v1.1.1 / 3 of 4 / 01 jun 02 / greg goebel / public domain
* The Grumman Mohawk was a major step forward in battlefield surveillance, but it was limited in range, endurance, and sensor capability. The RC-7 carries much better systems, but it was designed to provide moderate capability at moderate cost.
However, even before the RC-7 was conceived, the US Army was already working with the US Air Force to develop a much more powerful surveillance asset that could provide military commanders with a "God's eye view" of an entire battle theater. The result of this collaboration was the "Joint Surveillance & Target Acquisition Radar System (Joint-STARS)". This chapter provides a short description of Joint-STARS.
* In the 1970s, US military interest in more sophisticated and powerful surveillance systems led to development work towards an advanced SAR system named "Pave Mover" by the US Defense Advanced Research Projects Agency (DARPA) and the US Air Force (USAF). The Army was also considering a battlefield surveillance system based on the Sikorsky H-60 helicopter and designated the "Stand-Off Target Acquisition System (SOTAS)".
Costs of SOTAS soared, and the Army was forced to abandon the project. Shortly afterward, in 1982, the Army and the Air Force merged their programs, and spent the next two years combining their requirements. The result was Joint-STARS.
Joint-STARS was intended to provide an all-weather battlefield surveillance platform that could detect, locate, identify, classify, track, and target enemy assets on the battlefield, and pass this information on to US command and attack elements on land, sea, or in the air over data links. The Army was to obtain data from Joint-STARS through truck-mounted AN/TSQ-178 "Ground Station Modules (GSM)", which would be attached to headquarters organizations to give ground commanders a window onto the battlefield.
Grumman's Melbourne Systems Division in Florida won the contract in 1985, and began development of two "E-8A" prototype Joint-STARS platforms, based on "used" Boeing 707-320C jetliners obtained from commercial operators. Initial flight of the first E-8A was in 1988, with both E-8As available for operational test during the Gulf War in 1991, where they proved remarkably useful, even though they were not production-specification machines.
In the meantime, a contract was awarded for single production prototype E-8C in 1990, which would fly in March 1994, followed by award in 1993 of a "low rate initial production (LRIP)" contract for five E-8Cs, with deliveries beginning in 1995.
* The Boeing 707-300 series of airliners on which Joint-STARS is based is a "stretched" derivative of the original 707-100 series airliner, intended for trans-Atlantic passenger and cargo operations. There were a number of different subvariants in the 707-300 family, including all-passenger aircraft, and aircraft that could be "quick-changed" by the users to any desired mix of passengers and freight. The 707-300 is the most heavily produced of all 707 variants, with at least 545 built. The most visible external feature is that all but a few early-production 707-300s lack the ventral fin of most other 707 variants.
As the 707-300 is no longer in production, all Joint-STARS platforms are based on used machines, but the Boeing 707 is a robust aircraft, the airframes have plenty of life left in them, and the "used" market for the 707 is good. It is unclear if any one 707-300 subvariant is preferred for conversion to Joint-STARS configuration, though the E-8A conversions were based on the 707-323C "quick change" subvariant.
Other aircraft platforms, including new-build 707s with modern CFM turbofan engines, Boeing 757 or 767 airliners, or the McDonnell-Douglas MD-11 airliner, were considered, but the cost of new aircraft was simply too high, and basing Joint-STARS on used aircraft hopefully would reduce delays in reaching operational service. The new-build 707s had been seriously considered and in fact were to be the basis of an "E-8B" Joint-STARS, but Boeing finally shut down 707 production completely.
Some observers have suggested that the Pentagon made a foolish bargain in staying with used aircraft, producing analyses that show on a full "life-cycle" basis, the costs are not really lower, but the capability is. However, this dispute is impossible to resolve from the sidelines.
* Outside of the extensive fit of electronic systems, few changes have been made in the 707-300 aircraft itself. One obvious addition is a boom-refueling receptacle behind the cockpit, not a common fit on commercial aircraft. The cockpit layout remains much as it was in commercial service, with no update to modern "glass cockpit" standards.
Most significantly, the aircraft retains its original Pratt & Whitney JT3D-3B turbofan engines, known as "TF33s" in military service. They are reliable and effective engines, but by modern standards noisy, dirty, and inefficient. It would be desireable to update Joint-STARS platforms to modern CFM International F108 turbofans, which burn cleaner and quieter, and offer substantially more power and greater endurance, but the money doesn't seem to be there.
* Of course, the electronics fit is something the original designers of the 707-300 could have barely imagined. The interior is fitted with two rows of display and control consoles, while the fuselage prominently displays a 7.3 meter (24 foot) long "canoe" fairing mounted behind the nosewheel, which accommodates the antenna for the Norden-built "APY-3" phased-array multi-mode radar.
