Impact of Aerosol Forward Scattering on the ABL System.
Scientific rept. no. 10,
SPARTA INC LEXINGTON MA
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The AirBorne Laser ABL theater missile defense system involves the delivery of large amounts of highly focused energy across long, nearly horizontal paths in the upper troposphere and stratosphere. The current study addresses whether high amounts of aerosol forward scattering may impact ABL performance. The current study asserts that aerosol forward scattering effects are minimial for the ABL system and cannot account for the starlight scintillation behavior as measured by aircraft at ABL altitudes. Using appropriate scattering theories and numerical simulation techniques, the analysis considered possible contributions from the single scattering diffraction peak as well as multiple scattering near the optical axis. It was found that the characteristic scattering angles for background stratospheric aerosols and thin cirrus are too large, especially when compared with the transmitter divergence angles of the high energy laser and the tracking microradians to milliradians. Scattering energy is directed well away from the optical axis and, therefore, the energy received near on axis effectively equals the energy transmitted through the atmosphere. On-axis forward scattering effects become important for background stratospheric aerosols and thin cirrus only when scattering optical depths are on the order of 10 or greater.
- Directed Energy Weapons