The E-8 Joint-STARS

v2.1.0 / 01 aug 16 / greg goebel

* Aircraft had performed battlefield observation from the beginning of their use in warfare, but by the 1970s surveillance technology had advanced to the level where a single aircraft could provide a "God's eye view" of an entire battleground, relaying data about hazards and targets to forces on the ground. In the 1970s, the US Army worked with the US Air Force to develop such a surveillance platform; the result of this collaboration was the "E-8C Joint Surveillance & Target Acquisition Radar System (Joint-STARS)". This document provides a history and description of Joint-STARS.

E-8C Joint-STARS



* In the 1970s, US military interest in advanced battlefield surveillance systems led to development work towards an advanced synthetic-aperture radar (SAR) radar ground-mapping sensor codenamed PAVE MOVER by the US Defense Advanced Research Projects Agency (DARPA) and the US Air Force (USAF). The US Army was also considering a battlefield surveillance system based on the Sikorsky H-60 helicopter, 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 strike elements on land, sea, or in the air using datalinks. 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 first 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 a 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 jetliners on which Joint-STARS is based was a "stretched" derivative of the original 707-100 series jetliner, designed 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 was 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.

Since the 707-300 was no longer in production, all Joint-STARS platforms were rebuilt from used machines, but the Boeing 707 was built rugged, the airframes had plenty of life left in them, and the "used" market for the 707 was good. It is unclear if any one 707-300 subvariant was 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 the hope was that basing Joint-STARS on used aircraft would reduce delays in reaching operational service. 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.

* Outside of the extensive fit of electronic systems, few changes were made in the 707-300 aircraft itself. One obvious addition was a boom-refueling receptacle behind the cockpit, not a common item on commercial aircraft. The cockpit layout remained much as it was in commercial service, with no update to modern "glass cockpit" standards. Most significantly, the aircraft retained its original Pratt & Whitney JT3D turbofan engines, known as the "TF33" in military service. They were reliable and effective, but by modern standards noisy, dirty, and inefficient.

Of course, the electronics fit was something the original designers of the 707-300 could have barely imagined. The interior was fitted with two rows of display and control consoles, while the fuselage prominently displayed a 7.3 meter (24 foot) long "canoe" fairing mounted behind the nosewheel, which accommodated the antenna for the Norden-built AN/APY-3 phased-array multimode radar.

The antenna mechanically tilted from side to side for elevation scanning, but azimuth scanning was performed electronically through phase-interference techniques. The radar system provided four primary operating modes:

All reconnaissance data was stored on board and could be displayed on operator workstations or dumped to a fast laser printer. Data collected over a period of time could be displayed in a "movie" format to allow a battle commander to observe the evolution of the combat situation.


Communications to external stations were through a "Surveillance & Control Data Link (SCDL / Skittle)". The data was picked up by the truck-mounted GSMs, which had two display consoles and a laser printer, and GSM operators could access Joint-STARS data without intervention from the operators on board the aircraft. The GSMs included a telescoping antenna that could be jacked up to a height of 30 meters (100 feet), and towed a generator to provide power. The GSMs also included a GPS receiver to allow them to pinpoint their own locations using the GPS navigation satellite constellation. There was no real limit to the number of GSMs that could link up to Joint-STARS, though obviously communications bandwidth became a bottleneck as the numbers of GSMs increased.

Joint-STARS was also fitted with "Joint Tactical Information Distribution System (JTIDS)" datalinks, used to relay targeting and other data to strike aircraft, as well as to communicate 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 included 17 operator consoles, plus a "defensive systems" console. The defensive systems included warning sensors but no active countermeasures, and certainly no defensive armament.

The standard mission crew count was 21, and included both Air Force and Army personnel. Seating was provided for takeoff and landing, and there were six bunks and a rest area. Up to 34 crew could be taken on long-endurance missions, with the aircraft kept in flight with mid-air refueling.

