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This system has been used on ships in the marine environment to view small objects (say a person) floating in the water at distances exceeding one mile. Larger objects such as rubber rafts, wooden boats or small ships can be seen at much greater distance, even though these objects cannot typically be detected with conventional Radar. The maximum possible range that the system would be effective depends on many factors. These factors included atmospheric conditions, laser pulse energy and wavelength, camera sensitivity at the chosen wavelength, the aperture of the receiver zoom lens, reflectivity of the objects in the field (some objects will scatter more light than others, and they will appear “brighter” in the scene), and field of view of the zoom lens. The system can be tailored for long, medium or short range operation as required for particular applications. Using “eye safe” laser light at 1.57 um, the scattering effects of fog and / or smoke or haze in the atmosphere is minimized. Reliable imaging can be obtained at significant distances even with less than optimum atmospheric conditions. On the other hand, use of 850 nm light enables use of very inexpensive, sensitive silicon cameras, so lower cost imaging systems can be developed. To date our team has designed and delivered several laser units which will be integrated into the rest of the imaging system. In a harbor the situation is actually very similar. In this case the clutter is the large amount of traffic within the harbor. So the apparent scene is active, but unthreatening. A mechanism that will help distinguish a possible threat from the general clutter is essential to port security. Once again some level of automation is necessary, and the false alarm rate must be low enough that the operators do not become complacent.
Maritime ISR
Stellar Photonics and its strategic partners, have experience with laser illuminated active remote imaging systems. The infrared (non-visible) laser is used to illuminate a scene at a distance, and the infrared camera receiver system with a long range zoom lens generates the video image for the operator. The system runs at 30 Hz so full video frame rate is achieved. The laser and camera system are attached to a platform that can be pointed in directions and scanned as required for the particular imaging application being addressed. For more sophisticated systems, image analysis software can be employed to continuously monitor for particular threats.
Background
Security in a harbor environment or in the open ocean is essential to maritime commerce. While these environments seem only modestly connected to each other, the technological aspects of surveillance and the recognition of threats have a large degree of commonality.
The most famous example of security at sea, is the pirate activity off the coast of Somalia. In this case the pirates rely on the element of surprise to capture a larger vessel with little or no resistance. In the cases where the larger vessel was aware of the pirate while they were still at range the larger vessel has usually been able to thwart the attempt to take the vessel. So the key is the ability to recognize the threat with enough time to respond.
The pirates rely on the natural clutter of the environment, and low level of look out on the vessel, to hide their approach. When combine with the small size of the pirate boat the scene is very cluttered, and the threat does not stand out. Since there are very few crew members on these commercial vessel a technology is needed that will have a substantial level of automation to screen the entire scene for threats. The technology must be able to call attention to threats will a sufficiently low false alarm rate that alarms from the system will be investigated and not ignored.