A Range-Dependent Transmission Loss Database Application: Countermeasures Assessment Simulation at NRaD

This report documents the effort to build a range-dependent transmission loss database. which would be used to support countermeasures assessment simulation at the Naval Command. Control and Ocean Surveillance Center, San Diego, CA. This "new" methodology supplants previous approaches based on the use of range-independent acoustic models (i.e.. those that assume a single-profile, flat-bottom environmental input). The secondary purpose of this report is to introduce this capability to (he wider community of simulation modelers. The presumption has been (hat. for the ASW engagement, it is beneficial to precompute as many of he terms in the sonar equation as possible It follows that a database of modeled values of transmission loss (TL). a critical term in the sonar equation, would find widespread application in the ASW engagement segments of these analysis/training tools. The goal for this project was to produce a TL database by running the complex physics models, and then properly cataloging and storing the output for immediate retrieval and use. This procedure would then allow a modeled engagement to proceed in a timely manner through effective use of these "look-up tables." Although conventional thinking might have said that it is not feasible to model propagation loss for every 10 look direction for many combinations of source depth/receiver depth/frequency for scenarios in all of the world's oceans, this project has demonstrated that such a massive computational effort can be done, and is being done, given plenty of forethought, good science, and an abundance of automation. At the current rate of production, the resolution of the TL database averages one set of range-dependent TL model runs (i.e., one "node") every 1.5 degrees x 1.5 degrees square.

Prepared in collaboration with Planning Systems, Inc. Original contains color plates: All DTIC and NTIS reproductions will be in black and white.