Aviation Week & Space Technology
July 24, 2000
Pg. 59

Joint Strike Fighter Could Serve As Jammer

By David A. Fulghum, Washington

The multinational Joint Strike Fighter is being strongly considered as the replacement for the aging EA-6B Prowler radar and communications jamming aircraft. But rapidly improving electronics are creating concerns about what technology should be in the stealthy new strike aircraft and how it should be used to foil a foe’s antiaircraft weapons.

Modern improvements to radar that gave pilots a better awareness of the battle around them began in the 1960s with the ability to track a target while continuing to search for additional enemy aircraft. The F-14A was the first fighter with that capability. But due to data processing time lags, detection and tracking ranges were very different. That reduced the effective range of a fighter’s air-to-air weapons.

Today, there is a technology that transcends these traditional radar limitations. It’s the active electronically scanned array (AESA) radar which is to be installed in the Astor, F-22, F/A-18, upgraded F-15C and F-16, the Joint Strike Fighter and, eventually, space-based radar satellites. These AESA radars are made up of high-speed processors and 1,000-2,000 transmitter/receiver elements that can conduct a variety of tasks including nearly instantaneous update of target tracks, radar jamming and monitoring of enemy electronic emissions.

THE NEW AESA RADARS provide essentially the same track and detection ranges. This opens the door for development of air-to-air missiles with ranges of 100 mi. or more. Moreover, a reasonably talented pilot will be able to track scores of targets while plotting the location and type of enemy radars, a mission known as electronic support measures (ESM), and jam those radars that control antiaircraft weapons by applying electronic counter-measures (ECM). Veteran combat pilots say that they are still worried about task saturation and information overload when a one-man crew tries to handle the electronic warfare mission. The predecessor EF-111 and EA-6B each had a two-man crew, one of whom was an electronic warfare specialist.

The critical mission of jamming with an AESA will force radar manufacturers Raytheon (teamed with Boeing on the JSF) and Northrop Grumman (teamed with Lockheed Martin) to make a number of design decisions. They can either build their fighter radars to jam as many frequencies as possible (Raytheon’s solution), or they can fit the aircraft with a second radar antenna that can cover all the frequencies (Northrop Grumman’s solution).

Raytheon’s approach will lead to one radar that counters all lethal radar threats, including those associated with the most modern antiaircraft missile systems. Air Force officials say that among them are the Russian-made SA-10, -12 and -20 family that use very-high-frequency radars. It does not jam low-frequency early warning radar. These early warning radars are used to detect aircraft at long range, often spotting even stealth designs, but without the precision needed to direct a missile to them. However, these early warning radars could cue other radars and missiles that might be able to engage a stealthy U.S. aircraft at short range. Yugoslav early warning radars were able to use such a combination to shoot down a U.S. Air Force F-117 during the 1999 Kosovo air campaign.

Raytheon researchers believe that to counter the early warning radar threat, a specialized JSF derivative would have to be developed using one of a number of jamming options depending on the military’s requirements.

Northrop Grumman’s solution is to add a second AESA antenna and radome that would be designed to cover the lower frequencies and put out both barrage and pencil-beam jamming signals. However, an additional antenna would add weight, cost and cooling requirements to a design that is already hovering right at its critical weight.

THE ADDITIONAL EMISSIONS from a second radar antenna would make it harder to keep an aircraft stealthy or low-observable. In current AESA designs, the antenna, instead of pointing directly ahead, is angled upward at perhaps 30-45 deg. to keep the radar’s emissions and its antenna’s reflections from being tracked by ground radars. The waveforms used are low-probability-of-intercept to make it more difficult for ground-based electronic surveillance sites to pick up JSF radar emissions.

Since a good enemy electronic emissions tracking (ESM) system would eventually detect even a low-probability-of-intercept jamming signal, the solution would likely be to create high-power jamming signals that can be transmitted by an aircraft operating from a safe area, well away from the enemy radar it is jamming.

While standoff jammers of this type are critical to war fighting, they are built and used operationally in small numbers. Given their added cost and weight, such aircraft would likely be very specialized and wouldn’t need to be stealthy.

As a result, the Pentagon has a choice to make. Officials can buy a single, standard stealthy strike aircraft that jams the lethal threats and can penetrate near to the target. Or it could buy a small number of specialized variants that can jam all the radars, but may be forced to stand outside the range of the most sophisticated antiaircraft missiles. The Russian-built S-400 family of missiles, for example, is designed with a range of 250 mi.