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  • Writer's pictureTravis Turgeon

Securing the Maritime Domain with the Help of Radio Frequency (RF) Data

"One of the most effective approaches to validating or invalidating a ship’s AIS data is using Radio Frequency (RF) data."

Over the past decade, the capabilities of maritime tools and technologies have grown exponentially.

Because of this, those who wish to act illegally or unethically have more tools and capabilities than ever before. Now, governments, authorities, and those with a stake in the shipping sector are left trying to ‘keep up with’ and counter those nefarious efforts.

It’s no secret that AIS tracking technology has its flaws, but there are many reasons we continue to use it.

When used as intended, AIS technology is a reliable and consistent form of maritime monitoring. The problem is that it’s not always used as it should be, and those interested in operating undetected can simply switch the AIS transponder off and stop broadcasting a signal. There is also the common issue of AIS spoofing, in which a vessel intentionally broadcasts false signals to avoid detection of carrying out its actual movements. Again, a relatively easy AIS manipulation strategy to carry out. But while AIS does not present a robust and effective monitoring strategy on its own, it can be used with other technologies to make it a more valuable tool.

One of the most effective approaches to validating or invalidating a ship’s AIS data is using Radio Frequency (RF) data.

Not exactly sure what that is or how it's used for maritime position validation? Read on.

What is Radio Frequency (RF) Data?

Radio Frequency data, or RF data, is a broad term that describes the measurement of the electromagnetic radiation spectrum. As a radio wave oscillates in the electromagnetic spectrum, it outputs a frequency that can be measured between 300 GHz to 9 kHz.

Basically, every object that emits energy produces radio waves, and those radio frequencies are what we call “RF Data.”

While not all radio frequencies can be measured (i.e., those under 300 GHz), large objects like cars, ships, and machinery all produce significant RF data that can easily be measured.

How is RF Data Emitted from Ships?

Since maritime vessels operate with heavy machinery and numerous pieces of technology, you may assume that they emit a ton of RF data…. And you’d be right.

While there are relatively few flaws with AIS tracking, the ones that exist are quite severe. But when paired with RF data, satellite imagery, and open-source information, AIS-based tracking becomes far more reliable.

Since ships emit such a massive amount of RF data, maritime authorities can use the emissions data to identify dark shipping occurrences and verify or invalidate a ship’s supposed AIS positioning.

How is RF Data Collected and Analyzed?

While it’s clear that all things that produce energy have an RF signal, and things like cars and ships emit a ton of Radio Frequency data, it may be less apparent how that data is collected or used by those with an interest in it.

While tracking vessels for maritime domain awareness is a relatively new strategy, there is some serious interest in the approach. In 2022, the US Navy partnered with a nano-satellite company to begin testing RF data for vessel tracking. Since commercial ships rely primarily on AIS for tracking and transmitting data, significant gaps must be filled to enhance everything from national security to sanctions compliance to fisheries management.

Since the Navy and the rest of the US military is already familiar with using RF data to locate and track down targets of interest on land, it makes sense that they have such a strong interest in employing those same strategies at sea.

The Navy will collect RF data transmitted by ships with small groups or clusters of small satellites - designed to orbit the earth at a high rate. Many of these small satellite constellations can be manually positioned to further validate a suspected incident of AIS manipulation, AIS spoofing, or any other anomaly maritime authorities choose to investigate.

How RF Data is Used to Validate or Invalidate a Ship’s AIS Data

When a ship intentionally operates as a dark ship, it almost always points to unethical or illegal intentions.

In fact, AIS systems were first created as a collision avoidance measure to create a safer maritime domain, and there are few reasonable excuses for manually turning an AIS transponder off.

Most often, ships go dark to avoid detection during STS transfers, while fishing in regulated waters, or to make a quiet call to port to load or offload cargo - be it sanctioned crude oil or other unauthorized materials.

Using small satellites, space companies and satellite operators like Kleos Space (partnered with the US Navy described above) and Spire Global can monitor massive areas of the ocean’s surface by collecting significant loads of RF data.

The data can then be geolocated and traced back to the source, which can be further filtered using AIS data, satellite imagery, and open-source information to make more informed maritime decisions. Perhaps the most beneficial way to use RF data is to analyze where a ship was suspected of going dark on AIS, sweep a surrounding parameter for RF data, then use satellite imagery to confirm or refute a suspected ship's valid location.

By doing so, instances of illicit STS transfers, IUU fishing, or unauthorized calls to port can be identified, and strategies can be constructed to better mitigate similar occurrences in the future.

What’s more is that, according to Unseen Labs, every ship emits a unique RF signature, which is much harder to manipulate than AIS data. RF data can be seen during the day or at night, and variable weather conditions have little effect on collection efforts.

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