Why Countering Drones in Civilian Air Space Is So Problematic

What happens when a small unmanned aerial system (sUAS)—or drone—enters sensitive civilian air space? When such aircraft threaten public safety, law enforcement agencies face a significant challenge. Most technologies developed to take out intentionally rouge or negligent aircraft (called counter unmanned aerial systems, or CUAS) are based on radio frequency detection and interdiction. Many law enforcement units appear to be counting on such RF countermeasures. But this raises significant concerns.

Disabling remotely piloted aircraft using RF technology is a “cooperative” countermeasure because it requires advance knowledge of that drone’s RF signature. Even when using such cooperative countermeasures, relying on the drone to work as intended is a high-risk assumption. It would be like rolling a ball in front of a driverless car: the car may stop if programmed correctly and everything works, but then again, it may not.

Technological developments have demonstrated that autonomously guided drones are completely immune to all RF CUAS systems. They are not a problem for tomorrow, they are here today. Commercially available, small, autonomously guided aerial systems are already on the market, and more are coming out every day. These aircraft do not need a data link, GPS, or anything. They are invisible and immune to RF CUAS systems. This means that all of the energy, time, money, and confidence being invested in RF-dependent countermeasures may soon be obsolete and ineffective in countering present and future threats.

Regulations and laws matter, even if they can be waived in an emergency. Taking control of another aircraft is against the law. While it is likely that no law enforcement officer will be prosecuted for violating wiretap or privacy laws and constitutional guarantees if they take out a drone to save lives (whether the drone is intentionally or unintentionally flying off course), they cannot train for operations that would violate laws. Executing countermeasures during an emergency for the first time is dangerous.

All of this raises three troubling questions that demand more attention and thoughtful answers:

1. Should we really be betting the farm on cooperative engagement?

2. Why is non-cooperative engagement something we must prepare for?

3. Should law enforcement have to rely on exceptions rather than rules to engage drones?

The Limits of Technology

The majority of counter-UAS being developed or already on the market focus on exploiting radio frequency functions. This can be accomplished by interfering with a drone’s command and control uplink or datalink. The goal here is to interfere with or spoof  the instructions given to the aircraft by the controller.

But commercially available, RF-dependent CUAS do not “take control” of small unmanned systems as their manufacturers claim. Rather, what they do is to provide new data to the drone, leaving the drone still in control of its destiny. The potential for error is high, as the intruder drone may or may not act as it was designed. Or it may be manipulated to act in some other way, and by then it will be too late. Law enforcement officials may not always have a password or fingerprint allowing authorities access to commercially available drones, and they are unlikely have the fingerprint for do-it-yourself systems. Furthermore, the database with this information could be inaccessible for any number of reasons—or hacked.

This creates a significant operational challenge. Not only are most RF CUAS hampered by requiring detailed knowledge of the protocols and data formats used to control the system, they are also hampered by the ability of these small drones to be encrypted, making it nearly impossible to affect them in the 10-15 seconds available during an engagement. And, if the signal or fingerprint of the sUAS changes, in most cases the CUAS will not be able to “see” let alone affect the intruding drone.

Current RF CUAS are fundamentally “cooperative” in nature, meaning they rely on the cooperation of the drone to do as instructed or designed. This is a flawed strategy. A drone may malfunction, or ignore data input by design.

Trusting that commercial drones and DIY drones will work as hoped is a significant and possibly costly assumption. The majority of countermeasures designed to prevent small unmanned systems from entering into an area of concern rely on RF jamming of cyber systems that are intended to first detect then avoid collision. In the simplest terms this means that operators are betting on the reliability of both the drone and RF countermeasures working as they are supposed to.

Clearly, the need for non-cooperative engagement is imperative when addressing autonomously guided drones. What tools do law enforcement officials actually have to counter drones, beyond unreliable RF systems? Telephones and radios to alert authorities higher up the food chain that a remotely-piloted aircraft has been sighted in an area of concern. This is not confidence instilling for the public or law enforcement operators. The reputational risk for law enforcement would only compound an already highly scrutinized public image.

There are working groups and task forces looking at how to counter the risk and threat of negligent or deliberately intrusive drones. And not to be overlooked, the market is becoming flooded with alleged private sector solutions. Many of these solutions do technically work—but they are just not legally permitted in civilian environments. 

Legal Questions

There is certainly empathy for law enforcement officials facing this threat. It is unlikely that any would be prosecuted for interfering with an unmanned aircraft during an emergency. Somewhat analogous, it’s unlikely that any law enforcement officer would be prosecuted for attempting to save lives by violating wiretap or privacy laws and constitutional guarantees in response to an imminent threat. Yet, this will not help law enforcement to stay ahead of the threat or to legally develop trainable skills for coping with it.

Do we need more laws, or better interpretation of the law to permit use of CUAS? How can we ensure that training on CUAS will become legal? Asking law enforcement to be proficient on technology or devices they haven’t trained on is negligent. Trying out countermeasures for the first time during an emergency is a threat to public safety. A commitment to permissive legal training in contested environments is necessary.

In the absence of clear regulations and policies, manufacturers’ sales pitches are filling the void. As a result, many law enforcement agencies have purchased technology that they currently can’t use. What’s more, much of it may not actually work.

Michael Hopmeier is President of Unconventional Concepts, Inc., an engineering and policy consulting firm specializing in national security issues. He is also a consultant and senior advisor to numerous government agencies and organizations. Melissa S Hersh is a Washington D.C.-based risk analyst and consultant. She is also a Truman National Security Fellow and Non-Resident Fellow at the Stimson Center. Views expressed are their own.