Measurement of low-altitude infrared propagation.

Infrared propagation at low altitudes is determined by extinction that is due to molecules and aerosol particles and ray bending by refraction, three effects that control the mean value of the signal. Interference causes the signal to fluctuate, or scintillate, about the mean value. We discuss the design, calibration, and limitations of a field instrument for measuring optical propagation inside the midwave and long-wave infrared atmospheric windows.

Low-altitude infrared propagation in a coastal zone: refraction and scattering.

Midwave and long-wave infrared propagation were measured in the marine atmosphere close to the surface of the ocean. Data were collected near San Diego Bay for two weeks in November 1996 over a 15-km horizontal path. The data are interpreted in terms of effects expected from molecules, aerosol particles, and refraction.