   _____________________   _________________   _______________________
   spec                    metric              english
   _____________________   _________________   _______________________

   wingspan                44.4 meters         145 feet 9 inches
   wing area               283.35 sq_meters    3,050 sq_feet
   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
   _____________________   _________________   _______________________

   The E-8C was powered by four Pratt & Whitney JT3D-3B turbofans, with
   80.1 kN (8,165 kgp / 18,000 lbf) max dry thrust.  Some sources claim
   it used the slightly more powerful (84.5 kN / 8,615 kgp / 19,000 lbf
   thrust) JT3D-7.  Considering that all the E-8Cs were used aircraft,
   different machines may have different engine subvariants.


* 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 grimly commented on the Joint-STARS service in DESERT STORM: "Moving targets did not stay moving for long."

The Mother Of All Retreats

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, while 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 17 operational Joint-STARS aircraft, including updates of the two E-8As to full E-8C configuration, was authorized in September 1996. The last was delivered in early 2005. One was damaged beyond repair in a flight accident in 2009.



* Improvements were added to the E-8C in service. Radar system software was 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 were improved as well, including addition of a "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, featuring two commercial Compaq (now HP) "Alpha" processors that replaced the five mil-standard processors fitted on the earlier "Block 10" E-8Cs. The two Alpha processors had substantially more total processing power than the five older processors they replaced, and were based on "open" architectures, making them 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 were brought up to Block 20 specification.

Joint-STARS workstations

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 went off in a number of confusing directions, a matter discussed below.

* Ground systems were improved as well. The AN/TSQ-178 GSM was phased out in 1999, replaced by the more sophisticated AN/TSQ-179 "Joint-STARS Common Ground Station (CGS)". Like the GSM, the CGS was truck-mounted and highly mobile. CGS had secure direct radio and satellite data links to communicate with Joint-STARS, and could display and process Joint-STARS data for relay to field forces. CGS could obtain intelligence data from other assets, such as other crewed battlefield surveillance aircraft or unmanned aerial vehicles (UAVs). CGS could perform "data fusion" on multiple inputs to provide better intelligence output. CGS output was relayed to field units through a truck-mounted "Tactical Operations Center (TOC)". The Army obtained 96 CGS systems, while the Marine Corps obtained 3.

A simplified "man-portable" Joint-STARS terminal, the "Joint Services Work Station (JSWS)", was adopted by the the USAF and the US Navy. The JSWS gave access to a subset of Joint-STARS data. The Army also obtained an improved "Distributed CGS" to allow uniform access from the level of the battlefield commander with a workstation, to that of a squad leader with a portable computer.

* In 2005, a contract was finally awarded to upgrade the E-8C's cockpit from its 1950s "steam room" configuration to a modern glass cockpit. Other upgrades included a secure network to allow operators to chat with operators and end users elsewhere, and a software upgrade called the "Affordable Moving Surface Target Engagement" system to allow a Joint-STARS to take control of a long-range guided weapon fitted with a datalink and use it to attack naval vessels.

There was also a painful effort to upgrade the aircraft's TF33 engines, which were not only are old and increasingly hard to maintain, but also had inadequate power for full-gross-weight flight operation. Upgrading to CFM turbofans, which would be the technically sexy solution, was regarded as too expensive, but a cheaper and effective fix was available: replacing the original 707 JT3D turbofans with JT8D-219 turbofans.

At first sight that might have seemed like a step backward, since the original JT8D was a less powerful contemporary of the JT3D. However, in the early 1980s Pratt & Whitney introduced the second-generation JT8D Series 200 engine, which was largely redesigned and was a perfectly modern engine for the 1980s. It was more powerful than the JT3D, as well as much cleaner, much quieter, and more fuel-efficient. A JT8D could be swapped with a JT3D with minimal aircraft modifications since the form-factor and interfaces are similar. Advocates of JT8D re-engining claimed the new engine fit would actually have lower operating costs than a CFM upgrade.

