Introduction
Not long ago, Canada considered replacing its aging fleet of F-18 Hornets with F-35s. The merits of the F-35 were debated on a number of dimensions. One dimension was stealth. One of the F-35’s selling points was its status as a fifth generation stealth fighter.
In an interview with The Fifth Estate, Pierre Sprey, who was involved in the development of the F-16 Fighting Falcon and the A-10 Thunderbolt II, explained that long-wave radars used in the Battle of Britain could detect every stealth aircraft in the world. Russia never stopped building long-wave, low-frequency radars. They modernized them, deployed them, and are selling them all over the world.
Pierre Sprey’s interview on the Fifth Estate is illuminating, and can be watched here: Fifth Estate Interview on Stealth .
Now, the US and western countries never focused on the development of VHF radars for a number of reasons. America had a monopoly on stealth technology. However, time marches on, and peer adversaries have developed their own fifth generation fighters.
In my last SOFREP article, I elaborated on Sprey’s comments. I tried to give the reader an understanding of the physics underlying the F-35’s vulnerability to long-wave VHF radar. That article is available here Why WW2 Radars Can Still Detect Modern Stealth Aircraft . While one can read the current article on a stand-alone basis, it is recommended that the two articles be considered together.
While long-wave VHF radars can detect stealth aircraft, this does not guarantee that the aircraft can be shot down. Just because you can see it does not mean you can kill it. The advantage of stealth aircraft is the element of surprise. If the enemy has long-wave VHF radar, forget surprise. It’s gone, you’ve lost it. The topic of this article is the second question. How do we shoot down the stealth aircraft once its presence has been detected?
The answer lies in the Kill Chain.
The Kill Chain
A kill chain is a process to find, track, engage and destroy a target. A kill chain consists of a series of one or more radars, data links, and air defense weapons. When the target has been destroyed, we say, “The kill chain has been closed.”
Ideally, the kill chain is self-contained on one platform or installation. If an air defense site with dedicated radar and missiles can detect an F-35, track it, and guide a missile to destroy it, then that installation closed the chain. If an interceptor detects the F-35 with onboard radar, fires a missile and destroys it, that one platform closed the chain.
Stealth technology makes it difficult for a single platform to close the kill chain. More than one radar may be required, with data links to a weapons system.
Western radars almost exclusively operate at high frequencies and short wavelengths. There are two main reasons for this. First, short-wavelength radars are compact. An X-band radar fits into the nose of an F-16 or Eurofighter. The Battle of Britain radars, on the other hand, could be seen by the Germans from across the English Channel. Second, short-wavelength radars have higher resolution and are good at target discrimination and tracking.
Long-wave VHF radars can detect stealth aircraft but have low resolution. If we have four F-35s flying close together, the long-wave VHF radar will detect them but might only show a single contact. This is the beginning of the kill chain. The long-wave radar passes the contact to another radar, operating at a shorter wavelength. The second radar is able to discriminate four F-35s. It locks and tracks them. It may then pass the contacts to air defense missile batteries. The Russian Nebo-M VHF radar is frequently associated with S-400 air defense missile systems that have their own radars. These high-resolution radars guide the missiles to destroy individual targets.
It is important to remark that work is being done to improve the ability of long-wave VHF radars to discriminate and track targets. Engineers are striving for long-wave radar that can provide mid-course correction. If VHF radar can get a missile close enough to lock a target with the missile’s own onboard radar or infrared sensor, it will kill the enemy.
That’s the kill chain.
Radar System Frequencies
Because no single radar can operate across the entire electromagnetic spectrum, the anti-stealth kill chain requires operation of a system of radars that span the spectrum.
Let’s quickly review the electromagnetic spectrum shown in Figure 1. Notice that the spectrum includes visible radiation, near infrared, far infrared, UHF, and VHF. As one progresses from left to right in the chart, wavelengths become longer and frequencies become lower. The VHF frequencies that detect stealth are at the extreme right.
The military classifes frequencies and wavelengths into “bands.” Be careful when reading the literature and technical specifications. There are a number of organizations that use classifications that are confusing.
