AIS, Satellites and the Problems of Finding Things at Sea

Unlike the misplaced science fiction notion that space is an ocean, the two spheres are quite separate. Just how separate occurred to me while participating in the mini-symposium on Ocean Traffic Monitoring via Satellite Automatic Identification System (SAT-AIS), organized by the Dutch Space Society (NVR). In a series of half an hour lectures,  Carsten Tobehn of the European Space Agency (ESA) explained the merits of facilitating SAT-AIS and what ESA does to promote this; Jeffrey van Gils of the Rijkswaterstaat (Dutch Ministry of Infrastructure and Environment) gave an account from a user (mainly – seaports) perspective; and Jeroen Rotteveel, CEO of ISIS (Innovative Solutions in Space) who also hosted the event explained how his company’s specialisation (manufacturing and launching nano-satelites) will help with future SAT-AIS developments. Prior to this encounter, my impression of the contemporary seafaring landscape was that it is filled with identifiable vessels, creating a knowable landscape of movement and trajectories, aided by precise satellite locative technology.

The symposium proved me rather wrong. One can still disappear at sea in more than one way, and technology is often too costly or severely ineffective in tackling this. While GPS gives one’s possition, it is far less effective at giving contextual data which can benefit a ship’s crew and others in a variety of situations. ISIS (Innovative Solutions in Space) CEO Jeroen Rotteveel compared this by managing road traffic, where GPS-enabled devices are only one component in a system that takes into account traffic congestion and road works.

For this, the AIS system of transceivers was instituted globally. Automatic Identification System is a radio based device which is installed on a ship. In a nutshell, it does the following  [from Wikipedia]”

“AIS transponders automatically broadcast information, such as their position, speed, and navigational status, at regular intervals via a VHF transmitter built into the transponder. The information originates from the ship’s navigational sensors, typically its global navigation satellite system (GNSS) receiver and gyrocompass. Other information, such as the vessel name and VHF call sign, is programmed when installing the equipment and is also transmitted regularly. The signals are received by AIS transponders fitted on other ships or on land based systems, such as VTS systems. The received information can be displayed on a screen or chart plotter, showing the other vessels’ positions in much the same manner as a radar display.”

AIS is not a navigational application. Its main aim is to allow a ship or ground station to know what vessels are in its vicinity and the contextual data that each ship crew and devices (GPS, gyrocompass) feeds into the surrounding radio space.

The problem when applying satellites to the mix is that the system was never designed for anything more than tight grid (40 Nautical miles each cell), where conflicting signals can be worked around and identified. AIS signals CAN be picked from space, but two problem occur.

1. A satellite can pick up to 4000 ships in its tracking area, especially in crowded areas (Gulf of Mexico, certain parts of the Mediterranean), as opposed to approx. 30 as of current AIS tracking. This creates a major signal interference problem.
2. To achieve tactical usability, beyond that of current-generation ground-based AIS stations, an almost-real time signal coverage must be created. This requires several dozens of satellites in orbit (the main leader in commercial SAT-AIS services todat, ExactEarth, has four). Rotteveel estimated that operational global coverage can be achieved with between 12 to 20 satellites.

In a joint ESA-EMSA (European Maritime Safety Agency) pilot called “Blue Belt“, about 200 ships voluntarily disclosed satellite data for easier customs procedures. The required Time Update Interval (TUI – or how often a ship register in the system)  for the pilot was set at 2 hours for 85% of the ships. The results were that only 32% of the vessels on average achieved a 2 hours TUI, with best result at any given time being 43%. In other words, the out of the 200 ships participating in the pilot, on average only 32% were able to transmit information in a frequency of 2 hours or less.

With the advent of increased commercial space flight and miniature satellites, future applications of SAT-AIS seem promising. Creating a uniform standard to track and display marine vessels (on an Electronic Nautical Chart) will allow multiple actors to participate in supplying such data and using it. Already today, with proliferation of land-based AIS stations in amateur use  the Live Ships Map  is an example for a crowd-sourced, distributed attempt to make shipping data available and accessible. An intresting detail is how this technological platform becomes infused with social meaning, and how “serious” use is subverted by “playful” means, such as uploading “action-packed” shots to the Live Ship Map by the crews of the various ships. Another example is the messaging component of the AIS system itself whose users, for quite some time, supplemented the required ship position and bearings info with personal greetings and “coffee is ready” messages from the shore, annoying port officials and underlying how the most basic and utilitarian technology changes when immersed in a social realm.

To conclude, here are some of the potential uses of enhanced AIS-based naval systems, as distilled from all the speakers in the symposium:

1. Navigation aid, collision avoidance – AIS will allow for tighter oversight of maritime traffic. Creating virtual or synthetic AIS buoys may drastically decrease costs and enhance safety.
2. Law enforcement service – Fighting violations, piracy and smuggling. For example,  legal reasons declare that a violating ship must be photographed in order to be prosecuted. This proves difficult outside of coastal guard’s zones. Enhanced AIS will allow to utilize satellite photography to do so.
3. Maritime safety – AIS cannot be used for search and rescue directly (latency) but can be utilized for locating nearby ships in case of an emergency.
4. Fleet management services, logistics and efficiency for commercial users – reducing waiting time in ports, managing fleet locations and thus decreaing fuel consumption might benefit both commercial and environmental organizations.
5. Environment – Polar AIS tracking was utilized in tracking melting ice, via aggregation of changing shipping lanes in polar regions. AIS transceivers are cheap and versatile to implement in a variety of measuring equipment.