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 re-engining their Joint-STARS aircraft. This led to the initial flight of a 707 demonstrator with four JT8D-219 turbofans on 9 August 2001. P&W / Seven Q Seven estimated that there was a market for re-engining up to 70 militarized 707s with the JT8D, and were considering the idea of re-engining commercial 707s as well. Price of an upgrade was estimated at $20 million to $25 million USD.

The exercise went quiet again for a few years, but a contract was awarded to P&W for the re-engining exercise in 2008, with an re-engined E-8C performing its first flight in December of that year. The initial upgrade was for evaluation, with P&W planning to build new engines with minor improvements for the full upgrade program. The long lag in approving the effort was frustrating for the participants, as was the fact that the Air Force -- having been bitten by Congress and lawsuits -- insisted on performing the selection through a competition, with General Electric providing an alternate proposal that was shot down.

Joint-STARS JT8D-219 engine installation

The re-engining effort was to include new pylons and cowlings for the JT8D-219s, but an accounting analysis showed that the overall cost would be less than trying to maintain the antique JT3Ds. The increased power would not only give better reliability, lower operating costs, better availability rates, a higher operating altitude, and faster transit times, but also greatly increase the number of airports that could be used by the Joint-STARS by allowing use of shorter runways.

Or at least it would, had it ever happened. The re-engining was to begin in 2010, but it went dead, and this time didn't come back to life. Defense procurement must be a miserable job.



* The reason the re-engining effort fizzled out was because, after several years of vacillation, the E-8C was judged not to have a future. The story is complicated.

As mentioned previously, the military had been working on the RTIP upgrade, with the original intent to improve the capabilities of Joint-STARS. However, with surveillance being performed by business jets and drones, it seemed prudent to expand the scope of the program to "multi-platform" support, with the program's name changed appropriately to "MP-RTIP". A contract for the MP-RTIP system was awarded to Raytheon and Northrop Grumman in late 2000. Raytheon was to build the radar system itself, while Northrop Grumman handled systems integration, with the Northrop Grumman Hawk long-range drone targeted for initial implementation of MP-RTIP.

MP-RTIP is based on a next-generation X-band "active electronically scanned array (AESA)" system that can also track low-flying, stealthy, fast-moving missiles hundreds of kilometers away. An AESA can be thought of as a radio-frequency (RF) "array processor", composed of a grid of interconnected "transmit-receive" modules, each with its own RF, processing, and control electronics. The modules can work with each other to perform a wide variety of tasks -- active radar sensing, passive electronic sensing, communications, and jamming -- in an interleaved or parallel fashion. One of the advantages of an AESA is that it lends itself to a scalable design, since the array can be sized to different platforms by fitting fewer or more modules as required, with capability proportional to size.

MP-RTIP ended up being fielded, as the "AN/ZPY-2", on the Block 40 Global Hawk -- but ironically, not on Joint-STARS, which got bogged down in fumblings over a replacement platform. The Air Force had considered a follow-on to Joint-STARS designated the "Wide Area Surveillance (WAS)" aircraft, but this scheme was gradually seen as too limited. What complicated the issue was the USAF's parallel effort to obtain a replacement for their current Boeing KC-135 aerial tanker fleet, with the Boeing 767 jetliner selected as the best option at the time, and in fact eventually selecting the 767 for the role. In any case, as long as the Air Force was planning on acquiring the 767 for the tanker role, it seemed sensible to acquire it for the surveillance role as well.

Initially, there was some push to actually merge the two roles to an extent, with the tankers capable of carrying a pallet of SIGINT, surveillance gear, or battlefield communications relay gear, with the pallets swapped out as required by the mission; but the "smart tanker" concept gradually faded into the background, while the idea of using the 767 as a surveillance platform, initially designated the "Multi-Sensor Command & Control Aircraft (MC2A)", remained in the foreground. A Boeing 707 jetliner, configured as an experimental "MC2A-X" prototype of the production MC2A, performed its first flight on 18 April 2002. The machine was given the name "Paul Revere" to reflect its mission to provide warning of attack.