The antenna mechanically tilts from side to side for elevation scanning, but azimuth scanning is performed electronically through phase-interference techniques. The radar system provides at least three operating modes:
WAS/MTI gives battle commanders a "big picture" of what's happening on the battlefield. Targets are color-coded on the operator display to targets whose nature is known; targets that have not been identified; and targets that have come to rest, as opposed to those that are still moving.
WAS/MTI provides a number of interesting features, such as the ability to discriminate wheeled vehicles from tracked vehicles from the fact that the bottom of a track is motionless relative to the ground, while the top is moving twice as fast as the vehicle itself. A threshold can be set so that the MTI ignores vehicles moving above a certain speed, allowing the operator to focus on slow-moving tanks and not fast-moving automobiles. WAS/MTI also has a maritime mode, and has demonstrated the ability to target fast-moving helicopters.
In SAR mode, the radar has a range of 175 kilometers (110 miles) to either side of the aircraft from operating height. During a single eight-hour sortie, a million square kilometers (386,000 square miles) can be mapped.
All reconnaissance data is stored on board and can be displayed on operator consoles, or dumped to a fast laser printer. Data collected over a period of time can be displayed in a "movie" format so that a battle commander can observe the evolution of the combat situation.
Communications to external stations is through a "Surveillance & Control Data Link (SCDL / Skittle)". The data is picked up by the truck-mounted GSMs, which have two display consoles and a laser printer, and GSM operators can access Joint-STARS data without intervention from the operators on board the aircraft.
The GSMs include a telescoping antenna that can be jacked up to a height of 30 meters (100 feet), and tow a generator to provide power. The GSMs also include a "Global Positioning System (GPS)" receiver to allow them to pinpoint their own locations using the GPS navigation satellite constellation. There is no real limit to the number of GSMs that can link up to Joint-STARS, though obviously bandwidth becomes a problem as the numbers of GSMs increase.
Joint-STARS is also fitted with two "Joint Tactical Information Distribution System (JTIDS)" datalinks, one of which is used to relay targeting and other data to strike aircraft, the second of which is dedicated to communications with an "Airborne Warning And Control Systems (AWACS)" aircraft, presumably an E-3 Sentry, cooperating with Joint-STARS to control the battle.
In addition, the two E-8A Joint-STARS prototypes were fitted with a small fairing on the belly just behind the wings and in front of the little SCDL antenna. This fairing housed the antenna for the "Flight Test Data Link (FTDL / Fiddle)" and, as its name implies, was intended solely for development flight test purposes.
* The E-8A prototypes were fitted with a variable number of operator consoles, depending on the progress of development activity, and also included at least one test console. The production E-8C includes 17 operator consoles, plus a "defensive systems" console. The defensive systems include warning sensors but no active countermeasures as of yet, and certainly no defensive armament.
The standard mission crew count is 21, and includes both Air Force and Army
personnel. Seating is provided for takeoff and landing, and there are six
bunks and a rest area. Up to 34 crew may be taken on long-endurance
missions, with the aircraft kept in flight with mid-air refueling.
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spec metric english
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wingspan 44.4 meters 145 feet 9 inches
length 46.6 meters 152 feet 11 inches
height 13 meters 42 feet 6 inches
empty weight 77,600 kilograms 171,000 pounds
max loaded weight 152,400 kilograms 336,000 pounds
maximum speed 1,000 KPH 620 MPH / 540 KT
service ceiling 12,800 meters 42,000 feet
endurance (unrefueled) 11 hours
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* The two E-8As were sent to Riyadh, Saudi Arabia, to participate in OPERATION DESERT STORM, the offensive to drive the Iraqis out of Kuwait. The two aircraft arrived on the night of 11:12 January 1991, and were performing the first of 49 combat sorties on 14 January, two days before the start of the air war. They were supported by six GSMs, and protected in the air by fighter "barrier" combat air patrols.
Although this deployment was in principle simply an operational evaluation and the aircraft were only fitted with about ten operator consoles, the two Joint-STARS aircraft proved valuable combat assets, targeting Iraqi combat elements, particularly during their hasty and disastrous retreat from Kuwait. Joint-STARS sensor imagery mapped out the movements of Iraqi vehicles on the "Death Highway" and pinpointed them for attack. One senior USAF officer commented on the Joint-STARS service in DESERT STORM: "Moving targets did not stay moving for long."
The formal planned Joint-STARS operational evaluation did not actually begin until 1995, with stateside tests leading to deployment of one of the E-8As and the first E-8C to Germany to support OPERATION JOINT ENDEAVOR, the US peacekeeping mission to Bosnia. The second production E-8C was also deployed later. Joint-STARS flew missions over the Balkans from December 1995 through March 1996.
This exercise was to lead to full-scale production, but results were not entirely satisfactory. The old JT3D-3B engines simply weren't powerful enough to allow operation at specified maximum operational altitude and required long runways, and system reliability was not up to specification.
