Atmospheric characterization studies supporting the development of a long-range CO2 laser-based DIAL system

The Air Force Phillips Laboratory is testing the feasibility of developing a long-path, CO 2 laser-based DIAL system for remote sensing applications from an airborne platform. The validity of DIAL system performance simulations for long slant-range paths is being established by means of well-characterized field experiments in which the contributions of atmospheric transmission and atmospheric-turbulence-induced beam spreading and scintillation are being independently measured concurrently with DIAL system radiometric performance. Initial measurements were performed with both diffuse and specular targets using a 3.2 km path located at the Phillips Laboratory Starfire Optical Range. Measurements reported herein were performed using a slant-range path of 21.3 km originating at the Phillips Laboratory AMOS facility on Maui, Hawaii. The latter location offers a slant-range propagation path from 3.04 km above sea level (ASL) to near sea level. The DIAL system under test utilized a 4-joule class laser coupled to 61 cm aperture beam director telescope. Measurements were performed with the laser operating on the C 13 isotope in order to increase the atmospheric transmission with respect to a laser operating at C 12 O 2 16 wavelengths. Concurrent atmospheric optical characterization measurements were performed with an infrared scintillometer operating over the same path and at the same wavelength as the DIAL system. Results of atmospheric propagation characterization measurements are described in this paper and results of DIAL system performance and comparisons to simulations are described in accompanying papers.