In the summer of 2003, the Air Force awarded a contract to Boeing for a test-bed aircraft, based on the Boeing 767-400ER airliner. The production MC2A was to be designated the "E-10A". The original plan was to begin with the battlefield surveillance mission; then add an airborne early warning (AEW) capability to the E-10A, allowing it to replace the E-3 AWACS; and then add SIGINT capabilities, allowing it to replace the RC-135 Rivet Joint platform. Critics suggested that trying to have one aircraft do all three functions was flying in the face of the laws of physics, and the Air Force then considered separate "E-10B" AEW and "E-10C" SIGINT versions.

Although defense programs do tend to be moving targets during their early development, it was still unsurprising that the E-10A MC2A suffered some political difficulties because Congress found the Air Force's story on the machine exasperatingly fuzzy and inconsistent. Congressmen weren't the only ones baffled; AVIATION WEEK magazine summed up the exasperation in a short article titled "One Plane To Confuse Them All" -- no doubt the author was a Tolkien fan.

Other political difficulties were catching up with the program as well. It was about at this time that the program's linkage to the 767 tanker effort led to difficulties. The Air Force and Boeing came up with an unconventional funding scheme for the tankers based on a lease arrangement. The lease deal attracted some very negative attention from the US Congress, with critics claiming it amounted to a pay-off program for Boeing at taxpayer’s expense. That was only the start of the tanker program's political troubles, with the Air Force painfully stumbling through repeated cycles of trying to get the program off the ground, only finally managing to get a contract awarded to Boeing for the 767-based "KC-46" in 2011.

The details of the nightmarish tanker procurement effort cannot be considered here. Enough to say that the E-10 MC2A effort was caught in the turbulence, and its shifting definition didn't inspire confidence in the project in Congress, particularly at a time when the US armed services were heavily committed in the Middle East and money was tight. The E-10 was cut from the Fiscal Year 2008 budget.

* In the wake of this fiasco, the fallback plan was to upgrade the Joint-STARS fleet. With funds tight Northrop Grumman abandoned MP-RTIP, instead envisioning enhancements to the AN/APY-7 radar system and other avionics, along with the addition of of the MS-117 multispectral imager at the rear of the radar canoe fairing -- the imager had already been evaluated on a Joint-STARS -- and two AESA arrays in "cheek" positions on the side of the forward fuselage. The AESA arrays would be based on technology developed for the F-35 Joint Strike Fighter program, and would provide much of the capability of MP-RTIP at lower cost.

That ended up more or less a non-starter as well, since the Air Force finally decided to replace the fleet with the Global Hawk drone and with a smaller crewed platform. The simple reality is that system avionics have improved so much, becoming more compact and capable, that a smaller aircraft can do the job perfectly well. The replacement system will be much more automated and much cheaper to operate.

The Air Force conducted a "business fair" in 2014 to consider options, with Boeing, Bombardier, and Gulfstream flying in demonstrators; the Gulfstream 550 and Boeing 737-700 are seen as prime candidates. Risk-reduction investigations were funded in 2015, The current schedule envisions, possibly optimistically, an initial operational capability in 2023, with 17 new machines to be obtained in all, and the E-8C to be phased out from 2019.



* As concerns copyrights and permissions for this document, all illustrations and images credited to me are public domain. I reserve all rights to my writings. However, if anyone does want to make use of my writings, just contact me, and we can chat about it. I'm lenient in giving permissions, usually on the basis of being properly credited.

E-8C Joint-STARS

* Sources include:

Other materials were also found on the Federation of American Scientists website and US military sources found on the web.

* Revision history:

   v1.0   / 01 apr 01 
   v2.0.0 / 01 nov 10 / Broke out as stand-alone document.
   v2.0.1 / 01 oct 12 / Detuned futures.
   v2.0.2 / 01 sep 14 / Bizjet replacement.
   v2.1.0 / 01 aug 16 / General clean-up.

This item was originally released as part of a consolidated survey of battlefield surveillance aircraft. In 2010 I decided the survey was clumsy and hard to maintain, so broke it up into individual documents. I gave the new stand-alone Joint-STARS document a revcode of v2.0.0.