Kenneth M. Haught

Long-path high-resolution field measurements of absolute transmission in the 3.5- to 4.0-μm atmospheric window

An example of high-resolution (0.08 cm(-1)), absolute transmission spectra of a 5-km atmospheric path is presented. Precise transmission and wavenumber calibration of the spectra were obtained from infrared laser extinction measurements. A comparison of these spectra to line-by-line calculations shows excellent agreement in the spectral region between 2480 and 2800 cm(-1) (3.57 to 4.03 microm).

High Resolution Field Measurement Of Atmospheric Transmission

During the past several years the Optical Radiation Branch of the Naval Research Laboratory (NRL) has conducted extensive field experiments designed to validate high resolution atmospheric transmission codes for near-and mid-infrared wavelengths. The combined use of laser extinction data with Fourier transform spectrometer measurements over long atmospheric paths has produced several examples of high-quality, precisely calibrated transmission spectra. Instrumentation and procedures used in these experiments will be described and selected measurement results will be presented. Application of this information to current infrared atmospheric transmission problems will be discussed together with comparisons of the experimental data to high-resolution computer code calculations.

REALTRAN: Real-Time Implementation Of Atmospheric-Transmittance Codes

REALTRAN is the generic name given to a series of computer codes developed at NRL for predicting atmospheric transmittance in real time. The REALTRAN algorithms, tailored to meet the requirements of specific applications, are derived both from appropriately modified variants of codes such as HITRAN and LOWTRAN and from recent results of NRLs own atmospheric-propagation field experiments. REALTRAN codes have been developed for both laser and broadband applications. These codes are presently implemented on a Hewlett-Packard model 9825A calculator which has been configured to scan inputs from external sensors. REALTRAN provides cost-effective capabilities for using locally monitored meteorological conditions to forecast the operational performance of specific electrooptical systems.