Although the numerical modeling effort is making substantial progress toward solving several important problems, it faces a few significant hurdles. WRF applications at sub-kilometer grid scales, especially in unstable conditions, are problematic, because of limitations to the available turbulence physics parameterizations. Data assimilation at very fine scales is handicapped by the paucity of observations at comparable scales. BED is encouraged to pursue this legitimate but challenging research area. Many of the modeling initiatives undertaken during the past year have involved developing new techniques as well as importing of new expertise. It is not surprising, then, that BED has not yet had sufficient opportunity to perform adequate model verification, which is beginning to emerge from these recent developments, and which BED intends to continue.
Atmospheric Impacts Routing Tool This project is a continuation of an effort that has been presented in two prior reviews. This tool has matured and is ready to move beyond the prototype stage into operations. It applies the “A*” algorithm (a computer algorithm that is used in path finding and graph traversal) to the problem of “optimal” air and ground transportation routing. Ground routing involves multiple impact factors, such as Met forecasts, nowcast information, vehicle types, soil conditions, road states, and other factors. The algorithm “optimizes” paths in three-dimensional (3D) or four-dimensional (4D) space after building an architecture to support the ingestion of dynamic 3D data sets. It then makes an informed search for the “best” route, applying a set of criteria for what is best. It can adjust for desired goals, such as wanting higher than normal safety or faster speed to the goal point. Areas of avoidance can be declared as “no-go”/”no-fly” areas.
The project has been extended to respond not only to weather conditions but also to other threats or obstacles that could impede or preclude use of a particular route. The technology appears to run very fast, calculating optimized (for example, minimal time) routes while avoiding adverse conditions. It avoids many of the problems associated with pre-defined networks and instead finds a solution for an optimal path through a 3D grid, subject to the constraints imposed by the user or the different threats; it was originally based upon the A* algorithm but has been expanded to incorporate the D* and E* algorithms.
Of concern is that only a few methods can verify that the routing system is performing correctly, that is, generating an optimal route given a particular 3D arrangement of threats. One possible solution involves configuring the system to generate all possible routes through a given 3D grid, and then determining how the ensemble varies statistically from the optimal one. Although the results of the A* algorithm are very impressive, the development of a method for testing optimal routing techniques might represent an even more significant improvement. Also, this research has the potential to benefit from cross-disciplinary expertise, especially in optimization and computational methods for large-scale optimization, which is likely to exist in other divisions, such as CSD. Additionally, it would be beneficial if the research considered the value of clearly defined “near-best” and “near-optimal” solutions.
Optical Systems A project in early-stage development involves coherent, phased-array beam combining using single-seed laser sources and arrays of fiber amplifiers with antenna elements controlled both by individual phase modulators and piezo-actuated fiber positioners. This Intelligent Optics Laboratory (IOL) system has already demonstrated record power-combining at the multi-kilowatt level, including active servo control of the transmitter for some degree of atmospheric turbulence correction using element phase and beam tilt adjustment, with elaborate optimization of servo control to counter transit-time-induced loop delays. The team’s several hardware approaches demonstrated scalability, both in element power and number of elements, which has the potential to take the solution to weapons-level powers. The significant customer pull here (DARPA) provides strong evidence of the leading-edge nature of this work.