The first E-8C went into formal USAF operational service in June 1996, to be followed by the second in August 1996. Full production of a total of 19 operational Joint-STARS aircraft, including updates of the two E-8As to full E-8C configuration, was authorized in September 1996.
A total of 12 E-8Cs had been delivered as of early 2002, and five more are in various stages of construction. It is unclear if the final two will be built.
* As Joint-STARS has gone into service, improvements have been added. Radar system software has been updated to provide enhanced capabilities, such as improved target identification, and the ability to "underlay" various classes of map data on the operator displays.
Communications capabilities have been improved as well, including addition of a new "Link 16" datalink system, a superset of JTIDS, to improve communications with strike aircraft; an "Improved Data Modem (IDM)" for communications with Army air assets, particularly AH-64 Apache gunship helicopters; and receivers to allow Joint-STARS to pick up intelligence network broadcasts.
The 11th E-8C was the first "Block 20" aircraft, which featured two commercial Compaq "Alpha" processors that replaced the five mil-standard processors fitted on the earlier "Block 10" E-8Cs. The two Alpha processors have substantially more total processing power than the five older processors they replace, and are based on open architectures that are easier to expand and modify.
The Block 20 E-8C also featured new workstations, provided by Compaq; a new radar signal processor provided by General Dynamics; and a fiber-optic network for system interconnection on the aircraft. The earlier Block 10 E-8Cs will be brought up to Block 20 specification.
The most ambitious upgrade planned for Joint-STARS was the "Radar Technology Insertion Program (RTIP)", which was to provide the platform with a much more capable radar system. However, RTIP proved to be the "thin entering wedge" for where the entire concept of US battlefield surveillance was going, and went off in a number of directions. The status of RTIP is discussed in detail in the next chapter.
* Ground systems have been improved as well. The AN/TSQ-178 GSM was phased out in 1999, being replaced by the more sophisticated AN/TSQ-179 "Joint-STARS Common Ground Station (CGS)". Like the GSM, the CGS is truck-mounted and highly mobile. The CGS has secure direct radio and satellite data links to communicate with Joint-STARS and other assets, and can display and process Joint-STARS data for relay to field forces.
The CGS can also obtain intelligence data from other assets, such as the RQ-1 Predator and Shadow 200 UAVs; the RC-12 Guardrail; the RC-7B ARLM; the EC-135 Rivet Joint SIGINT platform; the EH-60 Advanced Quick Fix ELINT helicopter; and the new sensor-laden RAH-66 Commanche scout-attack helicopter.
CGS can perform "fusion" on multiple inputs to provide better intelligence output. CGS output is relayed to field units through a truck-mounted "Tactical Operations Center (TOC)". The Army plans to obtain 96 CGS systems by 2002, and the Marine Corps plans to obtain three in the same timeframe.
A simplified "man-portable" Joint-STARS terminal, the "Joint Services Work Station (JSWS)" is also in use with the USAF and the US Navy. The JSWS allows access to a subset of Joint-STARS data. The Army is also looking at an improved "Distributed CGS", to begin delivery in 2006, to allow uniform access from the level of the battlefield commander with a workstation, to that of a squad leader with a portable computer.
* There has also been consideration of upgrading the aircraft's engines, which have inadequate power for full-gross-weight flight operation. Upgrading to CFM turbofans, which would be the technically optimum solution, is regarded as too expensive, but there has been a push towards a more modest fix: replacing the original 707 JT3D turbojets with JT8D turbofans.
This is replacing a 1950s engine with a 1960s engine, which may seem like a weak solution, but the JT8D is quieter, cleaner-burning, more fuel efficient, incrementally more powerful, and much easier to maintain than the JT3D. Refurbished JT8Ds and spares are widely available at low cost, and a JT8D can be swapped with a JT3D with minimal aircraft modifications.
Pratt & Whitney formed a partnership with a San Antonio, Texas, based company named "Seven Q Seven" in the late 1990s to explore the possibilities for a JT8D upgrade for the various 707-based military platforms in service around the world. The partnership led to the flight of a 707 demonstrator with three JT3Ds and one JT8D in July 1999.
The effort went quiet for a while, but was revived when the Air Force issued a requirement for reengining their Joint-STARS aircraft. This led to the initial flight of a 707 demonstrator with four JT8D-219 turbofans on 9 August 2001. The aircraft is expected to receive FAA certification sometime in 2002.
Northrop Grumman is also competing in the USAF program. The Air Force expects to lease the engines and award the winner a contract to perform maintenance for the duration of the lease. Modern turbofans have not been completely ruled out, but it is likely that cost will drive the selection to the JT8D.
P&W / Seven Q Seven see a potential for re-engining up to 70 militarized 707s with the JT8D, and are open to the idea of re-engining commercial 707s as well. Price of an upgrade is estimated at $20 million to $25 million USD.