Figure 1. The electromagnetic spectrum, including visible light, infrared, and radar
Frequencies are measured in Hertz. Megahertz (MHz) is one million Hertz, and Gigahertz (GHz) is one thousand million Hertz. Examine the numbers in Table 1.
Table 1. Military band classification of frequencies and wavelengths
Russian anti-stealth radars like the Nebo-M operate in the VHF band, with frequencies of 30-300 MHz and wavelengths of 1 to 10 meters (3 to 30 feet). The vast majority of US and Western military radars operate in the S (2-4 GHz) and X (8-12 GHz) bands. Some modern radars are able to switch between two modes or use two modes simultaneously for different purposes. The Navy’s SPY-1 radar operates in S-band. The SPY-6 radar is a dual-band system that incorporates both S and X-band radars operating in conjunction under the guidance of a controller. The system is designed to discriminate, track, and engage targets from periscopes to ballistic missiles.
Your local police speed trap operates in the X, K, and Ka bands. The Ka radars operate at 33-36 GHz. Police have retired most X-band speed guns. As usual, size is a factor when police choose between K and Ka units. Your home microwave operates in the S-band. Like radars, the first microwave ovens were low-frequency and too large for practical use.
The Russian anti-stealth Nebo-M system consists of 3 separate radars networked and connected by data link to a command vehicle. The radars can be used as a system or independently. Figure 2 shows the components of the Nebo-M.
Figure 2. The 3 radars and command vehicle that comprise the Nebo-M system
The long-wave VHF radar detects the approach of stealth aircraft or missiles. It hands-off the contact by data link to the L-band and X-band units. Those units take on the role target discrimination and tracking. The contacts are integrated in the command vehicle. If necessary, contacts are either passed to an air defense battery’s radar or directly to the air defense missiles.
For export, Russia produces a Nebo-M with VHF and UHF radars. As expected, the capability of the export version is reduced. This documentary is an excellent description of the Nebo-M export version, as well as the history of Russian radar systems: Nebo-M Export Version .
The Nebo-M is under constant improvement. Figure 3 shows the Nebo-M VHF “Tall Rack” that has been deployed outside Moscow and is associated with S-400 and S-500 air defense batteries. The Tall Rack is a 3D long-wave VHF radar that may have additional target discrimination and midcourse guidance capability.
Figure 3. Nebo-M “Tall Rack” 3D VHF radar linked to S-400s outside Moscow
Table 2 shows a selection of army, navy, air, and space force platforms. It shows the bands, frequencies, and wavelengths in which their radars operate. I’ve included police radars for reference. It is purposeful for the reader to acquire a feel for the relative magnitudes involved.
The two fighter aircraft—the Eurofighter Typhoon and the F-16—both use X-band radars. Notice that the Israeli air defense radars—Iron Dome, David’s Sling, and Patriot—all operate in the C-band. For all intents and purposes, C-band looks like a compromise between S and X-bands. The SPY-6 system is a dual-band radar with both S and X-bands.
Table 2. Various platforms and the bands in which their radars operate
The only long-wave VHF radar in the table is the Nebo-MRLM-M. I have not included Chinese VHF radars. The longest wave western radar system is the PAVE/PAWS radar used for ICBM defense. The PAVE/PAWs and its derivatives operate in UHF.
Target Detection, Discrimination and Targeting
If we look at groups of radars—the Nebo-M suite, the Israeli radars, and the American radars, we notice they operate in layers. They are matched with layered missile defense to engage targets at different ranges and altitudes. Missile defense is beyond the scope of this article. For now, just notice that western radars generally don’t operate below S-band, with the special case of PAVE/PAWS, that operates in UHF.
Consider the Israeli radars. The Patriot, Iron Dome and David’s Sling are all C-band radars, but are configured differently to address different types of targets at different altitudes. Iron Dome, for example, is configured to tackle artillery shells and “dumb” rockets at relatively low altitudes. David’s Sling and Patriot are capable of engaging missiles and aircraft at higher altitudes. During the Iranian attack last April, discussed here, Electronic Warfare 101 , the Russian EW assets were able to map the types and locations of all these radars.
