Predicting the visibility of LEO satellites

We present a simple algorithm to determine the visibility-time function of a circular low Earth orbit (LEO) satellite at a terminal on the Earth´s surface. The simplicity of the algorithm is based on approximating the ground trace of the satellite (which is not a great circle due to Earth´s rotation) during a time interval of the order of in-view period, by a great-circle are. This enables us to use spherical geometry to compute the location and time epoch of the observation of the closest approach of the satellite´s ground trace to the terminal. This is also the epoch of the observation of the maximum elevation angle from the terminal to the satellite. Applying a result derived relating the maximum elevation angle to the in-view period, we obtain the visibility-time function of the satellite at the terminal. Numerical results illustrate the accuracy of the algorithm for a wide range of LEO orbit altitudes