Review of the atmospheric propagation in the SPC codes. A progress report

This is an initial progress report describing findings in critically analyzing and evaluating the atmospheric propagation submodels in the SPC1 and SPC2 models. These systems performance codes were developed by United Technologies Research Center as general purpose, end-to-end models for determining the overall effects on propagation of a laser beam from its source, either from the earth's surface or from an airborne platform, to a target. The SPC1 model is a trimmed down version of SPC2, while including the same coding for atmospheric propagation effects. As with other system models, the SPC codes attempt to include all essential processes to an accuracy commensurate with the use of the models for overall systems analysis and examination of system deployment scenarios. A basic conclusion of our study is that the SPC codes do appear to provide an appropriate framework for end-to-end model studies determining the overall impact of atmospheric effects on laser beam propagation. Nonetheless, our preliminary analysis has discovered a number of errors and limitations to the existing models. The modular structure of the codes will be an important benefit in making necessary improvements. 30 refs., 15 figs., 4 tabs