InfraMAP Propagation Modeling Enhancements and the Study of Recent Bolide Events
BBN TECHNOLOGIES ARLINGTON VA
Pagination or Media Count:
Enhancements to the propagation modeling capabilities of the InfraMAP analysis tool kit are being developed in several areas. InfraMAP Infrasound Modeling of Atmospheric Propagation consists of three infrasound propagation models 3-D ray trace, normal mode, and parabolic equation, two atmospheric characterizations HWM and MSISE, a global topography database, and user interfaces for model execution and data visualization. InfraMAP has been delivered to the research and development test bed and is currently being utilized by Comprehensive Nuclear-Test-Ban Treaty researchers and analysts. Three specific types of InfraMAP enhancements are addressed here. First, a low-frequency absorption model has been integrated for use by both ray- and parabolic-equation PE propagation analyses. The absorption model predicts both classical translation, diffusion and relaxation rotation, vibration losses. Absorption is calculated from temperature, pressure, and atmospheric gas densities, which are determined using the environmental model MSISE. Second, a waveform synthesis capability has been integrated into the ray model. Eigenray solutions for a specific source-receiver scenario are used to synthesize a time-based waveform. A user-defined source waveform is convolved with weighted impulse functions at the eigenray arrival times. The impulse weighting is based upon a calculated absorption loss along each ray path. Finally, improved environmental variability modeling capabilities are being pursued to model the propagation variability induced by the environment. A sample from the Naval Research Laboratory atmospheric statistics database has been investigated for use in improving predictions of propagation variability. Propagation modeling studies have been performed for several recent bolide events, including the 1997 El Paso, Texas, bolide, the 2000 Acapulco bolide, the 2000 Yukon bolide and the 2001 Pacific bolide.
- Atmospheric Physics