| Criminal evolution means threats are ever more challenging to detect. RF technology can augment existing systems by providing early warnings, detecting and geolocating suspicious signals, and feeding intelligence into C2 systems in real-time. |
The Alboran Sea is a natural barrier and a gateway, separating the economic stability and security of Europe from the struggles of Africa, where limited opportunities and instability drive migrants to seek a better life.
Migrants escaping conflicts, economic deprivation, and climate change make the perilous journey through the Sahel to Morocco, where Europe is only 15 kilometers away (at the shortest crossing point on the 861-kilometer Andalusian coastline). Many use unseaworthy boats, and criminals often traffic migrants using small dinghies to evade detection.
Drug traffickers from across the world see the Alboran Sea as a relatively easy route into the lucrative European market; the Moroccan Rif mountains are one of the world’s largest hashish-producing regions, and cocaine from South America via West Africa also travels north to Europe via this sea. Without the constraints of cost, drug traffickers use high-speed boats, jet skis, fishing vessels, and even transatlantic semi-submersibles to make the journey.
The Guardia Civil, Spain’s agency responsible for border control, faces enormous challenges in this 53,000-square-kilometre area east of the Gibraltar Straits, separating Spain from North Africa.
Image 1: Alboran Sea (Source: Google Maps)
Since 2002, the Guardia Civil has relied on sensor technology known as the Integrated System of External Vigilance (or Sistema Integrado de Vigilancia Exterior in Spanish) to combat illegal immigration, drug trafficking, and other illicit activities. The system includes radar, Infrared, and video and has successfully bolstered Spain’s capabilities to monitor and control its maritime borders.
However, threats crossing the Alboran Sea have evolved over the past twenty years. There are now threats on the surface, in the air, and underwater over a vast area of sea.
Vessels have become smaller and faster, and emerging threats now come from aerial drones and unmanned underwater vehicles (UUVs). Custom-built aerial drones capable of carrying up to 25kg of drugs can take just 30–40 minutes to fly across the straits or be flown from a vessel anywhere along the coast. In 2022, Spanish authorities seized a UUV designed to carry a load of 200kg.
Criminal evolution means threats are ever more challenging to detect. For example, radar may struggle to detect a semi-submersible and to discriminate between a bird and an aerial vehicle.
In this context, RF technology could augment existing systems by acting as an early warning system, detecting and geolocating suspected criminal activity, and feeding this RF intelligence into C2 systems in real-time.
RF sensors constantly monitor the electromagnetic spectrum and detect radio waves emitted by a transmitter at a given frequency. For example, a sensor could detect a Private Mobile Radio (PMR) operating in the VHF band between 136–174 MHz.
This data becomes helpful for border forces when command and control centers use software that can geolocate these signals. Imagine this scenario: a human trafficker is coordinating their operation using a PMR while crossing the Alboran Sea. If RF sensors detect a signal at 136 MHz without also detecting an automatic identification system (AIS) in the same place, this could indicate that the vessel’s operator is trying to remain undetected.
Image 2: Geolocation (pink dot) of a PMR using RFeye Site, a spectrum monitoring and geolocation toolkit.
Image 3: A comparison of the geolocated signal with open-source information from Marine Traffic shows that there is no AIS signal in the location where the PRM was geolocated. Source: Marine Traffic
Unmanned systems are likely to house several transmitters that emit radio waves—most likely from telemetry transmitters sending real-time flight data to a ground station or operator. RF sensors can detect these signals, and software can then geolocate them.
Adding spectrum monitoring capability primarily provides improved situational awareness; operators can make more informed decisions in real time by understanding the spectrum environment. Detecting signals used for communication between trafficking boats and any coordinating parties allows authorities to gather intelligence on their location, direction, and possibly even the intent.
RF sensors can be deployed flexibly and monitored from any location with a network connection using spectrum monitoring and geolocation software. RF technology provides command and control with a tool to locate maritime targets beyond the horizon—providing additional intelligence, surveillance, and reconnaissance (ISR) capabilities.
Unmanned aerial vehicles (UAVs) equipped with RF sensors provide a highly flexible and responsive way to monitor vast maritime areas. By increasing the line of sight above the water, UAV-mounted sensors can geolocate suspicious signals more effectively than ground-based or ship-mounted sensors.
With advanced RF geolocation technology, UAVs can detect and geolocate illicit radio transmissions, including push-to-talk radios and drone telemetry links, relaying real-time intelligence to command centers. By continuously monitoring RF emissions, UAVs enhance maritime domain awareness, covering areas beyond the reach of fixed sensors and enabling swift responses to threats.
Deploying a fixed RF sensor network along the Spanish and Moroccan coastlines would create a continuous monitoring capability across the Alboran Sea. These sensors, strategically placed at high-elevation sites and along coastal outposts, could detect by direction finding or triangulating signals from suspect vessels, drones, and traffickers using radios.
Image 4: Example deployment of RFeye Nodes across the Strait of Gibraltar.
A cross-border initiative between Spain and Morocco could enable real-time data sharing between security agencies, improving joint situational awareness and facilitating coordinated interception operations. Fixed RF sensors would complement radar and infrared systems by detecting the radio signals of traffickers attempting to evade other forms of surveillance.
Maritime patrol vessels could be equipped with RF sensors to detect unauthorized communications at sea. These mobile sensors would enable patrols to detect and geolocate signals indicative of smuggling activities.
Fitting unmanned surface vessels (USVs) with RF sensors could give the Guardia Civil an even higher degree of operational flexibility at a lower cost than manned vessels.
Spain’s southern maritime border poses a significant security challenge, with threats emerging from the air, sea, and underwater. RF technology provides a powerful means of monitoring illicit activities through a network of fixed, mobile, and deployable sensors. A joint Spanish-Moroccan RF intelligence initiative could significantly enhance border security, disrupting human trafficking and drug smuggling operations while improving maritime safety in the region.
White paper
This white paper was guided by the results of a border security survey aimed at border control, border security, and military personnel tasked with national security and defense. It examines how RF sensor technology can be used to tackle modern border security threats.
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