Slant Path Atmospheric Extinction Measurements

A commercial Fourier transform spectrometer is being used to collect 0.06cm-1 2-14μm slant path atmospheric spectra using the sun as the source of radiation. Using a Lambert plot approach, 10-15 spectra are collected at different air masses. The logarithm of the intensity versus air mass is used to calculate the extinctance for the atmosphere at arbitrary frequencies within the bandwidth. Over the past three years, spectra have been collected on over 120 days at White Sands Missile Range, New Mexico. This data base is being used to study seasonal variation of atmospheric extinction for CO2 and DF laser frequencies. Up to a factor of ten variation in the atmospheric extinction is observed at many CO2 laser frequencies which correlate with atmospheric water vapor measurements. Variations in the atmospheric extinction for DF frequencies are smaller and do not correlate with the water vapor measurements.