Refractivity of a Standard Atmosphere

stronomical observations near the horizon have historically been made for naval navigation and for determining the time of sunset. Recent applications include near-horizon daytime scene simulation to support infrared search and track and infrared seeker studies. The ray path of the setting or rising Sun can be highly distorted near the horizon, and it is seldom rectilinear. An accurate model of atmospheric refraction must include the observer’s altitude as well as range, frequency, and atmospheric pressure and temperature. At infrared through ultraviolet frequencies, refractivity depends strongly on the vertical temperature profile, and an explicit relationship between refractivity and temperature can be obtained. This article describes a refraction model we developed that closely reproduces the profile of the setting Sun. A Astronomical Refraction