In a small city, just a few hours drive from the Czech Republic capital of Prague, a quiet revolution is brewing in the field of passive surveillance. The technology developed here in Pardubice gives NATO an edge when it comes to detecting aerial and naval threats and could help international forces overcome Russia’s powerful electronic warfare capabilities.

Czech company Era is relatively unknown outside of the electronic surveillance community and civil aerospace sector, but along with its home city of Pardubice, it has a rich history in passive sensor technology. While Era was established in the 1990s, its lineage can be traced back to the Soviet era when it was part of the massive Czech conglomerate Tesla (unrelated to Elon Musk’s company of the same name).

Today, Era is supplying at least 20 nations with passive miltiary surveillance sensors and it supplies the NATO alliance for its deployable air command and control system.

“The countries around Russia, for example, are already equipped mostly with our technologies,” said Ondřej Chlost, Era’s commercial director.

A VERA-NG system is seen on the roof of Era's new headquarters in Pardubice, it is able to track aerial targets using only signals emitted from aircraft. (Photo: Grant Turnbull)

During a recent visit to the company’s new Pardubice headquarters, officials told C4ISRNET that there is now such significant demand for its fifth-generation passive sensor - known as VERA-NG – that the company can produce the technology without specific orders in place.

“In the military field, these technologies are usually more customized solutions,” Chlost, said. “But now we are even producing the military technologies on stock because there is such big demand from the market.”

VERA-NG works by detecting radiofrequency (RF) signals being emitted from aircraft or naval vessels, and unlike traditional sensors, such as radars, they do not emit any radio-frequecy itself. Over the years, traditional radar sensors within air defense networks have become far more vulnerable to countermeasures including electronic jamming and anti-radiation missiles.

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Chlost told C4ISRNET that active radars have a survivability rate of around 20 to 30 minutes in real combat, owing to advanced suppression of enemy air defense technologies. VERA-NG is designed to add another sensor layer to an air defence infrastructure, sniffing out RF sources across a significant bandwidth range and reducing the times an active surveillance radar needs to be switched on.

The technology is so sensitive that the sensors - usually three remote stations and a central processing station - can detect, and pinpoint, signals to 400 kilometers and possibly beyond. These signals can be anything from radars, data links, as well as identification friend or foe (IFF) transponders - meaning even stealth aircraft are visible.

“Even when there are 200 targets in the air, we are able to identify each aircraft and send the information to a command-and-control system,” said Chlost. “If your database is good enough, and your operators are good enough, you can even determine the tail number of the aircraft.”

This level of accuracy means it can directly interface and cue surface-to-air missiles, or cue an active radar to ensure it is only turned on for limited periods so as to not give away its position or electronic signature. If an adversary chooses to use RF jammers, as is a favored tactic by Russia, then the passive sensor will also be able to pinpoint the source.

Because the technology is deemed sensitive, likely classified, most countries do not disclose they have acquired it and Era does not talk about customers, apart from its domestic customer, the Czech Army, and NATO.

The technology is able to be “hidden in plain sight” usually on cell phone towers or atop high buildings, as well as be mast-mounted on forward-deployed military trucks. The latter will be the configuration utilised by the NATO alliance, which ordered the technology in 2014 as part of a multi-million dollar contract.

A common question for Era is, what happens if there are no emissions from aircraft? Officials say it’s very rare that today’s networked aircraft or vessels will not have some kind of RF being beamed off the platform, especially as net-centric warfare expands within and between domains.

“This is a beneficial environment for us,” Chlost said. “Data link systems are used on all aircraft and ships, and they are serving as a relay to have that over the horizon information sharing and networking.”

Earlier this year, Sweden’s Defence Materiel Administration (FMV) announced that it had also been trialling the technology as part of studies to upgrade its air defence network. “The special thing about passive systems is that they are difficult to detect for the opponent,” said an FMV official in a statement. “They only listen, while radar systems send out signals that are reflected against the object, making them easier to knock out.”

Sweden is just one country that is looking to bolster its conventional warfare capabilities as a result of Russian aggression in recent years, especially in the air defence realm with a purchase of the US Patriot system also announced.

Russia is understood to still possess some of its own passive sensor technology, mainly the “Ramona” second-generation ESM system acquired from Czechoslovakia during the Soviet era, although this is mainly obsolete now compared with the likes of VERA. “These systems are probably not even maintainable any more,” explained Chlost.

As part of its passive sensor roadmap, Era has unveiled a new Multistatic Primary Tracking Radar - known as SICORRA (Silent Correlation Radar) - that receives ambient signals that bounce off an aircraft but, again, does not emit itself. The signals received do not have to be from the aircraft, like VERA, but can be reflected FM signals from sources such as cellphone or television towers.

The German Air Force will test similar technology from domestic manufacturer Hensoldt. C4ISRNET reported last month that the Air Force would test the TwInvis system in southern Germany later this month.