Description
Objective: Develop a means to detect, determine the range of, and track low-observable surface targets utilizing active electro-optical sensors. Description: The Navy continues to field multiple systems incorporating imaging sensors (cameras). Taken collectively, the Navy has cameras covering both wide and narrow fields of view, with varying resolution (pixel count), and operating across essentially the entire span of visible to infrared (IR) wavelength bands. For surface ships, camera sensors are used for general situational awareness, to aid in navigation for target detection and tracking, and for targeting. Camera sensors, even those operating in the IR, provide information (video imagery) to the ship’s crew that is fundamentally familiar, intuitive, and contextual. However, that does not mean that the information is complete and unambiguous. A particularly challenging problem is the detection of low-observable surface objects (targets). These targets are small enough that their motion is subject to wave conditions as low as sea state 3. These objects rise and fall with the waves such that, for oblique observation angles, they are obscured from observation when at other than the crest of the wave. These objects are also typically submerged to a large degree, with only a fraction of their size breaking above the surface of the water. Low-observable targets include relatively benign objects such as drifting debris, buoys, and navigation markers. They also include lethal objects such as floating mines and semi-submersible crafts such as sea attack drones. In between these two extremes are a host of mine-like objects (MLOs), floating hazards (for example, shipping containers), personnel in the water, and marine mammals that are of high importance for general safety and safe navigation. While small commercial and civilian pleasure craft would typically not be considered low-observable objects (because they purposely make themselves observable with running lights), the Navy does occasionally assist in searching for small vessels in distress or downed aircraft that, under the circumstances, are considered low-observable objects. One final class of low-observable targets is periscopes and elements of submarine masts that have a small cross-section and are intermittent by nature. For strictly passive imaging sensors, low-observable targets are obscured by wave clutter and sun glint, even when in the direct line of sight. They are often only intermittently visible due to wave action. White caps, foam, and spray caused by breaking waves further obscure targets, present false targets, and significantly add clutter, especially in the visible band. Active sensors – essentially the incorporation of a laser, or multiple lasers, can improve the probability of accurate detection. In addition, incorporation of a laser provides the possibility of obtaining critical range information on the target, something that is quite difficult to do with strictly passive imaging sensors. However, active sensing presents its own challenges. Lasers are highly focused and must be directly incident on the target. Fast scanning or scanning in discrete steps with a focused beam runs a significant risk that small targets will be missed. Laser beams can be expanded into a fan pattern through incorporation of suitably chosen lens elements, but the incident laser power on the target is then correspondingly decreased, reducing the detection range. Increasing the laser power to compensate for this runs the risk of producing a hazard to friendly personnel, bystanders, marine life, and equipment. Hybrid detection schemes that incorporate multiple lasers or switch the beam(s) from broad to narrowly focused through opto-mechanical means add cost and system complexity. Semi-active means, whereby the laser acts as an illumination source with the returned light received by an imaging sensor, are possible, but this increases the complexity of determining range. The Navy seeks an active electro-optic/IR (EO/IR) sensing technology that compliments shipboard passive imaging sensors (cameras). This technology is needed to detect low-observable targets, as defined above, with no known commercially available solution. Detection is defined as determination of relative azimuth and range. Tracking will be accomplished by post-processing (software) of the detection data returned by the sensor over time and is not part of this effort. However, the detection update (re-visit) rate must be fast enough to support tracking, accounting for wave action, the resulting intermittent visibility of the targets, and the maximum expected speed of sea drones, periscopes, and other non-drifting targets. High probability of detection is prioritized over low false alarm rate as the system implementation anticipates cueing of narrow field of view cameras to confirm and identify targets with the help of target recognition algorithms and the human operator. Therefore, some false alarms can be tolerated but the goal is to reduce the false alarm rate to that which is manageable by a single human operator. Automatic target recognition software and the operator display are outside the scope of this effort. Acceptable solutions may employ lasers in lidar configurations or as laser illuminators in range-gated detection architectures (or any such combination). Solutions that utilize existing wide field of view cameras operating in the visible and mid-wave IR (MWIR) bands as receivers of the laser return are acceptable, provided no modification of those cameras (framerate, resolution, etc.) is required. Solutions that incorporate more than one laser are allowed. However, solutions that rely on hyperspectral imaging sensors are not permitted as the Navy does not intend to replace its existing suite of sensors to realize this capability. Because of blockages from the ship superstructure, the maximum field of regard is 190° (180° coverage plus 5° margin at either end). However, for purposes of the prototype delivered under this effort, design for and demonstration of 45° coverage is acceptable, provided that the solution can be readily extended to the full field of regard without loss of performance. As a performance metric, a probability of detection of 98% with an associated false alarm rate of no more than two per minute for conditions up to and including sea state 5 is the starting benchmark. Detection range is assumed to scale with laser power. However, an effective sensor range of 100 to 500 meters should be taken as the nominal requirement for demonstration of the solution. Longer range is highly desirable. Optical platforms for the Navy’s existing systems are already stabilized, therefore ship motion does not factor into the solution. A sensor location of 60 feet above water line should be assumed. The size and nature of the target also contributes significantly to the detection problem. For purposes of evaluating feasibility through modelling and simulation, analysis, or scaled or partial prototype testing, a steel or iron metal sphere with diameter of one-meter, matte surface finish (but wet), and 90% (by volume) submerged, with sea state 3 conditions is the preferred baseline for comparison. In demonstration of the full solution, at or near the end of Phase II, the awardee shall propose and select surrogate targets that are representative of the most stressful targets of interest described above. Full at-sea testing is understood to be beyond the scope of this effort. Therefore, innovative test procedures that demonstrate and measure the performance and utility of the solution are expected. Considering the requirements and objectives described above, system complexity and cost are the next most relevant factors. Systems that incorporate more than one laser or sensor element should strive to use a single aperture. If a dedicated focal plane array is included, it should be of the smallest possible size and cost and increase system complexity as little as possible. Mechanical components such as gimbals, steering mirrors, and scanning mechanisms should be minimized and made as simple as possible to reduce acquisition cost, ease repair, and maximize reliability. A solution that is eye-safe at the water surface is mandatory. An eye-safe solution at the aperture is highly desirable. Finally, solutions that utilize hard to detect laser wavelengths or covert (low probability of intercept) operating modes to deter detection by adversaries and mitigate interference with other Navy ships are also highly desirable. Work produced in Phase II may become classified. Note: The prospective contractor(s) must be U.S. owned and operated with no foreign influence as defined by 32 U.S.C. § 2004.20 et seq., National Industrial Security Program Executive Agent and Operating Manual, unless acceptable mitigating procedures can and have been implemented and approved by the Defense Counterintelligence and Security Agency (DCSA) formerly Defense Security Service (DSS). The selected contractor must be able to acquire and maintain a secret level facility and Personnel Security Clearances. This will allow contractor personnel to perform on advanced phases of this project as set forth by DCSA and NAVSEA in order to gain access to classified information pertaining to the national defense of the United States and its allies; this will be an inherent requirement. The selected company will be required to safeguard classified material during the advanced phases of this contract IAW the National Industrial Security Program Operating Manual (NISPOM), which can be found at Title 32, Part 2004.20 of the Code of Federal Regulations. Keywords: Low-Observable Surface Objects; Lidar; Active Sensing; Laser Illuminators; Imaging Sensors; Range-Gated Detection CMMC Level: Level 2 (Self)