Northrop Grumman E-8C Joint Stars

Grumman OV-1 MohawkThe threat from a surprise attack by the Warsaw Pact across the plains of West Germany lead to the development of a new type of aircraft designed to provide battlefield surveillance and detect the warning signs of an impending attack. In West Germany from the 1970’s the US Army operated a number of Grumman OV-1 Mohawk aircraft equipped with a large SLAR, however, these aircraft were limited in range, endurance and the SLAR had a fairly limited capability.

The US Army and the US Air Force recognised the need for a more up-to-date system and initially undertook separate studies to try and identify the most appropriate system. The US Army initially planned the Stand-Off Target Acquisition System (SOTAS) based on the Sikorsky H-60 helicopter, whilst the Air Force and the Defence Advanced Research Projects Agency (DARPA) were involved in developing an advanced Synthetic Aperture Radar (SAR) and Moving Target Indicator (MTI) system known as Pave Mover. Then in 1982 the Army and Air Force programmes were merged and in 1984 published their requirements for a new battlefield surveillance aircraft, named the Joint Surveillance and Target Attack Radar System (J-STARS).

E-8C J-STARSIn 1985 Grumman won a contract to produce two development E-8A prototype J-STARS based on two used Boeing 707-320C aircraft. The development of the new radar was subcontracted to Norden Systems. The first prototype E-8A finally flew in April 1988 without the radar installed and flew with the radar installed on 22 Dec 88. The second J-STARS made its first flight on 31 Aug 89 and later that year both aircraft conducted communication trials and made visits to Europe. The original acquisition plan called for 10 J-STARS aircraft, but in Apr 88 this was increased to 22 aircraft using new Boeing 707 airframes. However, Boeing was planning to close the 707 production line in May 91 and, as a consequence, the cost of each airframe was increasing. Eventually in Nov 89 it was decided to purchase a number of used Boeing 707-300 airframes and convert them into production E-8C J-STARS. In 1990 a contract for a single pre-production E-8C was awarded, this was followed in 1993 by another Low Rate Initial Production contract for five aircraft.

E-8C J-STARSIn the 1991 Gulf War it was decided to send the two development E-8As to the Middle East to conduct ‘operational tests’. The two aircraft flew a total of 49 combat missions and even though these aircraft were not up to the standard of the production E-8C they proved extremely useful in detecting and tracking large formations of Iraqi vehicles as they retreated north out of Kuwait. The first production E-8C was delivered in Jun 96 and J-STARS achieved initial operational capability in 1997 with the delivery of the third production aircraft. It was eventually decided that only 17 aircraft would be purchased and the final E-8C J-STARS was delivered in Mar 05. The last seven aircraft were all delivered to the final Block 20 standard, a progressive programme to bring the remaining 10 aircraft up to Block 20 standard configuration is already underway.

E-8C J-STARS radomeExternally the E-8C is little different from the Boeing 707-300 commercial airframe. The only really obvious difference is the 40-foot long canoe shaped radome mounted under the forward fuselage that houses the 24 –foot long APY-3 Norden Systems multi-mode phased array battlefield surveillance radar. The radar antenna is mechanically tiled from side-to-side for elevation scanning, azimuth scanning is performed electronically. The radar can operate in a variety of modes:

Wide Area Surveillance / Moving Target Indicator (WAS / MTI) is the primary operating mode and this can detect, locate and identify slow moving vehicles in a target area 200 square miles in size. The radar can differentiate between wheeled and tracked vehicles, has a maritime mode and can also track slow moving helicopters and has a maximum range in excess of 150nms.

Sector Search Mode (SSM) this mode allows the radar to be focussed on a target area 18nms x 18nms, with the radar refreshing the picture every 60 secs.

Attack Planning Mode (APM) this is a high resolution mode where the radar focussed on an area 7nms x 7nms and refreshes the picture every 6 secs.

Synthetic Aperture Radar / Fixed Target Indicator (SAR / FTI) - in SAR/FTI mode the radar can produce a near photographic image of the target area by building up a mosaic of images from multiple radar sweeps. In SAR/FTI mode the radar has a range of about 110 miles to either side of the aircraft from the usual operating height. Using this mode, in a single 8hr sortie an area of 386,000 can be accurately mapped. By using the MTI history alongside SAR/FTI, post attack assessments can be made.

