On-Board Orientation Control of a Steerable Antenna for Ground Station Tracking on LEO Satellites

In this paper, a guidance and control algorithm for satellite onboard antenna orientation is presented. The antenna is mounted on a Low-Earth Orbit (LEO) satellite, used in data download operations and has a 2-axis steering mechanism. The aim of the controller is to orient the antenna to the ground station by tracking a reference direction that is determined by the relative geometry between the satellite and the station. Tracking is done via proportional control, which inputs azimuth and elevation measurements and calculates angular speed commands to be sent to the mechanism. Continuous tracking within a certain error band is required whenever the satellite enters a certain communication cone during its pass over the ground station region. The performance of the algorithm is verified both by simulations and hardware tests performed on the actual satellite flight model.