Laser transmission through thin cirrus clouds

A near-infrared airborne-laser transmission model for thin cirrus clouds ha s been developed on the basis of the successive-order-of-scattering approac h to account for multiple scattering by randomly and horizontally oriented ice crystals associated with an aircraft-target system. Direct transmission and transmission due to multiple scattering are formulated specifically fo r this geometric system, in which scattering and absorption associated with aerosols, water vapor, and air are accounted for. A number of sensitivity experiments have been performed for investigation of the effect of aircraft -target position, cirrus cloud optical depth, and ice crystal size on laser transmission for tactical applications. We show that transmission contribu tions produced by orders of scattering higher than 1 are small and can be n eglected. The possibility of horizontal orientation of ice crystals can enh ance transmission of laser beams in the aircraft-target geometry. Transmitt ed energy is strongly dependent on the horizontal distance between the airc raft and the target and on the cloud optical depth as well as on whether th e cloud is above or below the aircraft. (C) 2000 Optical Society of America OCIS codes: 140.0140, 010.3310, 010.1320, 290.1090.