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.

Lanza Extravaganza

The UK’s acquisition of a single Indra Lanza LTR-25 deployable radar strengthens the British armed force’s operational/theatre level ground-based air defence.

The RAF’S procurement of a new Lanza LTR-25 radar will strengthen deployed, operational/theatre level ground-based air defence. (Indra)

The UK’s acquisition of a single Indra Lanza LTR-25 deployable radar strengthens the British armed force’s operational/theatre level ground-based air defence.

The UK has again strengthened its fleet of deployable radars. On 13 May Indra announced that the UK Ministry of Defence had procured a single Lanza LTR-25 L-band (1.215 gigahertz/GHz to 1.4GHz) ground-based air surveillance radar.

An official announcement from the company stated that the radar will equip the Royal Air Force (RAF) and delivery is expected by the end of the year. The radar has an instrumented range of 239 nautical miles/nm (444 kilometres/km). Although not articulated in the company’s press release the acquisition could be worth up to $13.4 million to the firm based on the derived price for this radar.The UK joins Argentina, Ecuador, Guatemala, the North Atlantic Treaty Organisation, Oman, Portugal, Rwanda, Thailand and Uruguay all of which have acquired variants of the Lanza radar over the past two decades. In British service the Lanza LTR-25 will supplement several deployable ground-based air surveillance radars. These include ten Saab Giraffe-AMB C-band (5.25GHz to 5.925GHz) ground-based air surveillance radars purchased and delivered between 2008 and 2018 jointly operated by the British Army and RAF. The Giraffe-AMB has an instrumented range of up to 54nm (100km) and is arguably configured to support short-to-medium range air defence. It is expected that  the Lanza LTR-25 will be provide surveillance to support theatre-level air defence.


Germany: Are You Receiving Me?

New Transmit Receive Module (Cassidian)
New Transmit Receive Module (Cassidian)

Cassidian has provided ChainHomeHigh with more details regarding its development of a new generation of Transmit/Receive (T/R) modules that the company has designed for Active Electronically Scanned Array (AESA) radars.

According to Cassidian, these T/R modules will deliver a high performance, and will be 30 percent cheaper to produce when compared to other T/R modules.

T/R modules provide major enhancements in radar performance by generating the Radio Frequency (RF) energy directly within the antenna, rather than requiring a dedicated separate transmitter. This helps to reduce the size and weight of radars at the same time improving their reliability. Other technical benefits afforded by the modules include a stable power output over one gigahertz and an impressive degree of reliability compared to previous generations of T/R modules.

Cassidian expects to use these T/R modules in a range of applications including the Captor-E AESA radar which the company is helping to develop for the Eurofighter Typhoon combat aircraft, its Spexer ground-surveillance radar family and also space-based radar surveillance applications.

A Cassidian spokesperson told ChainHomeHigh that the company used its own research and development budget to fund their design, and the company adds that the new modules could be used to retrofit existing AESA systems that a customer may have depending on their requirements.

United Kingdom: Sir Robert Watson-Watt Statue Project Moves Forward

The Sir Robert Watson-Watt Society of Brechin, southeast Scotland, has received a donation worth €12,278 ($16,108) to contribute towards its campaign to build a statue to commemorate the radar pioneer. Sir Robert was born in Brechin on 13th April 1892. The donation was made by Brechin Civic Trust.

The donation will allow work to continue on the design of a bronze statue of Sir Robert. Alan Herriot, a world-renown Scottish sculptor, is performing the work. This latest donation will allow the building a clay model of the statue. This will enable a mould to be constructed for a bronze foundry to cast the final statue.

Those seeking more information regarding the society’s work, or wishing to make a donation towards the statue project can find more details here: http://www.watsonwatt.org/index.htm

Sir Robert Watson-Watt (Wikimedia Commons)
Sir Robert Watson-Watt (Wikimedia Commons)

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