Rain Models

Crane 1985 Rain Model

This rain model uses the updated atmospheric distribution tables introduced in 1985 as well as the updated rain region map introduced in 1982. The world globe is divided into 12 rain regions. It is superseded by ITU-R P618-13. For additional information on the atmospheric distribution tables used in the Crane 85 model, refer to "Electromagnetic Wave Propagation Through Rain" Robert K. Crane, 1996.

The Crane models in STK refer to the Global (Crane) Attenuation Model. The algorithms used in both Crane models are the same, but the data tables used within the algorithms are different. The models calculate the amount of rain attenuation by dividing the globe into various rain regions. These rain regions, along with the object's instantaneous position and outage percentage, are used to determine the point-path rain rate. Furthermore, the calculation of the rain attenuation is dependent upon the rain rate, 0 degree isothermal height, specific attenuation tables, transmitter frequency, ground station to satellite elevation angle, ground station position and elevation, and curvature of the earth. The general algorithm for determining the rain attenuation is in "Radiowave Propagation In Satellite Communications", Louis J. Ippolito Jr, 1986.