E-8C J-STARS insideThe E-8C J-STARS has a flight crew of four, comprising pilot, co-pilot, flight engineer and navigator/self defence suite operator together with a mission crew of 18. The radar data is displayed on up to 17 identical operators consoles, based on the DEC Alpha system, positioned in the middle to rear of the fuselage. A single console is also dedicated to 'defensice systems'. On extended missions an additional 13 replacement crew members can be carried. Both US Air Force and Army personnel are employed as console operators. All aircraft are equipped wwith six bunks and a rest area. All the E-8C aircraft are assigned to the 116th Air Control Wing of the Georgia Air National Guard, based at Robins AFB Georgia and are frequently deployed on operations world-wide.

E-8C J-STARS consoleThe radar console operators usually interpret the radar data obtained by J-STARS. However, it is also down-linked in near real-time via the secure Cubic Systems Surveillance & Control Data Link (SCDL) to US Army operators located in mobile Common Ground Stations (CGS), enabling Army commanders to access the data and interpret it themselves. In addition, the J-STARS is equipped with SATCOM enabling it to still relay the radar data when out of range of the ground stations. It also has two JTIDS and a Tactical Data Information Link-J (TADIL-J) together with extensive UHF, VHF and SW communications.

E-8C J-STARSTo keep costs down when the aircraft were converted into E-8C configuration, it was decided to retain the original four P&W TF33-102C turbofan engines. In retrospect this was a mistake, as these old engines are noisy, dirty and inefficient, and it would have been far better to fit the refurbished aircraft with modern CFM-56 turbofan engines, as fitted to updated KC-135s / RC-135s. The old engines fitted on the J-STARS are really inadequate for full gross weight operations, particularly in hot/high conditions, with the aircraft needing 11,000 ft of runway to take-off and also restrict a fully loaded aircraft to operating at around 30-32,000ft. This lack of engine power impacts on the radars performance – the higher the aircraft can fly, the better the performance of the radar. A higher operating ceiling would also help reduce the effects of ‘terrain masking’, a particular problem in mountainous countries like the Balkans and Afghanistan. However, the USAF does not appear able to fund the CFM-56 engines for the J-STARS, instead it seems more likely that the aircraft will be ‘upgraded’ with refurbished P&W JT8D engines, replacing a 1950’s technology turbojet engine with a 1960’s turbofan engine – an improvement, but not what is really needed.

E-8C J-STARSThe entire J-STARS fleet are being progessively upgraded to the Block 20 configuration of the last seven production aircraft in a $40million programme, which has seen new Compaq workstations installed, together with a new General Dynamics radar signall processor and a fibre-optic network. A new open architecture configuration, using two commercial Compaq GS-320 'AlphaServer' processors will allow the aircraft to be upgraded more effectively in the future when new systems are developed. Another development planned for the future is the aircraft’s APY-3 radar benefiting from the $1.3 billion Multi-Platform Radar Technology Insertion Programme (MP-RTIP). Around 2012, the new APY-X two-dimensional electronically scanned active array radar could well replace the current APY-3 radar. In addition, it is also planned to improve the current SAR image resolution with the Enhanced Synthetic Aperture Radar (ESAR) and Inverse Synthetic Aperture Radar (ISAR) upgrades. Another upgrade programme for the J-STARS is the concept of Automatic Target Recognition (ATR) which will provide templating techniques to identify ground-based targets, using the processed ESAR and ISAR data. The MP-RTIP was originally intended to be installed in the E-10 Multi-Mission Command and Control Aircraft and the RQ-4 Global Hawk rather than the E-8, however, considerable doubts are being raised about the programme cost and appropriate E-10 acquision timescale and this could result in the radar being installed on the E-8. If the upgrade is approved, the first five RTIP equipped would be operational until around 2012.

E-8C J-STARSThe E-8C J-STARS has proved its worth in operations over Bosnia-Herzegovina in Operation Joint Endeavour in 1995, Operation Allied Force in 1999 and Operation Enduring Freedom in 2002. When they entered service the aircraft provided a unique capability, however, new battlefield surveillance aircraft are already planned which will have performance at least comparable with and might possibly even better than that provided by J-STARS. The RAF’s ASTOR R1 and NATO’s AGS programmes will greatly increase the numbers of battlefield surveillance aircraft and I imagine that when these aircraft enter service the E-8 J-STARS fleet will soon be progressively back in the hanger for appropriate engine and radar upgrades, ensuring thry remain at the cutting edge of this vital area of military capability.