Col Ben Robinson, commander of the USAir Force's 93rd Air Expeditionary Group (Provisional) says: "We shoot no missiles; we carry no cargo; our only product is information; and information dominance is the key to success." The system which brings so much to the modern battlefield without firing a shot is the US Army/Air Force Northrop Grumman E-8C Joint Surveillance Target Attack Radar System (JSTARS), mounted on converted Boeing 707 airframes as E-8Cs.

The latest deployment of the JSTARS, to Rhein Main AB in Frankfurt, Germany, marks a major, and long-awaited, development in the programme. On 15 November, 1996, the USAF undertook its first-ever operational mission with its first production E-8C (P-1). Since then, the P-1 and a pre-production E-8C (T-3) have been flown on an average of six missions a week over the former Yugoslavia. The flights were expected to continue for at least 60 days, with the two aircraft supported by five deployable ground stations.

The deployment has added significance for Northrop Grumman, which is trying to sell up to 18 JSTARS aircraft to NATO, and possibly an additional six to the UK for its Airborne Stand-Off Radar (ASTOR) requirement. Lockheed Martin and Raytheon are also expected to bid for the ASTOR requirement, with solutions based on the Gulfstream V and Bombardier Global Express business jets, respectively. NATO and the UK could both make their decisions as early as 1998.


T-3 mission

Flight International recently participated in a mission on board the T-3, which is fitted with a production-standard radar, but which still contains some Northrop Grumman test equipment. The aircraft has the standard 17 operator consoles, however, and the extra test hardware displaces three bunkbeds and an extra row of passenger seats which are included in the production version.

This aircraft was to be used for only a handful of further operational missions before being replaced at Frankfurt by the second production aircraft (P-2). The T-3 is due to be returned to prime contractor Northrop Grumman for use as a software-development testbed, based in Melbourne, Florida.

The USAF is to receive a total of 19 E-8Cs, 15 of which will equip three squadrons with five operational aircraft each, allowing two aircraft to be in maintenance and two to be used for training at any one time. Each of the $850 million aircraft will require the equivalent of two full crews. There is to be a heavy emphasis on training as deliveries of production-aircraft progress at the rate of about two a year - our crew included several students and instructors.

The aircraft carries a standard complement of 21 personnel, including two pilots, a flight engineer and a navigator. The five central computers (three primary, two for "calibration") which form the heart of the JSTARS are housed in the forward cabin, behind which are the 17, basically identical, operator consoles. There is an additional console for the navigator, located in the forward cabin, behind the flightdeck.

According to Lt Col Charles Freniere, commander of the 12th Airborne Command and Control Squadron, each of the 17 consoles alone "-has more computing power than the E-3 AWACS [Airborne Warning and Control System]". Freniere points out that it is this growth in available computing power that has made development of the JSTARS possible.

The E-8C airframe, meanwhile, is based on a remanufactured commercial Boeing 707-320C, and the original Pratt & Whitney JT3D engines and the analogue flightdeck have been retained, at least for the time being. The remanufacturing process, however, has not been without its problems. The P-1 was grounded for nearly a month in June, following the discovery that incorrect rivets had been used at several locations throughout the airframe. Following a comprehensive inspection by Boeing and Northrop Grumman engineers, the aircraft was cleared to fly, although operational restrictions were temporarily imposed. The aircraft is due to undergo a heavy check in late 1997, when the incorrect rivets will be replaced.

The performance and reliability of the converted 707 airframes was also criticised in 1996 in a report by the US Department of Defense's (DoD) director of operational test and evaluation. For example, the aircraft cannot use NATO-standard 2,400m (7,900ft) runways without a fuel reduction, says the report. Re-engineing could help solve these problems, but would be expensive. "[The airfield performance] constrains us at times," says Freniere, who points out that people always want more. "In flight, it doesn't matter," he adds.

On this mission, we took off at around 02:30, and headed towards the Adriatic, climbing slowly. It took around 1.5h to reach Bosnia from Frankfurt. Operation Joint Endeavour II involves the withdrawal of existing United Nations Implementation Force soldiers, and their replacement by Stabilisation Force troops. The JSTARS provides the unique ability to monitor this transition, while also monitoring compliance with the Dayton Peace Accords.

The aircraft commander was Capt Mike Edwards, and Maj Don Kepley was the mission- crew commander. For this mission, the crew was charged with monitoring Bosnia's south-eastern Multi-National Division (MND), or sector, where French ground forces are stationed. UK and US troops occupy the south- western and northern MNDs.

It was planned that our aircraft would be flown in an orbital pattern inside Bosnian airspace for 3-4h, before heading back out over the Adriatic to rendezvous with a Boeing KC-135R tanker for aerial refuelling. The aircraft would then return to its "orbit" for a further 3-4h.

Because of the resumption of commercial flights through the airspace above Bosnia, the JSTARS was flown below its normal operating altitude of around 35,000ft. Most of the mission was flown at about 29,000ft, which reduces slightly the area which the radar can monitor, and results in higher fuel consumption.

As the aircraft reached the Bosnian border, the navigator monitored its position relative to the planned course, which is shown on his large display, overlaid onto a map. The navigator's console is separate from the flightdeck, and is therefore equipped with several analogue displays providing primary flight information such as altitude, speed and heading. It is also fitted with a flight-management system (FMS)unit, identical to those in the cockpit. The FMS uses data from dual inertial-navigation systems and a global-positioning-system receiver to calculate the aircraft's position.

