Analysis: Wishful Thinking

Forthcoming USAF platforms such as the B-21 Raider strategic bomber maybe yet more resistant to radar detection than present day low-RCS platforms (USAF)

The People’s Republic of China has made grandiose claims for the performance of its JY-27A ground-based air surveillance radar. They should be treated with caution.

An article published in the Global Times, an offshoot of the People’s Daily, itself a mouthpiece for the People’s Republic of China’s ruling Communist Party, claimed on 28 May that the country’s new CETC JY-27A Very High Frequency (VHF: 30 megahertz/MHz to 300MHz) can detect aircraft with a low Radar Cross Section (RCS). The article said that, not only can the radar detect such aircraft, but can “guide missiles to destroy them.”

Low frequency radars detecting low RCS aircraft is not a new claim. This principle has been known for decades and has already been exploited in radars like Russia’s NNIIRT 1L119 Nebo-SVU VHF system. The long wavelength signals transmitted by VHF radars have meant that while low-RCS aircraft maybe detectable, they may not be detectable with the sharp precision required to guide an Air-to-Air Missile (AAM) or Surface-to-Air Missile (SAM) to its target. Put simply, this is why many fighter radars, ground- and ship-based fire control radars and missile radar seekers transmit in frequencies from X-band (8.5 gigahertz/GHz to 10.68GHz) and above. What these radars lose in detection range, compared to lower frequency radars, they make up for in precision. The Global Times article claimed that Chinese radar engineers have solved this precision deficit by networking together several radars positioned a known distance from one another, looking at the same patch of sky in different directions to determine an aircraft’s location. Once detected it could be possible to guide “long-range anti-aircraft missiles” to perform precision strikes on these targets.

Networked Radars

Distributed, networked radars to counter stealth is an established concept. The electronic warfare and radar expert Dr. Carlo Kopp discussed this approach in his seminal 2012 article in Defence Today entitled ‘Advancing Counter-Stealth Radar Technology’. He asserted that “Defeating stealth targets using networking and data fusion presupposes that some radars can see the target some of the time, also that the target’s stealth is considerably poorer in some directions compared to others, and finally that the target is visible to radars from varying aspects.” Basically, a low RCS aircraft may have a low radar signature when viewed from head on, of from a particular angle but not an equally low signature in all directions. By scattering and networking several antennas across a wide area, one of the antennas may get a lucky glimpse of part of the aircraft which is not so stealthy and thus detect it. Dr. Kopp adds that for this to be effective, the non-stealthy part of the aircraft needs to be visible to that particular radar for some time. An aircraft flying into hostile airspace is unlikely to hang around and may be travelling at very high speeds, thus only exposing itself to the radar for a very short time. To further complicate matters, aircraft such as the US Air Force’s Northrop Grumman B-2A Spirit strategic bomber and Lockheed Martin F/A-22A Raptor air superiority fighter use ‘all-aspect’ RCS reduction techniques. This means that they are stealthy regardless of the angle from which they are viewed by radar. Future US aircraft, such as the forthcoming Northrop Grumman B-21 Raider strategic bomber are likely to have even better RCS reduction design configurations.

Dr. Kopp concedes that “a networked data fusion system (fusing data from several distributed radars) is thus not a panacea, but is potentially quite effective against stealth designs that do not have genuine ‘all aspect’ stealth capability.” There is an additional problem. Airframe limitations mean that low-RCS aircraft cannot be designed to defeat all radar transmission wavelengths. Instead, airframes are optimised to defeat the radar systems most likely to be used for the precision detection of such a target and for fire control. This typically includes radars transmitting in S-band (2.3GHz to 2.5GHz/2.7GHz to 3.7GHz) and above. To summarise, a network of VHF radars maybe capable of detecting an aircraft with a low RCS but lacking all-aspect stealth, yet weapons still have to be guided with precision to the target. This is where a fighter aircraft’s X-band radar would come into play, or the guidance radars and radar seekers used by AAMs or SAMs transmitting in X-band and above. These are precisely the frequencies that low-RCS aircraft are designed to defeat. Networked VHF radars may give you a good fix on where the aircraft is in the sky, but the missile’s end game still depends on higher frequency radars which stealth aircraft are designed to outfox.

Arguably this could be overcome by a salvo launch of SAMs and AAMs into the area of sky where the aircraft is thought to be. This might not be done with too much precision, but a load of missiles could be launched ballistically with the hope of scoring a lucky hit. It could prove an expensive tactic as it would potentially waste missiles at an early stage of a conflict, the moment when low-RCS aircraft are most likely to be used.

