N [1995]
GUARDRAIL COMMON/SENSOR (SYSTEM 1) RC-12N [1995]	GUARDRAIL COMMON/SENSOR (SYSTEM 2) RC-12P [1998]	GUARDRAIL COMMON/SENSOR RC-12Q [1998]
Auxiliary Ground Equipment (AGE) Van Flightline Test Set AN/ARM-163(V)

SYSTEM SUMMARY

PRIME CONTRACTOR: ESL (Sunnyvale, CA)

Beech Aircraft (Wichita, KS)

SUBCONTRACTORS:
ESL; Sunnyvale, CA
Beech Aircraft; Wichita, KS
ESCO; St. Louis, MO
IBM; Owego, NY
UNISYS; Salt Lake City, UT

Deployment

One GR/CS system is authorized per Aerial Exploitation Battalion (AEB) in the MI Brigade at each Corps. Guardrail provided collection coverage along the inter-German border from 1972 through 1990, in Korea from 1974 to the present, and in Central America from 1983 through 1994. Two systems deployed to Southwest Asia during Operations DESERT SHIELD and DESERT STORM. GRCS (Minus) was fielded to Korea in 1988. The first GRCS system was fielded to Europe in 1991, and the second was fielded to XVIII Corps in 1994 with a remote relay capability that allowed forward deployment of aircraft while the ground processing facility remains in CONUS. As of May 1996, one system remained in Korea, one system was in Europe supporting Operation JOINT ENDEAVOR, the XVIII Airborne Corps system had deployed in support of the combined exercise Atlantic Resolve, and the fourth and final GRCS system is in the Engineering and Manufacturing Development phase in California to be fielded in FY97.

• 1st MI BN [Aerial Exploitation] - V Corps US Army Europe
• 3rd MI BN [Aerial Exploitation] - 501st MI BDE, Korea
• 15th MI BN [Aerial Exploitation] - III Corps
• 224th MI BN [Aerial Exploitation] - XVIII Corps