The Nebo-M has a clear anti-stealth kill chain. The VHF radar is under constant development to improve its discrimination and targeting ability. For the moment, it passes contacts to L band and X band radars. The L-band module is itself longer-wave than S band. One suspects this allows the Nebo-M system to better discriminate stealthy threats as they close distance.
Let’s look at the US kill chain. It’s relatively short because it’s not designed to defeat stealth. All of its radars operate in S to X-bands.
China, South Korea, and THAAD
In 2022, South Korea wanted to deploy US-built THAAD anti-ballistic missile batteries against North Korea.
China went berserk.
Understand that China is no great friend of North Korea. The two countries have a relationship touched by a lot of suspicion. Historically, North Korea’s real friend has been Russia. Diplomacy is complicated by Russia’s friendship with both.
China’s objection was not based on protectiveness toward North Korea. China was concerned that the THAAD X-band radar could see deep into its territory. THAAD radar could detect Chinese missile launches and gather vast amounts of intel.
THAAD X-band radar is designed to be interoperable with the SPY-1 radar on Aegis destroyers of the USN. Aegis destroyers have Standard 3 interceptors that can shoot down IRBMs. THAAD and SPY-1 are interoperable with Patriot C-band radars. Consider the flight path of missiles from east Eurasia toward the continental United States. THAAD and AEGIS constitute the point elements of the radar chain. THAAD can pass contacts to AEGIS SPY-1 via data links.
This brings us to PAVE/PAWS, shown in Figure 4. It operates in the UHF band. These are Over-the-Horizon radars built to warn the US of ICBM attack and track spy satellites. There are three in the continental US—one at Cape Cod AFS, one at Beale AFB California, and one at Clear AFS Alaska. There is one at RAF Base Fylingdales, England and another in Taiwan.
Figure 4. PAVE/PAWS UHF-band radar for ICBM and space surveillance
Stealth Warheads
One concern is that Russia is developing stealth warheads as part of its countermeasures against anti-ballistic missile defense. The US has X-band ABM radars in the Czech Republic to detect Russian missile launches, discriminate warheads from decoys, and hand off contacts to RAF Fylingdales.
Structural stealth optimizes the configuration of a vehicle (e.g. the F-117 Nighthawk) to minimize its radar cross section (RCS) as presented to a particular radar band (usually the S to X-band range). We know that the RCS is a function of target aspect. Simply put, if an F-35 approaches head-on, it shows a smaller RCS than if it flies overhead and the radar pulses strike its belly.
Among other countermeasures, Russia is developing ways to reduce the RCS of its nuclear warheads. Number one: separate the warhead and decoys from the booster vehicle and the RCS of the contacts are reduced. Number two: spin-stabilize the warhead so it does not tumble and it presents a consistent aspect. Number three, and this is key: orient the warhead in flight so that it points at the ABM radars. This re-orientation minimizes its RCS.
The RCS of a 3-meter-long warhead is about 15.5 inches without stealth. Re-oriented as described, the RCS can be reduced to1.5 square inches when presented to a UHF radar like PAVE/PAWS. The RCS would be much smaller to an X band radar. Simply put, the effective range of our radars is reduced. Warheads can skate by them.
Conclusion
The US and the west have dominated stealth for forty years. Perhaps as a consequence, our development and manufacture of radar has been focused almost exclusively on radars operating at high frequencies and short wavelengths.
Two things have happened. Peer adversaries have developed stealth platforms of their own, and have developed the tools, including long-wave VHF radars, to defeat our stealth aircraft. More troubling, they have developed hypersonic missiles that defeat radar, and they are in the process of developing low-observability warheads and other countermeasures.
We need to up our game.
Cameron Curtis
Cameron Curtis has spent thirty years on trade floors as a trader and risk manager. He was on the trade floor when Saddam’s tanks rolled into Kuwait, when the air wars opened over Baghdad and Belgrade, and when the financial crisis swallowed the world. He is the author of the Breed action thriller series, available on Amazon. The novels combine credible premises based on current events, strong characterization, and detailed plotting.
Check out his new Breed thriller, BLOWBACK, here: BLOWBACK by Cameron Curtis, available for preorder now for just $0.99
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It’s a real page-turner guaranteed to keep you on the edge of your seat. Drop a buck and pre-order your copy today! — GDM
