SBIR-STTR Award

The U.S. Navys Multi-Static Active Coherent (MSAC) sonobuoys provide a critical capability for battlespace awareness. Active source buoys (such as the AN/SSQ-125) and receive buoys (such as the AN/SSQ-101 ADAR buoy) stream information to the P8 aircraft platform where sonar operators use advanced tactical decision aids (TDA) to detect, classify, localize and track undersea targets. Several physical factors can conspire to undermine the performance of this processing chain, which stem from a lack of reliable information about the state of the buoys and of the surrounding oceanography. To that end, Metron and APL-UW propose to add motion and temperature sensors to the AN/SSQ-125 source sonobuoy. These sensors will provide a direct measure of array tilt, give some insight into buoy drift, and provide much greater spatial and temporal coverage of sound velocity field over the operation area (OPAREA). Monte Carlo simulations will be used to assess the extent to which these measurements can improve the accuracy and reliability of detection processing, with an objective of a 25% improvement. The proposed team has gained specific experience in MSAC data analysis and environmental modeling through a NAVAIR-sponsored STTR titled Detection Rate Improvements Through Understanding and Modeling Ocean Variability (N18A-T002). In that project, which is now in Phase II, the same team consisting of Metron and APL-UW are investigating the physical and oceanographic causes of transmission loss (TL) variability, with the goal of producing physics tools that will improve TL modeling accuracy. Key insights gained from that research suggest that unmodeled source buoy tilt, coupled with differences between ocean models and the actual ocean environment, are together responsible for often-observed large, unexplained, fluctuations in TL. This can happen in certain environments in which the source buoy, which is a vertical line array with a directional beam pattern, projects its acoustic energy through the environment in unexpected ways. Tilt information can be used to flag questionable pings, improve acoustic predictions, or even potentially adjust each ping produced from a tilted array in real time so as to stabilize its radiated beam pattern. These approaches are listed in order of difficulty and sophistication, and the proposed work plan addresses each of them in stages.

Benefit:
The anticipated long-term benefit of this project is that sonar operators will have access to more reliable tools for estimating Multi-Static Active Coherent (MSAC) buoy field performance. Specifically, the accuracy of detection predictions will improve as buoy and oceanographic information is incorporated into processing streams and physics models. The primary market for the proposed technology is the US Navy. The focus of this SBIR is to add non-acoustic sensors to the AN/SSQ-125 source buoy. However, in the future, the proposed technology could be applied to all Navy sonobuoys. In addition, the technology developed here could be used to estimate array tilt and shape for towed arrays on unmanned underwater vehicles (UUVs) in both the DoD and in commercial markets. In addition, there may also be applications in the estimation of the shape of airborne acoustic sensors carried by unmanned aerial vehicles (UAVs).

Keywords:
Sonobuoy, Sonobuoy, Transmission Loss, Probability of detection, Multistatic, tilt, Array, IMU, Active sonar

Transmission loss is a crucial input to the sonar equation for predicting the ability of an active sonar system to detect and track a target. The proposed technical effort centers on developing physics-based models to interpret and predict transmission loss (TL) variability caused by hydrodynamic tilt associated with the SSQ-125 projector array and a hardware solution to measure and mitigate tilt effects. The concept under development proposes the addition of motion and temperature sensors to the AN/SSQ-125 source sonobuoy. These sensors will provide a direct measure of array tilt, facilitate some insight into buoy drift, and provide much greater spatial and temporal estimates of the sound velocity field over the operation area (OPAREA). Monte Carlo simulations are used to assess the extent to which these measurements and interventions can improve the accuracy and reliability of detection processing, with an objective of a 25% improvement. The result is a performance simulation, hardware solution, and integrated algorithms that consume modeled and in situ oceanographic information, estimate the likelihood of occurrence of various physical phenomena that lead to SSQ-125 array tilt, mitigate the effects, and produce a 25% or greater improvement in MAC detection capability. Metron and APL-UW developed a basic, wind-only hydrodynamic performance model of SSQ-125 array motion. Metron also created a software simulation capability that they have named Multistatic Active Coherent Environmental Tactical Estimator (MAChETE). MAChETE incorporates the hydrodynamic model into a physics-based simulation to demonstrate the viability of the proposed hardware solution and supporting algorithms. MAChETE will support mission planning for a MAC system that can opportunistically exploit SSQ-125 array tilt and SSQ-125 buoys that can adjust projector ping elevation. In exploring this effort, Metron has also developed additional software approaches and solutions that increase MAC detection capability over traditional planning and employment methods that can be employed with or without Metron's proposed hardware implementation. The preliminary findings in our MAChETE simulations indicate that Metron's algorithms can achieve up to a 24% improvement in detection capability mid-mission and an 8-10% improvement in overall detection capability via mission planning software alone. MAChETE has also demonstrated that the Adaptive Intelligent Transmission (AIT) hardware delay logic can produce an 8% improvement in MAC system performance in some multi-path scenarios. Additionally, Metron's hardware and simulation approach indicates a more accurate CPD calculation than the current NAVAIR model is possible and likely required in conditions where ocean currents and hydrodynamic effects are prevalent. This capability will allow mission planners and operators to better gauge MAC system performance and realize an appreciable increase in detection capability.

Benefit:
The primary market for the proposed hardware solution and approach is the US Navy. The focus of this SBIR is to add non-acoustic sensors to the AN/SSQ-125 source buoy. However, in the future, the proposed technology could be applied to all sonobuoys and sonobuoy-like sensors. Over the last ten years, the Navy has increased requirements for unmanned underwater vehicles (UUVs) due to the Navys focus away from deep waters to the littorals. The DoDs Unmanned Systems Integrated Roadmap Fiscal Years 2011-2036 publication identified that all systems would continue to expand their roles and numbers across the US military, pointing to their role of working in tandem with unmanned surface vehicles as they are folded into the unmanned maritime section. The technology developed here could be used to estimate array tilt and shape for towed arrays on unmanned underwater vehicles (UUVs) in both the DoD and in commercial markets. There is an incredible demand for multistatics by US partners and allies. Multistatic Active Coherent Environmental Tactical Estimator (MAChETE) mission planning software could be developed outside the ASPECT product line to serve as the international mission planning capability. This transition could be viewed as a risk reduction step as ASPECT will likely underpin MAC-E and future US-only multi-static capability. Finally, the software and simulation approach that is being developed could become the cornerstone of sonobuoy and acoustic point sensor planning. MAChETE will combine the most complete environmental observation model data offered by the US Navys Fleet Numerical Oceanography team with advanced modeling of sonobuoy hydrodynamic performance and acoustic propagation into a lightweight, efficient prototype that can be fielded on a secure server in the cloud or at the tactical edge. The MAChETE tool is designed to wring every bit of performance out of the current MAC capability. Still, the overall approach of model and sensor pairing can be applied to all currently fielded acoustic sensors and future capabilities like MAC-E, NGAPS, TRAPS, CYFAR, etc. The sensor/model approach can also be applied to commercial applications in the energy and maritime sectors. The hardware technology proposed in this research is initially targeted for the AN/SSQ-125 sonobuoy. Other important transition platforms include the AN/SSQ-101 Air-Deployed Active Receiver (ADAR) sonobuoy, the AN/SSQ-53 DIFAR (Directional Frequency Analysis and Recording) sonobuoys, and the AN/SSQ-62 Directional Command Activated Sonobuoy System (DICASS) sonobuoy.

Keywords:
MAC, Multistatic Mission Planning, localization, detection, Classification, SSQ-125