Jamming

Moreover, these VHF radars, and fire control radars operating in higher wavebands would almost certainly be subjected to heavy electronic attack at the outset of a conflict. Aircraft such as the F/A-22A, B-2A, B-21 or Lockheed Martin’s F-35A/B/C Lightning-II fighters would be accompanied by jamming platforms like the US Navy’s E/A-18G Growler aircraft as they fly into contested airspace. The Block-2 Low Band Jammer (LBJ) segment of the latter aircraft’s Next Generation Jammer, which replaces its current Harris AN/ALQ-99 tactical jamming system, is thought to cover a waveband of 100 megahertz to two gigahertz. The US Navy is currently selecting a vendor for the Block-2 LBJ with a team comprising Northrop Grumman and Harris, and L3 vying for selection. While VHF radars like the JY-27A maybe trying to detect low RCS aircraft, they will be a prime target for both escort and stand-off jamming for aircraft like the E/A-18G. They will also be high priority targets for kinetic weapons. Given the frequencies they use, VHF radars tend to be big. In the case of the JY-27A PRC officials have hinted that several radars are required to detect low RCS aircraft. Such targets could show up well on aerial reconnaissance imagery. They also need to transmit, and once transmitting, will reveal their position to ELINT (Electronic Intelligence) gathering assets such as the US Air Force’s Boeing RC-135U Combat Sent aircraft. Once their position is betrayed, electronic and kinetic attack can be brought to bear.

Conclusions

The PRC maybe feeling emboldened by the development of the JY-27A and its touted capabilities. The death of low RCS airframe design has been predicted umpteen times since the B-2A and Lockheed Martin F-117A Nighthawk ground attack aircraft debuted in service in 1997 and 1983 respectively. The possible shortcomings of such radars are no excuse to be complacent, and such systems should be high priority electronic and kinetic targets at the start of any conflict. The JY-27A’s attributes may be accompanied with a healthy serving of hyperbole, but that is no excuse for complacency.

All At Sea

A variant of the FlyingFish SIGINT system will equip the UK’s forthcoming IOD-3 AMBER satellite. (Horizon Technologies)

The growing provision of private-sector signals intelligence gathering will take an important step forward with the launch of the UK’s IOD-3 AMBER CubeSat in 2020.

The IOD-3 AMBER will be the first of a constellation of satellites providing a global Signals Intelligence (SIGINT) footprint to enhance maritime security for the British government. While the exact number of satellites that will eventually be launched has not been revealed, it is expected to include less than ten spacecraft.

The satellites will possess both an L-band (1.3 gigahertz/GHz to 1.7GHz) and Automatic Identification System (AIS: 161.975 megahertz/MHz to 162.025MHz) SIGINT packages. This is derived from Horizon Technologies’ FlyingFish COMINT-gathering system. FlyingFish routinely equips aircraft particularly maritime surveillance, maritime patrol and signals intelligence-gathering platforms. These furnish several NATO (North Atlantic Treaty Organisation) navies, coastguards and border protection agencies. The L-band equipment will detect Satellite Communications (COMINT) from vessels across a waveband of one gigahertz to two gigahertz. AIS is mandated by the International Maritime Organisation for all vessels displacing in excess of 300 tonnes.

AIS transponders equipping vessels transmit an array of regarding a vessel’s voyage, identity and location. By correlating the AIS and the source of the L-band SATCOM it becomes possible to cross reference both sets of transmissions and match them to a vessel’s location. X-band (7.9-8.4GHz to 7.25GHz/7.75GHz) downlink and S-band (two to four gigahertz) SATCOM COMINT receivers will also be carried. Interestingly the concept of operations used for the constellation does not require a number of satellites to receive transmissions and then triangulate the position of a vessel, based upon signal’s time difference of arrival at each satellite. Instead, the IOD-3 uses “a new proprietary geolocation technology which does not include groups of satellites ‘flying in formation’” to perform direction-finding, notes John Beckner, chief executive officer of Horizon Technologies.