Meanwhile, the radar had already been switched on, confirmed by a series of "clunks" audible in the aircraft's cabin. The phased-array radar antenna, the largest ever mounted in an aircraft, is housed inside an 8m-long canoe-shaped radome beneath the forward fuselage.


'Race-track' orbit

Following a short holding period over the Adriatic with the crew awaiting final clearance, the E-8C was put into a "race-track" orbit as we entered Bosnian airspace. The orbit was oriented roughly east to west, and measured around 140km (75nm) in length by 18km wide, and centred some 65km north of the "intended area of interest", says Freniere.

Rob Faulk, an instructor navigator, says that the orbit is sometimes adjusted during a mission, "-to get the best radar data". He adds that so much information is available via the operator's consoles that an important aspect is rationalising what is displayed. "The biggest challenge is: 'What information do you want to manage to successfully do your job?'," he says , for the operator to avoid "information overload".

Behind the navigator's console are two communications consoles. The operators at these consoles manage surveillance and control datalinks with ground-station modules (GSMs), as well as ultra-high frequency, very- high-frequency and high-frequency voice channels and a satellite-communications datalink.

The JSTARS also communicates with AWACS aircraft via the Joint Tactical Information Distribution Systemsecure data-communications network. Each GSM consists of a ground data terminal and general-purpose data-processing and display equipment, mounted on a 5t truck.

These units allow commanders on the ground to receive and transmit information on a near-real-time basis. Near-real-time effectively means a "delay" of around 5-10min, says Freniere, as this is the minimum time required to detect "rates of change" while monitoring moving vehicles, and to carry out the necessary processing.

Also part of the JSTARS crew are a pair of airborne mission-systems specialists (AMSS), who act as "onboard technicians", troubleshooting problems with the radar system as they arise. The radar itself is interfaced with two sets of computers housed in the forward cargo bay of the aircraft - one of which inputs instructions to the radar, while the other gathers the raw data which are output. The five central computers in the aircraft's cabin are used for prioritising and managing the tasks requested by the crew, ensuring the most efficient use of the radar, and for interpreting the data.

The two fundamental operating modes of the radar are known as wide-area surveillance (WAS) and moving-target indicator (MTI), which are designed to locate and identify slow-moving targets. Using advanced signal processing, the system can even differentiate between wheeled and tracked vehicles. The synthetic-aperture-radar/fixed-target-indicator (SAR/ FTI) modes, meanwhile, are capable of producing photograph-like images of selected areas, which map the locations of critical fixed targets such as airports, bridges and buildings.

Although the majority of the WAS/MTI and SAR/FTI processing is performed by the central computers, some localised processing is also carried out at the consoles themselves. This "-frees up the [central] computers to do all the calculations they need to on the radar, and monitor the system", says Tech Sgt Dave Feagan, one of the AMSS in the crew.

Behind the AMSS consoles is the operations section, crewed by six Air Force personnel. These include a senior director, senior director technical, weapons director and three air operations technicians. The operations section is responsible for liaising with the AWACS, providing information on possible targets for air attack, although Freniere points out that the system does not yet have the capability to distinguish between hostile and friendly targets. In a conventional conflict, the JSTARS is able to look up to 200km into enemyterritory, beyond the so-called forward line of troops (FLOT), and anything beyond the FLOT line is considered to be a possible target, adds Freniere.

In WAS/MTI modes, vehicles on the ground are identified by small dots, which are coloured yellow or magenta, depending on their speed and direction. By overlaying the cumulative data gathered from radar sweeps over, for example, the previous 30min, the crew are quickly able to identify major routes and areas of high vehicle activity.


Overall trends

It is the job of the operations section to study this information and look for overall trends in the ground movements which the radar observes. The operators can call on aircraft, missiles or artillery for fire support. "The computer can't interpret what it sees," despite the high level of processing, points out senior director Keith Jones. He adds: "We have alternative radar modes coming in the future that will provide much more data with better resolution."

Another two consoles are manned by Army personnel, called target surveillance supervisors (TSS). The TSS communicate through the GSMs with Army commanders on the ground, who are able to issue so-called radar-service requests (RSRs), using voice links or on-line electronic mail. The RSRs usually call for SAR "shoots" of particular areas of interest. "You don't need to SAR the whole battlefield," says Freniere.

Freniere points out that the latest deployment of the JSTARS has provided an opportunity for crews to fine-tune many operational aspects of the system, as they build up experience. One example is the development of modified radar tactics, such as the so-called "Crescenta" orbit, which allows a given target area to be scanned more effectively by changing slightly the shape of the circuit that the aircraft flies (see diagram). "One reason we're over here is that we are trying to learn how best to use the radar," says Freniere.

During the final hour over Bosnia, an exercise was carried out with a pair of Lockheed Martin F-16s, which were directed to simulated targets on the ground. The JSTARS finally touched down at Frankfurt at 15:00, at the end of a mission which had lasted around 12.5h.

Despite the fact that October's DoD report also described the system's software as "immature", and in need of "substantial improvement", Air Force officials stress that the production-standard JSTARS is now considered fully operational. A software update planned for April is aimed at solving the majority of the outstanding software problems. There seems little doubt, however, that the JSTARS is playing a vital role over Bosnia. This, together with its highly praised performance during the Gulf War, when 49 combat sorties were flown, presents a strong case of justification for the cost of the programme.

Source: Flight International