TECHNOLOGY AREAS: Sensors

ACQUISITION PROGRAM: PMS 480 Anti-Terrorism Afloat

OBJECTIVE: Establish approaches to provide a laser warning sensor using atmospheric scattering for shipboard self-protection with broad wavelength coverage and reduced size and weight to existing systems.

DESCRIPTION: Naval vessels in port or operating close to shore can be threatened by rocket propelled munitions, mortars, or artillery systems that incorporate laser targeting systems (or target designators). The use of laser warning receivers (LWR) which can provide precise pointing to the illuminating laser source can enable valuable situation awareness and targeting for counterfire to protect the threatened platform. Traditional pulsed LWR systems rely on main beam or port scatter from the laser source. Large ships or groups of ships would require numerous such LWR sensors for full ship or group coverage. The feasibility of using atmospheric scattering of lasers as a detection signature has been demonstrated by the Office of Naval Research (ONR) to provide pointing directions back to the laser source. The use of atmospheric scattering minimizes the necessity of multiple sensors for full ship or group coverage. The current system design, however, is too large and bulky (> 1 cubic foot and 50 pounds per 90-degree sensor unit) to be useful on small platforms and has wavelength coverage only into the near infrared (to around 1.1 micrometers), which excludes current eye-safe laser rangefinders operating in the short-wave infrared (around 1.55 micrometers). Investigations of new technologies that could reduce the size and weight of the system and extend the wavelength coverage would significantly enhance shipboard self defense capabilities. Responders shall propose to develop and demonstrate a sensor system that will detect the atmospheric scattering of laser radiation over a field-of-view (FOV) of at least 90-degrees, expandable to full 360-degree coverage. The proposed system shall be sensitive to lasers operating at visible, near infrared, and shortwave infrared wavelengths out to at least 1.6 micrometers and be able to determine the azimuth angle of the laser source to 3-degrees accuracy or better. The proposed system should meet the requirements for a laser warning receiver, as outlined above, suitable for use in a shipboard environment. Performance, false alarm mitigation, ruggedization, and cost should be addressed.

PHASE I: Investigate candidate technologies and explore concepts to reduce the size/weight and extend wavelength coverage to include eye-safe rangefinders for laser warning systems using atmospheric scattering. Trade-off studies will outline technologies, capabilities and design approaches. Development of a technical plan will be developed recommending specific design approaches.

PHASE II: Optimization of Phase I design selected. Construct a prototype to prove feasibility. Perform laboratory and possible Government-sponsored field tests to demonstrate the effectiveness of the prototype. The final system evaluation report should address deficiencies and recommendations to further improve performance and size reduction. Note: the Phase II development plan will be reviewed to determine if it is necessary to classify certain operational or performance specifications of the developed system.

PHASE III: Optimize Phase II design and implement in prototype. Demonstrate the optimized system by participating in military and commercial field tests. Use successful demonstration test data to define the requirements for future implementation of this technology. Formulate plan for the engineering development of the concept, including integration with existing and new naval platforms. Note: the Phase III development plan will be reviewed to determine if it is necessary to classify certain operational or performance specifications of the developed system.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial benefits of the technologies may include commercial shipping protection as well as harbor defense and port security. The development of high sensitivity laser sensing technologies would also benefit open-air laser-based communications systems that can operate at much higher bit rates and over much broader bandwidths than conventional radio-frequency (RF)-based systems, but are currently limited to strictly line-of-sight installations.

REFERENCES:
1. The ONR funded Shipboard Laser Acquisition System (SBLAS) project demonstrated the ability to detect emissions from typical tactical military laser designators and rangefinders using atmospheric scattering in a maritime environment and localize the bearing angle to the laser source to within a few degrees accuracy. While some details of this project and the performance of the demonstration system are classified, the general statement of work and overall goals of the effort can be obtained by referencing Contract N66001-99-C-0031 awarded by the Space and Naval Warfare (SPAWAR) Systems Center, San Diego, in 1999 to Goodrich Corporation, Optical and Space Systems Division, Danbury, CT.

2. A very good technical overview of laser warning systems, including the relative contributions from direct and scattered radiation, can be found in "The Infrared and Electro-Optical Systems Handbook, Volume 7 - Countermeasure Systems," David H. Pollock (editor), SPIE Optical Engineering Press 1993, pp. 109-148.

KEYWORDS: laser warning, atmospheric scattering, optical sensors, optical sources

** TOPIC AUTHOR (TPOC) **

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