### ASA 127th Meeting M.I.T. 1994 June 6-10

## 4pUW20. A ray travel time inversion scheme. Part I. Theory and simulated
results.

**I-Tai Lu
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*Naval Res. Lab., Washington, DC
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A ray travel time inversion scheme is reported, not only for localizing
the source but also for determining the array position and environmental
parameters such as sound-speed profiles (in both water column and sediment),
bathymetry, etc. The approach consists of the following four steps: (1) Sort
out some ray arrivals and determine their arrival directions and times from the
observed data; (2) backpropagate these rays in a nominal model to their source
region; (3) compute the travel times of the corresponding eigenrays; (4)
compare the simulated results with observed data and determine the new model.
Some iterations of these steps may be required. Some key advantages of this
approach are (1) most of the unknowns can be searched sequentially because rays
characterize only local properties of the environment; (2) source localization
ambiguity is minimized by utilizing ray travel times as well as path
convergence; (3) ray tracing is a very efficient propagator in range-dependent
environments; (4) the approach does not require full-wave matched field
processing and the required knowledge about the environment is minimized; (5)
ray chaos can be avoided simply by excluding chaotic rays. [Work supported by
ONR and NRL.] [sup a)]On sabbatical leave from Polytech. Univ., Route 110,
Farmingdale, NY 11735.