OBJECTIVE: Due to reductions in ice cover, there is an increased focus on the potential for future operations in the Arctic region. This environment is a challenging and dangerous one in which to operate, which provides a strong incentive for autonomous platforms. However, an Arctic navigation capability for UUVs is problematic, as ice cover may hinder the ability to surface and gain a GPS fix, and the availability of GPS at high latitudes is severely limited as well. For underwater and under-ice operations, an opportunity exists to use acoustics to provide an in-water navigation capability. Such a navigation system could represent a dual-use capability by not only providing the necessary signals for triangulation, but the signals could be used for environmental sensing of the ocean (traditional tomography) as well as ice cover (via scattering statistics). DESCRIPTION: Due coverage by sea ice, UUVs will not reliably be able to periodically surface to obtain the high accuracy GPS fixes required to maintain accuracy in their navigation systems. Current navigation systems degrade over time, minimizing the reach of unmanned undersea systems to near the edges of the Arctic ice. Current transponder system are short range and require multiple systems to be installed which can add significant cost and time to setup and install on the ice surface. The goal of this effort is to develop technologies to enable a basin-scale under-ice navigation system that would allow for high accuracy navigation of UUV under the ice. From current research, new technologies are needed for this system to work. This SBIR will accept system proposal or critical technology proposals. The following are considered critical technology Low-power low-frequency transducers: To achieve the acoustic ranges necessary to reach across the Arctic basin, the acoustic sources must operate at low or very low frequencies (5-100Hz) in order to avoid the multiple scattering that will diminish propagation distances. They must also be relatively low-power and low-cost, as they may be moored in the deep ocean or integrated onto a UUV. New transducers are needed to reduce the power to 10 watts in operation, be neutrally buoyant, and be no larger than 3"in diameter and 8"in length to enable integration onto a UUV. Signal processing: The Arctic has a different acoustic environment with multi- path propagation due to the reflection on the bottom and off the ice. New navigation algorithms are needed to properly account for this specialized environment and resolve accuracies to within a few meters with an objective of one meter. Methods for receiving GPS or other signals through the ice: This may include design of ice hardened antennas that can cut through the ice or new antenna designs and algorithms that can detect GPS or other signals through sea ice cover. PHASE I: Develop a preliminary design for the system or critical components. Provide the theoretical predictions of the system and develop a technology development plan for Phase II. The deliverable should be a preliminary design of the system. If the design or components of the design are high risk, a risk reduction plan should be included PHASE II: Complete the system design. This task should include any risk reduction tests, detailed design review, and test plan. Fabricate two prototype system or technology components and complete laboratory and development tests. Support government integration of the proposed system onto ONR UUVs. Support at sea tests of the prototypes on a government UUVs. PHASE III: The proposed system will be integrated into current navy oceanographic sensing systems. The technology will be integrated on board both S&T and Acquisition unmanned vehicles and used in oceanographic sensing mission in the arctic. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: There is significant interest in Arctic operations and logistics from the science community and commercial industry. There is significant interest from international partners in Arctic research which could utilize this technology to advance scientific research in the Arctic. Private industry is very interested in Arctic sensing technology development, as the Arctic may contain a vast amount of untapped natural resources. The oil and gas industry continues to gather as much information on this area as possible to plan for future oil drilling operations.