ASTRAL propagation model

The Astral propagation model is an underwater sound propagation loss model. It began as a model for predicting range-smoothed (over 30–40 nm) propagation loss (PL) in a range dependent environment in the late 1970s and was developed by C. W. Spoffard.C. W. Spofford, [http://apps.dtic.mil/dtic/tr/fulltext/u2/a956124.pdf The ASTRAL Model, Vol. I: Technical Description], Report SAI-79-742-WA, January 1979. Retrieved 20 August 2013 A convergence zone and surface duct capability was addedD. White, ASTRAL 2.0: A Preliminary Report, Surface Ducts and Convergence Zone Modifications, Report SAIC-86/6562, December 1986 in the mid-1980s, after which it underwent testing by the US Navy along with range dependent Raymode and the Parabolic Equation (PE) model. As a result of these tests, ASTRAL became one of the official US Navy's range dependent PL models along with PE.