N131-046 TITLE: Maritime Dynamic Atmospheric Characterization for Naval Laser Weapons System

TECHNOLOGY AREAS: Sensors

ACQUISITION PROGRAM: Solid State Laser Technical Maturation Program

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop an innovative atmospheric attenuation measurement system capable of 24/7 operation and suitable for integration on a shipboard platform to determine expected atmospheric attenuation prior to a high power laser engagement.

DESCRIPTION: The potential for deployment of Laser Weapons Systems aboard Naval Vessels necessitates the ability to dynamically characterize the maritime atmosphere to predict laser effectiveness. The Navy is seeking novel approaches to allow a ship to determine atmospheric attenuation on a continuous or discrete basis, and use this information to generate a 'Laser Effectiveness Range' for use by the ships tactical team to determine whether the laser system is an appropriate weapon choice for a given threat. Atmospheric characterization in both azimuth and elevation is desired to allow for improved weapons selection ability against surface and airborne targets. Systems (ref 1) designed to operate with reduced or minimal maintenance requirements and/or operate as a stand-alone device will be more strongly considered. Offerors should concentrate their efforts on the 1.0-1.1 micron optical transmission window of the atmosphere, the anticipated bandwidth for shipboard naval laser weapons.

Having a method to measure the anticipated attenuation along the propagation path prior to a high power laser engagement is necessary to determine weapon effectiveness. Two different mechanisms contribute to the attenuation that a laser will experience while propagating through the atmosphere - absorption and scattering. In a maritime environment, scattering from water droplets is a primary contributor to overall attenuation, especially for horizontal paths along the ocean surface. Molecular absorption has been well characterized and modeling codes exist to allow for accurate predictions of transmission as a function of wavelength. A system to measure total attenuation must take both factors into account.

Both passive and active techniques exist for measuring atmospheric attenuation. Active systems such as transmissometers (ref 2) and nephelometers sample a known atmospheric path at a specific wavelength and have separate transmit and receive modules. Transceiver type systems are similar to transmissometers except that the transmitter and receiver are co-located and they utilize a cooperative target such as a corner cube reflector to measure the round trip extinction. Light Detection and Ranging systems utilize a laser source to analyze the aerosol backscatter along the laser path and can determine aerosol attenuation based on these measurements. Active systems have the advantage that they can be designed to operate at the same wavelength as the high power laser source. However, some of these systems are designed to sample the atmosphere over a very short distance which may not take into account changing atmospheric conditions away from the ship. In addition, the use of a laser or other light source can act as a beacon to enemy threats, revealing the ships position and/or status.

Passive systems are attractive because they do not require a laser "beacon" to make the measurement. These systems analyze the contrast between a dark target or object at a known range and the horizon. It may be possible to utilize existing shipboard sensor systems to function as a contrast imager. However, these systems can be susceptible to particular environmental conditions that can affect the contrast measurement but not the actual extinction along the path. In addition, they may have difficulty working at night.

The goal of this topic is to conceive and determine the feasibility of a novel atmospheric attenuation measurement system capable of 24/7 operation in a maritime, shipboard environment. Ideally, the system will collect information at the laser wavelength between 1.0 and 1.1 microns and should be capable of measuring attenuation along horizontal paths near the ocean surface as well as non-horizontal slant paths.

PHASE I: The company will develop concepts for an atmospheric attenuation measurement system that satisfies the requirements described above. Active or passive approaches are acceptable but approaches that require no additional shipboard logistics are preferred. The company will demonstrate the feasibility of the concepts in meeting Navy Needs and will establish that the concepts can be feasibly developed into a useful product for the Navy. Feasibility will be established by material testing and analytical modeling. The small business will also provide a Phase II development plan with key performance parameters for the system, key technical milestones to be achieved and a risk assessment with mitigation strategies to reduce high and moderate risk aspects of the plan.

PHASE II: Based on the results of the Phase I and Phase II development plan, Phase II will focus on the fabrication of a prototype system for test and evaluation. The prototype will be evaluated to determine its capability in meeting the performance goals and milestones defined in a Phase II development plan. Testing will be conducted in both a laboratory setting to establish system baseline performance and at a suitable outdoor test facility, preferably one that has an over water test range that allows for measurements over propagation distances exceeding one kilometer. Evaluation of early test data will be used to refine the prototype into an initial design that will be robust and durable for use in a shipboard environment. A functional prototype of the initial working device including software required to fully operate the prototype will be made available to a naval surface warfare center for subsequent verification of test results and for assessment of the device’s capability to operate in a maritime environment without significant degradation. The company will prepare a Phase III development plan to transition the technology to Navy use.

PHASE III: If Phase II is successful, the company will be expected to support the Navy in transitioning the technology for Navy use. The company will transition the prototype design to a robust and durable system capable of operation in a maritime environment. The system will be tested to ensure it meets military standards for temperature, shock, vibration and other requirements. At sea, field testing will be conducted to ensure proper performance in a relevant environment. The company will support the Navy for test and validation to certify and qualify the system for production and Navy use.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Private sector use of this technology could be in the areas of enhanced visibility measurements for transportation applications such as airports, highways, and shipping ports. It also has applications for free space atmospheric communication links.

REFERENCES:
1. Shields, Janet E., et al, "Multispectral scattering measurements along extended paths over the ocean surface using an imaging system," Proc. Of SPIE, Vol. 6303, 6303E, 2006.

2. Malm, William C., "Considerations in the accuracy of a long-path transmissometer," Aerosol Science and Technology, 14: 459-471, 1991.

KEYWORDS: Laser propagation; atmospheric attenuation; absorption; scattering; long-path transmissometer; nephelometers

** TOPIC AUTHOR (TPOC) **

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