Estimates of Atmospheric Distortion Number for Nonlinear Refraction
Abstract
A characteristic nondimensional distortion number Nd was derived in the 1970s that allows inference of the degree of nonlinear refraction or thermal blooming associated with an atmospheric laser path. For a continuous-wave (CW) laser with a Gaussian-shaped beam, the distortion number is a function of several variables including laser power and aperture size, optical wavelength, atmospheric absorption and extinction, index of refraction, temperature, air density, and the air speed or flow transverse to the laser beam. Scenario-dependent calculations of atmospheric distortion number Nd are developed for different geographic regions and seasons using the Air Force Research Laboratory's global thermosonde database, the HITRAN molecular spectroscopic database, and global climatological aerosol model extinction profiles. Tactical air-to-ground scenarios are described as a function of altitude, target distance, and laser-to-target azimuth angle for the COIL wavelength (1.315 micrometers). The results are interpreted in light of seasonal and geographical factors as well as path-integrated moisture.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2007
- Accession Number
- ADA472624
Entities
People
- G. Y. Jumper
- J. R. Roadcap
- P. J. Mcnicholl
- R. R. Beland
Organizations
- Boston College