Paul Lewis/MELBOURNE, FLORIDA
After years of deliberation, NATO has embarked on a programme that could see the alliance field its own version of the US Joint Surveillance Target Attack Radar System (Joint STARS) by 2007. Northrop Grumman is determined to bounce back from its recent disappointment in the UK's Airborne Stand-off Radar (ASTOR) competition with an offer to Europe which leverages off the US Air Force's newly funded Radar Technology Insertion Programme (RTIP) upgrade of the E-8C Joint STARS.
The NATO Conference of National Armament Directors (CNAD) has initiated a programme definition phase for the Airborne Ground Surveillance (AGS) system following the conclusion of a year-long concept study this year. This process is expected to lead to a development contract being awarded by mid-2002 for a NATO-owned and operated AGS force.
Planning calls for the initial deployment in 2007 of six AGS aircraft modelled on the Boeing E-3A-equipped NATO Airborne Early Warning Force based at Geilenkirchen, Germany. It would complement the USAF's expanding E-8C Joint STARS fleet, which totals 14 funded aircraft, and the UK's planned five Raytheon ASTOR-equipped Bombardier Global Express jets.
The need for an organic NATO Joint STARS-type capability has again been more than amply demonstrated in Europe's own backyard by the recent Kosovo conflict.
"Kosovo gave Joint STARS a shot in the arm," claims Frank Dogaer, Northrop Grumman's international programme director, AGS and battle management systems. "Modern conflicts with an elusive enemy operating in not-very-well-defined battlespace, intermixed with civilians and anything else to stay safe, is driving surveillance requirements astronomically. This has been brought home by the accidental targeting and destruction of non-military vehicles," he adds.
NATO is no stranger to the Northrop Grumman Joint STARS programme, having already examined and rejected the baseline Boeing 707-300 airframe. The Melbourne, Florida-based company's response to a subsequent CNAD request for fresh concepts has been to take full advantage of the USAF's planned RTIP upgrade for the E-8C and repackage the improved system into a platform more palatable to Europe.
"In the past we were offering the 707. There has been European resistance to a total US system. We've now changed this and saying you can put the radar on anything you want," says Robert Zaeiser, Northrop Grumman's director of international customer requirements, surveillance and battle management. A range of alternatives has been studied, including compacting the system into either the Global Express or Gulfstream V business jets à la ASTOR, or installing the system in a larger Airbus Industrie A320 series narrowbody jet.
Northrop Grumman's recommended solution is the stretched A321 member of the mid-size aircraft family (Flight International, 13-19 October). Business jets are large enough to accommodate equipment for only three radar workstations, whereas NATO is looking for at least eight and as many 12 operator positions. Aside from internal cabin volume, the A321 has the benefit of a longer forward fuselage from which to mount the Joint STARS antenna, so maximising the radar's azimuth sweep clear of interference from the engine and wing.
At the heart of the USAF's $1.2 billion RTIP upgrade, launched last year, is a new APY-X active two-dimensional electronically scanned array radar. The new 7.3m (24ft)-long system is a replacement for the APY-3, which relies on a combination of a phased array for azimuth scanning and mechanical steering in elevation.
Not only is the new system lighter and much faster, with the radar revisit rate measured in just a few seconds rather tens of seconds, it can be scaled in size. Dogaer explains: "Our approach to this is to develop a family of modular radars, with which we hope to proliferate the skies using a series of platforms, starting with Joint STARS, going down to something we can put into NATO, business jets and all the way down to unmanned aerial vehicles [UAVs]. It looks like it's technically feasible to do. Since it's active, most of the radar is in the antenna array."
A separately funded $132 million commercial-off-the-shelf (COTS) improvement programme under way since 1997 has reduced the number of Joint STARS central computers from five to two line replaceable units, saving on space and weight. Not only is there a massive increase in signal processing and memory capacity, costs have been cut by adopting Compaq and Cortran COTS hardware in place of military-specified equipment. As an example, the cost of a keyboard has been slashed from $30,000 to $2,000.
RTIP will provide a significant jump in detection and tracking capability. For the first time it will permit virtual simultaneous use of the Joint STARS baseline moving target indicator (MTI) and synthetic aperture radar (SAR) modes. MTI sweeps reportedly have to be stopped for 60s or more to shoot an SAR image of a fixed object, during which time track fidelity is compromised and there is the danger of a target being lost, particularly in crowded traffic or difficult terrain.
"That's a drawback to the design of today's system. RTIP fixes that by the fact that it is an active electronically scanned array which allows you to move the beam almost instantaneously and in effect giving you simultaneous modes," says Dogaer. It is a capability even the new UK ASTOR will not have. Instead it will continue to rely on interleaving MTI and SAR.
RTIP furthermore introduces two detection and tracking modes - high-range resolution MTI (HRRMTI) and inverse SAR (ISAR). The former runs continually and permits the measurement of individual vehicles being tracked. HRRMTI can be programmed to flag targets over a certain length, enabling mobile missile launchers to be distinguished from tractors.
ISAR uses technology developed for maritime operations to generate images of moving targets. "This allows you to take the same kind of picture at the same resolution of a vehicle on the move. Rather than using the movement of the sensor to create an image, it uses the motion of a vehicle to create a picture. It is a function of what's moving," says Dogaer.
The APY-X's concurrent multimode capability will enable operators to view a composite picture combining different overlaid MTI and SAR/ISAR images seen from more than 250km (135nm) away. Moving targets can be tracked relative to fixed objects such as bridges and roads, while displays can be scaled from wide area surveillance of an army corps down to tracking and classifying of individual vehicles, all from the one common set of data. A picture-in-picture display capability has also demonstrated viewing remote UAV imagery and data.
The next logical step is to harness and correlate HRRMTI and ISAR information to provide automatic target recognition, a capability about which little has been said to date.
"Our ultimate goal is the ability to pre-position weapons on a target. If you back up far enough that's what the surveillance guy is trying to eventually get done," suggest Dogaer.
Northrop Grumman has moved quickly to try and cement support for Joint STARS, forming a working group of 24 companies from 15 of NATO's 19 member states. Its message is clear: RTIP offers Europe a one-off opportunity to field its own Joint STARS capability, the development of which has already been funded by the USA. The alternative is a go-it-alone European development devoid of any US financial support and without any operational interoperability or system commonality with the E-8C.
Source: Flight International
