Effect of atmospheric refraction on limb detecting

Abstract

The gradient of the refractive index of the atmosphere causes the route to bend when the light propagates in the atmosphere, thereby the propagation path will change. For the applications of optical atmospheric detection and star-light navigation positioning, in order to obtain the precise position of the target, the influence of atmospheric refraction needs to be considered. This paper introduces a widely-used refractive index calculation model. The relationships between the index of atmospheric refraction and wavelength, atmospheric pressure, temperature and water vapor content are analyzed. Based on the limb detection method, the effect of atmospheric refraction on the line of sight is calculated and analyzed. At the condition of the 1km tangent height, ignoring the atmospheric refraction will cause the limb line path length up to 148.3 km added. In the limb detection mode, the deflected angle caused by atmospheric refraction decreases rapidly as the pitch angle increases. The difference of the tangent height caused by atmospheric refraction increases rapidly with the decreasing observation point height. When the observing point height is 7 km, variation of the tangent height caused by atmospheric refraction is 0.282 km and the deflected angle is 0.195°. Which indicates that the atmospheric refraction has a great influence on the path of limb observation, especially for tangent height below 30 km.