Why is such technology needed? The high seas are home to criminal activities whether that be narcotics or people smuggling, illegal fishing or environmental damage. Sometimes such activities are betrayed by a vessel switching off its AIS transponder, or altering its transmissions. This can have the effect of making the vessel appear in a different location, or to be moving at speeds not routinely associated with marine traffic. Should AIS transmissions be spotted from a vessel that seems to be in two locations, the simultaneous collection of SATCOM COMINT will indicate the likely real location of the ship: SATCOM transmissions will not, for example, also be coming from the false position. The version of the Flying Fish COMINT system equipping the satellite can also demodulate L-band SATCOM transmissions. This means that users can directly listen to these communications. This is important for gathering intelligence on what the targeted vessel maybe doing. Secondly, AIS can be switched off by a vessel. Should this happen and then SATCOM be initiated, this could reveal that the vessel is engaged in suspect, or illegal activity. From a humanitarian perspective monitoring L-band SATCOM can enable the user to instantly receive distress calls and to immediately organise assistance given that the vessel’s location can be determined through its SATCOM and AIS transmissions. For example, satellite phones using the Thuraya (1.525GHz to 1.661GHz) network are routinely used by people smugglers in the Mediterranean. The phones are often the only means of communications with the outside world that boats carrying refugees have. In this context, aircraft equipped with the Flying Fish payload have helped saved numerous lives by intercepting distress calls from these craft when they run into trouble.

The IOD-3 Amber satellite will transmit its SIGINT to the Goonhilly teleport in southwest England. There, the data will be analysed using Horizon Technologies’ AMBER Ground Exploitation System. The IOD-3 will be launched from the International Space Station (ISS) in 2020. The satellite bus has been developed by AAC Clyde Space. Several undisclosed UK government agencies will receive the SIGINT collected by the satellites. The capability is being procured via a public-private partnership: Horizon Technologies and AAC Clyde has joined forces with the UK’s Satellite Applications Catapult technology incubator and Nanoracks which is organising the launch from the ISS. Meanwhile, the British government is funding the initiative and will be the customer for the intelligence.

Location, Location, Location

Raytheon’s AN/ALQ-213 is routinely used by the F-16CJ and Tornado-ECR to provide the precise geo-location of hostile radars. (Raytheon)

India might need a new electronic warfare system to accompany its NGARM anti-radar missile.

A senior source close to the Indian Air Force (IAF) Electronic Warfare (EW) community has told chainhomehigh that the force may need an emitter locator system to accompany its forthcoming New Generation Anti-Radiation Missile (NGARM). This new weapon, which performed flight tests from an IAF Sukhoi Su-30MKI fighter on 18 January, is under development. It represents a step change for the IAF’s Suppression of Enemy Air Defence (SEAD) posture and could enter service in the next five years.

An emitter locator system would be an important addition to hone the weapon’s accuracy. SEAD aircraft such as the US Air Force’s Lockheed Martin F-16CJ Viper Weasel and the Luftwaffe/Aeronautica Militaire (German and Italian Air Force) Panavia Tornado-ECR jets use Raytheon’s AN/ASQ-213 HARM (High Speed Anti Radiation Missile) and ELS (Emitter Location System) respectively. These provides highly precise targeting coordinates for the aircraft’s Raytheon AGM-88B/C/E HARMs though the geolocation of ground-based air surveillance and fire control/ground controlled interception radars using those radars’ emissions. Both systems are thought to cover a waveband of 0.5 megahertz to 20GHz encompassing the majority of the wavebands used by these radars. The ability of the AN/ASQ-213 and ELS allow the missiles to target low-band ground-based air surveillance radars routinely used to detect aircraft with a low radar cross section. Both the AN/ASQ-213 and the ELS are though to have a residual role collecting electronic Intelligence. This can be either recorded for later analysis or shared with other platforms to enable near-real time off-board kinetic or electronic attack to be directed against such targets.

While aircraft configured to deploy the AGM-88 series can do so without a locator system, the addition of the latter significantly sharpens the aircraft’s accuracy vis-à-vis the threat. It also enables threat prioritisation, and multiple threats to be engaged in a rapid sequence. This is important as it moves a platform beyond simply using an anti-radiation missile for self-protection, by which it will fire the weapon using the threat information presented by its radar warning receiver. Instead, an emitter locator system allows the aircraft to be used as a SEAD platform engaged in the identification and roll-back of an adversary’s ground-based air defences at the tactical and/or operational levels. The IAF is no stranger to SEAD. For example, it performed such missions against ground-based air surveillance radars located at Badin in southwest Pakistan during India’s 1965 war with the latter using English Electric Canberra-B Mk.56 medium bombers.

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